Non-UK_NP1 authors_NN2 omitted_VVN THE_AT DEVELOPMENT_NN1 OF_IO DARWIN_NP1 'S_GE GENERAL_JJ BIOLOGICAL_JJ THEORIZING_NN1 M.J.S._NP1 HODGE_NP1 Charles_NP1 Darwin_NP1 (_( 18091882_MC )_) was_VBDZ only_RR twenty_MC seven_MC when_RRQ he_PPHS1 returned_VVD ,_, in_II 1836_MC ,_, from_II the_AT five-year_JJ voyage_NN1 of_IO HMS_NNB Beagle_NP1 ._. 
What_DDQ is_VBZ more_RRR ,_, within_II the_AT next_MD five_MC years_NNT2 he_PPHS1 reached_VVD all_DB those_DD2 conclusions_NN2 in_RR21 general_RR22 biological_JJ theory_NN1 that_CST his_APPGE books_NN2 were_VBDR to_TO expound_VVI three_MC decades_NNT2 later_RRR ._. 
For_IF ,_, by_II 1841_MC ,_, he_PPHS1 had_VHD worked_VVN out_RP not_XX only_RR his_APPGE theory_NN1 of_IO the_AT origin_NN1 of_IO species_NN ,_, natural_JJ selection_NN1 ,_, but_CCB also_RR ,_, it_PPH1 seems_VVZ ,_, his_APPGE theory_NN1 of_IO generation_NN1 (_( or_CC reproduction_NN1 ,_, including_II heredity_NN1 ,_, variation_NN1 and_RR31 so_RR32 on_RR33 )_) ,_, pangenesis_NN1 ._. 
This_DD1 chapter_NN1 surveys_VVZ the_AT development_NN1 of_IO his_APPGE general_JJ biological_JJ theorizing_NN1 over_II that_DD1 remarkable_JJ early_JJ period_NN1 ._. 
The_AT analysis_NN1 draws_VVZ throughout_RL on_II the_AT work_NN1 done_VDN in_II the_AT last_MD decade_NNT1 by_II Gruber_NP1 (_( 1974_MC )_) ,_, Herbert_NP1 (_( 1974_MC ,_, 1977_MC )_) ,_, Ghiselin_NP1 (_( 1975_MC )_) ,_, Ruse_NN1 (_( 1975a_FO ,_, b_ZZ1 ;_; 1979_MC )_) ,_, Schweber_NP1 (_( 1977_MC ,_, 1980_MC )_) ,_, Kottler_NP1 (_( 1978_MC )_) ,_, Manier_NP1 (_( 1978_MC )_) ,_, Sulloway_NP1 (_( 1979_MC ,_, 1982a_FO ,_, b_ZZ1 )_) ,_, Kohn_NP1 (_( 1980_MC )_) ,_, Ospovat_NP1 (_( 1981_MC )_) ,_, and_CC Sloan_NP1 (_( 1983a_FO ,_, b_ZZ1 )_) and_CC is_VBZ derived_VVN from_II studies_NN2 by_II the_AT present_JJ writer_NN1 (_( Hodge_NP1 ,_, 1982_MC ,_, 1986_MC ;_; Hodge_NP1 &amp;_CC Kohn_NP1 ,_, 1986_MC )_) where_RRQ full_JJ reference_NN1 is_VBZ made_VVN to_II the_AT documentary_NN1 sources_NN2 and_CC secondary_JJ literature_NN1 ._. 
Such_DA a_AT1 survey_NN1 can_VM serve_VVI more_DAR than_CSN mere_JJ biographical_JJ curiosity_NN1 ,_, and_CC a_AT1 final_JJ section_NN1 will_VM suggest_VVI how_RRQ it_PPH1 may_VM clarify_VVI some_DD issues_NN2 of_IO current_JJ interest_NN1 to_II historians_NN2 ,_, to_II philosophers_NN2 and_CC to_II biologists_NN2 ._. 
It_PPH1 can_VM also_RR free_VVI us_PPIO2 from_II many_DA2 mistaken_JJ myths_NN2 about_II Darwin_NP1 himself_PPX1 ._. 
These_DD2 myths_NN2 mostly_RR trace_VV0 to_II his_APPGE own_DA misleading_JJ reminiscences_NN2 later_RRR in_II life_NN1 ,_, and_CC have_VH0 been_VBN relentlessly_RR reaffirmed_VVN since_CS ,_, at_II the_AT 1959_MC centennial_JJ symposia_NN1 for_REX21 example_REX22 and_CC in_II the_AT 1978_MC BBC-TV_JJ series_NN on_II Darwin_NP1 ;_; but_CCB they_PPHS2 are_VBR nonetheless_RR discredited_VVN by_II the_AT scholarly_JJ industry_NN1 now_RT grown_VVN up_RP around_II the_AT rich_JJ manuscript_NN1 archive_NN1 from_II Darwin_NP1 's_GE early_JJ years_NNT2 (_( Kohn_NP1 ,_, 1986_MC )_) ._. 
One_MC1 is_VBZ the_AT romantic_JJ ,_, really_RR Wordsworthian_JJ ,_, individualist_NN1 myth_NN1 so_RG dear_JJ to_II the_AT literary_JJ guardians_NN2 of_IO English_JJ national_JJ cultural_JJ stereotypes_NN2 ._. 
It_PPH1 depicts_VVZ the_AT young_JJ Darwin_NP1 as_II a_AT1 lone_JJ ,_, sporting_JJ gentleman_NN1 ,_, an_AT1 amateur_JJ beetle-collector_NN1 seeing_VVG nature_NN1 as_CSA she_PPHS1 really_RR is_VBZ by_II simply_RR looking_VVG with_IW the_AT clear_JJ gaze_NN1 of_IO genius_NN1 ,_, unimpeded_JJ by_II any_DD scientific_JJ training_NN1 ,_, theological_JJ prejudice_NN1 ,_, professional_JJ ambition_NN1 and_RR31 so_RR32 on_RR33 ._. 
Another_DD1 is_VBZ the_AT Whiggish_NN1 ,_, anachronistic_JJ myth_NN1 that_CST Darwin_NP1 's_GE general_JJ biological_JJ thought_NN1 consists_VVZ of_IO a_AT1 molecule_NN1 comprising_VVG just_RR two_MC atoms_NN2 :_: the_AT idea_NN1 of_IO evolution_NN1 and_CC the_AT idea_NN1 of_IO natural_JJ selection_NN1 ._. 
It_PPH1 depicts_VVZ his_APPGE early_JJ intellectual_JJ development_NN1 as_CSA reducing_VVG to_II two_MC moments_NN2 of_IO discovery_NN1 ,_, whereby_RRQ he_PPHS1 moves_VVZ from_II having_VHG no_AT coherent_JJ ideas_NN2 to_II having_VHG just_RR those_DD2 ideas_NN2 ._. 
Fortunately_RR ,_, there_EX is_VBZ a_AT1 single_JJ antidote_NN1 effective_JJ against_II both_DB2 these_DD2 myths_NN2 ;_; ,_, and_CC that_DD1 is_VBZ to_TO start_VVI all_RR over_II again_RT with_IW the_AT most_RGT decisive_JJ source_NN1 of_IO Darwin_NP1 's_GE new_JJ identity_NN1 ,_, on_II the_AT voyage_NN1 ,_, as_CSA a_AT1 committed_JJ man_NN1 of_IO science_NN1 :_: his_APPGE zealous_JJ discipleship_NN1 of_IO Charles_NP1 Lyell_NP1 's_GE (_( 17971875_MC )_) views_NN2 in_II geology_NN1 (_( including_II biogeography_NN1 and_CC ecology_NN1 )_) ._. 
This_DD1 antidote_NN1 is_VBZ effective_JJ against_II the_AT romantic-individualist_NN1 myth_NN1 ,_, because_CS ,_, as_CSA a_AT1 protg_NN1 of_IO Lyell_NP1 ,_, the_AT young_JJ Darwin_NP1 of_IO the_AT Beagle_NN1 is_VBZ at_RR21 once_RR22 invested_VVN with_IW all_DB the_AT intellectual_NN1 and_CC institutional_JJ context_NN1 that_CST that_DD1 myth_NN1 would_VM suppress_VVI ._. 
It_PPH1 is_VBZ effective_JJ against_II the_AT myth_NN1 ,_, because_CS it_PPH1 forces_VVZ us_PPIO2 to_TO reconstruct_VVI the_AT narrative_NN1 of_IO his_APPGE subsequent_JJ theorizing_NN1 not_XX as_RG so_RG many_DA2 unknowing_JJ steps_NN2 towards_II his_APPGE final_JJ positions_NN2 ,_, but_CCB as_CSA so_RG many_DA2 deliberate_JJ departures_NN2 from_II positions_NN2 initially_RR shared_VVN with_IW his_APPGE mentor_NN1 ._. 
Darwin_NP1 as_II a_AT1 protg_NN1 of_IO Lyell_NP1 (_( 18347_MC )_) Darwin_NP1 's_GE acceptance_NN1 of_IO Lyell_NP1 's_GE views_NN2 was_VBDZ complete_JJ by_II mid-1834_MC when_RRQ he_PPHS1 sailed_VVD around_II the_AT Horn_NN1 ._. 
Having_VHG now_RT studied_VVN all_DB three_MC volumes_NN2 of_IO the_AT Principles_NN2 of_IO Geology_NN1 (_( 18303_MC )_) ,_, he_PPHS1 was_VBDZ applying_VVG Lyell_NP1 's_GE entire_JJ system_NN1 ,_, physical_JJ and_CC organic_JJ worlds_NN2 alike_RR ,_, to_II South_ND1 America_NP1 and_CC beyond_RL that_CST the_AT whole_JJ earth_NN1 ._. 
Henceforth_RT this_DD1 system_NN1 provided_CS the_AT framework_NN1 for_IF his_APPGE preoccupation_NN1 with_IW the_AT problems_NN2 of_IO the_AT extinction_NN1 and_CC origin_NN1 of_IO species_NN ._. 
All_DB the_AT causes_NN2 of_IO change_NN1 are_VBR presumed_VVN ,_, in_II Lyell_NP1 's_GE system_NN1 ,_, to_TO persist_VVI undiminished_JJ into_II the_AT present_NN1 ,_, the_AT human_JJ period_NN1 ,_, and_CC on_RP into_II the_AT future_NN1 ._. 
Now_RT ,_, as_CSA at_II all_DB times_NNT2 ,_, habitable_JJ dry_JJ land_NN1 is_VBZ being_VBG destroyed_VVN by_II subsidence_NN1 and_CC erosion_NN1 in_II some_DD regions_NN2 ,_, while_CS it_PPH1 is_VBZ being_VBG produced_VVN by_II sediment_NN1 consolidation_NN1 ,_, lava_NN1 eruption_NN1 and_CC elevationary_JJ earthquake_NN1 action_NN1 in_II others_NN2 ._. 
Equally_RR ,_, Lyell_NP1 has_VHZ the_AT long_JJ succession_NN1 of_IO faunas_NN2 and_CC floras_NN2 brought_VVN about_RP by_II a_AT1 continual_JJ ,_, one-by-one_MC extinction_NN1 of_IO species_NN and_CC their_APPGE replacement_NN1 by_II new_JJ ones_NN2 ._. 
The_AT epistemological_JJ rationale_NN1 for_IF his_APPGE presumption_NN1 ,_, of_IO the_AT persistence_NN1 of_IO all_DB such_DA causes_NN2 of_IO change_NN1 into_II the_AT present_NN1 and_CC future_NN1 ,_, is_VBZ the_AT ideal_NN1 of_IO explanation_NN1 by_II real_JJ or_CC existing_JJ causes_NN2 ,_, verae_NN2 causae_NN2 ._. 
Like_II his_APPGE friend_NN1 (_( and_CC the_AT undergraduate_NN1 Darwin_NP1 's_GE scientific_JJ hero_NN1 )_) the_AT physicist_NN1 John_NP1 Herschel_NP1 (_( 17921871_MC )_) ,_, Lyell_NP1 followed_VVD earlier_JJR writers_NN2 ,_, most_RGT notably_RR the_AT Scottish_JJ philosopher_NN1 Thomas_NP1 Reid_NP1 (_( 17101796_MC )_) ,_, who_PNQS had_VHD drawn_VVN this_DD1 moral_JJ from_II the_AT superior_JJ evidential_JJ credentials_NN2 of_IO the_AT Newtonian_JJ gravitational_JJ force_NN1 over_II the_AT Cartesian_JJ ethereal_JJ vortices_NN2 :_: any_DD causes_NN2 invoked_VVN in_II an_AT1 explanatory_JJ theory_NN1 should_VM ,_, ideally_RR ,_, be_VBI known_VVN to_TO exist_VVI through_II direct_JJ observation_NN1 independently_RR of_IO the_AT facts_NN2 they_PPHS2 are_VBR supposed_JJ to_TO explain_VVI ._. 
That_DD1 force_NN1 ,_, unlike_II those_DD2 vortices_NN2 ,_, was_VBDZ a_AT1 well-evidenced_JJ explanation_NN1 for_IF the_AT planets_NN2 '_GE orbits_NN2 because_CS ,_, the_AT argument_NN1 went_VVD ,_, the_AT orbits_NN2 themselves_PPX2 were_VBDR not_XX the_AT sole_JJ evidence_NN1 for_IF its_APPGE existence_NN1 ._. 
It_PPH1 was_VBDZ a_AT1 real_JJ not_XX a_AT1 conjectural_JJ cause_NN1 ;_; for_IF it_PPH1 was_VBDZ known_VVN to_TO exist_VVI from_II observations_NN2 of_IO swinging_JJ pendulums_NN2 and_CC falling_VVG stones_NN2 down_RP here_RL on_II earth_NN1 ._. 
Lyell_NP1 's_GE system_NN1 was_VBDZ ,_, therefore_RR ,_, to_TO exemplify_VVI an_AT1 epistemological_JJ analogy_NN1 ._. 
In_II geology_NN1 ,_, only_RR causes_VVZ active_JJ in_II the_AT present_NN1 ,_, human_JJ period_NN1 are_VBR accessible_JJ in_II principle_NN1 ,_, although_CS often_RR not_XX in_II practice_NN1 ,_, to_TO direct_VVI observation_NN1 ._. 
So_RR ,_, in_II this_DD1 science_NN1 ,_, the_AT present_NN1 is_VBZ to_II the_AT past_NN1 as_II the_AT terrestrial_JJ is_VBZ to_II the_AT celestial_JJ in_II Newtonian_JJ physical_JJ astronomy_NN1 ._. 
Such_DA ,_, then_RT ,_, was_VBDZ the_AT context_NN1 ,_, at_RR21 once_RR22 systematic_JJ and_CC epistemological_JJ wherein_RRQ Darwin_NP1 ,_, from_II 1834_MC on_II ,_, was_VBDZ theorizing_VVG about_II species_NN extinctions_NN2 and_CC origins_NN2 ._. 
His_APPGE own_DA thinking_NN1 over_II the_AT next_MD three_MC years_NNT2 was_VBDZ developed_VVN ,_, accordingly_RR ,_, through_II successive_JJ disagreements_NN2 with_IW Lyell_NP1 's_GE views_NN2 on_II the_AT organic_JJ world_NN1 ,_, while_CS he_PPHS1 continued_VVD to_TO accept_VVI his_APPGE mentor_NN1 's_VBZ teaching_VVG on_II the_AT physical_JJ world_NN1 of_IO land_NN1 ,_, sea_NN1 and_CC climate_NN1 changes_NN2 ._. 
Lyell_NP1 had_VHD made_VVN adaptational_JJ considerations_NN2 alone_RR completely_RR decisive_JJ in_II determining_VVG the_AT timing_NN1 and_CC placing_NN1 of_IO both_RR species_NN extinctions_NN2 and_CC species_NN origins_NN2 ._. 
Any_DD species_NN must_VM eventually_RR become_VVI extinct_JJ ;_; for_IF changes_NN2 in_II local_JJ conditions_NN2 will_VM sooner_RRR or_CC later_RRR allow_VV0 other_JJ species_NN better_RRR adapted_VVN to_II the_AT changed_JJ conditions_NN2 to_TO invade_VVI and_CC conquer_VVI in_II the_AT struggle_NN1 for_IF existence_NN1 ._. 
As_II21 for_II22 species_NN origins_NN2 ,_, Lyell_NP1 had_VHD argued_VVN against_II spontaneous_JJ generation_NN1 and_CC against_II new_JJ species_NN arising_VVG by_II the_AT modification_NN1 (_( '_GE transmutation_NN1 '_GE )_) of_IO older_JJR ones_NN2 ._. 
But_CCB ,_, in_II offering_VVG no_AT positive_JJ alternative_JJ account_NN1 ,_, he_PPHS1 had_VHD left_VVN the_AT means_NN whereby_RRQ new_JJ species_NN originate_VV0 quite_RG mysterious_JJ if_CS not_XX miraculous_JJ ._. 
He_PPHS1 had_VHD held_VVN explicitly_RR ,_, however_RR ,_, that_CST when_CS and_CC where_CS any_DD given_JJ species_NN is_VBZ created_VVN is_VBZ determined_VVN by_II the_AT conditions_NN2 it_PPH1 needs_VVZ to_TO flourish_VVI ._. 
Conversely_RR ,_, the_AT character_NN1 and_CC so_RR the_AT supraspecific_JJ group_NN1 membership_NN1 of_IO the_AT species_NN that_CST have_VH0 originated_VVN in_II any_DD area_NN1 is_VBZ determined_VVN by_II conditions_NN2 there_RL ._. 
So_RR ,_, on_II Lyell_NP1 's_GE account_NN1 ,_, if_CS two_MC areas_NN2 are_VBR very_RG similar_JJ in_II conditions_NN2 they_PPHS2 will_VM have_VHI congeneric_JJ or_CC cofamilial_JJ endemic_JJ species_NN ;_; if_CS they_PPHS2 are_VBR very_RG dissimilar_JJ ,_, then_RT their_APPGE endemic_JJ species_NN will_VM be_VBI of_IO distinct_JJ families_NN2 or_CC orders_NN2 ._. 
Now_RT ,_, by_II early_JJ spring_NN1 1837_MC ,_, Darwin_NP1 had_VHD decided_VVN that_CST such_DA purely_RR adaptational_JJ explanations_NN2 could_VM not_XX account_VVI adequately_RR for_IF the_AT timing_NN1 and_CC placing_NN1 of_IO either_RR the_AT extinctions_NN2 of_IO old_JJ species_NN or_CC the_AT origins_NN2 of_IO new_JJ ones_NN2 ._. 
And_CC he_PPHS1 was_VBDZ emphasizing_VVG ,_, in_II his_APPGE Red_JJ Notebook_NN1 ,_, the_AT parallel_NN1 in_II the_AT explanatory_JJ inadequacy_NN1 of_IO adaptation_NN1 in_II the_AT two_MC cases_NN2 (_( Herbert_NP1 ,_, 1980_MC )_) ._. 
Already_RR ,_, in_II 1835_MC ,_, he_PPHS1 had_VHD concluded_VVN that_CST several_DA2 species_NN of_IO large_JJ mammals_NN2 ,_, formerly_RR flourishing_VVG on_II the_AT eastern_JJ plains_NN2 of_IO South_ND1 America_NP1 ,_, had_VHD later_RRR become_VV0 extinct_JJ while_CS no_AT change_NN1 in_II conditions_NN2 physical_JJ or_CC ecological_JJ had_VHD occurred_VVN ._. 
And_CC he_PPHS1 had_VHD adopted_VVN another_DD1 theory_NN1 of_IO extinction_NN1 ,_, discussed_VVN but_CCB rejected_VVD by_II Lyell_NP1 ,_, wherein_RRQ species_NN are_VBR like_JJ individuals_NN2 and_CC die_VV0 of_IO old_JJ age_NN1 ._. 
A_AT1 species_NN ,_, as_CSA a_AT1 succession_NN1 of_IO organisms_NN2 produced_VVD sexually_RR ,_, might_VM have_VHI only_RR a_AT1 limited_JJ total_JJ lifetime_NNT1 ,_, Darwin_NP1 argued_VVD ;_; just_RR as_II a_AT1 succession_NN1 of_IO apple_NN1 trees_NN2 propagated_VVN by_II grafts_NN2 was_VBDZ supposed_JJ to_TO last_VVI only_RR so_RG long_RR before_II degenerating_VVG and_CC dying_JJ as_CS21 if_CS22 it_PPH1 were_VBDR merely_RR the_AT extension_NN1 of_IO a_AT1 single_JJ limited_JJ life_NN1 ._. 
As_II21 for_II22 the_AT origin_NN1 of_IO species_NN ,_, reflection_NN1 on_II many_DA2 palaeontological_JJ and_CC biogeographical_JJ facts_NN2 ,_, including_II those_DD2 established_VVN by_II the_AT expert_NN1 judgments_NN2 of_IO Richard_NP1 Owen_NP1 and_CC John_NP1 Gould_NP1 on_II the_AT voyage_NN1 material_NN1 ,_, had_VHD convinced_VVN Darwin_NP1 ,_, by_II early_JJ spring_NN1 1837_MC ,_, that_CST the_AT close_JJ similarity_NN1 seen_VVN between_II any_DD congeneric_JJ endemic_JJ species_NN in_II two_MC areas_NN2 was_VBDZ not_XX always_RR explicable_JJ as_II a_AT1 common_JJ adaptation_NN1 to_II common_JJ conditions_NN2 ;_; for_IF often_RR the_AT two_MC sets_NN2 of_IO species_NN were_VBDR endemic_JJ in_II areas_NN2 with_IW very_RG different_JJ climate_NN1 ,_, soil_VV0 and_RR31 so_RR32 on_RR33 ._. 
However_RR ,_, if_CS more_RGR recent_JJ species_NN could_VM descend_VVI from_II earlier_JJR ones_NN2 ,_, ancestry_NN1 could_VM explain_VVI what_DDQ adaptation_NN1 could_VM not_XX ._. 
Why_RRQ did_VDD the_AT species_NN on_II younger_JJR land_NN1 the_AT Galapagos_NP1 islands_NN2 or_CC the_AT southern_JJ Patagonian_JJ plains_NN2 ,_, for_REX21 instance_REX22 often_RR resemble_VV0 closely_RR other_JJ species_NN on_II the_AT nearest_JJT older_JJR land_NN1 ?_? 
Because_CS they_PPHS2 were_VBDR descended_VVN from_II them_PPHO2 ,_, many_DA2 sometimes_RT descending_VVG from_II a_AT1 single_JJ ancestral_JJ species_NN ._. 
Thus_RR did_VDD Darwin_NP1 conclude_VVI that_CST resemblances_NN2 between_II species_NN are_VBR often_RR not_XX due_JJ to_II adaptation_NN1 but_CCB to_II inheritance_NN1 from_II common_JJ ancestors_NN2 ;_; while_CS differences_NN2 are_VBR often_RR adaptive_JJ and_CC are_VBR due_II21 to_II22 differing_VVG ,_, multiple_JJ divergences_NN2 from_II those_DD2 common_JJ ancestors_NN2 ._. 
It_PPH1 is_VBZ not_XX ,_, as_CSA he_PPHS1 saw_VVD it_PPH1 ,_, that_DD1 species_NN are_VBR not_XX exquisitely_RR adapted_VVN to_II their_APPGE respective_JJ places_NN2 in_II the_AT economy_NN1 of_IO nature_NN1 ._. 
They_PPHS2 are_VBR and_CC any_DD theory_NN1 of_IO species_NN origins_NN2 must_VM explain_VVI why_RRQ ._. 
It_PPH1 is_VBZ simply_RR that_DD1 adaptation_NN1 and_CC ancestry_NN1 can_VM explain_VVI what_DDQ adaptation_NN1 alone_RR can_VM not_XX ._. 
On_II such_DA grounds_NN2 Darwin_NP1 had_VHD decided_VVN ,_, by_II that_DD1 spring_NN1 ,_, for_IF transmutation_NN1 and_CC common_JJ descent_NN1 ._. 
Always_RR the_AT bold_JJ '_GE philosopher_NN1 '_GE as_RG much_DA1 as_CSA the_AT cautious_58 '_GE naturalist_NN1 '_GE ,_, he_PPHS1 soon_RR went_VVD far_RR beyond_II these_DD2 disagreements_NN2 with_IW Lyell_NP1 ._. 
He_PPHS1 did_VDD so_RR in_II a_AT1 new_JJ sequence_NN1 of_IO theoretical_JJ notebooks_NN2 ,_, B-E_VBI (_( 18379_MC )_) and_CC M-_JJ N_ZZ1 (_( 18389_MC )_) M_ZZ1 for_IF '_GE metaphysics_NN1 '_GE ,_, meaning_VVG mind_NN1 ,_, man_NN1 ,_, materialism_NN1 ,_, morals_NN2 and_RR31 so_RR32 on_RR33 ._. 
(_( See_VV0 a_AT1 note_NN1 at_II the_AT end_NN1 of_IO this_DD1 chapter_NN1 on_II editions_NN2 of_IO these_DD2 texts_NN2 ._. )_) 
He_PPHS1 did_VDD so_RR ,_, moreover_RR ,_, in_II two_MC ways_NN2 that_CST were_VBDR consciously_RR conditioned_VVN from_II the_AT start_NN1 by_II his_APPGE immediate_JJ context_NN1 and_CC resources_NN2 in_II 1837_MC as_II a_AT1 biological_JJ theorist_NN1 ._. 
First_MD ,_, from_II way_NN1 back_RP in_II his_APPGE Edinburgh_NP1 days_NNT2 and_CC his_APPGE apprenticeship_NN1 to_II Robert_NP1 Grant_NP1 in_II invertebrate_JJ zoology_NN1 ,_, he_PPHS1 had_VHD been_VBN much_DA1 pre-occupied_JJ with_IW comprehensive_JJ generalizations_NN2 about_II sexual_JJ and_CC asexual_JJ modes_NN2 of_IO generation_NN1 (_( Sloan_NP1 ,_, personal_JJ communication_NN1 )_) ._. 
His_APPGE extinction_NN1 theorizing_NN1 had_VHD thus_RR been_VBN developed_VVN ,_, since_II 1835_MC ,_, at_II the_AT first_MD intersection_NN1 of_IO that_DD1 old_JJ preoccupation_NN1 with_IW his_APPGE newer_JJR devotion_NN1 to_II Lyellian_JJ geology_NN1 ._. 
Now_RT ,_, in_II the_AT summer_NNT1 of_IO 1837_MC ,_, he_PPHS1 would_VM understand_VVI the_AT origins_NN2 no_AT less_DAR than_CSN the_AT extinctions_NN2 of_IO species_NN through_II appropriate_JJ comparisons_NN2 and_CC contrasts_VVZ between_II sexual_JJ and_CC asexual_JJ generation_NN1 ._. 
Having_VHG read_VVN again_RT a_AT1 book_NN1 he_PPHS1 had_VHD admired_VVN when_CS studying_VVG at_II Edinburgh_NP1 ,_, a_AT1 book_NN1 much_RR concerned_JJ with_IW precisely_RR such_DA comparisons_NN2 and_CC contrasts_VVZ his_APPGE grandfather_NN1 Brasmus_NP1 Darwin_NP1 's_GE Zonomia_NP1 (_( 17946_MC )_) he_PPHS1 was_VBDZ soon_RR taking_VVG its_APPGE title_NN1 for_IF the_AT opening_NN1 heading_NN1 of_IO his_APPGE Notebook_NN1 B_ZZ1 ,_, where_CS he_PPHS1 was_VBDZ now_RT to_TO pursue_VVI his_APPGE own_DA inquiry_NN1 into_II '_GE the_AT laws_NN2 of_IO life_NN1 '_GE ._. 
He_PPHS1 was_VBDZ soon_RR making_VVG explicit_JJ ,_, too_RR ,_, a_AT1 fundamental_JJ teleological_JJ analogy_NN1 ,_, in_II which_DDQ changing_JJ conditions_NN2 are_VBR to_II sexual_JJ generation_NN1 as_CSA sexual_JJ crossing_NN1 is_VBZ to_II asexual_JJ generation_NN1 ._. 
Although_CS it_PPH1 can_VM extend_VVI an_AT1 individual_JJ life_NN1 ,_, continued_JJ grafting_NN1 eventually_RR brings_VVZ death_NN1 without_IW issue_NN1 ;_; and_CC likewise_RR sexual_JJ generation_NN1 in_II unchanging_JJ conditions_NN2 brings_VVZ death_NN1 ,_, extinction_NN1 of_IO the_AT species_NN ,_, without_IW issue_NN1 ._. 
With_IW sexual_JJ crossing_NN1 ,_, however_RR ,_, an_AT1 individual_NN1 whose_DDQGE life_NN1 has_VHZ been_VBN extended_VVN by_II grafting_NN1 ,_, although_CS not_XX enabled_VVN to_TO go_VVI on_II itself_PPX1 ,_, can_VM give_VVI rise_NN1 to_II a_AT1 new_JJ individual_NN1 with_IW a_AT1 new_JJ lease_NN1 on_II life_NN1 ._. 
Likewise_RR ,_, then_RT ,_, in_II changing_JJ conditions_NN2 ,_, sexual_JJ generation_NN1 is_VBZ the_AT providential_JJ means_NN whereby_RRQ a_AT1 species_NN can_VM change_VVI into_II another_DD1 ,_, a_AT1 new_JJ species_NN adapted_VVN to_II the_AT new_JJ conditions_NN2 ,_, so_RR avoiding_VVG the_AT extinction_NN1 without_IW issue_NN1 that_CST would_VM otherwise_RR occur_VVI ._. 
Second_MD ,_, Lyell_NP1 had_VHD outlined_VVN very_RG fully_RR and_CC of_RR21 course_RR22 rejected_VVD the_AT comprehensive_JJ transmutationist_NN1 system_NN1 of_IO biology_NN1 developed_VVN by_II jean_NN1 Lamarck_NP1 ,_, praising_VVG the_AT French_JJ zoologist_NN1 for_IF his_APPGE courage_NN1 in_II extending_VVG his_APPGE repugnant_JJ ideas_NN2 to_II our_APPGE own_DA species_NN ,_, man_NN1 ._. 
Darwin_NP1 accordingly_RR opened_VVD his_APPGE Notebook_NN1 B_ZZ1 ,_, in_II July_NPM1 1837_MC ,_, with_IW an_AT1 integrated_JJ sequence_NN1 of_IO entries_NN2 whose_DDQGE twenty-seven_MC pages_NN2 of_IO argumentation_NN1 were_VBDR to_TO match_VVI the_AT structure_NN1 of_IO Lyell_NP1 's_GE exposition_NN1 of_IO Lamarck_NP1 ._. 
Darwin_NP1 ,_, like_II Lamarck_NP1 as_CSA presented_VVN (_( and_CC misrepresented_VVN )_) by_II Lyell_NP1 would_VM now_RT trace_VVI any_DD degrees_NN2 of_IO difference_NN1 ,_, no_RGQV31 matter_RGQV32 how_RGQV33 wide_JJ ,_, to_II long-run_JJ divergences_NN2 from_II common_JJ stocks_NN2 ._. 
And_CC he_PPHS1 would_VM trace_VVI any_DD higher_JJR levels_NN2 of_IO bodily_JJ organization_NN1 and_CC mental_JJ faculties_NN2 ,_, explicitly_RR including_II those_DD2 in_II man_NN1 ,_, to_II long-run_JJ progress_NN1 from_II remote_JJ starting_NN1 points_VVZ in_II the_AT simplest_JJT organisms_NN2 of_IO all_DB ,_, infusorian_JJ monads_NN2 ._. 
With_IW these_DD2 decisions_NN2 Darwin_NP1 became_VVD more_DAR than_CSN the_AT protg_NN1 of_IO Lyell_NP1 ._. 
He_PPHS1 would_VM be_VBI ever_RR hereafter_RT his_APPGE own_DA successor_NN1 in_II developing_JJ sequels_NN2 to_II the_AT steps_NN2 he_PPHS1 had_VHD taken_VVN in_II the_AT spring_NN1 and_CC summer_NNT1 of_IO 1837_MC ._. 
The_AT new_JJ programme_NN1 pursued_VVN (_( 18378_MC )_) Darwin_NP1 himself_PPX1 often_RR reflected_VVN in_II his_APPGE notebooks_NN2 on_II his_APPGE new_JJ programme_NN1 's_GE presuppositions_NN2 concerning_II God_NP1 ,_, nature_NN1 ,_, man_NN1 and_CC science_NN1 ._. 
God_NP1 was_VBDZ ,_, for_IF Darwin_NP1 then_RT ,_, still_RR the_AT traditional_JJ good_JJ and_CC wise_JJ creator_NN1 ,_, but_CCB one_PN1 never_RR working_VVG in_RP so_RG many_DA2 separate_JJ acts_NN2 of_IO miraculous_JJ interference_NN1 ,_, always_RR through_II the_AT natural_JJ consequences_NN2 of_IO a_AT1 few_DA2 initial_JJ enactments_NN2 of_IO general_JJ causal_JJ laws_NN2 :_: as_CSA with_IW planetary_JJ orbits_NN2 and_CC the_AT law_NN1 of_IO gravitation_NN1 ,_, so_RR ,_, Darwin_NP1 insisted_VVD ,_, with_IW species_NN origins_NN2 and_CC the_AT laws_NN2 of_IO generation_NN1 ._. 
As_II21 for_II22 man_NN1 ,_, he_PPHS1 is_VBZ a_AT1 species_NN produced_VVN like_II any_DD other_JJ ,_, lawfully_RR ,_, his_APPGE mental_JJ faculties_NN2 the_AT causal_JJ consequences_NN2 of_IO his_APPGE bodily_JJ organization_NN1 and_CC not_XX miraculously_RR superadded_VVD ;_; while_CS science_NN1 is_VBZ a_AT1 quest_NN1 for_IF lawful_JJ causes_NN2 that_CST are_VBR evidenced_VVN both_RR directly_RR and_CC independently_RR of_IO the_AT many_DA2 ,_, diverse_JJ facts_NN2 they_PPHS2 can_VM explain_VVI ,_, and_CC indirectly_RR and_CC dependently_RR ,_, by_II the_AT very_JJ multitude_NN1 and_CC diversity_NN1 of_IO those_DD2 facts_NN2 ._. 
The_AT place_NN1 in_II the_AT programme_NN1 of_IO his_APPGE generational_JJ theory_NN1 of_IO species_NN origins_NN2 Darwin_NP1 understood_VVD through_II the_AT analogy_NN1 of_IO a_AT1 tree_NN1 of_IO life_NN1 ._. 
By_II the_AT autumn_NNT1 of_IO 1837_MC ,_, he_PPHS1 had_VHD developed_VVN this_DD1 analogy_NN1 so_BCL21 as_BCL22 to_TO understand_VVI all_DB long-run_JJ trends_NN2 in_II diversification_NN1 and_CC progress_NN1 through_II an_AT1 arboriform_JJ extrapolation_NN1 ,_, on_II a_AT1 changing_JJ but_CCB stable_JJ Lyellian_JJ earth_NN1 's_GE surface_NN1 ,_, of_IO successive_JJ species_NN propagations_NN2 ;_; these_DD2 being_VBG analogous_JJ to_II the_AT successive_JJ bud_NN1 propagations_NN2 whereby_RRQ any_DD tree_NN1 grows_VVZ ,_, with_IW many_DA2 buds_NN2 ending_VVG without_IW branching_JJ ,_, in_II species_NN extinctions_NN2 ,_, while_CS other_JJ buds_NN2 branch_VV0 without_IW ending_NN1 ,_, in_II species_NN multiplications_NN2 ._. 
His_APPGE species_NN propagation_NN1 theorizing_VVG itself_PPX1 was_VBDZ accordingly_RR constructed_VVN ,_, from_II the_AT very_JJ opening_NN1 of_IO Notebook_NN1 B_ZZ1 ,_, as_CSA an_AT1 argument_NN1 that_CST starts_VVZ with_IW the_AT sexual_JJ generation_NN1 of_IO one_MC1 individual_JJ organism_NN1 from_II another_DD1 and_CC ends_VVZ with_IW the_AT propagation_NN1 of_IO one_MC1 species_NN from_II another_DD1 ._. 
Moreover_RR ,_, this_DD1 species_NN propagation_NN1 is_VBZ ultimately_RR made_VVN possible_JJ by_II the_AT two_MC features_NN2 that_CST Darwin_NP1 sees_VVZ distinguishing_JJ sexual_JJ from_II asexual_JJ generation_NN1 :_: namely_REX ,_, maturation_NN1 in_II the_AT offspring_NN and_CC the_AT interaction_NN1 of_IO two_MC parents_NN2 in_II their_APPGE production_NN1 ._. 
Thanks_II21 to_II22 the_AT impressionability_NN1 of_IO immature_JJ organization_NN1 ,_, hereditary_JJ adaptive_JJ variation_NN1 accompanies_VVZ sexual_JJ generation_NN1 in_II changing_JJ conditions_NN2 ._. 
But_CCB how_RRQ then_RT can_VV0 any_DD species_NN be_VBI constant_JJ in_II character_NN1 across_II its_APPGE entire_JJ range_NN1 ?_? 
Because_CS crossing_VVG with_IW the_AT blending_NN1 of_IO parental_JJ characters_NN2 keeps_VVZ the_AT species_NN constant_JJ as_CS31 long_CS32 as_CS33 the_AT conditions_NN2 are_VBR constant_JJ overall_NN1 ,_, only_RR changing_VVG temporarily_RR and_CC locally_RR ._. 
Conversely_RR ,_, then_RT ,_, a_AT1 new_JJ variety_NN1 can_VM be_VBI formed_VVN if_CS this_DD1 conservative_JJ action_NN1 of_IO crossing_NN1 is_VBZ circumvented_VVN by_II reproductive_JJ isolation_NN1 of_IO a_AT1 few_DA2 individuals_NN2 in_II new_JJ conditions_NN2 ,_, whether_CSW that_DD1 isolation_NN1 arises_VVZ with_IW or_CC without_IW geographical_JJ segregation_NN1 ._. 
And_CC how_RRQ may_VM this_DD1 variety_NN1 formation_NN1 proceed_VV0 to_II new_JJ species_NN formation_NN1 ._. )_) 
As_CSA Darwin_NP1 knew_VVD ,_, the_AT usual_JJ criteria_NN2 for_IF specific_JJ rather_II21 than_II22 mere_JJ varietal_JJ distinctions_NN2 were_VBDR those_DD2 that_CST Swedes_NN2 and_CC Italians_NN2 do_VD0 not_XX satisfy_VVI ,_, but_CCB lions_NN2 and_CC tigers_NN2 do_VD0 :_: namely_REX ,_, true_JJ breeding_NN1 ,_, lack_NN1 of_IO intermediate_JJ forms_NN2 and_CC unwillingness_NN1 or_CC inability_NN1 to_TO produce_VVI fertile_JJ hybrids_NN2 on_II crossing_NN1 ._. 
So_RR ,_, the_AT final_JJ stage_NN1 in_II Darwin_NP1 's_GE argumentation_NN1 concerns_VVZ how_RRQ a_AT1 species_NN meeting_VVG those_DD2 three_MC criteria_NN2 would_VM eventually_RR arise_VVI with_IW prolonged_JJ isolation_NN1 and_CC divergence_NN1 ._. 
Over_II the_AT next_MD year_NNT1 ,_, through_II the_AT summer_NNT1 of_IO 1838_MC ,_, it_PPH1 is_VBZ the_AT variety_NN1 and_CC species_NN formation_NN1 stages_NN2 of_IO this_DD1 argument_NN1 that_CST Darwin_NP1 develops_VVZ most_RGT fully_RR and_CC explicitly_RR ._. 
The_AT character_NN1 gaps_NN2 between_II good_JJ species_NN he_PPHS1 explains_VVZ by_II continued_JJ divergence_NN1 and_CC by_II the_AT extinction_NN1 of_IO intermediate_JJ varieties_NN2 ._. 
The_AT true_JJ breeding_NN1 he_PPHS1 explains_VVZ by_II the_AT law_NN1 that_CST in_II crossing_VVG the_AT characters_NN2 of_IO an_AT1 older_JJR domestic_JJ race_NN1 dominate_VV0 those_DD2 of_IO a_AT1 younger_JJR one_PN1 ._. 
This_DD1 dominance_NN1 shows_NN2 ,_, Darwin_NP1 reasons_NN2 ,_, that_DD1 older_JJR characters_NN2 are_VBR more_RGR permanent_JJ ,_, more_RGR deeply_RR embedded_VVN in_II the_AT hereditary_JJ constitution_NN1 and_CC so_RR more_RGR resistant_JJ to_II the_AT influence_NN1 either_RR of_IO mates_NN2 in_II crossing_NN1 or_CC of_IO changing_VVG external_JJ conditions_NN2 ._. 
Such_DA permanent_JJ divergences_NN2 in_II character_NN1 have_VH0 often_RR arisen_VVN in_II the_AT distinct_JJ races_NN2 of_IO a_AT1 domesticated_JJ species_NN ,_, and_CC in_II the_AT wild_JJ they_PPHS2 would_VM be_VBI accompanied_VVN by_II an_AT1 unwillingness_NN1 or_CC inability_NN1 to_TO interbreed_VVI ;_; for_IF there_RL ,_, Darwin_NP1 argues_VVZ ,_, the_AT reproductive_JJ system_NN1 ,_, with_IW the_AT associated_JJ instincts_NN2 ,_, is_VBZ not_XX disrupted_VVN as_CSA it_PPH1 is_VBZ in_II domesticated_JJ species_NN ._. 
So_RR ,_, for_IF Darwin_NP1 ,_, in_II the_AT early_JJ summer_NNT1 of_IO 1838_MC ,_, the_AT races_NN2 of_IO domesticated_JJ species_NN are_VBR providing_VVG positive_JJ analogies_NN2 ,_, especially_RR for_IF the_AT final_NN1 ,_, species_NN formation_NN1 ,_, steps_NN2 in_II his_APPGE argument_NN1 ._. 
But_CCB at_II the_AT other_JJ ,_, the_AT opening_NN1 end_NN1 of_IO that_DD1 argument_NN1 ,_, concerning_VVG the_AT initiation_NN1 and_CC transmission_NN1 of_IO adaptive_JJ change_NN1 ,_, they_PPHS2 are_VBR a_AT1 source_NN1 of_IO contrasts_NN2 and_CC not_XX of_IO comparison_NN1 ._. 
Thus_RR he_PPHS1 says_VVZ that_CST many_DA2 varieties_NN2 of_IO domesticated_JJ species_NN ,_, fancy_JJ pigeon_NN1 breeds_NN2 for_REX21 example_REX22 ,_, are_VBR monstrous_JJ not_XX adaptive_JJ ;_; they_PPHS2 can_VM only_RR be_VBI maintained_VVN by_II artificial_JJ feeding_NN1 and_CC breeding_NN1 ,_, including_II selective_JJ breeding_NN1 ;_; they_PPHS2 are_VBR quite_RG unlike_JJ wild_JJ ,_, natural_JJ and_CC adaptive_JJ varieties_NN2 and_CC even_RR more_RGR unlike_JJ wild_JJ species_NN ._. 
Now_RT ,_, as_CSA Darwin_NP1 sees_VVZ it_PPH1 ,_, at_II this_DD1 time_NNT1 ,_, for_IF a_AT1 change_NN1 to_TO be_VBI an_AT1 adaptation_NN1 it_PPH1 must_VM be_VBI more_DAR than_CSN merely_RR hereditary_JJ and_CC advantageous_JJ ;_; it_PPH1 must_VM be_VBI necessary_JJ rather_II21 than_II22 accidental_JJ ,_, elicited_VVD ,_, that_REX21 is_REX22 ,_, by_II the_AT very_JJ conditions_NN2 that_CST make_VV0 it_PPH1 advantageous_JJ ,_, as_CSA albinism_NN1 sometimes_RT seems_VVZ to_TO be_VBI by_II cold_NN1 ._. 
And_CC it_PPH1 must_VM be_VBI acquired_VVN by_II the_AT whole_NN1 of_IO the_AT race_NN1 faced_VVN with_IW those_DD2 conditions_NN2 ,_, so_RR as_CSA not_XX to_TO be_VBI lost_VVN in_II crossing_NN1 ._. 
Then_RT ,_, as_CSA with_IW reproductive_JJ isolation_NN1 ,_, changed_VVD habits_NN2 can_VM initiate_VVI permanent_JJ adaptive_JJ changes_NN2 in_II structure_NN1 ,_, especially_RR in_II higher_JJR animals_NN2 by_II entailing_VVG changes_NN2 in_II the_AT conditions_NN2 of_IO foetal_JJ maturation_NN1 ._. 
All_DB these_DD2 developments_NN2 ,_, in_II Darwin_NP1 's_GE comprehensive_JJ species_NN propagation_NN1 argumentation_NN1 ,_, are_VBR reinforced_VVN and_CC not_XX rejected_VVN in_II further_JJR developments_NN2 ,_, consummated_VVD in_II mid-September_NPM1 ,_, 1838_MC ,_, in_II his_APPGE Notebook_NN1 D_ZZ1 conjectures_NN2 about_II sexual_JJ and_CC asexual_JJ generation_NN1 ,_, more_RGR particularly_RR about_II sexual_JJ buds_NN2 (_( or_CC ova_NN2 )_) and_CC asexual_JJ buds_NN2 ._. 
A_AT1 sexual_JJ bud_NN1 or_CC ovum_NN1 has_VHZ started_VVN life_NN1 ,_, he_PPHS1 supposes_VVZ ,_, as_CSA a_AT1 bud_NN1 from_II the_AT mother_NN1 when_CS she_PPHS1 was_VBDZ herself_PPX1 a_AT1 newly_RR fertilized_JJ egg_NN1 in_II her_APPGE mother_NN1 ,_, the_AT grandmother_NN1 ._. 
Why_RRQ then_RT does_VDZ it_PPH1 not_XX eventually_RR become_VVI an_AT1 exact_JJ facsimile_NN1 of_IO that_DD1 mother_NN1 ?_? 
Because_CS ,_, he_PPHS1 answers_VVZ ,_, of_IO two_MC lots_PN of_IO differences_NN2 ._. 
During_II its_APPGE maturation_NN1 it_PPH1 is_VBZ subject_II21 to_II22 conditions_NN2 not_XX exactly_RR like_II those_DD2 the_AT mother_NN1 matured_VVD in_RP ;_; and_CC at_II fertilization_NN1 it_PPH1 is_VBZ acted_VVN on_RP by_II a_AT1 mate_NN1 with_IW a_AT1 constitution_NN1 unlike_II its_APPGE own_DA and_CC unlike_II its_APPGE mother_NN1 's_GE ._. 
The_AT whole_JJ object_NN1 of_IO sex_NN1 is_VBZ to_TO have_VHI unlike_JJ acting_NN1 on_II unlike_JJ so_BCL21 as_BCL22 to_TO make_VVI possible_JJ the_AT production_NN1 of_IO unlike_JJ offspring_NN ,_, thus_RR allowing_VVG for_IF adaptive_JJ change_NN1 ,_, Darwin_NP1 argues_VVZ ._. 
But_CCB where_RRQ does_VDZ the_AT constitutional_JJ unlikeness_NN1 of_IO the_AT two_MC mates_NN2 come_VV0 from_II ?_? 
Well_RR ,_, since_CS each_DD1 has_VHZ the_AT same_DA ancestry_NN1 ,_, their_APPGE constitutional_JJ difference_NN1 must_VM trace_VVI to_II the_AT cumulative_JJ influence_NN1 of_IO different_JJ conditions_NN2 in_II the_AT two_MC lines_NN2 of_IO descent_NN1 from_II those_DD2 ancestors_NN2 ._. 
So_RR ,_, sexual_JJ generation_NN1 is_VBZ the_AT means_NN whereby_RRQ the_AT past_JJ influences_NN2 of_IO changing_JJ conditions_NN2 can_VM be_VBI accumulated_VVN and_CC combined_VVN with_IW present_JJ ones_NN2 to_TO ensure_VVI continued_JJ variability_NN1 ._. 
If_CS conditions_NN2 change_VV0 only_RR locally_RR and_CC temporarily_RR then_RT only_RR individual_JJ differences_NN2 will_VM result_VVI ,_, but_CCB ,_, Darwin_NP1 concludes_VVZ ,_, if_CS conditions_NN2 change_VV0 overall_JJ and_CC permanently_RR then_RT a_AT1 new_JJ species_NN will_VM eventually_RR be_VBI formed_VVN ._. 
Darwin_NP1 is_VBZ pleased_JJ with_IW this_DD1 novel_JJ analysis_NN1 of_IO how_RRQ sex_NN1 enables_VVZ new_JJ species_NN to_TO arise_VVI from_II old_JJ ._. 
But_CCB he_PPHS1 admits_VVZ that_CST it_PPH1 leaves_VVZ as_RG mysterious_JJ as_CSA in_II 1837_MC ,_, how_RRQ the_AT maturation_NN1 of_IO the_AT individual_JJ fertilized_JJ ovum_NN1 ensures_VVZ that_CST the_AT changes_NN2 be_VBI adaptive_JJ in_II each_DD1 generation_NN1 ._. 
He_PPHS1 can_VM only_RR conjecture_VVI that_DD1 additional_JJ maturational_JJ innovations_NN2 will_VM not_XX become_VVI hereditary_JJ unless_CS they_PPHS2 harmonize_VV0 with_IW the_AT previous_JJ ones_NN2 that_CST are_VBR already_RR being_VBG recapitulated_VVN in_II maturation_NN1 ._. 
Adaptive_JJ innovations_NN2 could_VM thus_RR be_VBI separated_VVN ,_, as_CSA the_AT ones_NN2 that_CST are_VBR hereditarily_RR transmitted_VVN ,_, from_II the_AT maladaptive_JJ ,_, as_CSA the_AT ones_NN2 that_CST are_VBR not_XX ;_; although_CS Darwin_NP1 notes_VVZ that_CST hereditary_JJ diseases_NN2 show_VV0 that_CST this_DD1 separation_NN1 is_VBZ often_RR fallible_JJ ._. 
Such_DA is_VBZ Darwin_NP1 's_GE species_NN origin_NN1 theorizing_VVG in_II mid-September_NPM1 1838_MC ._. 
It_PPH1 compounds_VVZ still_RR further_RRR those_DD2 two_MC legacies_NN2 so_RG actively_RR conjoined_VVD since_CS the_AT previous_JJ summer_NNT1 of_IO 1837_MC :_: the_AT historical_JJ ,_, biogeographical_JJ (_( including_II ecological_JJ )_) concerns_VVZ that_CST he_PPHS1 had_VHD inherited_VVN from_II Lyell_NP1 ,_, and_CC the_AT generational_JJ concerns_NN2 deriving_VVG from_II his_APPGE study_NN1 with_IW Grant_NP1 and_CC subsequent_JJ reading_NN1 in_II Erasmus_NP1 Darwin_NP1 ._. 
Consider_VV0 ,_, then_RT ,_, what_DDQ geography_NN1 and_CC generation_NN1 together_RL have_VH0 done_VDN for_IF Darwin_NP1 's_GE understanding_NN1 of_IO the_AT problems_NN2 of_IO organic_JJ diversity_NN1 and_CC the_AT origin_NN1 of_IO species_NN ._. 
First_MD ,_, his_APPGE explanation_NN1 of_IO resemblances_NN2 and_CC differences_NN2 among_II species_NN contrasts_VVZ directly_RR with_IW any_DD developmental_JJ stage_NN1 theorizing_NN1 as_CSA found_VVN most_RGT famously_RR in_II Robert_NP1 Chambers_NP1 ,_, Herbert_NP1 Spencer_NP1 or_CC Karl_NP1 Marx_NP1 ._. 
A_AT1 developmental_JJ stage_NN1 theory_NN1 refers_VVZ similarities_NN2 and_CC differences_NN2 to_II moreor-less-equal_JJ advances_NN2 made_VVN from_II the_AT lowest_JJT point_NN1 on_II a_AT1 universal_JJ scale_NN1 of_IO advance_NN1 ._. 
Thus_RR Chambers_NP1 explains_VVZ the_AT similarities_NN2 between_II Old_JJ and_CC New_JJ World_NN1 monkeys_NN2 as_CSA due_II21 to_II22 life_NN1 having_VHG advanced_VVN to_II the_AT same_DA level_NN1 of_IO organization_NN1 from_II quite_RG independent_JJ origins_NN2 of_IO life_NN1 in_II the_AT two_MC hemispheres_NN2 (_( Hodge_NP1 ,_, 1972_MC )_) ._. 
By_II contrast_NN1 ,_, for_IF Darwin_NP1 as_II a_AT1 genealogical_JJ (_( ancestry_NN1 and_CC descent_NN1 )_) theorist_NN1 of_IO historical_JJ biogeography_NN1 ,_, resemblances_NN2 and_CC differences_NN2 are_VBR not_XX traced_VVN to_II developmental_JJ advances_NN2 ,_, but_CCB to_II ramifying_VVG migrations_NN2 and_CC adaptive_JJ divergences_NN2 from_II common_JJ ancestors_NN2 that_CST are_VBR more_RGR or_CC less_RGR remote_JJ from_II their_APPGE diverse_JJ descendants_NN2 in_II time_NNT1 ,_, place_NN1 and_CC character_NN1 ._. 
Now_RT ,_, Darwin_NP1 at_II this_DD1 time_NNT1 is_VBZ explicitly_RR taking_VVG each_DD1 organism_NN1 's_GE ontogeny_NN1 to_TO recapitulate_VVI its_APPGE phylogeny_NN1 ._. 
But_CCB his_APPGE very_JJ assumption_NN1 that_CST many_DA2 descendant_NN1 species_NN may_VM diverge_VVI from_II a_AT1 single_JJ common_JJ ancestry_NN1 precludes_VVZ his_APPGE construing_JJ descendants_NN2 as_CSA grown-up_JJ ancestors_NN2 and_CC ancestors_NN2 as_CSA descendants_NN2 in_II embryo_NN1 ;_; for_IF any_DD given_JJ immature_JJ ,_, embryonic_JJ life_NN1 already_RR has_VHZ but_CCB one_MC1 determinate_JJ mature_JJ adult_NN1 future_NN1 ;_; if_CS a_AT1 puppy_NN1 as_II a_AT1 dog_NN1 ,_, if_CS a_AT1 tadpole_NN1 as_II a_AT1 frog_NN1 ._. 
It_PPH1 is_VBZ ,_, then_RT ,_, because_CS he_PPHS1 is_VBZ explaining_VVG differences_NN2 and_CC resemblances_NN2 as_CSA he_PPHS1 is_VBZ that_CST Darwin_NP1 ,_, in_II 1838_MC ,_, needs_VVZ a_AT1 theory_NN1 of_IO purely_RR opportunistic_JJ adaptive_JJ change_NN1 in_II changing_JJ conditions_NN2 ,_, a_AT1 theory_NN1 making_VVG no_AT developmentalist_NN1 assumption_NN1 as_II21 to_II22 a_AT1 preferred_JJ direction_NN1 that_CST life_NN1 will_VM take_VVI provided_CS it_PPH1 can_VM go_VVI on_RP at_RR21 all_RR22 ._. 
And_CC his_APPGE thinking_NN1 is_VBZ indeed_RR knowingly_RR premised_VVN on_II the_AT assumption_NN1 that_CST in_II the_AT complete_JJ absence_NN1 of_IO change_NN1 in_II conditions_NN2 there_EX would_VM be_VBI no_AT changes_NN2 in_II organization_NN1 ;_; so_CS21 that_CS22 whatever_DDQV different_JJ changes_NN2 in_II organization_NN1 have_VH0 occurred_VVN in_II the_AT many_DA2 lines_NN2 descending_VVG from_II some_DD common_JJ stock_NN1 are_VBR due_II21 to_II22 differences_NN2 in_II the_AT conditions_NN2 in_II those_DD2 lines_NN2 ._. 
Darwin_NP1 ,_, as_CSA a_AT1 genealogical_JJ biogeographer_NN1 ,_, thinking_VVG horizontally_RR as_II31 well_II32 as_II33 vertically_RR ,_, to_TO use_VVI Ernst_NP1 Mayr_NP1 's_GE (_( 1982_MC )_) terms_NN2 ,_, would_VM explain_VVI change_NN1 generationally_RR but_CCB not_XX developmentally_RR ._. 
This_DD1 integration_NN1 of_IO horizontal_JJ ,_, genealogical_JJ ,_, geographical_JJ and_CC generational_JJ constraints_NN2 is_VBZ also_RR the_AT source_NN1 for_IF what_DDQ Ernst_NP1 Mayr_NP1 (_( 1982_MC )_) calls_VVZ Darwin_NP1 's_GE populationist_NN1 thinking_VVG about_II species_NN ._. 
For_IF it_PPH1 has_VHZ led_VVN Darwin_NP1 to_TO think_VVI of_IO each_DD1 species_NN as_CSA spreading_VVG out_RP into_II varying_JJ conditions_NN2 ,_, over_II a_AT1 range_NN1 ,_, over_II time_NNT1 ._. 
And_CC only_RR the_AT extension_NN1 of_IO a_AT1 species_NN ,_, not_XX its_APPGE intension_NN1 ,_, as_CSA philosophers_NN2 say_VV0 only_RR the_AT collective_JJ membership_NN1 of_IO a_AT1 species_NN ,_, not_XX the_AT properties_NN2 earning_VVG the_AT members_NN2 their_APPGE membership_NN1 in_II it_PPH1 can_VM have_VHI a_AT1 geographical_JJ range_NN1 and_CC a_AT1 historical_JJ career_NN1 ._. 
Now_RT ,_, recall_VV0 his_APPGE account_NN1 of_IO individual_JJ adaptations_NN2 to_II conditions_NN2 as_CSA arising_VVG in_II individual_JJ maturations_NN2 in_II sexual_JJ generation_NN1 ;_; and_CC recall_VV0 his_APPGE account_NN1 of_IO hereditary_JJ variation_NN1 as_CSA embedded_VVN constitutionally_RR through_II successive_JJ individual_JJ matings_NN2 ._. 
And_CC then_RT it_PPH1 is_VBZ clear_JJ how_RRQ Darwin_NP1 has_VHZ come_VVN to_TO be_VBI thinking_VVG of_IO a_AT1 species_NN as_II a_AT1 population_NN1 of_IO individuals_NN2 ,_, with_IW each_DD1 member_NN1 differing_VVG from_II every_AT1 other_JJ because_CS arising_VVG in_II a_AT1 unique_JJ sequence_NN1 of_IO influences_NN2 exerted_VVN by_II a_AT1 unique_JJ succession_NN1 of_IO conditions_NN2 and_CC mates_NN2 ._. 
The_AT origins_NN2 of_IO natural_JJ selection_NN1 and_CC pangenesis_NN1 (_( 183842_MC )_) Darwin_NP1 's_GE mid-September_NPM1 1838_MC theorizing_NN1 ,_, as_CSA developed_VVN in_II his_APPGE Notebook_NN1 D_ZZ1 ,_, provided_CS the_AT immediate_JJ context_NN1 for_IF his_APPGE most_RGT celebrated_JJ innovation_NN1 of_IO all_DB :_: the_AT theory_NN1 of_IO natural_JJ selection_NN1 ._. 
For_IF contrary_II21 to_II22 the_AT legend_NN1 that_CST it_PPH1 was_VBDZ all_RR thought_VVN through_RP in_II a_AT1 day_NNT1 this_DD1 theory_NN1 was_VBDZ worked_VVN out_RP in_II three_MC main_JJ stages_NN2 over_II the_AT next_MD half_DB year_NNT1 ._. 
The_AT first_MD stage_NN1 involved_VVD only_RR the_AT opening_NN1 steps_NN2 in_II Darwin_NP1 's_GE overall_JJ argumentation_NN1 from_II individual_JJ generation_NN1 to_II species_NN formation_NN1 ._. 
For_IF it_PPH1 sees_VVZ him_PPHO1 changing_VVG his_APPGE mind_NN1 about_II the_AT adaptiveness_NN1 of_IO structural_JJ change_NN1 rather_II21 than_II22 about_II species_NN formation_NN1 as_II such_DA ._. 
This_DD1 first_MD stage_NN1 did_VDD come_VVI on_II reading_VVG Thomas_NP1 Malthus_NP1 's_GE (_( 1766_MC 1834_MC )_) Essay_NN1 on_II the_AT Principle_NN1 of_IO Population_NN1 ,_, on_II 28_MC September_NPM1 1838_MC ;_; after_CS a_AT1 generational_JJ conjecture_NN1 that_CST higher_JJR animal_NN1 foetuses_NN2 are_VBR initially_RR hermaphrodite_NN1 had_VHD led_VVN him_PPHO1 to_II Adolphe_NP1 Quetelet_NP1 's_GE findings_NN2 on_II the_AT sex_NN1 ratio_NN1 at_II birth_NN1 and_CC so_RR ,_, it_PPH1 seems_VVZ ,_, to_II Malthus_NP1 as_II an_AT1 author_NN1 linked_VVN by_II a_AT1 reviewer_NN1 with_IW the_AT Belgian_JJ social_JJ statistician_NN1 (_( Schweber_NP1 ,_, 1977_MC )_) ._. 
Now_RT ,_, what_DDQ Darwin_NP1 's_GE reflections_NN2 on_II Malthus_NP1 did_VDD was_VBDZ to_TO move_VVI him_PPHO1 away_II21 from_II22 a_AT1 prenatal_JJ ,_, maturational_JJ sorting_NN1 of_IO adaptive_JJ from_II maladaptive_JJ variation_NN1 ._. 
For_CS he_PPHS1 moved_VVD at_RR21 once_RR22 to_II a_AT1 post-natal_JJ ,_, ecological_JJ sorting_NN1 wherein_RRQ individual_JJ adaptive_JJ variants_NN2 are_VBR retained_VVN ,_, while_CS the_AT maladaptive_JJ are_VBR eliminated_VVN in_II the_AT Malthusian_JJ crush_NN1 of_IO population_NN1 ._. 
These_DD2 initial_JJ reflections_NN2 did_VDD not_XX include_VVI ,_, then_RT ,_, any_DD analogy_NN1 between_II artificially_RR and_CC naturally_RR selective_JJ breeding_NN1 ._. 
But_CCB Darwin_NP1 did_VDD draw_VVI an_AT1 explicit_JJ analogy_NN1 between_II this_DD1 teleology_NN1 of_IO population_NN1 pressure_NN1 and_CC sorting_VVG ,_, as_CSA ensuring_VVG adaptation_NN1 of_IO plant_NN1 and_CC animal_NN1 structure_NN1 to_II changing_JJ conditions_NN2 and_CC Malthus_NP1 's_GE theistic_JJ teleology_NN1 of_IO superfecundity_NN1 ,_, as_CSA ensuing_VVG the_AT energetic_JJ dispersal_NN1 of_IO ancient_JJ tribes_NN2 beyond_II the_AT original_JJ Asian_JJ seat_NN1 of_IO the_AT human_JJ species_NN ._. 
Man_NN1 ,_, naturally_RR slothful_JJ according_II21 to_II22 Malthus_NP1 ,_, only_RR spread_VVN into_II more_RGR adverse_JJ climes_NN2 thanks_NN2 to_II the_AT local_JJ scarcities_NN2 of_IO food_NN1 entailed_VVN by_II his_APPGE excess_JJ fertility_NN1 ;_; with_IW later_JJR settlers_NN2 always_RR eventually_RR victorious_JJ because_CS made_VVN doubly_RR energetic_JJ in_II struggling_VVG with_IW both_DB2 rigorous_JJ conditions_NN2 and_CC previous_JJ settlers_NN2 ._. 
Alien_JJ species_NN beating_VVG natives_NN2 on_II their_APPGE home_NN1 ground_NN1 had_VHD been_VBN decisive_JJ for_IF Lyell_NP1 's_GE species_NN extinction_NN1 theorising_VVG ,_, where_CS the_AT analogy_NN1 with_IW the_AT European_JJ human_JJ conquests_NN2 over_II America_NP1 Indians_NN2 was_VBDZ explicit_JJ ._. 
Colonizing_NN1 species_NN of_IO alien_JJ genera_NN2 doing_VDG likewise_RR had_VHD long_RR been_VBN decisive_JJ for_IF Darwin_NP1 's_GE species_NN origin_NN1 theorizing_NN1 ,_, where_CS the_AT analogy_NN1 with_IW the_AT European_JJ human_JJ conquests_NN2 over_II Australasian_JJ natives_NN2 was_VBDZ hardly_RR less_RGR explicit_JJ ._. 
Throughout_II 1838_MC ,_, Darwin_NP1 had_VHD been_VBN allowing_VVG for_IF Lyellian_JJ competitive_JJ defeats_NN2 to_TO extinguish_VVI some_DD species_NN before_II their_APPGE predetermined_JJ ageing_JJ overcame_VVD them_PPHO2 ._. 
Now_RT ,_, his_APPGE Malthusian_JJ reflections_NN2 prompted_VVD both_RR a_AT1 new_JJ ecological_JJ understanding_NN1 of_IO adaptive_JJ sorting_NN1 and_CC a_AT1 final_JJ return_NN1 to_II Lyellian_JJ ecology_NN1 for_IF all_DB extinctions_NN2 ._. 
Thus_RR did_VDD ecological_JJ explanations_NN2 regain_VV0 ground_NN1 earlier_RRR lost_VVN to_II generational_JJ ones_NN2 ._. 
The_AT second_MD stage_NN1 began_VVD around_II the_AT end_NN1 of_IO November_NPM1 1838_MC ._. 
For_IF Darwin_NP1 then_RT drew_VVD his_APPGE first_MD explicit_JJ analogies_NN2 between_II adaptation_NN1 in_II wild_JJ species_NN and_CC the_AT fitness_NN1 for_IF human_JJ ends_NN2 of_IO domestic_JJ races_NN2 ,_, as_CSA both_RR due_II21 to_II22 selective_JJ breeding_NN1 ._. 
To_TO make_VVI this_DD1 new_JJ comparison_NN1 Darwin_NP1 had_VHD to_TO drop_VVI his_APPGE old_JJ contrast_NN1 between_II monstrous_JJ ,_, selected_VVN ,_, domestic_JJ races_NN2 and_CC adaptive_JJ ,_, not_XX selected_VVN ,_, wild_JJ species_NN ._. 
He_PPHS1 dropped_VVD it_PPH1 first_MD ,_, it_PPH1 seems_VVZ ,_, on_II considering_VVG sportingdog_NN1 breeds_NN2 ,_, notably_RR greyhounds_NN2 ;_; for_IF these_DD2 ,_, although_CS formed_VVN by_II the_AT human_JJ artifice_NN1 of_IO selective_JJ breeding_NN1 ,_, had_VHD been_VBN given_VVN both_RR structures_NN2 and_CC instincts_NN2 useful_JJ in_II the_AT wild_JJ ._. 
(_( Hence_RR the_AT carnivorous_JJ canines_NN2 In_II Darwin_NP1 's_GE later_JJR thought-experiments_NN2 on_II natural_JJ selection_NN1 ._. )_) 
Up_II21 to_II22 now_RT ,_, domestic_JJ race_NN1 formation_NN1 had_VHD provided_VVN Darwin_NP1 only_RR with_IW analogies_NN2 for_IF the_AT formation_NN1 of_IO wild_JJ species_NN as_CSA ancient_JJ ,_, true_JJ breeding_NN1 and_CC intersterile_JJ races_NN2 ._. 
With_IW this_DD1 new_JJ selective_JJ breeding_NN1 analogy_NN1 ,_, domestic_JJ races_NN2 ,_, as_CSA adaptations_NN2 ,_, are_VBR also_RR providing_VVG analogies_NN2 for_IF the_AT formation_NN1 of_IO wild_JJ species_NN as_CSA ancient_JJ and_CC perfectly_RR adapted_VVN races_NN2 ._. 
The_AT third_MD stage_NN1 came_VVD seemingly_RR early_RR in_II 1839_MC ,_, when_RRQ this_DD1 new_JJ analogy_NN1 prompted_VVD a_AT1 further_JJR revision_NN1 to_II the_AT opening_NN1 steps_NN2 of_IO the_AT overall_JJ argumentation_NN1 ._. 
In_II artificial_JJ selection_NN1 ,_, the_AT chosen_JJ end_NN1 ,_, for_IF which_DDQ the_AT race_NN1 is_VBZ being_VBG fitted_VVN ,_, does_VDZ not_XX elicit_VVI the_AT variation_NN1 being_VBG selected_VVN ._. 
So_RR ,_, Darwin_NP1 reasoned_VVD ,_, natural_JJ selection_NN1 likewise_RR could_VM work_VVI with_IW variation_NN1 that_CST is_VBZ accidentally_RR rather_II21 than_II22 necessarily_RR adaptive_JJ ._. 
If_CS changes_NN2 in_II conditions_NN2 disrupt_VV0 the_AT precise_JJ replication_NN1 of_IO parental_JJ characters_NN2 so_BCL21 as_BCL22 to_TO yield_VVI hereditary_JJ variation_NN1 ,_, then_RT ,_, providing_VVG only_RR that_CST some_DD of_IO it_PPH1 happens_VVZ to_TO be_VBI adaptive_JJ ,_, this_DD1 will_VM suffice_VVI in_II the_AT long_JJ run_NN1 for_IF selection_NN1 as_II a_AT1 cause_NN1 of_IO adaptive_JJ species_NN formations_NN2 ._. 
With_IW these_DD2 developments_NN2 beyond_II his_APPGE mid-September_NPM1 1838_MC positions_NN2 ,_, Darwin_NP1 had_VHD reached_VVN the_AT theory_NN1 of_IO natural_JJ selection_NN1 much_RR as_CSA he_PPHS1 would_VM publish_VVI it_PPH1 later_RRR ._. 
In_II March_NPM1 1839_MC ,_, he_PPHS1 even_RR outlined_VVD the_AT argumentative_JJ structure_NN1 that_CST opens_VVZ his_APPGE Sketch_NN1 of_IO 1842_MC (_( F._NP1 Darwin_NP1 ,_, 1909_MC )_) ,_, the_AT first_MD ,_, manuscript_NN1 ,_, version_NN1 of_IO The_AT Origin_NN1 of_IO Species_NN (_( 1859_MC )_) ._. 
By_II 1841_MC ,_, he_PPHS1 had_VHD very_RG probably_RR worked_VVN out_RP ,_, also_RR ,_, his_APPGE later_JJR theory_NN1 of_IO individual_JJ organism_NN1 generation_NN1 :_: pangenesis_NN1 ._. 
The_AT theory_NN1 ,_, as_CSA eventually_RR set_VVN forth_RR (_( 1868_MC )_) ,_, was_VBDZ constituted_VVN by_II two_MC theses_NN2 :_: that_CST the_AT generative_JJ material_NN1 comes_VVZ from_II all_RR over_II the_AT parent_NN1 body_NN1 or_CC bodies_NN2 ,_, and_CC that_CST it_PPH1 consists_VVZ of_IO minute_NNT1 '_GE gemmules_NN2 '_GE budded_VVD off_RP from_II every_AT1 part_NN1 ._. 
Darwin_NP1 's_GE preoccupation_NN1 with_IW generation_NN1 went_VVD back_RP to_II Edinburgh_NP1 and_CC to_II consequent_JJ inquiry_NN1 ,_, when_CS on_II the_AT voyage_NN1 ,_, into_II modes_NN2 of_IO reproduction_NN1 common_JJ to_II various_JJ invertebrate_JJ groups_NN2 (_( Sloan_NP1 ,_, personal_JJ communication_NN1 )_) ._. 
In_II early_RR 1837_MC ,_, he_PPHS1 had_VHD supported_VVN the_AT senescence_NN1 analogy_NN1 between_II sexual_JJ and_CC asexual_JJ generation_NN1 by_II interpreting_VVG all_DB generation_NN1 as_CSA division_NN1 ,_, whether_CSW artificial_JJ or_CC natural_JJ ,_, complete_JJ or_CC incomplete_JJ ,_, simultaneous_JJ or_CC successive_JJ ._. 
This_DD1 thesis_NN1 ,_, that_CST all_DB generation_NN1 is_VBZ division_NN1 ,_, continued_VVD throughout_II the_AT B_ZZ1 ,_, C_ZZ1 and_CC D_ZZ1 notebooks_NN2 and_CC was_VBDZ reinforced_VVN by_II an_AT1 explicit_JJ equating_VVG ,_, in_II September_NPM1 1838_MC ,_, of_IO division_NN1 and_CC gemmation_NN1 or_CC budding_JJ ._. 
The_AT equation_NN1 made_VVD all_DB generation_NN1 ,_, sexual_JJ or_CC otherwise_RR ,_, a_AT1 form_NN1 of_IO budding_JJ ._. 
However_RR ,_, in_II his_APPGE theorizing_NN1 about_II sexual_JJ generation_NN1 ,_, as_CSA being_VBG unique_JJ in_II allowing_VVG variation_NN1 and_CC adaptation_NN1 ,_, Darwin_NP1 made_VVD a_AT1 fundamental_JJ distinction_NN1 between_II sexual_JJ buds_NN2 ,_, such_II21 as_II22 ova_NN2 ,_, and_CC asexual_JJ buds_NN2 ._. 
According_II21 to_II22 this_DD1 distinction_NN1 ,_, all_DB and_CC only_RR sexual_JJ buds_NN2 are_VBR involved_JJ in_II maturation_NN1 and_CC fertilization_NN1 ._. 
Consequently_RR all_DB and_CC only_RR sexual_JJ buds_NN2 are_VBR impressionable_JJ ,_, whether_CSW by_II the_AT action_NN1 of_IO changed_JJ conditions_NN2 or_CC by_II a_AT1 sexual_JJ element_NN1 from_II a_AT1 mate_NN1 of_IO unlike_JJ constitution_NN1 ._. 
Conversely_RR ,_, while_CS lacking_VVG those_DD2 powers_NN2 an_AT1 asexual_JJ bud_NN1 ,_, or_CC even_RR a_AT1 severed_JJ flatworm_NN1 fragment_NN1 ,_, can_VM do_VDI what_DDQ an_AT1 unfertilized_JJ ovum_NN1 can_VM not_XX :_: namely_REX ,_, produce_VV0 a_AT1 whole_JJ organism_NN1 without_IW interactive_JJ collaboration_NN1 with_IW any_DD other_JJ part_NN1 ;_; this_DD1 power_NN1 being_VBG credited_VVN by_II Darwin_NP1 to_II the_AT presence_NN1 in_II such_DA a_AT1 bud_NN1 or_CC fragment_NN1 ,_, indeed_RR in_II any_DD healing_JJ flesh_NN1 ,_, of_IO material_JJ determining_JJ growth_NN1 for_IF all_DB the_AT parts_NN2 of_IO the_AT whole_JJ organism_NN1 ._. 
Switching_VVG now_RT from_II 1838_MC to_II 1868_MC ,_, one_MC1 sees_VVZ ,_, in_II direct_JJ contrast_NN1 with_IW this_DD1 earlier_JJR view_NN1 ,_, that_CST a_AT1 principal_JJ object_NN1 of_IO pangenesis_NN1 is_VBZ to_TO explain_VVI how_RRQ in_II all_DB generation_NN1 ,_, sexual_JJ and_CC asexual_JJ ,_, the_AT powers_NN2 are_VBR the_AT same_DA and_CC so_RR ,_, too_RR ,_, the_AT material_NN1 ._. 
To_II this_DD1 end_NN1 ,_, Darwin_NP1 adduces_VVZ ,_, most_RGT especially_RR ,_, those_DD2 phenomena_NN2 that_CST would_VM be_VBI anomalous_JJ for_IF any_DD exclusive_JJ correlation_NN1 of_IO maturation_NN1 ,_, fertilization_NN1 and_CC impressionability_NN1 with_IW sexual_JJ rather_II21 than_II22 asexual_JJ modes_NN2 of_IO generation_NN1 ._. 
Thus_RR aphid_NN1 parthenogenesis_NN1 shows_VVZ an_AT1 unfertilized_JJ ovum_NN1 producing_VVG a_AT1 maturing_JJ organism_NN1 with_IW no_AT prior_JJ interaction_NN1 with_IW a_AT1 male_JJ element_NN1 ;_; again_RT ,_, so-called_JJ graft_NN1 hybrids_NN2 and_CC the_AT effects_NN2 of_IO pollen_NN1 on_II non-germinal_JJ tissue_NN1 in_II a_AT1 female_JJ plant_NN1 both_RR show_VV0 impressionability_NN1 without_IW fertilization_NN1 and_CC maturation_NN1 ;_; while_CS sporting_VVG and_CC reversion_NN1 in_II asexual_JJ plant_NN1 buds_NN2 show_VV0 variation_NN1 without_IW fertilization_NN1 or_CC maturation_NN1 ._. 
So_RR ,_, as_CSA contrasted_VVN with_IW his_APPGE September_NPM1 1838_MC position_NN1 ,_, Darwin_NP1 sees_VVZ pangenesis_NN1 as_II an_AT1 evening_NNT1 up_RP ,_, on_II both_DB2 sides_NN2 ,_, of_IO all_DB the_AT powers_NN2 of_IO the_AT sexual_JJ and_CC asexual_JJ parts_NN2 of_IO any_DD organism_NN1 ._. 
Pangenesis_NN1 is_VBZ itself_PPX1 presented_VVN as_II a_AT1 theory_NN1 of_IO how_RRQ this_DD1 identity_NN1 of_IO powers_NN2 arises_VVZ in_II development_NN1 ._. 
In_II a_AT1 developing_JJ organism_NN1 ,_, starting_VVG as_II a_AT1 fertilized_JJ egg_NN1 ,_, each_DD1 cell_NN1 or_CC tissue_NN1 ,_, throughout_II its_APPGE own_DA maturation_NN1 ,_, is_VBZ budding_JJ off_II miniature_JJ facsimiles_NN2 of_IO itself_PPX1 ,_, the_AT '_GE gemmules_NN2 '_GE ._. 
The_AT whole_JJ organism_NN1 can_VM then_RT have_VHI ,_, as_CSA an_AT1 adult_NN1 ,_, the_AT same_DA powers_NN2 in_II its_APPGE asexual_JJ buds_NN2 and_CC its_APPGE sexual_JJ organs_NN2 ,_, because_CS the_AT same_DA material_NN1 is_VBZ there_RL :_: namely_REX ,_, '_GE gemmules_NN2 '_GE collected_JJ from_II all_RR over_II the_AT body_NN1 ._. 
These_DD2 gemmules_NN2 have_VH0 ,_, accordingly_RR ,_, been_VBN invested_VVN by_II Darwin_NP1 with_IW two_MC sorts_NN2 of_IO properties_NN2 :_: those_DD2 credited_VVN to_II every_AT1 asexual_JJ part_NN1 of_IO the_AT body_NN1 ,_, in_II 1838_MC ,_, to_TO explain_VVI its_APPGE generative_JJ and_CC regenerative_JJ powers_NN2 ,_, and_CC those_DD2 invoked_VVN then_RT to_TO explain_VVI the_AT impressionability_NN1 and_CC variability_NN1 of_IO immature_JJ ova_NN2 ._. 
So_RR ,_, pangenesis_NN1 could_VM have_VHI been_VBN derived_VVN from_II the_AT 1838_MC position_NN1 ,_, by_II pandynamic_JJ extension_NN1 to_II the_AT ova_NN2 of_IO powers_NN2 previously_RR denied_VVN to_II them_PPHO2 ,_, and_CC by_II a_AT1 panovulational_JJ extension_NN1 to_II all_DB other_JJ parts_NN2 of_IO powers_NN2 and_CC matters_NN2 formerly_RR reserved_VVN for_IF the_AT ovary_NN1 ._. 
But_CCB is_VBZ that_DD1 ,_, in_II fact_NN1 ,_, how_RRQ Darwin_NP1 arrived_VVD at_II pangenesis_NN1 ?_? 
No_AT known_JJ document_NN1 confirms_VVZ that_CST it_PPH1 was_VBDZ ._. 
But_CCB all_DB the_AT indirect_JJ evidence_NN1 ,_, including_II the_AT records_NN2 of_IO his_APPGE reading_NN1 in_II such_DA writers_NN2 on_II generation_NN1 as_CSA Erasmus_NP1 Darwin_NP1 ,_, Johannes_NP2 Mller_NN1 and_CC Giorgio_NP1 Gallesio_NP1 ,_, makes_VVZ it_PPH1 most_RRT probable_JJ that_CST he_PPHS1 came_VVD to_II pangenesis_NN1 in_II such_DA a_AT1 revision_NN1 of_IO his_APPGE 1838_MC position_NN1 ,_, and_CC that_CST he_PPHS1 did_VDD so_RR in_II the_AT years_NNT2 18401_MC ._. 
However_RR and_CC whenever_RRQV it_PPH1 was_VBDZ first_MD formulated_VVN ,_, this_DD1 pangenetic_JJ reduction_NN1 of_IO every_AT1 mode_NN1 of_IO generation_NN1 to_TO micro-ovulo-gemmation_VVI could_VM take_VVI inheritance_NN1 ,_, in_CS41 so_CS42 far_CS43 as_CS44 it_PPH1 was_VBDZ completely_RR conservative_JJ ,_, to_TO be_VBI effected_VVN by_II an_AT1 exact_JJ replication_NN1 of_IO a_AT1 whole_NN1 in_II all_DB its_APPGE parts_NN2 ;_; so_CS21 that_CS22 variation_NN1 ,_, reversion_NN1 and_RR31 so_RR32 on_RR33 are_VBR explicable_JJ as_CSA disturbances_NN2 ,_, suspensions_NN2 and_CC complications_NN2 of_IO that_DD1 fundamental_JJ replicative_JJ tendency_NN1 ._. 
Thus_RR could_VM pangenesis_NN1 unify_VV0 all_DB Darwin_NP1 's_GE generation_NN1 theorizing_VVG from_II gemmules_NN2 to_II organisms_NN2 and_CC on_II21 to_II22 species_NN ,_, and_CC beyond_II them_PPHO2 the_AT whole_JJ tree_NN1 of_IO life_NN1 ._. 
Pangenesis_NN1 was_VBDZ never_RR ,_, however_RR ,_, to_TO meet_VVI the_AT vera_NN1 causa_FW evidential_JJ ideal_JJ ,_, as_CSA Darwin_NP1 himself_PPX1 was_VBDZ keenly_RR aware_JJ ,_, and_CC he_PPHS1 published_VVD it_PPH1 only_RR after_II natural_JJ selection_NN1 had_VHD been_VBN launched_VVN unencumbered_JJ by_II any_DD such_DA conjectural_JJ causation_NN1 for_IF generation_NN1 ._. 
The_AT argument_NN1 of_IO the_AT 1842_MC Sketch_NN1 (_( and_CC so_RR ,_, too_RR ,_, of_IO the_AT Origin_NN1 )_) was_VBDZ knowingly_RR structured_VVN to_TO accord_VVI with_IW that_DD1 vera_NN1 causa_FW ideal_JJ (_( Hodge_NP1 ,_, 1977_MC )_) ._. 
The_AT existence_NN1 of_IO natural_JJ selection_NN1 as_II a_AT1 causal_JJ agency_NN1 is_VBZ evidenced_VVN first_MD ;_; then_RT its_APPGE adequacy_NN1 to_TO produce_VVI new_JJ species_NN from_II old_JJ is_VBZ argued_VVN by_II analogy_NN1 from_II the_AT ability_NN1 of_IO artificial_JJ selection_NN1 ,_, although_CS much_RR less_RGR precise_JJ and_CC prolonged_JJ ,_, to_TO produce_VVI domestic_JJ races_NN2 ._. 
Finally_RR ,_, Darwin_NP1 displays_VVZ the_AT indirect_JJ evidence_NN1 for_IF the_AT theory_NN1 :_: the_AT explanations_NN2 it_PPH1 provides_VVZ for_IF a_AT1 wide_JJ array_NN1 of_IO facts_NN2 in_II biogeography_NN1 ,_, geology_NN1 ,_, embryology_NN1 and_RR31 so_RR32 on_RR33 ._. 
With_IW the_AT 1842_MC Sketch_NN1 written_VVN ,_, Darwin_NP1 's_GE most_RGT creative_JJ period_NN1 was_VBDZ ended_VVN ._. 
That_DD1 year_NNT1 he_PPHS1 moved_VVD out_II21 of_II22 London_NP1 to_II the_AT Kent_NP1 countryside_NN1 and_CC was_VBDZ henceforth_RT mainly_RR writing_VVG books_NN2 ,_, raising_VVG children_NN2 and_CC nursing_VVG his_APPGE health_NN1 ._. 
He_PPHS1 never_RR had_VHD another_DD1 fundamentally_RR novel_JJ idea_NN1 in_RR21 general_RR22 biological_JJ theory_NN1 ._. 
But_CCB then_RT he_PPHS1 had_VHD already_RR had_VHN enough_DD to_TO keep_VVI him_PPHO1 and_CC many_DA2 others_NN2 occupied_VVN for_IF a_AT1 very_RG long_JJ time_NNT1 ._. 
The_AT nature_NN1 of_IO Darwin_NP1 's_GE science_NN1 Even_RR this_DD1 brief_JJ analysis_NN1 of_IO Darwin_NP1 's_GE biological_JJ theorizing_NN1 in_II these_DD2 early_JJ years_NNT2 suggests_VVZ the_AT following_JJ conclusions_NN2 about_II the_AT nature_NN1 of_IO his_APPGE science_NN1 in_II its_APPGE formative_JJ phase_NN1 ._. 
The_AT social_JJ context_NN1 ._. 
The_AT traditional_JJ way_NN1 to_TO connect_VVI Darwin_NP1 's_GE science_NN1 with_IW his_APPGE society_NN1 is_VBZ through_II Malthus_NP1 's_GE laissez_NN121 faire_NN122 political_JJ economy_NN1 ._. 
But_CCB this_DD1 can_VM not_XX be_VBI adequate_JJ ._. 
A_AT1 capitalism_NN1 connection_NN1 is_VBZ relevant_JJ in_II the_AT 1840s_MC2 and_CC 1850s_MC2 when_CS Darwin_NP1 is_VBZ applying_VVG division_NN1 of_IO labour_NN1 theory_NN1 to_II the_AT problems_NN2 of_IO divergence_NN1 (_( Schweber_NP1 ,_, 1980_MC ;_; Ospovat_NP1 ,_, 1981_MC )_) ._. 
But_CCB in_II 1838_MC it_PPH1 was_VBDZ Malthus_NP1 's_GE theodicy_NN1 of_IO ancient_JJ empires_NN2 ,_, not_XX his_APPGE political_JJ economy_NN1 of_IO the_AT modern_JJ state_NN1 that_CST bore_VVD decisively_RR on_II Darwin_NP1 's_GE biogeography_NN1 and_CC ecology_NN1 (_( Bowler_NN1 ,_, 1976_MC )_) ._. 
More_RGR generally_RR ,_, any_DD laissez_NN121 faire_NN122 connection_NN1 helps_VVZ very_RG little_DA1 in_II understanding_VVG how_RRQ Darwin_NP1 came_VVD to_TO take_VVI up_RP the_AT problems_NN2 his_APPGE theorizing_NN1 was_VBDZ to_TO solve_VVI ._. 
Here_RL it_PPH1 is_VBZ his_APPGE family_NN1 ,_, especially_RR his_APPGE grandfather_NN1 ,_, and_CC his_APPGE mentor_NN1 Lyell_NP1 ,_, that_CST indicate_VV0 connections_NN2 with_IW movements_NN2 of_IO thought_NN1 directly_RR linked_VVN with_IW fundamental_JJ social_JJ change_NN1 ._. 
Erasmus_NP1 Darwin_NP1 ,_, a_AT1 Birmingham_NP1 Lunar_JJ Society_NN1 man_NN1 ,_, belonged_VVD to_II a_AT1 provincial_JJ movement_NN1 of_IO '_GE radical_NN1 '_GE dissent_NN1 from_II national_JJ and_CC metropolitan_JJ orthodoxies_NN2 in_II politics_NN1 and_CC religion_NN1 ._. 
Lyell_NP1 was_VBDZ a_AT1 '_GE liberal_NN1 '_GE Scots_JJ Whig_NN1 very_RG much_DA1 in_II the_AT Edinburgh_NP1 Review_NN1 tradition_NN1 of_IO John_NP1 Playfair_NP1 and_CC his_APPGE own_DA father-in-law_NN1 Leonard_NP1 Horner_NP1 ,_, a_AT1 tradition_NN1 bent_VVN on_II using_VVG electoral_JJ and_CC educational_JJ ,_, including_II university_NN1 ,_, reforms_NN2 to_TO break_VVI the_AT national_JJ and_CC metropolitan_JJ hegemony_NN1 of_IO the_AT Tory_JJ ,_, Oxonian_JJ ,_, Anglican_JJ establishment_NN1 ._. 
It_PPH1 is_VBZ in_II such_DA mediating_JJ contexts_NN2 ,_, rather_CS21 than_CS22 in_II any_DD direct_JJ tie_NN1 to_II capital_NN1 through_II laissez_NN121 faire_NN122 ,_, that_CST the_AT social_JJ history_NN1 of_IO Darwin_NP1 's_GE science_NN1 should_VM be_VBI sought_VVN ._. 
Laws_NN2 ,_, causes_NN2 and_CC chances_NN2 ._. 
To_II Darwin_NP1 ,_, natural_JJ selection_NN1 ,_, as_CSA a_AT1 causal_JJ agency_NN1 and_CC lawful_JJ process_NN1 ,_, was_VBDZ akin_JJ ,_, in_II its_APPGE vera_NN1 causa_FW credentials_NN2 ,_, to_II gravitational_JJ force_NN1 in_II celestial_JJ mechanics_NN2 ._. 
But_CCB his_APPGE earliest_JJT critics_NN2 often_RR judged_VVD his_APPGE theorizing_NN1 not_XX to_TO match_VVI the_AT standards_NN2 set_VVN by_II Newtonian_JJ physics_NN1 (_( Hull_NP1 ,_, 1973_MC )_) ._. 
Was_VBDZ Darwin_NP1 ,_, then_RT ,_, mistaken_VVN in_II so_RR relating_VVG his_APPGE own_DA science_NN1 to_II Newton_NP1 's_GE ?_? 
He_PPHS1 was_VBDZ ,_, in_CS41 so_CS42 far_CS43 as_CS44 he_PPHS1 underestimated_VVD the_AT implications_NN2 of_IO one_MC1 major_JJ disanalogy_NN1 :_: he_PPHS1 had_VHD no_AT law_NN1 that_CST was_VBDZ to_II natural_JJ selection_NN1 as_II the_AT Newtonian_JJ inverse_JJ square_JJ law_NN1 (_( with_IW proportionality_NN1 to_II mass_JJ products_NN2 )_) was_VBDZ to_II gravitational_JJ attraction_NN1 ._. 
For_IF this_DD1 disanalogy_NN1 arose_VVD from_II another_DD1 :_: Darwin_NP1 's_GE natural_JJ selection_NN1 as_II a_AT1 lawn_NN1 process_NN1 was_VBDZ complex_JJ ,_, being_VBG compounded_VVN from_II heredity_NN1 ,_, variation_NN1 and_CC superfecundity_NN1 ,_, each_DD1 of_IO those_DD2 processes_NN2 having_VHG its_APPGE own_DA laws_NN2 ;_; while_CS Newton_NP1 's_GE gravitational_JJ force_NN1 was_VBDZ not_XX compound_NN1 and_CC had_VHD a_AT1 single_JJ law_NN1 of_IO its_APPGE own_DA ._. 
Now_RT ,_, from_II these_DD2 disanalogies_NN2 arose_VVD a_AT1 further_JJR one_PN1 ._. 
In_II simple_JJ cases_NN2 ,_, the_AT consequences_NN2 in_II certain_JJ conditions_NN2 of_IO Newtonian_JJ gravitational_JJ attraction_NN1 could_VM be_VBI deduced_VVN and_CC the_AT adequacy_NN1 of_IO this_DD1 cause_NN1 for_IF certain_JJ phenomena_NN2 ,_, most_RGT notably_RR elliptical_JJ planetary_JJ orbits_NN2 ,_, thereby_RR established_VVN ._. 
By_II contrast_NN1 ,_, the_AT consequences_NN2 and_CC so_RR competences_NN2 ,_, and_CC hence_RR the_AT adequacies_NN2 or_CC inadequacies_NN2 ,_, of_IO natural_JJ selection_NN1 ,_, especially_RR for_IF long-run_JJ effects_NN2 ,_, were_VBDR practically_RR impossible_JJ to_TO decide_VVI ,_, at_RR21 least_RR22 for_IF a_AT1 finite_JJ intellect_NN1 ;_; although_CS the_AT young_JJ Darwin_NP1 himself_PPX1 could_VM consistently_RR suppose_VVI that_CST God_NP1 in_II choosing_VVG this_DD1 means_VVZ for_IF adapting_VVG life_NN1 to_II a_AT1 changing_JJ earth_NN1 had_VHD foreseen_VVN all_DB its_APPGE consequences_NN2 ._. 
However_RR ,_, although_CS these_DD2 disanalogies_NN2 were_VBDR fundamental_JJ ,_, Darwin_NP1 's_GE theorizing_NN1 had_VHD not_XX taken_VVN him_PPHO1 out_II21 of_II22 the_AT causal_JJ ,_, lawful_JJ ,_, deterministic_JJ Newtonian_JJ universe_NN1 ,_, into_II one_PN1 as_RG irreducibly_RR acausal_JJ and_CC absolutely_RR probabilistic_JJ as_CSA is_VBZ sometimes_RT thought_VVN implicit_JJ in_II quantum_NN1 mechanics_NN2 ._. 
Any_DD natural_JJ selection_NN1 involves_VVZ differential_JJ reproductive_JJ success_NN1 that_CST is_VBZ nonfortuitous_JJ because_CS determined_VVN by_II the_AT way_NN1 variant_NN1 organisms_NN2 are_VBR interacting_VVG with_IW an_AT1 environment_NN1 that_CST is_VBZ causally_RR sensitive_JJ to_II those_DD2 particular_JJ physical_JJ differences_NN2 in_II the_AT organisms_NN2 ._. 
If_CS more_RGR red_JJ than_CSN green_JJ members_NN2 of_IO a_AT1 species_NN of_IO moth_NN1 living_VVG on_II green_JJ foliage_NN1 are_VBR being_VBG killed_VVN by_II predators_NN2 ,_, that_DD1 may_VM be_VBI selection_NN1 ;_; but_CCB only_RR if_CS the_AT predators_NN2 are_VBR not_XX colour-blind_JJ ;_; if_CS they_PPHS2 are_VBR it_PPH1 is_VBZ random_JJ sampling_NN1 error_NN1 ._. 
But_CCB even_CS21 when_CS22 killed_VVN by_II colour-blind_JJ predators_NN2 the_AT moths_NN2 are_VBR not_XX victims_NN2 of_IO any_DD capricious_JJ cosmic_JJ indeterminacy_NN1 ;_; for_IF each_DD1 of_IO their_APPGE deaths_NN2 is_VBZ a_AT1 causally_RR determined_JJ event_NN1 ._. 
It_PPH1 is_VBZ only_RR as_CSA deaths_NN2 of_IO red_JJ or_CC green_JJ moths_NN2 in_II that_DD1 environment_NN1 that_CST these_DD2 are_VBR fortuitous_JJ events_NN2 ;_; this_DD1 fortuitousness_NN1 being_VBG ,_, as_CSA philosophers_NN2 say_VV0 ,_, description_NN1 relative_NN1 ._. 
Again_RT ,_, as_CSA Darwin_NP1 saw_VVD it_PPH1 ,_, the_AT chanciness_NN1 of_IO hereditary_JJ variation_NN1 is_VBZ relative_JJ ,_, not_XX absolute_JJ ._. 
The_AT processes_NN2 generating_VVG this_DD1 variation_NN1 he_PPHS1 supposed_JJ to_TO be_VBI lawful_JJ ,_, causal_JJ and_CC so_RG determinate_JJ ;_; but_CCB not_XX causally_RR sensitive_JJ to_II environmental_JJ conditions_NN2 in_II such_DA a_AT1 way_NN1 that_CST any_DD particular_JJ change_NN1 in_II conditions_NN2 elicits_VVZ an_AT1 increased_JJ supply_NN1 of_IO those_DD2 variants_NN2 that_CST are_VBR adaptive_JJ in_II the_AT new_JJ conditions_NN2 ._. 
So_RR ,_, the_AT distinctions_NN2 decisive_JJ for_IF Darwin_NP1 's_GE account_NN1 of_IO the_AT generation_NN1 and_CC the_AT fate_NN1 of_IO variation_NN1 are_VBR distinctions_NN2 drawn_VVN within_II the_AT presuppositions_NN2 of_IO a_AT1 deterministic_JJ universe_NN1 ._. 
In_II its_APPGE dependence_NN1 on_II those_DD2 presuppositions_NN2 his_APPGE biology_NN1 was_VBDZ more_RRR like_II statistical_JJ than_CSN either_RR celestial_JJ or_CC quantum_NN1 mechanics_NN2 (_( Hull_NP1 ,_, 1974_MC )_) ._. 
The_AT non-tautologousness_NN1 of_IO natural_JJ selection_NN1 ._. 
Darwin_NP1 's_GE vera_NN1 causa_FW argumentation_NN1 shows_VVZ that_CST natural_JJ selection_NN1 is_VBZ not_XX tautologous_JJ for_IF one_MC1 reason_NN1 ,_, ultimately_RR ._. 
The_AT definitional_JJ question_NN1 ,_, of_IO what_DDQ natural_JJ selection_NN1 is_VBZ ,_, can_VM be_VBI answered_VVN by_II specifying_VVG necessary_JJ and_CC sufficient_JJ conditions_NN2 for_IF its_APPGE occurrence_NN1 ,_, namely_REX hereditary_JJ variation_NN1 that_CST is_VBZ causally_RR relevant_JJ to_II reproductive_JJ success_NN1 thanks_NN2 to_II organism-environment_JJ interactions_NN2 ;_; it_PPH1 can_VM ,_, then_RT ,_, be_VBI answered_VVN without_IW begging_VVG in_II advance_NN1 of_IO empirical_JJ inquiry_NN1 all_DB those_DD2 further_JJR questions_NN2 as_II21 to_II22 whether_CSW these_DD2 conditions_NN2 are_VBR ever_RR met_VVN :_: whether_CSW ,_, that_REX21 is_REX22 ,_, any_DD natural_JJ selection_NN1 exists_VVZ ;_; and_CC ,_, if_CS so_RR ,_, how_RRQ it_PPH1 is_VBZ distributed_VVN ,_, what_DDQ it_PPH1 can_VM do_VDI now_RT and_CC what_DDQ it_PPH1 has_VHZ been_VBN responsible_JJ for_IF in_II the_AT past_NN1 ._. 
It_PPH1 is_VBZ ,_, then_RT ,_, a_AT1 mistake_NN1 to_TO defend_VVI natural_JJ selection_NN1 against_II the_AT tautology_NN1 objection_NN1 by_II proposing_VVG criteria_NN2 of_IO fitness_NN1 independent_NN1 of_IO reproductive_JJ success_NN1 ._. 
Fitness_NN1 differences_NN2 are_VBR best_RRT understood_VVN as_CSA reproductive_JJ expectancy_NN1 differences_NN2 analogous_JJ to_II normalized_JJ life_NN1 expectancy_NN1 differences_NN2 ._. 
And_CC as_CSA such_DA they_PPHS2 have_VH0 no_AT causal_JJ or_CC explanatory_JJ power_NN1 of_IO their_APPGE own_DA ._. 
If_CS Jones_NP1 has_VHZ outlived_VVN Smith_NP1 this_DD1 can_VM not_XX be_VBI explained_VVN by_II showing_VVG that_CST he_PPHS1 earlier_RRR had_VHD the_AT higher_JJR life_NN1 expectancy_NN1 ,_, and_CC then_RT arguing_VVG that_CST this_DD1 duly_RR caused_VVD him_PPHO1 to_TO live_VVI the_AT longer_JJR life_NN1 ._. 
It_PPH1 can_VM be_VBI explained_VVN by_II citing_VVG earlier_JJR physical_JJ differences_NN2 ;_; perhaps_RR Jones_NP1 jogged_VVD while_CS Smith_NP1 smoked_VVD ._. 
Likewise_RR ,_, in_II natural_JJ selection_NN1 it_PPH1 is_VBZ physical_JJ differences_NN2 ,_, not_XX the_AT differences_NN2 in_II reproductive_JJ expectancies_NN2 estimated_VVN from_II them_PPHO2 ,_, that_DD1 can_VM cause_VVI and_CC can_VM explain_VVI subsequent_JJ reproductive_JJ performance_NN1 differences_NN2 ._. 
As_CSA differing_JJ expectancies_NN2 ,_, fitnesses_NN2 can_VM neither_RR cause_VVI reproductive_JJ performance_NN1 differences_NN2 nor_CC be_VBI definitionally_RR equated_VVN with_IW them_PPHO2 ._. 
So_RR ,_, natural_JJ selection_NN1 is_VBZ no_AT untestable_JJ tautology_NN1 ,_, but_CCB not_XX because_CS fitness_NN1 measurements_NN2 ,_, as_CSA expectancy_NN1 estimates_NN2 ,_, can_VM sometimes_RT be_VBI falsified_VVN by_II later_JJR performance_NN1 measurements_NN2 ._. 
Natural_JJ selection_NN1 is_VBZ no_AT tautology_NN1 ,_, because_CS there_EX is_VBZ no_AT a_JJ21 priori_JJ22 proof_NN1 ,_, from_II its_APPGE definition_NN1 alone_RR ,_, for_IF its_APPGE existence_NN1 ,_, nor_CC then_RT for_IF its_APPGE prevalence_NN1 ,_, or_CC its_APPGE adequacy_NN1 or_CC its_APPGE responsibility_NN1 for_IF evolution_NN1 ._. 
If_CS there_EX were_VBDR ,_, then_RT the_AT last_MD decade_NNT1 and_CC a_AT1 half_NN1 of_IO selectionist-neutralist_NN1 controversies_NN2 over_II all_DB these_DD2 different_JJ non-definitional_JJ issues_NN2 could_VM have_VHI been_VBN settled_VVN in_II advance_NN1 without_IW recourse_NN1 to_II empirical_JJ data_NN ,_, in_II an_AT1 armchair_NN1 with_IW a_AT1 scientist_NN1 's_GE glossary_NN1 and_CC a_AT1 logician_NN1 's_GE truth_NN1 table_NN1 ._. 
As_CSA Michael_NP1 Ruse_NN1 observes_VVZ (_( 1981_MC )_) if_CS selectionism_NN1 is_VBZ a_AT1 tautology_NN1 ,_, neutralism_NN1 is_VBZ a_AT1 contradiction_NN1 ,_, Darwin_NP1 's_GE strategy_NN1 in_II structuring_VVG his_APPGE argumentation_NN1 to_TO conform_VVI to_II the_AT vera_NN1 causa_FW ideal_JJ shows_NN2 why_RRQ it_PPH1 is_VBZ not_XX ._. 
Evolution_NN1 ,_, cytology_NN1 ,_, genetics_NN1 and_CC the_AT unification_NN1 of_IO nineteenth-century_JJ biological_JJ theory_NN1 ._. 
Early_RR in_II 1900_MC ,_, the_AT doyen_NN1 of_IO Columbia_NP1 University_NN1 biology_NN1 ,_, E._NP1 B._NP1 Wilson_NP1 ,_, introduced_VVD the_AT new_JJ second_MD edition_NN1 of_IO his_APPGE treatise_NN1 ,_, The_AT Cell_NN1 ,_, by_II arguing_VVG that_CST the_AT main_JJ challenge_NN1 then_RT facing_VVG biological_JJ science_NN1 was_VBDZ to_TO integrate_VVI its_APPGE two_MC greatest_JJT achievements_NN2 in_II the_AT past_JJ century_NNT1 :_: the_AT theory_NN1 of_IO evolution_NN1 and_CC the_AT theory_NN1 of_IO cells_NN2 ._. 
And_CC he_PPHS1 explained_VVD why_RRQ he_PPHS1 saw_VVD August_NPM1 Weismann_NP1 's_GE theory_NN1 of_IO the_AT continuity_NN1 of_IO the_AT germ_NN1 plasm_NN1 as_II the_AT most_RGT promising_JJ foundation_NN1 for_IF any_DD such_DA integration_NN1 ._. 
Wilson_NP1 's_GE position_NN1 makes_VVZ sense_NN1 of_IO a_AT1 great_JJ deal_NN1 in_II the_AT history_NN1 of_IO general_JJ biological_JJ theory_NN1 before_II and_CC since_II 1900_MC ._. 
It_PPH1 has_VHZ often_RR been_VBN said_VVN that_CST the_AT decisive_JJ development_NN1 since_CS Darwin_NP1 was_VBDZ a_AT1 new_JJ synthesis_NN1 ,_, in_II the_AT 1920s_MC2 and_CC 1930s_MC2 ,_, of_IO Mendel_NP1 on_II heredity_NN1 and_CC Darwin_NP1 on_II selection_NN1 ._. 
Wilson_NP1 brings_VVZ out_RP the_AT importance_NN1 of_IO that_DD1 earlier_RRR and_CC no_AT less_RGR fundamental_JJ post-Darwinian_JJ synthesis_NN1 ,_, which_DDQ this_DD1 later_JJR one_PN1 presupposed_VVD :_: the_AT synthesis_NN1 of_IO evolution_NN1 and_CC cytology_NN1 ._. 
Since_CS Wilson_NP1 's_GE teachings_NN2 were_VBDR a_AT1 principal_JJ inspiration_NN1 for_IF the_AT Morgan_NP1 school_NN1 ,_, the_AT twentieth_MD century_NNT1 science_NN1 of_IO genetics_NN1 may_VM be_VBI said_VVN to_TO have_VHI arisen_VVN within_II his_APPGE Weismannist_JJ programme_NN1 for_IF the_AT integration_NN1 of_IO evolutionary_JJ and_CC cytological_JJ theorizing_NN1 (_( Mayr_NP1 ,_, 1982_MC )_) ._. 
Darwin_NP1 's_GE integration_NN1 of_IO evolutionary_JJ and_CC physiological_JJ biology_NN1 had_VHD been_VBN attempted_VVN ,_, in_II the_AT 1840s_MC2 ,_, through_II pangenesis_NN1 ._. 
But_CCB pangenesis_NN1 was_VBDZ not_XX reconcilable_JJ with_IW the_AT cytological_JJ consensus_NN1 just_RR emerging_VVG when_RRQ Darwin_NP1 published_VVD it_PPH1 a_AT1 quarter_NN1 of_IO a_AT1 century_NNT1 later_RRR ._. 
Physiologists_NN2 were_VBDR then_RT increasingly_RR agreeing_VVG that_CST every_AT1 cellular_JJ organism_NN1 is_VBZ either_RR a_AT1 single_JJ cell_NN1 or_CC a_AT1 cell_NN1 colony_NN1 arising_VVG from_II the_AT successive_JJ divisions_NN2 of_IO a_AT1 single_JJ cell_NN1 ,_, and_CC that_CST two_MC cells_NN2 come_VV0 together_RL to_TO form_VVI one_PN1 at_II fertilization_NN1 ,_, each_DD1 having_VHG arisen_VVN by_II the_AT division_NN1 of_IO one_MC1 cell_NN1 in_II the_AT respective_JJ parent_NN1 body_NN1 ._. 
In_II Darwin_NP1 's_GE version_NN1 pangenesis_NN1 could_VM not_XX be_VBI squared_VVN with_IW these_DD2 cytological_JJ generalizations_NN2 ;_; for_IF ,_, if_CS each_DD1 of_IO the_AT two_MC masses_NN2 of_IO gemmules_NN2 coming_VVG together_RL at_II fertilization_NN1 is_VBZ taken_VVN to_TO be_VBI one_MC1 cell_NN1 ,_, then_RT it_PPH1 has_VHZ not_XX arisen_VVN in_II the_AT division_NN1 of_IO one_MC1 cell_NN1 in_II that_DD1 parent_NN1 ;_; while_CS ,_, if_CS each_DD1 is_VBZ taken_VVN to_TO be_VBI a_AT1 myriad_NN1 of_IO cells_NN2 ,_, then_RT far_RR too_RG many_DA2 are_VBR coming_VVG together_RL at_II fertilization_NN1 ._. 
The_AT problem_NN1 of_IO transforming_VVG Darwin_NP1 's_GE pangenetic_JJ theory_NN1 to_TO square_VVI it_PPH1 with_IW cytology_NN1 in_RR21 general_RR22 ,_, and_CC with_IW Weismann_NP1 's_GE theory_NN1 in_RR21 particular_RR22 ,_, was_VBDZ taken_VVN up_RP most_RGT systematically_RR by_II De_NP1 Vries_NP1 ;_; and_CC later_JJR developments_NN2 leading_VVG to_II the_AT theory_NN1 of_IO the_AT gene_NN1 were_VBDR to_TO owe_VVI much_RR to_II his_APPGE solution_NN1 :_: '_GE intracellular_JJ pangenesis_NN1 '_GE ._. 
So_RR ,_, Darwin_NP1 's_GE attempt_NN1 to_TO integrate_VVI evolutionary_JJ and_CC physiological_JJ biology_NN1 contributed_VVD indirectly_RR to_II the_AT unification_NN1 that_CST was_VBDZ called_VVN for_IF in_II Wilson_NP1 's_GE 1900_MC programme_NN1 and_CC that_DD1 genetics_NN1 was_VBDZ to_TO secure_VVI ._. 
That_DD1 Darwin_NP1 's_GE ideas_NN2 could_VM have_VHI such_DA manifold_JJ influence_NN1 throughout_II the_AT entire_JJ structure_NN1 of_IO modern_JJ biological_JJ theory_NN1 should_VM not_XX now_RT be_VBI surprising_JJ ._. 
Compulsive_NP1 ,_, selfconscious_JJ intellectual_NN1 ,_, '_GE philosopher_NN1 '_GE no_AT less_DAR than_CSN '_GE naturalist_NN1 '_GE ,_, he_PPHS1 had_VHD worked_VVN from_II his_APPGE earliest_JJT years_NNT2 on_II a_AT1 very_RG broad_JJ canvas_NN1 indeed_RR ._. 
A_AT1 DARWINIAN_JJ PLANT_NN1 ECOLOGY_NN1 John_NP1 L._NP1 HARPER_NP1 '_GE ..._... on_II a_AT1 piece_NN1 of_IO ground_NN1 3_MC feet_NN2 long_JJ and_CC 2_MC feet_NN2 wide_JJ ,_, dug_VVD and_CC cleared_VVD ,_, and_CC where_CS there_EX could_VM be_VBI no_AT choking_NN1 from_II other_JJ plants_NN2 ,_, I_PPIS1 marked_VVD all_DB the_AT seedlings_NN2 of_IO our_APPGE native_JJ weeds_NN2 as_CSA they_PPHS2 came_VVD up_RP ,_, and_CC out_II21 of_II22 357_MC no_AT less_DAR than_CSN 295_MC were_VBDR destroyed_VVN ,_, chiefly_RR by_II slugs_NN2 and_CC insects_NN2 ._. 
If_CS turf_NN1 which_DDQ has_VHZ long_RR been_VBN mown_NN1 ,_, and_CC the_AT case_NN1 would_VM be_VBI the_AT same_DA with_IW turf_NN1 closely_RR browsed_VVN by_II quadrupeds_NN2 ,_, be_VBI let_VVN to_TO grow_VVI ,_, the_AT more_RGR vigorous_JJ plants_NN2 gradually_RR kill_VV0 the_AT less_RGR vigorous_JJ ,_, though_CS fully_RR grown_VVN plants_NN2 ;_; thus_RR out_II21 of_II22 20_MC species_NN growing_VVG on_II a_AT1 little_JJ plot_NN1 of_IO mown_NN1 turf_NN1 (_( 3_MC feet_NN2 by_II 4_MC feet_NN2 )_) 9_MC species_NN perished_VVD ,_, from_II the_AT other_JJ species_NN being_VBG allowed_VVN to_TO grow_VVI up_RP freely_RR '_GE (_( The_AT Origin_NN1 of_IO Species_NN )_) ._. 
It_PPH1 is_VBZ difficult_JJ to_TO detect_VVI any_DD direct_JJ influence_NN1 of_IO Darwin_NP1 's_GE writings_NN2 on_II the_AT development_NN1 of_IO the_AT main_JJ stream_NN1 of_IO plant_NN1 ecology_NN1 ._. 
The_AT extreme_JJ reductionist_NN1 approach_NN1 that_CST is_VBZ represented_VVN in_II the_AT above_JJ quotation_NN1 ,_, and_CC is_VBZ apparent_JJ again_RT and_CC again_RT in_II his_APPGE writings_NN2 ,_, not_XX only_RR in_II The_AT Origin_NN1 of_IO Species_NN but_CCB in_II many_DA2 of_IO his_APPGE later_JJR books_NN2 ,_, is_VBZ conspicuous_JJ by_II its_APPGE absence_NN1 from_II early_JJ plant_NN1 ecological_JJ texts_NN2 and_CC is_VBZ barely_RR represented_VVN in_II the_AT ecological_JJ literature_NN1 until_CS towards_II the_AT middle_NN1 of_IO the_AT twentieth_MD century_NNT1 ._. 
The_AT approach_NN1 that_CST involved_VVD marking_VVG individual_JJ plants_NN2 or_CC seedlings_NN2 in_II the_AT field_NN1 ,_, tracing_VVG the_AT fate_NN1 of_IO individual_JJ leaves_NN2 as_CSA they_PPHS2 are_VBR pulled_VVN down_RP earthworm_NN1 burrows_NN2 ,_, the_AT behaviour_NN1 of_IO tendrils_NN2 as_CSA they_PPHS2 touch_VV0 a_AT1 support_NN1 ,_, the_AT fate_NN1 of_IO insects_NN2 as_CSA they_PPHS2 land_VV0 on_II a_AT1 Drosera_NN1 leaf_NN1 ,_, or_CC recording_VVG the_AT number_NN1 of_IO seeds_NN2 at_II the_AT bottom_NN1 of_IO an_AT1 earthworm_NN1 burrow_NN1 ,_, represented_VVD a_AT1 reductionist_NN1 level_NN1 of_IO concentrated_JJ observation_NN1 that_CST contrasted_VVD with_IW the_AT geographical_JJ view_NN1 of_IO vegetation_NN1 with_IW which_DDQ Warming_NN1 and_CC others_NN2 set_VV0 the_AT early_JJ direction_NN1 of_IO plant_NN1 ecology_NN1 ._. 
There_EX is_VBZ no_AT way_NN1 in_II which_DDQ Darwin_NP1 can_VM be_VBI regarded_VVN as_II a_AT1 parent_NN1 of_IO the_AT science_NN1 of_IO plant_NN1 ecology_NN1 ._. 
Nothing_PN1 illustrates_VVZ this_DD1 point_NN1 so_RG clearly_RR as_CSA the_AT fate_NN1 of_IO a_AT1 paper_NN1 published_VVN in_II 1874_MC by_II C._NP1 Ngeli_NP1 entitled_VVD Verdrngung_NP1 der_FU Pflanzenformen_NN2 durch_VV0 ihre_FW Mitbewerber_NP1 ._. 
This_DD1 paper_NN1 was_VBDZ directly_RR stimulated_VVN by_II The_AT Origin_NN1 of_IO Species_NN and_CC in_II it_PPH1 Ngeli_JJ developed_JJ mathematical_JJ models_NN2 that_CST describe_VV0 the_AT interaction_NN1 between_II populations_NN2 of_IO two_MC species_NN of_IO plants_NN2 ._. 
His_APPGE models_NN2 attempt_VV0 to_TO describe_VVI in_II formal_JJ mathematical_JJ terms_NN2 the_AT replacement_NN1 of_IO a_AT1 population_NN1 of_IO one_MC1 species_NN by_II another_DD1 and_CC also_RR situations_NN2 in_II which_DDQ pairs_NN2 of_IO species_NN persist_VV0 together_RL as_CSA stable_JJ ,_, mixed_VVD populations_NN2 ._. 
Ngeli_NP1 's_GE models_NN2 included_VVD density-dependent_JJ and_CC frequency-dependent_JJ situations_NN2 and_CC came_VVD very_RG close_JJ to_II providing_VVG a_AT1 formal_JJ description_NN1 of_IO the_AT niche_NN1 ._. 
It_PPH1 might_VM have_VHI been_VBN expected_VVN that_CST such_DA a_AT1 paper_NN1 from_II Ngeli_NP1 ,_, who_PNQS was_VBDZ one_MC1 of_IO the_AT most_RGT distinguished_JJ botanists_NN2 in_II Europe_NP1 at_II that_DD1 time_NNT1 ,_, would_VM have_VHI had_VHN immense_JJ impact_NN1 on_II the_AT early_JJ development_NN1 of_IO plant_NN1 ecology_NN1 ._. 
Instead_RR ,_, it_PPH1 appears_VVZ to_TO have_VHI been_VBN wholly_RR ignored_VVN for_IF 60_MC years_NNT2 until_CS it_PPH1 was_VBDZ mentioned_VVN briefly_RR by_II Gauze_NP1 (_( 1934_MC )_) in_II his_APPGE book_NN1 The_AT Struggle_NN1 for_IF Existence_NN1 ._. 
Plant_NN1 ecology_NN1 developed_VVN not_XX as_II a_AT1 study_NN1 of_IO the_AT factors_NN2 affecting_VVG the_AT lives_NN2 and_CC deaths_NN2 of_IO individual_JJ plants_NN2 and_CC their_APPGE parts_NN2 but_CCB as_II a_AT1 study_NN1 of_IO the_AT distribution_NN1 of_IO vegetation_NN1 types_NN2 and_CC of_IO particular_JJ species_NN ._. 
It_PPH1 included_VVD also_RR the_AT description_NN1 of_IO those_DD2 specialized_JJ features_NN2 of_IO morphology_NN1 and_CC physiology_NN1 that_CST distinguish_VV0 species_NN and_CC might_VM (_( often_RR by_II more_RGR or_CC less_RGR inspired_JJ guesswork_NN1 )_) be_VBI said_VVN to_TO account_VVI for_IF the_AT differences_NN2 in_II their_APPGE distribution_NN1 ._. 
That_CST these_DD2 features_NN2 were_VBDR often_RR called_JJ '_GE adaptations_NN2 '_GE did_VDD nothing_PN1 to_TO explain_VVI them_PPHO2 ._. 
Much_DA1 of_IO the_AT early_JJ science_NN1 of_IO plant_NN1 ecology_NN1 sought_VVN for_IF correlations_NN2 between_II vegetation_NN1 and_CC physical_JJ ,_, not_XX biotic_JJ ,_, factors_NN2 in_II the_AT environment_NN1 ,_, most_RGT particularly_RR temperature_NN1 ,_, water_NN1 supply_NN1 and_CC soil_NN1 types_NN2 ._. 
These_DD2 forces_NN2 have_VH0 been_VBN described_VVN as_II '_GE Wallacian_NN1 '_GE (_( Harper_NP1 ,_, 1977_MC )_) ,_, because_CS they_PPHS2 represent_VV0 those_DD2 agents_NN2 of_IO natural_JJ selection_NN1 that_CST were_VBDR of_IO more_DAR concern_NN1 to_II Wallace_NP1 than_CSN to_II Darwin_NP1 in_II accounting_VVG for_IF how_RRQ organisms_NN2 are_VBR as_CSA they_PPHS2 are_VBR and_CC behave_VV0 as_CSA they_PPHS2 do_VD0 ._. 
The_AT role_NN1 of_IO biotic_JJ (_( Darwinian_JJ )_) forces_NN2 in_II determining_VVG the_AT distribution_NN1 and_CC abundance_NN1 of_IO species_NN was_VBDZ largely_RR neglected_VVN except_CS by_II token_JJ reference_NN1 to_II grazing_JJ animals_NN2 ._. 
The_AT essentially_RR Darwinian_JJ forces_NN2 of_IO struggle_NN1 for_IF existence_NN1 ,_, involving_VVG competitive_JJ interactions_NN2 between_II members_NN2 of_IO the_AT same_DA species_NN and_CC between_II different_JJ species_NN ,_, played_VVD a_AT1 negligible_JJ part_NN1 in_II the_AT interpretation_NN1 of_IO natural_JJ vegetation_NN1 ._. 
The_AT Darwinian_JJ approach_NN1 ,_, involving_VVG reductionist_NN1 concentration_NN1 on_II individual_JJ plants_NN2 and_CC the_AT hazards_NN2 that_CST they_PPHS2 experience_VV0 ,_, particularly_RR the_AT interference_NN1 from_II their_APPGE neighbours_NN2 ,_, entered_VVD the_AT science_NN1 of_IO plant_NN1 ecology_NN1 in_II the_AT late_JJ nineteen_MC twenties_MC2 in_II simple_JJ experiments_NN2 involving_VVG mixed_JJ populations_NN2 of_IO two_MC or_CC more_DAR species_NN and_CC I_PPIS1 have_VH0 described_VVN elsewhere_RL (_( Harper_NP1 ,_, 1967_MC )_) the_AT curious_JJ piece_NN1 of_IO history_NN1 in_II which_DDQ three_MC leading_JJ ecologists_NN2 ,_, Sukatschev_NP1 in_II Russia_NP1 ,_, Clements_NP1 in_II the_AT United_NP1 States_NP1 and_CC Tansley_NP1 in_II Britain_NP1 ,_, all_DB made_VVD simple_JJ competition_NN1 experiments_NN2 involving_VVG deliberately-sown_JJ plant_NN1 populations_NN2 ._. 
None_PN of_IO these_DD2 authors_NN2 continued_VVN with_IW this_DD1 type_NN1 of_IO study_NN1 and_CC all_DB returned_VVN to_II essentially_RR descriptive_JJ studies_NN2 of_IO vegetation_NN1 ._. 
It_PPH1 was_VBDZ as_CS21 if_CS22 they_PPHS2 had_VHD found_VVN it_PPH1 too_RG difficult_JJ to_TO bridge_VVI the_AT gap_NN1 between_II simple_JJ experimental_JJ systems_NN2 and_CC the_AT complexity_NN1 of_IO nature_NN1 as_CS21 if_CS22 the_AT reductionism_NN1 of_IO the_AT experimental_JJ method_NN1 lost_VVD the_AT holist_NN1 qualities_NN2 of_IO the_AT integrated_JJ complex_JJ whole_NN1 that_CST these_DD2 distinguished_JJ ecologists_NN2 saw_VVD in_II natural_JJ vegetation_NN1 ._. 
Both_DB2 Clements_NP1 '_GE Community_NN1 as_II an_AT1 Organism_NN1 and_CC Tansley_NP1 's_GE Ecosystem_NN1 can_VM be_VBI represented_VVN as_II a_AT1 retreat_NN1 to_II community_NN1 holism_NN1 after_II a_AT1 brief_JJ flirtation_NN1 with_IW an_AT1 organismal_JJ ,_, Darwinian_JJ ecology_NN1 ._. 
A_AT1 piece_NN1 of_IO ecological_JJ history_NN1 that_CST remains_VVZ to_TO be_VBI fully_RR researched_VVN was_VBDZ the_AT decision_NN1 by_II a_AT1 number_NN1 of_IO individuals_NN2 ,_, many_DA2 apparently_RR working_VVG in_II isolation_NN1 from_II each_PPX221 other_PPX222 ,_, to_TO establish_VVI ,_, like_II Darwin_NP1 ,_, permanent_JJ plots_NN2 within_II which_DDQ the_AT fate_NN1 of_IO individual_JJ plants_NN2 could_VM be_VBI recorded_VVN over_II time_NNT1 ._. 
The_AT great_JJ classic_NN1 amongst_II such_DA observations_NN2 is_VBZ the_AT work_NN1 of_IO Carl_NP1 Olaf_NP1 Tamm_NP1 (_( 1948_MC ,_, 19721_MC who_PNQS marked_VVD out_RP permanent_JJ quadrats_NN2 in_II woodland_NN1 and_CC grassland_NN1 near_II his_APPGE country_NN1 home_NN1 and_CC as_II a_AT1 hobby_NN1 mapped_VVN ,_, remapped_VVD and_CC continues_VVZ to_TO map_VVI the_AT plants_NN2 within_II them_PPHO2 ._. 
Tamm_NP1 attributes_VVZ his_APPGE decision_NN1 to_TO embark_VVI on_II this_DD1 long-term_JJ programme_NN1 to_II stimulus_NN1 from_II Romell_NP1 ,_, a_AT1 distinguished_JJ Swedish_JJ ecologist_NN1 and_CC soil_NN1 scientist_NN1 ._. 
Other_JJ permanent_JJ quadrats_NN2 were_VBDR set_VVN up_RP by_II Forrest_NP1 Shreve_NP1 (_( 1915_MC )_) at_II the_AT Desert_NN1 Laboratory_NN1 of_IO the_AT Carnegie_NP1 Institute_NN1 of_IO Washington_NP1 at_II Tucson_NP1 ,_, Arizona_NP1 ,_, and_CC it_PPH1 appears_VVZ to_TO be_VBI through_II a_AT1 colleague_NN1 of_IO Shreve_NP1 ,_, W._NP1 A._NP1 Cannon_NP1 ,_, that_CST T._NP1 G._NP1 B._NP1 Osborn_NP1 was_VBDZ stimulated_VVN in_II 1926_MC to_TO set_VVI up_RP permanent_JJ quadrats_NN2 in_II heavily_RR used_JJ shrub_NN1 land_NN1 and_CC a_AT1 reserve_NN1 released_VVN from_II grazing_VVG at_II Koonamore_NP1 in_II S._NP1 Australia_NP1 (_( Osborn_NP1 ,_, Wood_NP1 &amp;_CC Partridge_NN ,_, 1935_MC ;_; O._NP1 B._NP1 Williams_NP1 &amp;_CC Mott_NP1 ,_, 1981_MC )_) ._. 
There_EX is_VBZ also_RR a_AT1 European_JJ tradition_NN1 that_CST precedes_VVZ the_AT work_NN1 of_IO Tamm_NP1 ,_, associated_VVN with_IW the_AT name_NN1 of_IO Bogdanovskaya-Gienef_NP1 (_( 1926_MC )_) who_PNQS seems_VVZ to_TO have_VHI been_VBN a_AT1 pupil_NN1 of_IO Sukatschev_NP1 and_CC to_TO have_VHI influenced_VVN the_AT reductionist_NN1 approach_NN1 to_II ecology_NN1 later_RRR developed_VVN by_II Rabotnov_NP1 ,_, Uranov_NP1 and_CC their_APPGE pupils_NN2 in_II Russia_NP1 ._. 
She_PPHS1 reported_VVD her_APPGE two-year_JJ study_NN1 of_IO four_MC 20_MC 20_MC cm_NNU quadrats_NN2 ._. 
Her_APPGE publications_NN2 list_NN1 appears_VVZ to_TO consist_VVI of_IO only_RR two_MC papers_NN2 ,_, but_CCB she_PPHS1 may_VM have_VHI had_VHN a_AT1 greater_JJR influence_NN1 than_CSN this_DD1 suggests_VVZ (_( J._NP1 White_NP1 ,_, personal_JJ communication_NN1 )_) ._. 
The_AT peculiar_JJ quality_NN1 of_IO Tamm_NP1 's_GE work_NN1 was_VBDZ that_CST he_PPHS1 recorded_VVD individual_JJ plants_NN2 ,_, shoots_NN2 or_CC rosettes_NN2 ,_, within_II his_APPGE populations_NN2 and_CC this_DD1 enabled_VVD him_PPHO1 to_TO follow_VVI the_AT fates_NN2 of_IO individual_JJ plant_NN1 units_NN2 (_( often_RR tillers_NN2 or_CC ramets_NN2 )_) rather_CS21 than_CS22 to_II study_NN1 the_AT grosser_JJR vegetational_JJ change_NN1 that_CST was_VBDZ the_AT aim_NN1 of_IO many_DA2 others_NN2 who_PNQS set_VVD up_RP permanent_JJ quadrats_NN2 ._. 
The_AT data_NN obtained_VVN from_II Tamm_NP1 's_GE studies_NN2 revealed_VVD ,_, for_IF the_AT first_MD time_NNT1 ,_, the_AT magnitude_NN1 of_IO the_AT flux_NN1 that_CST underlay_VVD ,_, the_AT apparent_JJ stability_NN1 of_IO many_DA2 plant_NN1 communities_NN2 and_CC (_( after_CS Darwin_NP1 )_) gave_VVD the_AT first_MD real_JJ insight_NN1 into_II plant_NN1 community_NN1 dynamics_NN dominated_VVN by_II establishment_NN1 and_CC deaths_NN2 ._. 
Vegetation_NN1 is_VBZ composed_VVN of_IO the_AT few_DA2 plants_NN2 that_CST survive_VV0 and_CC grow_VV0 :_: to_TO explain_VVI that_DD1 vegetation_NN1 it_PPH1 may_VM be_VBI more_RGR important_JJ to_TO study_VVI the_AT many_DA2 that_CST die_VV0 ._. 
In_II many_DA2 of_IO Tamm_NP1 's_GE populations_NN2 it_PPH1 can_VM be_VBI shown_VVN (_( Harper_NP1 ,_, 1967_MC )_) that_CST the_AT plants_NN2 originally_RR present_JJ were_VBDR progressively_RR lost_VVN and_CC that_CST the_AT rate_NN1 of_IO loss_NN1 was_VBDZ remarkably_RR constant_JJ ._. 
Half-lives_NN2 could_VM be_VBI calculated_VVN for_IF the_AT populations_NN2 differing_VVG from_II species_NN to_II species_NN but_CCB constant_JJ over_II the_AT years_NNT2 ._. 
Such_DA data_NN made_VVD it_PPH1 clear_JJ that_CST (_( i_ZZ1 )_) it_PPH1 was_VBDZ realistic_JJ and_CC profitable_JJ to_TO study_VVI individual_JJ species_NN ,_, even_RR within_II a_AT1 complex_JJ community_NN1 and_CC (_( ii_MC )_) that_CST the_AT dynamics_NN of_IO the_AT populations_NN2 appeared_VVD to_TO be_VBI largely_RR independent_JJ of_IO year-to-year_JJ fluctuations_NN2 in_II climate_NN1 ._. 
Later_JJR studies_NN2 of_IO permanent_JJ quadrats_NN2 in_II grassland_NN1 by_II Sagar_NP1 ,_, Sarukhn_NP1 ,_, Hawthorn_NN1 and_CC others_NN2 (_( see_VV0 Harper_NP1 ,_, 1977_MC )_) extended_VVD over_RP fewer_DAR years_NNT2 but_CCB involved_VVD repeated_JJ observations_NN2 within_II each_DD1 year_NNT1 ._. 
They_PPHS2 showed_VVD that_CST the_AT death_NN1 risks_NN2 to_II plants_NN2 in_II populations_NN2 within_II years_NNT2 were_VBDR commonly_RR greatest_JJT when_CS the_AT survivors_NN2 were_VBDR growing_JJ fastest_JJT not_XX during_II the_AT periods_NN2 when_RRQ the_AT botanist_NN1 would_VM regard_VVI the_AT physical_JJ environment_NN1 as_II '_GE harsh_JJ '_GE ._. 
The_AT likely_JJ explanation_NN1 is_VBZ that_CST it_PPH1 is_VBZ biotic_JJ pressure_NN1 from_II competing_JJ neighbours_NN2 rather_II21 than_II22 '_GE harshness_NN1 '_GE of_IO the_AT physical_JJ environment_NN1 that_CST is_VBZ the_AT prime_JJ cause_NN1 of_IO death_NN1 of_IO most_DAT plants_NN2 and_CC perhaps_RR of_IO natural_JJ selection_NN1 ._. 
Most_DAT of_IO these_DD2 detailed_JJ demographic_JJ studies_NN2 have_VH0 been_VBN made_VVN with_IW pasture_NN1 or_CC woodland_NN1 systems_NN2 in_II northern_JJ temperate_JJ regions_NN2 and_CC it_PPH1 could_VM well_RR be_VBI that_CST in_II arid_JJ zones_NN2 ,_, and_CC some_DD other_JJ extreme_JJ environments_NN2 ,_, biotic_JJ pressures_NN2 are_VBR less_RGR dominant_JJ and_CC then_RT climatic_JJ factors_NN2 may_VM play_VVI the_AT major_JJ role_NN1 in_II killing_VVG plants_NN2 and_CC in_II natural_JJ selection_NN1 ._. 
At_II a_AT1 Symposium_NN1 organized_VVD to_TO pay_VVI tribute_NN1 to_II Darwin_NP1 a_AT1 hundred_NNO years_NNT2 after_II his_APPGE death_NN1 ,_, it_PPH1 is_VBZ perhaps_RR permitted_VVN to_TO expand_VVI on_II one_MC1 tiny_JJ fragment_NN1 of_IO ecological_JJ research_NN1 that_CST may_VM truly_RR be_VBI said_VVN to_TO have_VHI been_VBN directly_RR stimulated_VVN by_II Darwin_NP1 's_GE own_DA writings_NN2 ,_, in_RR21 particular_RR22 by_II the_AT paragraph_NN1 quoted_VVN as_CSA heading_VVG to_II this_DD1 paper_NN1 ._. 
Early_RR in_II the_AT 1960s_MC2 the_AT decision_NN1 was_VBDZ made_VVN to_TO concentrate_VVI a_AT1 number_NN1 of_IO intensive_JJ ecological_JJ studies_NN2 based_VVN at_II Bangor_NP1 ,_, North_ND1 Wales_NP1 ,_, on_II a_AT1 single_JJ ,_, small_JJ (_( 1_MC1 ha_UH )_) field_NN1 of_IO permanent_JJ grassland_NN1 ,_, part_NN1 of_IO the_AT College_NN1 Farm_NN1 at_II Henfaes_NP2 ,_, Aber_NP1 ,_, near_II Bangor_NP1 ._. 
The_AT field_NN1 was_VBDZ chosen_VVN because_CS it_PPH1 was_VBDZ superficially_RR very_RG dull_JJ lacking_VVG any_DD obvious_JJ heterogeneity_NN1 of_IO contour_NN1 and_CC relatively_RR homogeneous_JJ in_II soil_NN1 properties_NN2 ._. 
The_AT field_NN1 had_VHD not_XX been_VBN ploughed_VVN for_IF at_RR21 least_RR22 80_MC years_NNT2 (_( probably_RR not_XX for_IF more_DAR than_CSN 150_MC years_NNT2 )_) and_CC there_EX is_VBZ no_AT record_NN1 of_IO fertilizer_NN1 or_CC herbicide_VV0 ever_RR having_VHG been_VBN applied_VVN ._. 
A_AT1 general_JJ description_NN1 of_IO the_AT field_NN1 is_VBZ given_VVN in_II Turkington_NP1 &amp;_CC Harper_NP1 (_( 1979a_FO )_) and_CC more_RGR detailed_JJ analysis_NN1 of_IO the_AT soil_NN1 and_CC flora_NN in_II Turkington_NP1 (_( 1975_MC )_) ._. 
Many_DA2 graduate_VV0 students_NN2 and_CC overseas_JJ visitors_NN2 have_VH0 worked_VVN on_II aspects_NN2 of_IO the_AT ecology_NN1 of_IO this_DD1 field_NN1 ._. 
In_II many_DA2 cases_NN2 the_AT studies_NN2 have_VH0 concentrated_VVN on_II populations_NN2 of_IO a_AT1 single_JJ species_NN within_II 1_MC1 m&amp;sup2_FO ;_; quadrats_NN2 ,_, though_CS sometimes_RT the_AT reductionist_NN1 level_NN1 of_IO study_NN1 has_VHZ been_VBN yet_RR smaller_JJR a_AT1 scale_NN1 of_IO 1_MC1 cm&amp;sup2_FO ;_; (_( Thorhallsdottir_NP1 ,_, 1983_MC )_) ._. 
The_AT concentration_NN1 of_IO effort_NN1 within_II one_MC1 small_JJ field_NN1 ,_, and_CC on_II small_JJ quadrats_NN2 within_II it_PPH1 ,_, gives_VVZ the_AT studies_NN2 high_JJ precision_NN1 and_CC high_JJ relevance_NN1 but_CCB with_IW an_AT1 absolute_JJ sacrifice_NN1 of_IO generality_NN1 ._. 
We_PPIS2 do_VD0 not_XX know_VVI whether_CSW most_DAT of_IO what_DDQ we_PPIS2 have_VH0 observed_VVN in_II this_DD1 field_NN1 can_VM be_VBI generalized_VVN to_II other_JJ fields_NN2 or_CC ,_, indeed_RR ,_, to_II less_RGR intensively_RR studied_VVN parts_NN2 of_IO the_AT same_DA field_NN1 ._. 
The_AT vegetation_NN1 of_IO the_AT field_NN1 was_VBDZ analysed_VVN by_II ordination_NN1 and_CC correlation_NN1 techniques_NN2 which_DDQ showed_VVD that_CST only_RR a_AT1 minor_JJ part_NN1 of_IO the_AT variation_NN1 in_II species_NN distribution_NN1 could_VM be_VBI accounted_VVN for_IF by_II underlying_VVG edaphic_JJ factors_NN2 ,_, though_CS in_II the_AT peripheral_JJ areas_NN2 of_IO the_AT pasture_NN1 the_AT presence_NN1 of_IO hedges_NN2 and_CC trees_NN2 accounted_VVN for_IF significant_JJ changes_NN2 in_II the_AT vegetation_NN1 e.g._REX Dadtylis_NP1 glomerata_NN1 occurred_VVD mainly_RR in_RP or_CC close_RR to_II the_AT shade_NN1 of_IO the_AT trees_NN2 ._. 
Two_MC common_JJ species_NN ,_, Lolium_NP1 perenne_NN1 and_CC Trifolium_NP1 repens_VVZ were_VBDR usually_RR positively_RR associated_VVN in_II their_APPGE microdistribution_NN1 and_CC negatively_RR associated_VVN with_IW other_JJ species_NN ._. 
The_AT structure_NN1 of_IO the_AT vegetation_NN1 was_VBDZ interpreted_VVN as_CSA determined_VVN by_II regeneration_NN1 cycles_NN2 directed_VVN by_II T._NP1 repens_VVZ and_CC L._NP1 perenne_NN1 the_AT species_NN themselves_PPX2 appeared_VVD to_TO be_VBI the_AT prime_JJ determinants_NN2 of_IO each_DD1 others_NN2 distribution_NN1 (_( Turkington_NP1 and_CC Harper_NP1 ,_, 1979a_FO ,_, b_ZZ1 )_) ._. 
The_AT most_RGT intensive_JJ studies_NN2 on_II the_AT field_NN1 have_VH0 been_VBN made_VVN on_II populations_NN2 of_IO three_MC species_NN of_IO Ranunculus_NP1 and_CC on_II Trifolium_NP1 repens_VVZ ._. 
Some_DD of_IO the_AT work_NN1 is_VBZ still_RR in_II midstream_RL and_CC consequently_RR some_DD material_NN1 referred_VVN to_II in_II this_DD1 paper_NN1 represents_VVZ an_AT1 interim_JJ report_NN1 ._. 
Two_MC of_IO the_AT species_NN present_NN1 in_II the_AT field_NN1 are_VBR of_IO particular_JJ interest_NN1 ,_, both_RR to_II population_NN1 biologists_NN2 interested_JJ in_II the_AT manner_NN1 in_II which_DDQ the_AT numbers_NN2 of_IO plants_NN2 are_VBR regulated_VVN and_CC to_II evolutionists_NN2 concerned_JJ with_IW the_AT extent_NN1 and_CC significance_NN1 of_IO natural_JJ variation_NN1 ._. 
The_AT two_MC species_NN are_VBR Ranunculus_NP1 repens_VVZ and_CC Trifolium_NP1 repens_VVZ ._. 
Both_DB2 possess_VV0 the_AT property_NN1 of_IO clonal_JJ growth_NN1 by_II which_DDQ the_AT product_NN1 of_IO a_AT1 single_JJ zygote_NN1 forms_VVZ a_AT1 spreading_JJ clone_NN1 of_IO rooted_JJ nodes_NN2 capable_JJ of_IO vegetative_JJ extension_NN1 through_II the_AT sward_NN1 ._. 
Such_DA plants_NN2 have_VH0 the_AT potential_NN1 for_IF a_AT1 single_JJ clone_NN1 or_CC genet_NN1 (_( product_NN1 of_IO a_AT1 single_JJ zygote_NN1 )_) to_TO dominate_VVI large_JJ areas_NN2 of_IO the_AT vegetation_NN1 ._. 
Indeed_RR ,_, it_PPH1 would_VM be_VBI theoretically_RR possible_JJ for_IF one_MC1 genet_NN1 of_IO Trifolium_NP1 repens_VVZ or_CC Ranunculus_NP1 repens_VVZ to_TO have_VHI occupied_VVN the_AT whole_NN1 of_IO the_AT Henfaes_NP2 field_NN1 ._. 
In_II other_JJ plants_NN2 with_IW such_DA clonal_JJ growth_NN1 it_PPH1 is_VBZ known_VVN that_CST the_AT product_NN1 of_IO a_AT1 single_JJ zygote_NN1 may_VM indeed_RR occupy_VVI considerable_JJ areas_NN2 of_IO land_NN1 ._. 
An_AT1 extreme_JJ example_NN1 is_VBZ bracken_NN1 ,_, Pteridium_NP1 aquilinum_NN1 ;_; Oinonen_NP1 (_( 1967_MC )_) showed_VVD that_CST individual_JJ clones_NN2 in_II Finland_NP1 were_VBDR up_RG21 to_RG22 1440_MC years_NNT2 old_JJ and_CC one_MC1 old_JJ clone_NN1 extended_VVD over_RP an_AT1 area_NN1 of_IO 474_MC 292_MC m_NNO ._. 
There_EX are_VBR other_JJ cases_NN2 in_II which_DDQ clone-forming_JJ species_NN are_VBR known_VVN to_TO produce_VVI large_JJ areas_NN2 of_IO genetic_JJ monotony_NN1 ,_, e.g._REX Festuca_NP1 rubra_NN1 (_( Harberd_NP1 ,_, 1961_MC )_) and_CC Holcus_FW mollis_NN2 (_( Harberd_NP1 1967_MC )_) ._. 
It_PPH1 might_VM be_VBI expected_VVN that_CST where_CS such_DA clonal_JJ growth_NN1 is_VBZ possible_JJ ,_, the_AT struggle_NN1 for_IF existence_NN1 over_II long_JJ periods_NN2 of_IO stable_JJ management_NN1 would_VM lead_VVI to_II the_AT local_JJ dominance_NN1 of_IO single_JJ clones_NN2 those_DD2 that_CST had_VHD succeeded_VVN in_II a_AT1 struggle_NN1 for_IF existence_NN1 with_IW others_NN2 ._. 
The_AT population_NN1 dynamics_NN and_CC genetics_NN1 of_IO these_DD2 two_MC species_NN in_II the_AT permanent_JJ pasture_NN1 at_II Henfaes_NP2 seemed_VVD to_II over_II the_AT opportunity_NN1 to_TO study_VVI natural_JJ selection_NN1 in_II action_NN1 Hutchinson_NP1 's_GE '_GE ecological_JJ theater_NN1 and_CC evolutionary_JJ play_NN1 '_GE ._. 
Population_NN1 dynamics_NN of_IO Ranunculus_NP1 repens_VVZ The_AT detailed_JJ demographic_JJ studies_NN2 of_IO Ranunculus_NP1 repens_VVZ made_VVN by_II Sarukhn_NP1 in_II the_AT field_NN1 at_II Henfaes_NP2 and_CC followed_VVN by_II unpublished_JJ studies_NN2 by_II Soane_NP1 made_VVD it_PPH1 possible_JJ to_TO give_VVI quantitative_JJ measures_NN2 to_II the_AT population_NN1 dynamics_NN of_IO this_DD1 species_NN ._. 
These_DD2 are_VBR summarized_VVN in_II the_AT life-cycle_NN1 diagram_NN1 of_IO Fig._NN1 16.1_MC ._. 
Populations_NN2 of_IO this_DD1 species_NN showed_VVD vigorous_JJ vegetative_JJ growth_NN1 ,_, and_CC most_RGT new_JJ rosettes_NN2 recruited_VVN to_II the_AT population_NN1 appeared_VVD as_CSA ramets_NN2 (_( clonal_JJ replicates_VVZ )_) from_II existing_JJ rosettes_NN2 ._. 
The_AT input_NN1 of_IO new_JJ seedlings_NN2 was_VBDZ small_JJ and_CC the_AT number_NN1 eventually_RR contributing_VVG to_TO mature_VVI rosettes_NN2 in_II the_AT pasture_NN1 seemed_VVD insignificant_JJ in_II31 comparison_II32 with_II33 the_AT contribution_NN1 from_II clonal_JJ growth_NN1 ._. 
In_II31 comparison_II32 with_II33 the_AT other_JJ two_MC species_NN of_IO Ranunculus_NP1 ,_, R._NP1 acris_NN1 and_CC R._NP1 bulbosus_NN1 present_NN1 in_II the_AT pasture_NN1 ,_, seed_NN1 production_NN1 and_CC the_AT numbers_NN2 of_IO seedlings_NN2 observed_VVD was_VBDZ very_RG small_JJ ._. 
Plants_NN2 of_IO Ranunculus_NP1 repens_VVZ produced_VVN on_II average_NN1 less_DAR than_CSN one_MC1 seed_NN1 per_II rosette_NN1 (_( cf._VV0 ca_VM 10_MC for_IF R._NP1 acris_NN1 ,_, ca._NNU 15_MC for_IF R._NP1 bulbosus_NN1 )_) ._. 
In_II the_AT studied_JJ quadrats_NN2 ,_, 25_MC seedlings_NN2 of_IO Ranunculus_NP1 repens_VVZ emerged_VVN per_II metre_NNU1 square_NN1 from_II the_AT long-lived_JJ bank_NN1 of_IO seeds_NN2 in_II the_AT soil_NN1 ,_, in_II contrast_NN1 with_IW 176_MC of_IO Ranunculus_NP1 acris_NN1 and_CC 95_MC of_IO Ranunculus_NP1 bulbosus_NN1 ._. 
The_AT dynamics_NN of_IO Ranunculus_NP1 repens_VVZ populations_NN2 was_VBDZ followed_VVN over_RG four_MC years_NNT2 during_II which_DDQ new_JJ seedlings_NN2 that_CST died_VVD and_CC those_DD2 that_CST survived_VVD to_TO form_VVI rosettes_NN2 were_VBDR recorded_VVN ._. 
The_AT development_NN1 of_IO clones_NN2 from_II the_AT rosettes_NN2 present_VV0 at_II the_AT beginning_NN1 of_IO the_AT study_NN1 was_VBDZ also_RR recorded_VVN in_II detail_NN1 so_CS21 that_CS22 the_AT clonal_JJ parent_NN1 was_VBDZ known_VVN for_IF almost_RR every_AT1 rosette_NN1 present_NN1 in_II the_AT quadrats_NN2 at_II the_AT end_NN1 of_IO the_AT study_NN1 ._. 
These_DD2 data_NN allowed_VVD Soane_NP1 &amp;_CC Watkinson_NP1 (_( 1979_MC )_) to_TO build_VVI a_AT1 computer_NN1 simulation_NN1 model_NN1 to_TO examine_VVI the_AT relationship_NN1 between_II the_AT flux_NN1 of_IO ramets_NN2 ,_, the_AT recruitment_NN1 of_IO seedlings_NN2 and_CC the_AT diversity_NN1 of_IO genets_NN2 within_II the_AT populations_NN2 ._. 
The_AT computer_NN1 models_NN2 simulated_VVD the_AT actual_JJ flux_NN1 of_IO ramets_NN2 in_II each_DD1 of_IO eight_MC studied_JJ populations_NN2 and_CC followed_VVD the_AT fates_NN2 of_IO ramets_NN2 and_CC families_NN2 of_IO ramets_NN2 assuming_VVG no_AT selection_NN1 between_II families_NN2 ._. 
The_AT real_JJ and_CC simulated_JJ changes_NN2 in_II the_AT populations_NN2 are_VBR shown_VVN in_II Fig._NN1 16.2_MC ._. 
Agreement_NN1 is_VBZ extremely_RR close_JJ and_CC provides_VVZ little_DA1 evidence_NN1 for_IF selection_NN1 between_II families_NN2 or_CC against_II new_JJ seedling_NN1 recruits_NN2 ._. 
In_II the_AT simulation_NN1 model_NN1 ,_, in_II the_AT absence_NN1 of_IO selection_NN1 ,_, the_AT number_NN1 of_IO original_JJ families_NN2 present_VV0 in_II the_AT population_NN1 declined_VVN at_II an_AT1 approximately_RR exponential_NN1 rate_NN1 ._. 
With_IW the_AT passage_NN1 of_IO time_NNT1 the_AT contribution_NN1 that_CST these_DD2 families_NN2 made_VVN to_II the_AT total_JJ genetic_JJ diversity_NN1 of_IO the_AT population_NN1 became_VVD subordinate_JJ to_II the_AT seedling_NN1 recruits_VVZ :_: although_CS the_AT number_NN1 of_IO seedlings_NN2 appears_VVZ to_TO be_VBI very_RG small_JJ ,_, their_APPGE contribution_NN1 to_II the_AT total_JJ number_NN1 of_IO genetic_JJ individuals_NN2 in_II the_AT population_NN1 is_VBZ clearly_RR significant_JJ in_II determining_VVG the_AT number_NN1 of_IO clones_NN2 or_CC genets_NN2 that_CST are_VBR present_JJ ._. 
In_II the_AT absence_NN1 of_IO selection_NN1 ,_, the_AT observed_JJ small_JJ numbers_NN2 of_IO seedling_NN1 recruits_NN2 would_VM apparently_RR be_VBI sufficient_JJ to_TO maintain_VVI potentially_RR high_JJ genet_NN1 diversity_NN1 within_II such_DA a_AT1 vigorously_RR clonal_JJ plant_NN1 population_NN1 ._. 
Such_DA genetic_JJ diversity_NN1 was_VBDZ indeed_RR present_JJ ,_, because_CS there_EX was_VBDZ visible_JJ genetic_JJ polymorphism_NN1 within_II the_AT populations_NN2 and_CC it_PPH1 was_VBDZ shown_VVN (_( M._NN1 J._NP1 Lawrence_NP1 ,_, personal_JJ communication_NN1 )_) that_CST there_EX was_VBDZ considerable_JJ genetic_JJ variability_NN1 both_RR in_II quantitative_JJ characters_NN2 and_CC in_II polymorphism_NN1 at_II two_MC enzyme_NN1 loci_NN2 in_II populations_NN2 immediately_RR adjacent_II21 to_II22 the_AT permanent_JJ quadrats_NN2 ._. 
Population_NN1 dynamics_NN and_CC genetic_JJ variation_NN1 in_II Trifolium_NP1 repens_VVZ Analysis_NN1 of_IO the_AT population_NN1 dynamics_NN and_CC associated_JJ genetics_NN1 of_IO Trifolium_NP1 repens_VVZ in_II the_AT same_DA pasture_NN1 is_VBZ even_RR more_RGR revealing_JJ ._. 
Trifolium_NN1 repens_VVZ is_VBZ unusual_JJ in_II that_DD1 much_DA1 of_IO the_AT genetic_JJ variation_NN1 present_NN1 within_II the_AT populations_NN2 is_VBZ easily_RR recognised_VVN in_II phenotypic_JJ differences_NN2 that_CST are_VBR visible_JJ or_CC easily_RR determined_VVN on_II plants_NN2 in_II the_AT field_NN1 ._. 
Leaf_NN1 mark_NN1 polymorphism_NN1 is_VBZ one_MC1 such_DA property_NN1 ._. 
A_AT1 variety_NN1 of_IO white_JJ leaf_NN1 marks_NN2 is_VBZ found_VVN in_II natural_JJ populations_NN2 and_CC these_DD2 are_VBR represented_VVN by_II multiple_JJ alleles_NN2 at_II a_AT1 single_JJ locus_NN1 ._. 
In_II mid-summer_NNT1 ,_, when_CS the_AT marks_NN2 are_VBR most_RGT fully_RR expressed_VVN ,_, the_AT genotypes_NN2 of_IO most_DAT plants_NN2 can_VM be_VBI identified_VVN in_II the_AT field_NN1 and_CC an_AT1 estimate_NN1 of_IO the_AT number_NN1 of_IO clones_NN2 present_VV0 within_II an_AT1 area_NN1 can_VM be_VBI made_VVN :_: it_PPH1 will_VM ,_, of_RR21 course_RR22 ,_, be_VBI a_AT1 minimal_JJ estimate_NN1 ._. 
Cahn_NP1 &amp;_CC Harper_NP1 (_( 1976a_FO )_) determined_VVD the_AT number_NN1 of_IO clones_NN2 present_VV0 within_II 10_MC 10_MC cm_NNU quadrats_NN2 and_CC found_VVD ,_, to_II considerable_JJ surprise_NN1 ,_, that_CST between_II 3_MC and_CC 4_MC clones_NN2 per_II quadrat_NN1 was_VBDZ the_AT most_RGT common_JJ situation_NN1 in_II the_AT field_NN1 ._. 
This_DD1 level_NN1 of_IO genetic_JJ diversity_NN1 at_II a_AT1 fine_JJ scale_NN1 was_VBDZ confirmed_VVN in_II other_JJ permanent_JJ grasslands_NN2 in_II Britain_NP1 including_II Port_NP1 Meadow_NP1 ,_, Oxford_NP1 ,_, which_DDQ is_VBZ at_RR21 least_RR22 896_MC years_NNT2 old_JJ !_! 
Clearly_RR ,_, single_JJ clones_NN2 did_VDD not_XX dominate_VVI patches_NN2 even_RR at_II this_DD1 very_RG fine_JJ scale_NN1 ._. 
More_RGR recently_RR ,_, Trathan_NP1 has_VHZ identified_VVN genetic_JJ individuals_NN2 with_IW more_DAR precision_NN1 using_VVG isoenzyme_NN1 analysis_NN1 ._. 
He_PPHS1 finds_VVZ 4850_MC distinct_JJ genotypes_NN2 present_VV0 per_II metre_NNU1 square_NN1 ._. 
The_AT various_JJ clones_NN2 weave_VV0 amongst_II and_CC intermingle_VV0 with_IW each_PPX221 other_PPX222 and_CC amongst_II grasses_NN2 and_CC associated_JJ herbs_NN2 ._. 
The_AT degree_NN1 of_IO intermingling_NN1 may_VM itself_PPX1 reflect_VVI the_AT growth_NN1 form_NN1 of_IO stoloniferous_JJ species_NN ._. 
Both_DB2 Ranunculus_NP1 repens_VVZ and_CC Trifolium_NP1 repens_VVZ have_VH0 '_GE guerrilla_NN1 '_GE growth_NN1 forms_VVZ in_II contrast_NN1 to_II the_AT predominantly_RR '_GE phalanx_NN1 '_GE forms_NN2 of_IO the_AT associated_JJ grass_NN1 species_NN ._. 
By_II '_GE guerrilla_NN1 '_GE growth_NN1 form_NN1 is_VBZ implied_VVN one_PN1 that_CST is_VBZ continually_RR wandering_VVG amidst_II associated_JJ vegetation_NN1 ,_, creeping_VVG into_II new_JJ and_CC escaping_VVG from_II old_JJ patches_NN2 in_II the_AT community_NN1 ._. 
In_II contrast_NN1 ,_, '_GE phalanx_NN1 '_GE growth_NN1 forms_NN2 develop_VV0 a_AT1 structure_NN1 of_IO tightly_RR packed_JJ shoots_NN2 (_( most_DAT of_IO the_AT pasture_NN1 grasses_NN2 and_CC some_DD pasture_NN1 dicots_VVZ such_II21 as_II22 Bellis_NP1 perennis_NN1 )_) (_( Lovett_NP1 Doust_NP1 ,_, 1981_MC )_) ._. 
Not_XX only_RR has_VHZ Trifolium_NP1 repens_VVZ a_AT1 guerrilla_NN1 growth_NN1 form_NN1 but_CCB its_APPGE guerrilla_NN1 character_NN1 is_VBZ exaggerated_VVN when_CS it_PPH1 is_VBZ growing_VVG with_IW grasses_NN2 ;_; its_APPGE branching_JJ then_RT tends_VVZ to_TO be_VBI reduced_VVN and_CC growth_NN1 is_VBZ concentrated_VVN in_II linear_JJ extension_NN1 ._. 
Instead_II21 of_II22 a_AT1 genet_NN1 locally_RR consolidating_VVG its_APPGE occupancy_NN1 of_IO a_AT1 site_NN1 ,_, individual_JJ stolons_NN2 wander_VV0 as_RG linear_JJ extensions_NN2 of_IO the_AT genet_NN1 into_II surrounding_JJ vegetation_NN1 ._. 
This_DD1 growth_NN1 form_NN1 itself_PPX1 maximises_VVZ the_AT chance_NN1 that_CST genets_NN2 will_VM intermingle_VVI :_: it_PPH1 maximizes_VVZ the_AT role_NN1 of_IO interspecific_JJ contacts_NN2 in_II the_AT life_NN1 of_IO the_AT genet_NN1 ._. 
Darwin_NP1 commented_VVD on_II the_AT growth_NN1 of_IO such_DA plants_NN2 and_CC the_AT ways_NN2 in_II which_DDQ they_PPHS2 penetrate_VV0 amongst_II other_JJ vegetation_NN1 ._. 
He_PPHS1 describes_VVZ his_APPGE own_DA (_( very_RG Darwinian_JJ !_! )_) experiment_NN1 in_II which_DDQ he_PPHS1 allowed_VVD the_AT stolons_NN2 of_IO Saxifraga_NP1 sarmentosa_NN1 (_( a_AT1 classic_NN1 '_GE guerrilla_NN1 '_GE growth_NN1 form_NN1 )_) to_TO encounter_VVI an_AT1 artificial_JJ vegetation_NN1 that_CST he_PPHS1 had_VHD constructed_VVN :_: '_GE Many_DA2 long_JJ pins_NN2 were_VBDR next_MD driven_VVN rather_RG close_JJ together_RL into_II the_AT sand_NN1 ,_, so_BCL21 as_BCL22 to_TO form_VVI a_AT1 crowd_NN1 in_II31 front_II32 of_II33 ..._... two_MC thin_JJ lateral_JJ branches_NN2 ;_; but_CCB these_DD2 easily_RR wound_VVD their_APPGE way_NN1 through_II the_AT crowd_NN1 ._. 
A_AT1 thick_JJ stolon_NN1 was_VBDZ much_RR delayed_VVN in_II its_APPGE passage_NN1 ;_; at_II one_MC1 place_VV0 it_PPH1 was_VBDZ forced_VVN to_TO turn_VVI at_II right_JJ angles_NN2 to_II its_APPGE former_DA course_NN1 ;_; at_II another_DD1 place_NN1 it_PPH1 could_VM not_XX pass_VVI through_II the_AT pins_NN2 ,_, and_CC the_AT hinder_VV0 part_NN1 became_VVD bowed_VVN ;_; it_PPH1 then_RT curved_VVD upwards_RL and_CC passed_VVD through_II an_AT1 opening_NN1 between_II the_AT upper_JJ part_NN1 of_IO some_DD pins_NN2 which_DDQ happen_VV0 to_TO diverge_VVI ;_; it_PPH1 then_RT descended_VVN and_CC finally_RR emerged_VVD through_II the_AT crowd_NN1 '_GE (_( Darwin_NP1 ,_, 1880_MC )_) ._. 
Another_DD1 approach_NN1 to_II the_AT study_NN1 of_IO variation_NN1 within_II populations_NN2 of_IO white_JJ clover_NN1 in_II the_AT Henfaes_NP2 field_NN1 was_VBDZ made_VVN by_II Burdon_NP1 (_( 1980_MC )_) ._. 
He_PPHS1 sampled_VVD 50_MC white_JJ clover_NN1 clones_NN2 from_II a_AT1 grid_NN1 covering_VVG the_AT whole_JJ field_NN1 ._. 
He_PPHS1 multiplied_VVD the_AT clones_NN2 in_II the_AT glasshouse_NN1 and_CC screened_VVD them_PPHO2 for_IF a_AT1 variety_NN1 of_IO characters_NN2 (_( Fig._NN1 16.3_MC )_) ._. 
These_DD2 included_VVN a_AT1 number_NN1 with_IW simple_JJ Mendelian_JJ inheritance_NN1 and_CC a_AT1 number_NN1 of_IO characters_NN2 of_IO agronomic_JJ importance_NN1 with_IW polygenically_RR controlled_VVN expression_NN1 ._. 
He_PPHS1 was_VBDZ able_JK to_TO use_VVI these_DD2 characters_NN2 to_TO produce_VVI identity_NN1 diagrams_NN2 that_CST distinguished_JJ and_CC '_GE finger-printed_NN1 '_GE each_DD1 clone_NN1 ._. 
The_AT 50_MC clones_NN2 differed_VVN on_II average_NN1 from_II one_PPX121 another_PPX122 in_II 3._MC 3_MC vegetative_JJ characters_NN2 ._. 
If_CS floral_JJ characters_NN2 were_VBDR included_VVN in_II the_AT comparison_NN1 the_AT average_JJ difference_NN1 between_II clones_NN2 was_VBDZ 5.4_MC characters_NN2 ._. 
(_( One_MC1 pair_NN of_IO clones_NN2 differed_VVN in_II 13_MC statistically_RR significant_JJ and_CC apparently_RR independent_JJ respects_NN2 !_! )_) 
Many_DA2 of_IO the_AT characters_NN2 considered_VVD had_VHD been_VBN shown_VVN by_II other_JJ workers_NN2 to_TO be_VBI of_IO selective_JJ importance_NN1 in_II white_JJ clover_NN1 or_CC another_DD1 species_NN of_IO Trifolium_NP1 (_( e.g._REX Cahn_NP1 &amp;_CC Harper_NP1 (_( 1976b_FO )_) had_VHD presented_VVN evidence_NN1 suggesting_VVG that_CST sheep_NN selected_VVN between_II leaf_NN1 marks_NN2 ;_; Dirzo_NP1 &amp;_CC Harper_NP1 (_( 1982a_FO )_) and_CC others_NN2 have_VH0 shown_VVN that_CST slugs_NN2 select_VV0 between_II cyanogenic_JJ and_CC acyanogenic_JJ forms_NN2 ;_; Black_NP1 (_( 1960_MC )_) had_VHD shown_VVN the_AT selective_JJ value_NN1 of_IO long_JJ petioles_NN2 )_) ._. 
The_AT polymorphisms_NN2 in_II the_AT Henfaes_NP2 population_NN1 were_VBDR not_XX exhausted_VVN in_II Burdon_NP1 's_GE study_NN1 ._. 
It_PPH1 has_VHZ now_RT been_VBN shown_VVN that_DD1 variation_NN1 in_II relative_JJ growth_NN1 rates_NN2 can_VM be_VBI added_VVN to_II the_AT list_NN1 (_( Burdon_NP1 &amp;_CC Harper_NP1 ,_, 1980_MC )_) ._. 
Natural_JJ populations_NN2 of_IO white_JJ clover_NN1 are_VBR polymorphic_JJ for_IF incompatibility_NN1 alleles_NN2 and_CC for_IF the_AT ability_NN1 to_TO form_VVI nitrogen_NN1 fixing_NN1 symbioses_VVZ with_IW strains_NN2 of_IO Rhizobium_NN1 but_CCB these_DD2 have_VH0 not_XX been_VBN looked_VVN at_II at_II Henfaes_NP2 ._. 
Berrington_NP1 (_( personal_JJ communication_NN1 )_) has_VHZ recently_RR shown_VVN that_CST clones_NN2 within_II the_AT field_NN1 differ_VV0 in_II their_APPGE ability_NN1 to_TO form_VVI endotrophic_JJ mycorrhizal_JJ associations_NN2 ._. 
The_AT polymorphism_NN1 that_CST is_VBZ found_VVN within_II white_JJ clover_NN1 populations_NN2 in_II the_AT field_NN1 represents_VVZ therefore_RR a_AT1 subtle_JJ (_( or_CC ?_? random_NN1 )_) variety_NN1 of_IO unique_JJ associations_NN2 of_IO apparently_RR selectively_RR important_JJ properties_NN2 ._. 
The_AT imagination_NN1 of_IO the_AT most_RGT extreme_JJ selectionist_NN1 is_VBZ stretched_VVN to_II breaking_NN1 point_NN1 by_II such_DA a_AT1 situation_NN1 ._. 
Evidence_NN1 for_IF local_JJ specialization_NN1 within_II white_JJ clover_NN1 Plants_NN2 that_CST are_VBR capable_JJ of_IO clonal_JJ growth_NN1 offer_VV0 peculiar_JJ opportunities_NN2 for_IF testing_VVG the_AT extent_NN1 to_II which_DDQ particular_JJ genets_NN2 are_VBR locally_RR specialized_VVN ._. 
A_AT1 plant_NN1 may_VM be_VBI sampled_VVN from_II the_AT field_NN1 ,_, multiplied_VVD clonally_RR and_CC the_AT clonal_JJ products_NN2 (_( genetic_JJ identities_NN2 )_) can_VM then_RT be_VBI reinserted_VVN into_II the_AT field_NN1 ,_, both_RR in_II the_AT places_NN2 from_II which_DDQ the_AT clones_NN2 originally_RR came_VVD and_CC into_II other_JJ places_NN2 ._. 
Plants_NN2 of_IO the_AT same_DA genotype_NN1 can_VM then_RT be_VBI tested_VVN in_II different_JJ environments_NN2 ._. 
Turkington_NP1 made_VVD such_DA an_AT1 experiment_NN1 with_IW white_JJ clover_NN1 in_II the_AT field_NN1 at_II Henfaes_NP2 (_( Turkington_NP1 &amp;_CC Harper_NP1 ,_, 1979b_FO )_) ._. 
Clones_NN2 of_IO white_JJ clover_NN1 were_VBDR sampled_VVN from_II within_II patches_NN2 in_II the_AT field_NN1 dominated_VVN by_II each_DD1 of_IO four_MC common_JJ grasses_NN2 ,_, Lolium_NP1 perenne_NN1 ,_, Holcus_FW lanatus_NN1 ,_, Agrostis_NP1 tenuis_NN1 and_CC Cynosurus_NP1 cristatus_NN1 ._. 
The_AT clones_NN2 were_VBDR multiplied_VVN in_II the_AT glasshouse_NN1 and_CC then_RT transplanted_VVD back_RP into_II patches_NN2 of_IO the_AT field_NN1 dominated_VVN by_II the_AT four_MC grass_NN1 species_NN ._. 
The_AT performance_NN1 of_IO the_AT transplants_NN2 was_VBDZ measured_VVN by_II vegetative_JJ growth_NN1 expressed_VVN as_CSA dry_JJ weight_NN1 at_II harvest_NN1 after_II twelve_MC months_NNT2 ._. 
The_AT results_NN2 are_VBR shown_VVN in_II Fig._NN1 16.4_MC ._. 
Over_II the_AT whole_JJ experiment_NN1 clones_NN2 of_IO clover_NN1 that_CST were_VBDR returned_VVN to_II their_APPGE original_JJ grass_NN1 associate_NN1 made_VVD more_DAR growth_NN1 than_CSN those_DD2 introduced_VVN to_II alien_JJ sites_NN2 (_( significant_JJ at_II P_ZZ1 &lt;_FO 0.001_MC )_) ._. 
The_AT clover_NN1 clones_NN2 had_VHD also_RR been_VBN introduced_VVN into_II sites_NN2 from_II which_DDQ the_AT existing_JJ vegetation_NN1 had_VHD been_VBN denuded_VVN by_II treatment_NN1 with_IW the_AT paraquat_NN1 herbicide_NN1 ._. 
Some_DD of_IO the_AT '_GE principal_JJ diagonal_JJ effect_NN1 '_GE remained_VVD ,_, though_CS the_AT difference_NN1 in_II yield_NN1 between_II clones_NN2 returned_VVN to_II their_APPGE site_NN1 and_CC those_DD2 returned_VVN to_II alien_JJ sites_NN2 was_VBDZ now_RT significant_JJ only_RR at_II P_ZZ1 &lt;_FO 0.05_MC ._. 
Turkington_NP1 made_VVD a_AT1 further_JJR experiment_NN1 in_II which_DDQ he_PPHS1 introduced_VVD the_AT four_MC clone_NN1 types_NN2 of_IO white_JJ clover_NN1 into_II pure_JJ swards_NN2 of_IO the_AT four_MC grass_NN1 species_NN that_CST had_VHD been_VBN sown_VVN on_II soil_NN1 sampled_VVN from_II the_AT experimental_JJ field_NN1 ._. 
This_DD1 part_NN1 of_IO the_AT experiment_NN1 was_VBDZ designed_VVN to_TO remove_VVI possible_JJ place-to-place_JJ variations_NN2 in_II soil_NN1 conditions_NN2 in_II the_AT studied_JJ field_NN1 from_II the_AT comparison_NN1 ._. 
The_AT yield_NN1 of_IO clones_NN2 grown_VVN with_IW the_AT grass_NN1 species_NN from_II which_DDQ they_PPHS2 had_VHD originally_RR been_VBN sampled_VVN again_RT exceeded_VVD that_CST made_VVD when_CS they_PPHS2 were_VBDR grown_VVN in_II an_AT1 '_GE alien_NN1 '_GE sward_NN1 ,_, P_ZZ1 &lt;_FO 0.00001_MC ._. 
It_PPH1 is_VBZ difficult_JJ to_TO interpret_VVI the_AT results_NN2 of_IO this_DD1 experiment_NN1 as_CSA representing_VVG anything_RR21 but_RR22 evidence_NN1 of_IO precise_JJ specialization_NN1 of_IO clover_NN1 clones_NN2 in_II their_APPGE ability_NN1 to_TO grow_VVI in_II31 association_II32 with_II33 particular_JJ grass_NN1 neighbours_NN2 ._. 
It_PPH1 suggests_VVZ that_CST ,_, within_II the_AT pasture_NN1 ,_, strains_NN2 of_IO white_JJ clover_NN1 have_VH0 been_VBN selected_VVN by_II competitive_JJ interaction_NN1 with_IW associated_JJ grasses_NN2 and_CC that_DD1 different_JJ species_NN of_IO grass_NN1 contribute_VV0 to_II the_AT diversifying_NN1 or_CC disruptive_JJ selection_NN1 operating_NN1 upon_II the_AT population_NN1 of_IO white_JJ clover_NN1 ._. 
Some_DD ,_, at_RR21 least_RR22 ,_, of_IO the_AT variation_NN1 within_II the_AT white_JJ clover_NN1 populations_NN2 thus_RR appears_VVZ to_TO be_VBI directly_RR interpretable_JJ in_II31 terms_II32 of_II33 attributes_NN2 contributing_VVG to_TO present_VVI fitness_NN1 ._. 
It_PPH1 is_VBZ a_AT1 very_RG Darwinian_JJ interpretation_NN1 to_TO suggest_VVI that_CST the_AT grass_NN1 neighbours_NN2 may_VM be_VBI primary_JJ forces_NN2 selecting_VVG and_CC diversifying_VVG the_AT clover_NN1 populations_NN2 ._. 
Hill_NP1 (_( 1976_MC )_) grew_VVD a_AT1 single_JJ clone_NN1 of_IO white_JJ clover_NN1 with_IW a_AT1 variety_NN1 of_IO clones_NN2 of_IO Lolium_NP1 perenne_NN1 ._. 
Quite_RG distinct_JJ phenotypic_JJ modifications_NN2 were_VBDR elicited_VVN from_II the_AT clone_NN1 by_II the_AT different_JJ ryegrass_NN1 strains_NN2 ._. 
If_CS different_JJ strains_NN2 of_IO Lolium_NP1 perenne_NN1 produce_VV0 different_JJ phenotypes_NN2 from_II the_AT same_DA clone_NN1 of_IO white_JJ clover_NN1 ,_, it_PPH1 is_VBZ difficult_JJ to_TO escape_VVI the_AT conclusion_NN1 that_CST different_JJ species_NN of_IO grass_NN1 are_VBR even_RR more_RGR likely_JJ to_TO exert_VVI different_JJ selective_JJ pressures_NN2 within_II populations_NN2 of_IO white_JJ clover_NN1 ._. 
It_PPH1 is_VBZ not_XX easy_JJ to_TO measure_VVI and_CC describe_VVI just_RR how_RRQ the_AT different_JJ clones_NN2 of_IO white_JJ clover_NN1 differ_VV0 in_II their_APPGE reaction_NN1 to_II different_JJ neighbouring_JJ grass_NN1 species_NN or_CC forms_NN2 ._. 
Survivorship_NN1 and_CC dry_JJ matter_NN1 production_NN1 are_VBR very_RG gross_JJ measures_NN2 of_IO a_AT1 plant_NN1 's_GE reaction_NN1 to_II different_JJ types_NN2 of_IO neighbour_NN1 ._. 
We_PPIS2 have_VH0 ,_, at_RR21 present_RR22 ,_, no_AT real_JJ indication_NN1 of_IO the_AT manner_NN1 in_II which_DDQ ecological_JJ compatibility_NN1 (_( ecological_JJ combining_JJ ability_NN1 )_) between_II particular_JJ strains_NN2 of_IO white_JJ clover_NN1 and_CC particular_JJ pasture_NN1 grasses_NN2 is_VBZ accomplished_VVN ._. 
It_PPH1 may_VM represent_VVI subtle_JJ differences_NN2 in_II growth_NN1 cycle_NN1 or_CC growth_NN1 form_NN1 or_CC more_RGR complex_JJ interactions_NN2 involving_VVG the_AT soil_NN1 microflora_NN1 ,_, perhaps_RR the_AT mycorrhizae_NN2 ._. 
There_EX may_VM be_VBI subtleties_NN2 of_IO interaction_NN1 below_II the_AT soil_NN1 surface_NN1 of_IO which_DDQ we_PPIS2 know_VV0 little_JJ or_CC nothing_PN1 ._. 
The_AT hazards_NN2 in_II the_AT life_NN1 of_IO a_AT1 plant_NN1 in_II the_AT field_NN1 are_VBR not_XX only_RR those_DD2 of_IO competition_NN1 from_II neighbours_NN2 ,_, though_CS it_PPH1 may_VM be_VBI these_DD2 that_CST are_VBR the_AT most_RGT relentless_JJ ._. 
Hazards_NN2 in_II the_AT life_NN1 of_IO a_AT1 plant_NN1 in_II the_AT field_NN1 Some_DD of_IO the_AT hazards_NN2 to_II the_AT life_NN1 of_IO a_AT1 plant_NN1 in_II the_AT field_NN1 can_VM be_VBI measured_VVN by_II studying_VVG the_AT fate_NN1 of_IO individual_JJ leaves_NN2 or_CC flowers_NN2 or_CC seeds_NN2 ._. 
An_AT1 attempt_NN1 to_TO catalogue_VVI and_CC quantify_VVI these_DD2 hazards_NN2 in_II the_AT field_NN1 at_II Henfaes_NP2 was_VBDZ made_VVN by_II Peters_NP (_( 1980_MC )_) who_PNQS included_VVD white_JJ clover_NN1 amongst_II the_AT species_NN that_CST he_PPHS1 studied_VVD ._. 
He_PPHS1 marked_VVD young_JJ leaves_NN2 as_CSA they_PPHS2 began_VVD to_TO expand_VVI and_CC then_RT followed_VVD their_APPGE fate_NN1 by_II repeated_JJ observation_NN1 ._. 
From_II this_DD1 he_PPHS1 could_VM obtain_VVI survivorship_NN1 curves_NN2 for_IF cohorts_NN2 of_IO leaves_NN2 born_VVN in_II the_AT same_DA time_NNT1 period_NN1 and_CC record_VV0 some_DD of_IO the_AT causes_NN2 of_IO death_NN1 or_CC damage_NN1 within_II the_AT populations_NN2 (_( Fig._NN1 16.5_MC )_) ._. 
Some_DD leaf_NN1 predators_NN2 leave_VV0 tell-tale_JJ records_NN2 of_IO their_APPGE activity_NN1 ._. 
In_RR21 particular_RR22 ,_, grazing_VVG molluscs_NN2 leave_VV0 characteristic_JJ erosions_NN2 from_II a_AT1 leaf_NN1 edge_NN1 ;_; birds_NN2 ,_, particularly_RR the_AT wood-pigeon_NN1 ,_, feed_VV0 on_II clover_NN1 and_CC often_RR leave_VV0 characteristic_JJ beak-marks_NN2 ;_; weevils_NN2 remove_VV0 circles_NN2 of_IO tissue_NN1 ,_, often_RR leaving_VVG the_AT upper_JJ epidermis_NN1 intact_JJ ;_; sheep_NN (_( causing_VVG damage_NN1 probably_RR indistinguishable_JJ from_II that_DD1 caused_VVN by_II rabbits_NN2 )_) remove_VV0 whole_JJ leaves_NN2 ,_, leaving_VVG torn_JJ petioles_NN2 or_CC leave_VV0 their_APPGE bite_NN1 marks_NN2 on_II the_AT leaflets_NN2 that_CST remain_VV0 ._. 
Tracking_VVG the_AT fate_NN1 of_IO individual_JJ leaves_NN2 immediately_RR reveals_VVZ a_AT1 number_NN1 of_IO other_JJ hazards_NN2 ._. 
Leaves_NN2 may_VM be_VBI submerged_VVN under_II a_AT1 dropping_NN1 of_IO dung_NN1 ,_, soused_VVN in_II a_AT1 downpour_NN1 of_IO urine_NN1 ,_, trodden_VVN on_RP ,_, pulled_VVN into_II the_AT ground_NN1 by_II earthworms_NN2 (_( further_RRR shades_NN2 of_IO Darwin_NP1 )_) or_CC damaged_VVN by_II frost_NN1 ._. 
The_AT frequency_NN1 of_IO these_DD2 various_JJ events_NN2 in_RP ,_, or_CC ending_NN1 ,_, the_AT life_NN1 of_IO a_AT1 leaf_NN1 are_VBR shown_VVN in_II Table_NN1 16.1_MC ._. 
Grazing_JJ animals_NN2 are_VBR ,_, however_RR ,_, the_AT major_JJ hazards_NN2 for_IF a_AT1 leaf_NN1 though_CS all_DB leaves_NN2 in_II a_AT1 pasture_NN1 are_VBR not_XX equally_RR at_II risk_NN1 ._. 
Weevils_NN2 bite_VV0 holes_NN2 in_II the_AT leaves_NN2 of_IO white_JJ clover_NN1 and_CC of_IO Ranunculus_NP1 species_NN but_CCB the_AT relative_JJ severity_NN1 of_IO attacks_NN2 on_II Trifolium_NP1 and_CC Ranunculus_NP1 change_NN1 through_II the_AT season_NNT1 ,_, Trifolium_NP1 being_VBG more_RRR attacked_VVN in_II early_JJ ,_, and_CC Ranunculus_NN1 in_II late_JJ ,_, summer_NNT1 ._. 
Fig._NN1 16.6_MC shows_VVZ the_AT relative_JJ proportion_NN1 of_IO the_AT leaf_NN1 population_NN1 that_CST suffered_VVD damage_NN1 from_II leaf_NN1 grazers_NN2 in_II populations_NN2 of_IO T._NP1 repens_VVZ and_CC R._NP1 repens_VVZ ._. 
Surprisingly_RR ,_, the_AT leaves_NN2 of_IO white_JJ clover_NN1 suffered_VVD proportionately_RR much_DA1 less_DAR from_II grazing_VVG by_II sheep_NN than_CSN did_VDD those_DD2 of_IO R._NP1 repens_VVZ ,_, but_CCB leaves_NN2 of_IO T._NP1 repens_VVZ suffered_VVN much_DA1 more_DAR from_II both_RR slugs_NN2 and_CC weevils_NN2 (_( except_CS towards_II the_AT end_NN1 of_IO the_AT growing_JJ season_NNT1 )_) ._. 
Grazing_VVG by_II molluscs_NN2 figured_VVD so_RG strongly_RR among_II the_AT hazards_NN2 to_II a_AT1 clover_NN1 leaf_NN1 that_CST it_PPH1 seems_VVZ reasonable_JJ to_TO expect_VVI that_DD1 ,_, in_II those_DD2 years_NNT2 when_RRQ slugs_NN2 or_CC snails_NN2 were_VBDR abundant_JJ ,_, they_PPHS2 may_VM act_VVI as_RG important_JJ selective_JJ forces_NN2 within_II clover_NN1 populations_NN2 ._. 
White_JJ clover_NN1 is_VBZ polymorphic_JJ for_IF the_AT presence_NN1 or_CC absence_NN1 of_IO cyanogenic_JJ glucosinolates_NN2 and_CC is_VBZ also_RR polymorphic_JJ for_IF the_AT beta_NN1 glucosidases_VVZ that_CST release_VV0 HCN_NP1 from_II glucosinolates_NN2 when_RRQ a_AT1 leaf_NN1 is_VBZ damaged_VVN ._. 
There_EX is_VBZ considerable_JJ variation_NN1 in_II the_AT extent_NN1 to_II which_DDQ cyanogenic_JJ properties_NN2 are_VBR expressed_VVN and_CC there_EX is_VBZ some_DD seasonal_JJ and_CC perhaps_RR other_JJ causes_NN2 of_IO variation_NN1 in_II expression_NN1 ._. 
Nevertheless_RR ,_, it_PPH1 is_VBZ possible_JJ to_TO classify_VVI plants_NN2 in_II the_AT field_NN1 by_II taking_VVG leaf_NN1 samples_NN2 and_CC performing_VVG appropriate_JJ tests_NN2 (_( see_VV0 Dirzo_NN1 &amp;_CC Harper_NP1 ,_, 1982a_FO )_) and_CC to_TO categorize_VVI the_AT plants_NN2 into_II four_MC groups_NN2 Ac_NN1 Li_NP1 ,_, Ac_NN1 li_MC ,_, ac_NN1 Li_NP1 ,_, ac_NN1 li_MC ._. 
After_CS a_AT1 period_NN1 of_IO exposure_NN1 to_II grazing_VVG one_PN1 can_VM then_RT test_VVI for_IF the_AT frequency_NN1 of_IO the_AT various_JJ types_NN2 of_IO damage_NN1 to_II clover_NN1 leaves_VVZ with_IW the_AT different_JJ genotypes_NN2 and_CC afterwards_RT reconfirm_VV0 the_AT cyanogenic_JJ or_CC acyanogenic_JJ status_NN1 of_IO the_AT plant_NN1 (_( Fig._NN1 16.7_MC )_) ._. 
There_EX have_VH0 been_VBN many_DA2 studies_NN2 of_IO selection_NN1 by_II molluscs_NN2 on_II cyanogenic_JJ and_CC acyanogenic_JJ morphs_NN2 of_IO white_JJ clover_NN1 under_II laboratory_NN1 or_CC other_JJ controlled_JJ conditions_NN2 ._. 
It_PPH1 seemed_VVD that_CST it_PPH1 might_VM be_VBI possible_JJ to_TO relate_VVI the_AT variation_NN1 in_II the_AT polymorphism_NN1 to_TO slug_VVI density_NN1 in_II the_AT Henfaes_NP2 field_NN1 ._. 
The_AT density_NN1 of_IO slugs_NN2 was_VBDZ determined_VVN at_II sites_NN2 arranged_VVN on_II a_AT1 grid_NN1 across_II the_AT field_NN1 at_II Henfaes_NP2 ._. 
Dirzo_NP1 (_( 1982b_FO )_) used_VVD trend-surface_JJ analysis_NN1 to_TO draw_VVI contours_NN2 of_IO mollusc_NN1 density_NN1 (_( see_VV0 Fig._NN1 16.8_MC )_) and_CC added_VVD some_DD further_JJR information_NN1 from_II visual_JJ inspection_NN1 of_IO the_AT field_NN1 ._. 
Most_RGT notably_RR ,_, he_PPHS1 added_VVD one_MC1 big_JJ and_CC two_MC small_JJ islands_NN2 (_( shown_VVN in_II Fig._NN1 16.8_MC as_CSA having_VHG high_JJ and_CC very_RG high_JJ slug_NN1 densities_NN2 )_) which_DDQ were_VBDR patches_NN2 of_IO nettle_NN1 ,_, Urtica_NP1 dioica_NN1 ._. 
Slugs_NN2 tend_VV0 to_TO concentrate_VVI in_II such_DA refuges_NN2 ,_, presumably_RR because_CS they_PPHS2 give_VV0 protection_NN1 from_II desiccation_NN1 ._. 
He_PPHS1 then_RT determined_VVD the_AT cyanogenesis_NN1 category_NN1 of_IO the_AT clover_NN1 plant_NN1 nearest_II21 to_II22 each_DD1 grid_NN1 intersection_NN1 ._. 
Table_NN1 16.2_MC shows_VVZ the_AT distribution_NN1 of_IO the_AT different_JJ glucosinolate_NN1 morphs_NN2 of_IO T._NP1 repens_VVZ between_II areas_NN2 with_IW different_JJ densities_NN2 of_IO active_JJ molluscs_NN2 ._. 
There_EX is_VBZ a_AT1 clear_JJ excess_NN1 over_II expectation_NN1 of_IO cyanogenic_JJ forms_NN2 in_II the_AT areas_NN2 of_IO high_JJ and_CC very_RG high_JJ mollusc_NN1 density_NN1 and_CC of_IO acyanogenic_JJ forms_NN2 in_II the_AT areas_NN2 of_IO very_RG low_JJ mollusc_NN1 density_NN1 ._. 
It_PPH1 appears_VVZ that_CST some_DD at_RR21 least_RR22 of_IO the_AT variation_NN1 in_II the_AT cyanogenesis_NN1 polymorphism_NN1 over_II the_AT field_NN1 can_VM be_VBI explained_VVN as_CSA local_JJ micro-evolution_NN1 in_II31 response_II32 to_II33 locally_RR patchy_JJ selection._NNU pp._NNU2 337338_MC :_: FIGURES_NN2 Two_MC strands_NN2 of_IO evidence_NN1 ,_, that_CST from_II the_AT reciprocal_JJ transplanting_NN1 of_IO clover_NN1 into_II the_AT neighbourhood_NN1 of_IO different_JJ grasses_NN2 and_CC that_CST from_II the_AT study_NN1 of_IO the_AT distribution_NN1 of_IO cyanogenic_JJ properties_NN2 and_CC the_AT distribution_NN1 of_IO slugs_NN2 ,_, allow_VV0 an_AT1 easy_JJ interpretation_NN1 in_II31 terms_II32 of_II33 immediate_JJ and_CC present_JJ selective_JJ forces_NN2 ._. 
How_RGQ far_RR this_DD1 interpretation_NN1 can_VM be_VBI extended_VVN to_II the_AT whole_JJ gamut_NN1 of_IO characters_NN2 for_IF which_DDQ Burdon_NP1 had_VHD shown_VVN the_AT populations_NN2 to_TO be_VBI polymorphic_JJ must_VM be_VBI very_RG doubtful_JJ ._. 
Certainly_RR almost_RR all_DB of_IO the_AT characters_NN2 that_CST Burdon_NP1 lists_NN2 have_VH0 been_VBN shown_VVN to_TO be_VBI of_IO selective_JJ importance_NN1 either_RR in_II clover_NN1 or_CC in_II some_DD related_JJ species_NN ,_, though_CS sometimes_RT under_II very_RG specialized_JJ circumstances_NN2 ._. 
The_AT scientific_JJ method_NN1 may_VM sometimes_RT mislead_VVI ._. 
We_PPIS2 commonly_RR test_VV0 for_IF the_AT selective_JJ value_NN1 of_IO a_AT1 particular_JJ feature_NN1 by_II holding_VVG background_NN1 variation_NN1 of_IO both_RR genotype_NN1 and_CC environment_NN1 at_II a_AT1 minimum_NN1 ._. 
We_PPIS2 thereby_RR maximise_VV0 our_APPGE chance_NN1 of_IO demonstrating_VVG what_DDQ we_PPIS2 are_VBR looking_VVG for_IF ._. 
The_AT real_JJ measure_NN1 should_VM be_VBI whether_CSW selection_NN1 is_VBZ significant_JJ against_II normal_JJ levels_NN2 of_IO background_NN1 variation_NN1 ._. 
This_DD1 is_VBZ why_RRQ it_PPH1 was_VBDZ important_JJ to_TO test_VVI the_AT effects_NN2 of_IO cyanogenesis_NN1 and_CC reaction_NN1 to_II neighbours_NN2 in_II the_AT field_NN1 ._. 
It_PPH1 is_VBZ difficult_JJ to_TO believe_VVI that_CST any_DD of_IO the_AT characters_NN2 examined_VVN by_II Burdon_NP1 could_VM be_VBI selectively_RR neutral_JJ ._. 
However_RR ,_, the_AT contribution_NN1 of_IO each_DD1 property_NN1 to_II fitness_NN1 must_VM vary_VVI dramatically_RR from_II year_NNT1 to_II year_NNT1 as_II31 well_II32 as_II33 from_II place_NN1 to_II place_NN1 within_II the_AT field_NN1 ._. 
Most_DAT winters_NNT2 at_II Henfaes_NP2 (_( only_RR 400_MC m_NNO from_II the_AT sea_NN1 )_) are_VBR mild_JJ and_CC frost_NN1 is_VBZ rare_JJ ._. 
Occasionally_RR ,_, as_CSA in_II the_AT winter_NNT1 of_IO 1982_MC ,_, there_EX is_VBZ severe_JJ frost_NN1 ._. 
Populations_NN2 of_IO molluscs_NN2 fluctuate_VV0 wildly_RR from_II year_NNT1 to_II year_NNT1 in_II North_ND1 Wales_NP1 ._. 
In_II some_DD years_NNT2 spring_NN1 growth_NN1 of_IO the_AT sward_NN1 is_VBZ vigorous_JJ and_CC exceeds_VVZ the_AT capacity_NN1 of_IO sheep_NN and_CC the_AT other_JJ grazing_JJ animals_NN2 to_TO keep_VVI it_PPH1 fully_RR grazed_VVN ._. 
In_II other_JJ years_NNT2 ,_, as_CSA in_II the_AT spring_NN1 of_IO 1982_MC ,_, a_AT1 protracted_JJ spring_NN1 drought_NN1 slowed_VVD the_AT growth_NN1 of_IO the_AT sward_NN1 and_CC it_PPH1 became_VVD tightly_RR graze_VV0 ._. 
A_AT1 severe_JJ drought_NN1 is_VBZ not_XX a_AT1 common_JJ feature_NN1 on_II the_AT field_NN1 but_CCB when_CS it_PPH1 occurs_VVZ it_PPH1 may_VM be_VBI in_II any_DD month_NNT1 from_II April_NPM1 to_II September_NPM1 ._. 
During_II the_AT period_NN1 of_IO our_APPGE observations_NN2 we_PPIS2 have_VH0 detected_VVN three_MC significant_JJ leaf_NN1 pathogens_NN2 on_II white_JJ clover_NN1 in_II the_AT field_NN1 ,_, Uromyces_VVZ trifolii_NN2 ,_, Cymadothea_NP1 trifolii_NN2 and_CC Pseudopeziza_NP1 trifolii_NN2 ._. 
It_PPH1 seems_VVZ unlikely_JJ that_CST these_DD2 three_MC diseases_NN2 attack_VV0 with_IW equal_JJ intensity_NN1 in_II all_DB seasons_NNT2 and_CC in_II all_DB years_NNT2 ._. 
In_II a_AT1 field_NN1 that_CST is_VBZ patchy_JJ in_II space_NN1 and_CC time_NNT1 ,_, be_VBI it_PPH1 ever_RG21 so_RG22 small_JJ ,_, we_PPIS2 may_VM expect_VVI that_CST the_AT populations_NN2 of_IO a_AT1 species_NN such_II21 as_II22 white_JJ clover_NN1 will_VM ,_, at_II any_DD time_NNT1 ,_, reflect_VV0 selective_JJ forces_NN2 from_II its_APPGE past_NN1 ._. 
The_AT genotypic_JJ composition_NN1 of_IO the_AT population_NN1 may_VM in_II some_DD cases_NN2 dimly_RR reflect_VV0 forces_NN2 that_CST operated_VVD twenty_MC or_CC thirty_MC years_NNT2 ago_RA ._. 
Other_JJ selective_JJ forces_NN2 may_VM have_VHI operated_VVN quite_RG recently_RR and_CC left_VVN a_AT1 strong_JJ memory_NN1 or_CC image_NN1 in_II the_AT structure_NN1 of_IO the_AT population_NN1 's_GE genetics_NN1 ._. 
If_CS this_DD1 is_VBZ the_AT case_NN1 ,_, we_PPIS2 would_VM expect_VVI to_TO find_VVI only_RR a_AT1 few_DA2 of_IO the_AT many_DA2 polymorphisms_NN2 readily_RR interpretable_JJ as_CSA responsive_JJ to_TO present_VVI proximal_JJ selective_JJ forces_NN2 ._. 
Much_DA1 of_IO the_AT polymorphism_NN1 could_VM be_VBI transient_JJ and_CC ,_, without_IW an_AT1 even_RR more_RGR detailed_JJ history_NN1 of_IO the_AT field_NN1 ,_, uninterpretable_JJ ._. 
It_PPH1 is_VBZ doubtful_JJ whether_CSW such_DA an_AT1 explanation_NN1 of_IO naturally_RR occurring_VVG polymorphism_NN1 could_VM be_VBI tested_VVN without_IW long-term_JJ ,_, detailed_JJ recording_NN1 ,_, not_XX only_RR of_IO the_AT variety_NN1 of_IO genetic_JJ changes_NN2 occurring_VVG within_II clover_NN1 populations_NN2 ,_, but_CCB at_II the_AT same_DA time_NNT1 of_IO a_AT1 detailed_JJ recording_NN1 of_IO the_AT known_JJ hazards_NN2 in_II the_AT life_NN1 of_IO the_AT clover_NN1 plant_NN1 over_II the_AT seasons_NNT2 and_CC the_AT years_NNT2 ._. 
Conclusions_NN2 The_AT studies_NN2 that_CST I_PPIS1 have_VH0 described_VVN ,_, concentrated_VVN in_II the_AT field_NN1 at_II Henfaes_NP2 ,_, are_VBR now_RT being_VBG extended_VVN by_II deliberate_JJ experimentation_NN1 within_II the_AT field_NN1 ._. 
We_PPIS2 are_VBR destroying_VVG the_AT site_NN1 as_II a_AT1 long-term_JJ study_NN1 on_II a_AT1 supposedly_RR stable_JJ system_NN1 by_II introducing_VVG a_AT1 variety_NN1 of_IO perturbations_NN2 such_II21 as_II22 transplant_NN1 experiments_NN2 ,_, the_AT creation_NN1 of_IO islands_NN2 for_IF invasion_NN1 and_CC further_JJR perturbations_NN2 are_VBR planned_VVN ._. 
The_AT study_NN1 has_VHZ involved_VVN a_AT1 curious_JJ concentration_NN1 of_IO effort_NN1 in_II one_MC1 very_RG specialized_JJ environment_NN1 ._. 
The_AT type_NN1 of_IO observations_NN2 that_CST have_VH0 been_VBN made_VVN have_VHI been_VBN quintessentially_RR Darwinian_JJ ._. 
Another_DD1 great_JJ naturalist_NN1 ,_, Thoreau_NP1 ,_, has_VHZ focussed_VVN attention_NN1 at_II the_AT same_DA scale_NN1 :_: '_GE Nature_NN1 will_VM bear_VVI the_AT closest_JJT inspection_NN1 ._. 
She_PPHS1 invites_VVZ us_PPIO2 to_TO lay_VVI our_APPGE eye_NN1 level_NN1 with_IW her_APPGE smallest_JJT leaf_NN1 ,_, and_CC take_VV0 an_AT1 insect-view_NN1 of_IO its_APPGE plain'_NN1 ._. 
If_CS we_PPIS2 are_VBR to_TO see_VVI evolutionary_JJ processes_NN2 in_II action_NN1 in_II plant_NN1 communities_NN2 and_CC the_AT proximal_JJ events_NN2 determining_VVG their_APPGE character_NN1 we_PPIS2 must_VM focus_VVI our_APPGE attention_NN1 away_II21 from_II22 an_AT1 anthropomorphic_JJ scale_NN1 of_IO acres_NNU2 or_CC square_JJ metres_NNU2 and_CC onto_II a_AT1 scale_NN1 appropriate_JJ to_II the_AT organisms_NN2 with_IW which_DDQ we_PPIS2 are_VBR concerned_JJ ._. 
The_AT appropriate_JJ scale_NN1 is_VBZ determined_VVN by_II the_AT organism_NN1 and_CC not_XX by_II us_PPIO2 ._. 
It_PPH1 will_VM be_VBI different_JJ for_IF different_JJ species_NN ._. 
We_PPIS2 ask_VV0 for_IF a_AT1 plant_NN1 's_GE eye_NN1 view_NN1 of_IO life_NN1 and_CC death_NN1 in_II a_AT1 sward_NN1 and_CC hope_VV0 ultimately_RR to_TO be_VBI able_JK to_TO collect_VVI these_DD2 reductionist_NN1 observations_NN2 into_II statements_NN2 about_II the_AT population_NN1 ,_, the_AT species_NN or_CC even_RR possibly_RR the_AT community_NN1 ._. 
I_PPIS1 doubt_VV0 if_CSW it_PPH1 is_VBZ possible_JJ to_TO hold_VVI the_AT view_NN1 of_IO Margalef_NP1 (_( 1968_MC )_) that_DD1 '_VBZ Relevant_JJ evidence_NN1 does_VDZ not_XX consist_VVI of_IO a_AT1 massive_JJ accumulation_NN1 of_IO trivia_NN1 '_GE and_CC reconcile_VV0 it_PPH1 with_IW his_58 '_GE Ecology_NN1 ..._... is_VBZ the_AT study_NN1 of_IO systems_NN2 at_II a_AT1 level_NN1 at_II which_DDQ individuals_NN2 or_CC whole_JJ organisms_NN2 may_VM be_VBI considered_VVN elements_NN2 of_IO interaction_NN1 ..._... '_GE ._. 
It_PPH1 was_VBDZ ,_, indeed_RR ,_, from_II the_AT massive_JJ accumulation_NN1 of_IO trivia_NN1 and_CC tiny_JJ details_NN2 ,_, that_CST Darwin_NP1 assembled_VVD the_AT evidence_NN1 for_IF The_AT Origin_NN1 of_IO Species_NN ._. 
In_II a_AT1 volume_NN1 commemorating_VVG Darwin_NP1 's_GE death_NN1 ,_, I_PPIS1 have_VH0 tried_VVN to_TO show_VVI how_RRQ his_APPGE way_NN1 of_IO looking_VVG at_II the_AT behaviour_NN1 of_IO individual_JJ plants_NN2 in_II nature_NN1 can_VM be_VBI extended_VVN ._. 
A_AT1 hundred_NNO years_NNT2 after_II his_APPGE death_NN1 his_APPGE approach_NN1 seems_VVZ more_RGR relevant_JJ to_II botanical_JJ studies_NN2 than_CSN it_PPH1 has_VHZ ever_RR been_VBN ._. 
This_DD1 part_NN1 of_IO his_APPGE intellectual_JJ legacy_NN1 has_VHZ not_XX yet_RR been_VBN fully_RR invested_VVN ._. 
A_AT1 part_NN1 of_IO the_AT legacy_NN1 ,_, however_RR ,_, ceases_VVZ to_TO bear_VVI interest_NN1 ._. 
He_PPHS1 was_VBDZ writing_VVG in_II the_AT Origin_NN1 for_IF readers_NN2 most_DAT of_IO whom_PNQO were_VBDR steeped_VVN in_II Victorian_JJ optimism_NN1 ,_, religion_NN1 and_CC the_AT romantic_JJ movement_NN1 ._. 
It_PPH1 was_VBDZ necessary_JJ in_II 1859_MC to_TO write_VVI about_II the_AT process_NN1 of_IO evolution_NN1 as_CS21 if_CS22 it_PPH1 produced_VVD the_AT best_JJT of_IO all_DB possible_JJ worlds_NN2 ,_, a_AT1 substitute_NN1 for_IF the_AT finger_NN1 of_IO the_AT Almighty_JJ at_II work_NN1 ._. 
If_CS the_AT process_NN1 of_IO evolution_NN1 had_VHD not_XX been_VBN presented_VVN in_II this_DD1 way_NN1 (_( though_CS with_IW careful_JJ caveats_NN2 )_) it_PPH1 is_VBZ very_RG questionable_JJ whether_CSW it_PPH1 could_VM have_VHI been_VBN accepted_VVN so_RG rapidly_RR by_II Victorian_JJ society_NN1 ._. 
It_PPH1 was_VBDZ then_RT appropriate_VV0 to_TO show_VVI how_RRQ '_" ..._... from_II so_RG simple_JJ a_AT1 beginning_NN1 endless_JJ forms_NN2 most_RGT beautiful_JJ and_CC most_RGT wonderful_JJ have_VH0 been_VBN ,_, and_CC are_VBR being_VBG evolved_JJ '_GE ._. 
But_CCB '_GE beauty_NN1 '_GE and_CC '_GE wonder_NN1 '_GE are_VBR in_II the_AT eye_NN1 of_IO the_AT beholder_NN1 and_CC that_DD1 eye_NN1 has_VHZ itself_PPX1 evolved_VVN ._. 
The_AT teleology_NN1 of_IO evolution_NN1 as_II a_AT1 goal-seeking_JJ activity_NN1 persists_VVZ in_II indefensible_JJ form_NN1 a_AT1 hundred_NNO years_NNT2 later_RRR in_II the_AT writing_NN1 of_IO biologists_NN2 ._. 
This_DD1 particular_JJ heritage_NN1 may_VM be_VBI a_AT1 millstone_NN1 around_II the_AT neck_NN1 of_IO scientific_JJ natural_JJ history_NN1 ._. 
Most_RGT particularly_RR ,_, it_PPH1 harms_VVZ biology_NN1 as_II a_AT1 means_NN of_IO teaching_NN1 science_NN1 to_II the_AT young_JJ (_( Harper_NP1 ,_, 1982_MC )_) ._. 
Looking_VVG back_RP at_II the_AT variety_NN1 of_IO studies_NN2 conducted_VVN on_II plants_NN2 in_II the_AT little_JJ field_NN1 at_II Henfaes_NP2 ,_, I_PPIS1 feel_VV0 little_JJ temptation_NN1 to_TO explain_VVI the_AT behaviour_NN1 of_IO organisms_NN2 within_II it_PPH1 as_RG perfectly_RR fitted_VVN for_IF adaptive_JJ optima_NN1 in_II an_AT1 ideally_RR evolved_JJ ecosystem_NN1 ._. 
Rather_RR ,_, I_PPIS1 see_VV0 the_AT population_NN1 of_IO plants_NN2 trapped_VVD in_RP narrowly_RR constrained_VVN evolved_JJ ruts_NN2 ,_, bearing_VVG the_AT battered_JJ imprint_NN1 of_IO recent_JJ and_CC not-so-recent_JJ selective_JJ and_CC other_JJ forces_NN2 ._. 
'_" I_PPIS1 returned_VVD ,_, and_CC saw_VVD under_II the_AT sun_NN1 ,_, that_CST the_AT race_NN1 is_VBZ not_XX to_II the_AT swift_JJ ,_, nor_CC the_AT battle_NN1 to_II the_AT strong_JJ ,_, neither_RR yet_RR bread_NN1 to_II the_AT wise_JJ ,_, nor_CC yet_RR riches_NN2 to_II men_NN2 of_IO understanding_NN1 ,_, not_XX yet_RR favour_VV0 to_II men_NN2 of_IO skill_NN1 ;_; but_CCB time_VV0 and_CC chance_NN1 happeneth_VVZ to_II them_PPHO2 all_RR '_GE (_( Ecclesiastes_NP1 )_) ._. 
PLATE_NN1 TECTONICS_NN2 AND_CC EVOLUTION_NN1 A._NP1 HALLAM_NP1 In_II his_APPGE famous_JJ concluding_JJ paragraph_NN1 of_IO The_AT Origin_NN1 of_IO Species_NN Darwin_NP1 expressed_VVD wonder_NN1 that_CST the_AT diversity_NN1 of_IO the_AT organic_JJ world_NN1 can_VM have_VHI been_VBN produced_VVN from_II one_MC1 or_CC a_AT1 few_DA2 ancestors_NN2 by_II the_AT operation_NN1 of_IO several_DA2 natural_JJ laws_NN2 '_GE there_EX is_VBZ grandeur_NN1 in_II this_DD1 view_NN1 of_IO life_NN1 ..._... '_GE ._. 
The_AT preferential_JJ replication_NN1 of_IO genes_NN2 by_II31 means_II32 of_II33 natural_JJ selection_NN1 may_VM well_RR be_VBI a_AT1 necessary_JJ condition_NN1 for_IF evolution_NN1 to_TO take_VVI place_NN1 ,_, but_CCB it_PPH1 is_VBZ hardly_RR a_AT1 sufficient_JJ explanation_NN1 for_IF how_RRQ the_AT enormous_JJ diversity_NN1 of_IO life_NN1 in_II space_NN1 and_CC time_NNT1 has_VHZ come_VVN about_RP ._. 
That_CST there_EX are_VBR ,_, for_REX21 instance_REX22 ,_, kangaroos_NN2 in_II Australia_NP1 and_CC lemurs_VVZ in_II Madagascar_NP1 ,_, and_CC that_CST antelopes_NN2 rather_II21 than_II22 dinosaurs_NN2 currently_RR roam_VV0 the_AT plains_NN2 of_IO Africa_NP1 ,_, is_VBZ among_II other_JJ things_NN2 consequent_JJ upon_II a_AT1 whole_JJ series_NN of_IO historical_JJ contingencies_NN2 ._. 
The_AT study_NN1 of_IO palaeontology_NN1 in_II31 conjunction_II32 with_II33 geology_NN1 ought_VMK to_TO throw_VVI light_NN1 on_II the_AT interaction_NN1 of_IO historical_JJ events_NN2 and_CC the_AT evolution_NN1 of_IO a_AT1 substantial_JJ sample_NN1 of_IO the_AT organisms_NN2 that_CST have_VH0 inhabited_VVN this_DD1 planet_NN1 ._. 
Darwin_NP1 viewed_VVD biotic_JJ interactions_NN2 the_AT struggle_NN1 for_IF existence_NN1 as_CSA being_VBG the_AT major_JJ promoter_NN1 of_IO evolution_NN1 ._. 
This_DD1 is_VBZ clearly_RR indicated_VVN in_II the_AT following_JJ passage_NN1 from_II The_AT Origin_NN1 of_IO Species_NN ._. 
'_" As_CSA species_NN are_VBR produced_VVN and_CC exterminated_VVN by_II slowly_RR acting_VVG causes_NN2 ,_, and_CC not_XX by_II miraculous_JJ acts_NN2 of_IO creation_NN1 ;_; and_CC as_II the_AT most_RGT important_JJ of_IO all_DB causes_NN2 of_IO organic_JJ change_NN1 is_VBZ one_PN1 which_DDQ is_VBZ almost_RR independent_JJ of_IO altered_JJ and_CC perhaps_RR suddenly_RR altered_JJ physical_JJ conditions_NN2 ,_, namely_REX ,_, the_AT mutual_JJ relation_NN1 of_IO organism_NN1 to_II organism_NN1 the_AT improvement_NN1 of_IO one_MC1 organism_NN1 entailing_VVG the_AT improvement_NN1 or_CC the_AT extermination_NN1 of_IO others_NN2 '_GE ._. 
Such_DA a_AT1 view_NN1 would_VM imply_VVI ,_, for_REX21 instance_REX22 ,_, that_CST the_AT mammals_NN2 progressively_RR outcompeted_VVD the_AT dinosaurs_NN2 in_II the_AT late_JJ Mesozoic_JJ to_TO become_VVI the_AT dominant_JJ terrestrial_JJ vertebrates_NN2 in_II the_AT early_JJ Tertiary_JJ ._. 
We_PPIS2 have_VH0 known_VVN for_IF some_DD time_NNT1 that_CST this_DD1 can_VM not_XX have_VHI been_VBN the_AT case_NN1 ._. 
For_IF many_DA2 millions_NNO2 of_IO years_NNT2 ,_, through_II the_AT Jurassic_NP1 and_CC Cretaceous_JJ periods_NN2 ,_, primitive_JJ mammals_NN2 coexisted_VVD with_IW dinosaurs_NN2 ,_, but_CCB remained_VVD low_JJ in_II diversity_NN1 and_CC small_JJ in_II size_NN1 ._. 
Not_XX until_CS after_CS the_AT dinosaurs_NN2 finally_RR became_VVD extinct_JJ at_II the_AT end_NN1 of_IO the_AT Cretaceous_JJ did_VDD the_AT mammals_NN2 radiate_VVI explosively_RR into_II a_AT1 great_JJ diversity_NN1 of_IO forms_NN2 such_II21 as_II22 we_PPIS2 see_VV0 today_RT ,_, to_TO occupy_VVI an_AT1 even_RR wider_JJR range_NN1 of_IO ecological_JJ niches_NN2 than_CSN those_DD2 vacated_VVN by_II the_AT dinosaurs_NN2 ._. 
It_PPH1 is_VBZ quite_RG likely_JJ that_CST the_AT early_JJ mammals_NN2 were_VBDR nocturnal_JJ in_II habit_NN1 and_CC thereby_RR avoided_VVN direct_JJ competition_NN1 with_IW the_AT smaller_JJR dinosaurs_NN2 ._. 
With_IW hindsight_NN1 we_PPIS2 can_VM envisage_VVI them_PPHO2 as_CSA biding_VVG their_APPGE time_NNT1 ,_, as_RR31 it_RR32 were_RR33 ,_, until_CS their_APPGE reptilian_JJ competitors_NN2 disappeared_VVD ._. 
This_DD1 pattern_NN1 of_IO change_NN1 is_VBZ by_RR31 no_RR32 means_RR33 exceptional_JJ in_II the_AT fossil_NN1 record_NN1 (_( see_VV0 ,_, for_REX21 example_REX22 ,_, Gould_NP1 &amp;_CC Calloway_NP1 ,_, 1980_MC )_) ._. 
Indeed_RR it_PPH1 seems_VVZ to_TO be_VBI rather_RG characteristic_JJ ,_, as_CSA is_VBZ the_AT close_JJ coincidence_NN1 in_II time_NNT1 of_IO episodes_NN2 of_IO mass_JJ extinction_NN1 and_CC radiation_NN1 of_IO a_AT1 wide_JJ variety_NN1 of_IO animal_NN1 and_CC plant_NN1 groups_NN2 ,_, both_RR terrestrial_JJ and_CC marine_JJ ._. 
There_EX is_VBZ a_AT1 clear_JJ implication_NN1 that_CST such_DA significant_JJ evolutionary_JJ episodes_NN2 may_VM be_VBI the_AT consequence_NN1 of_IO major_JJ physical_JJ events_NN2 in_II earth_NN1 history_NN1 ._. 
Following_VVG the_AT earth_NN1 sciences_NN2 revolution_NN1 within_II the_AT last_MD couple_NN1 of_IO decades_NNT2 (_( Hallam_NP1 ,_, 1973_MC )_) it_PPH1 is_VBZ natural_JJ to_TO investigate_VVI what_DDQ relationship_NN1 ,_, if_CS any_DD ,_, exists_VVZ between_II major_JJ biogeographic_JJ ,_, radiation_NN1 and_CC extinction_NN1 episodes_NN2 and_CC plate_NN1 tectonics_NN2 ,_, which_DDQ appear_VV0 to_TO have_VHI controlled_VVN first_MD order_NN1 events_NN2 in_II the_AT physical_JJ environment_NN1 for_IF at_RR21 least_RR22 as_CS31 long_CS32 as_CS33 a_AT1 diverse_JJ metazoan_JJ fauna_NN became_VVD established_VVN in_II the_AT Cambrian_JJ ,_, nearly_RR six_MC hundred_NNO million_NNO years_NNT2 ago_RA ._. 
Because_II21 of_II22 my_APPGE limited_JJ space_NN1 ,_, I_PPIS1 can_VM do_VDI no_AT more_RRR ,_, of_RR21 course_RR22 ,_, than_CSN outline_VV0 some_DD of_IO the_AT more_RGR significant_JJ features_NN2 as_CSA they_PPHS2 are_VBR currently_RR understood_VVN ._. 
Physical_JJ effects_NN2 of_IO plate_NN1 movements_NN2 The_AT theory_NN1 of_IO plate_NN1 tectonics_NN1 states_VVZ that_CST the_AT outer_JJ layer_NN1 of_IO the_AT earth_NN1 ,_, the_AT lithosphere_NN1 (_( 100_MC km_NNU thick_JJ )_) comprises_VVZ a_AT1 small_JJ number_NN1 of_IO (_( relatively_RR )_) rigid_JJ plates_NN2 which_DDQ are_VBR separated_VVN by_II narrow_JJ zones_NN2 along_II which_DDQ most_DAT tectonic_JJ ,_, seismic_JJ and_CC volcanic_JJ activity_NN1 is_VBZ concentrated_VVN ._. 
These_DD2 plate_NN1 margins_NN2 are_VBR of_IO three_MC types_NN2 :_: (_( 1_MC1 )_) divergent_JJ ,_, where_CS crustal_JJ material_NN1 moves_VVZ apart_RL ,_, under_II the_AT oceans_NN2 by_II a_AT1 process_NN1 known_VVN as_II sea-floor_NN1 spreading_NN1 ;_; (_( 2_MC )_) convergent_JJ ,_, where_CS one_MC1 plate_NN1 plunges_VVZ down_RP into_II the_AT underlying_JJ mantle_NN1 (_( also_RR known_VVN as_II subduction_NN1 zones_NN2 )_) ;_; (_( 3_MC )_) transform_VV0 faults_NN2 ,_, where_CS one_MC1 plate_NN1 slides_VVZ laterally_RR with_II31 respect_II32 to_II33 its_APPGE neighbour_NN1 ,_, crust_NN1 being_VBG here_RL neither_RR created_VVN (_( 1_MC1 )_) nor_CC destroyed_VVN (_( 2_MC )_) (_( Fig._NN1 18.1_MC )_) ._. 
The_AT most_RGT obvious_JJ effect_NN1 of_IO plate_NN1 tectonics_NN1 is_VBZ that_CST continents_NN2 can_VM be_VBI split_VVN and_CC their_APPGE components_NN2 driven_VVN apart_RL if_CS a_AT1 divergent_JJ plate_NN1 margin_NN1 becomes_VVZ established_VVN beneath_II them_PPHO2 ,_, and_CC can_VM be_VBI caused_VVN to_TO collide_VVI with_IW each_PPX221 other_PPX222 along_II the_AT lines_NN2 of_IO subduction_NN1 zones_NN2 ,_, where_CS mountain_NN1 belts_NN2 such_II21 as_II22 the_AT Himalayas_NP2 may_VM thereby_RR be_VBI generated_VVN ._. 
Other_JJ mountain_NN1 belts_NN2 such_II21 as_II22 the_AT Andes_NP2 are_VBR also_RR produced_VVN by_II subduction_NN1 but_CCB at_II the_AT boundary_NN1 of_IO continent_NN1 and_CC ocean_NN1 floor_NN1 ,_, which_DDQ have_VH0 very_RG different_JJ geological_JJ character_NN1 ._. 
Plate_NN1 tectonics_NN1 is_VBZ not_XX the_AT same_DA as_CSA continental_JJ drift_NN1 ._. 
Continents_NN2 are_VBR carried_VVN passively_RR on_II moving_VVG sectors_NN2 of_IO plates_NN2 which_DDQ also_RR embrace_VV0 ocean_NN1 floor_NN1 ;_; they_PPHS2 do_VD0 not_XX '_GE drift_NN1 '_GE across_II the_AT latter_DA (_( Fig._NN1 18.2_MC )_) ._. 
Migrating_VVG continents_NN2 have_VH0 obvious_JJ implications_NN2 for_IF biogeography_NN1 and_CC evolution_NN1 ,_, but_CCB there_EX are_VBR other_JJ consequences_NN2 of_IO plate_NN1 movements_NN2 which_DDQ may_VM alter_VVI the_AT physical_JJ environment_NN1 in_II such_DA a_AT1 way_NN1 as_CSA to_TO affect_VVI the_AT biosphere_NN1 just_RR as_RG profoundly_RR ._. 
Firstly_RR ,_, it_PPH1 is_VBZ widely_RR accepted_VVN ,_, though_CS admittedly_RR not_XX conclusively_RR established_VVN ,_, that_DD1 major_JJ ice_NN1 ages_NN2 may_VM result_VVI from_II the_AT siting_NN1 of_IO large_JJ continental_JJ masses_NN2 in_II the_AT polar_JJ regions_NN2 ,_, because_CS only_RR in_II such_DA circumstances_NN2 can_VM extensive_JJ ice_NN1 sheets_NN2 become_VV0 established_VVN ,_, with_IW significant_JJ consequences_NN2 for_IF world_NN1 climate_NN1 (_( Frakes_NP2 ,_, 1979_MC )_) ._. 
In_II Phanerozoic_JJ time_NNT1 (_( the_AT time_NNT1 which_DDQ has_VHZ elapsed_VVN since_CS the_AT beginning_NN1 of_IO the_AT Cambrian_JJ )_) there_EX have_VH0 been_VBN three_MC such_DA ice_NN1 ages_NN2 ,_, separated_VVN by_II intervals_NN2 of_IO a_AT1 few_DA2 hundred_NNO million_NNO years_NNT2 when_RRQ the_AT world_NN1 enjoyed_VVD a_AT1 more_RGR equable_JJ climate_NN1 and_CC lacked_VVD extensive_JJ polar_JJ ice_NN1 caps_NN2 ._. 
Such_DA a_AT1 gross_JJ cyclicity_NN1 is_VBZ not_XX ,_, of_RR21 course_RR22 ,_, to_TO be_VBI confused_VVN with_IW the_AT much_RR shorter-phase_JJ climatic_JJ cycles_NN2 such_II21 as_II22 within_II the_AT most_RGT recent_JJ ,_, Pleistocene_JJ ,_, ice_NN1 age_NN1 ,_, which_DDQ appear_VV0 to_TO be_VBI the_AT consequence_NN1 of_IO an_AT1 interaction_NN1 of_IO several_DA2 astronomical_JJ variables_NN2 (_( Imbrie_NP1 &amp;_CC Imbrie_NP1 ,_, 1979_MC )_) ._. 
The_AT short-term_JJ climatic_JJ fluctuations_NN2 of_IO the_AT Pleistocene_JJ have_VH0 resulted_VVN in_II rapid_JJ world-wide_JJ (_( or_CC eustatic_JJ )_) falls_NN2 and_CC rises_NN2 of_IO sea_NN1 level_NN1 as_CSA polar_JJ ice_NN1 has_VHZ alternately_RR frozen_VVN and_CC melted_VVN ._. 
The_AT stratigraphic_JJ record_NN1 indicates_VVZ ,_, however_RR ,_, that_DD1 eustatic_JJ changes_NN2 have_VH0 also_RR occurred_VVN during_II the_AT long_JJ equable_JJ periods_NN2 when_RRQ the_AT available_JJ evidence_NN1 suggests_VVZ that_CST polar_JJ ice_NN1 was_VBDZ absent_JJ ._. 
These_DD2 sea-level_JJ fluctuations_NN2 must_VM therefore_RR have_VHI been_VBN produced_VVN by_II changes_NN2 in_II the_AT cubic_JJ capacity_NN1 of_IO the_AT ocean_NN1 basins_NN2 ._. 
By_II plotting_VVG the_AT areal_JJ distribution_NN1 of_IO marine_JJ strata_NN2 and_CC making_VVG reasonable_JJ inferences_NN2 from_II facies_NN2 distributions_NN2 about_II the_AT location_NN1 of_IO former_DA shorelines_NN2 ,_, it_PPH1 has_VHZ been_VBN established_VVN that_CST for_IF long_JJ periods_NN2 of_IO time_NNT1 in_II the_AT Phanerozoic_NN1 ,_, especially_RR in_II the_AT early_JJ Palaeozoic_JJ and_CC late_JJ Cretaceous_JJ ,_, the_AT continents_NN2 have_VH0 been_VBN inundated_VVN by_II up_RG21 to_RG22 two_MC thirds_MF of_IO the_AT present_JJ area_NN1 by_II epicontinental_JJ seas_NN2 ._. 
The_AT present_JJ shelf_NN1 ,_, or_CC neritic_JJ zone_NN1 ,_, is_VBZ in_II comparison_NN1 a_AT1 mere_JJ pericontinental_JJ fringe_NN1 (_( Hallam_NP1 ,_, 1981c_FO )_) ._. 
p_ZZ1 370_MC :_: FIGURE_NN1 By_RR21 far_RR22 the_AT most_RGT effective_JJ way_NN1 of_IO changing_VVG the_AT cubic_JJ capacity_NN1 of_IO the_AT ocean_NN1 basins_NN2 is_VBZ to_TO vary_VVI the_AT volume_NN1 of_IO the_AT mid-ocean_NN1 ridges_NN2 ;_; increase_VV0 in_II volume_NN1 will_VM cause_VVI a_AT1 displacement_NN1 of_IO sea_NN1 water_NN1 on_II21 to_II22 the_AT continents_NN2 and_CC vice_RR21 versa_RR22 ._. 
One_MC1 popular_JJ hypothesis_NN1 has_VHZ it_PPH1 that_CST variations_NN2 in_II rates_NN2 of_IO sea-floor_NN1 spreading_NN1 are_VBR the_AT controlling_JJ factor_NN1 (_( Hays_NP1 &amp;_CC Pitman_NP1 ,_, 1973_MC )_) ._. 
Since_CS ocean-floor_JJ basalt_NN1 subsides_VVZ as_CSA it_PPH1 cools_VVZ while_CS migrating_VVG away_II21 from_II22 the_AT spreading_JJ axis_NN1 ,_, a_AT1 faster-spreading_JJR ridge_NN1 will_VM be_VBI hotter_JJR and_CC more_RGR buoyant_JJ over_II a_AT1 larger_JJR area_NN1 and_CC hence_RR will_VM cause_VVI more_DAR displacement_NN1 of_IO sea_NN1 water_NN1 over_II the_AT continents_NN2 ._. 
The_AT rate_NN1 of_IO eustatic_JJ change_NN1 producible_JJ by_II this_DD1 process_NN1 has_VHZ been_VBN estimated_VVN to_TO be_VBI about_RG three_MC orders_NN2 of_IO magnitude_NN1 slower_RRR than_CSN that_DD1 produced_VVN by_II the_AT climatically_RR induced_VVN fluctuations_NN2 of_IO the_AT Pleistocene_JJ (_( Pitman_NP1 ,_, 1978_MC )_) ._. 
Alternatively_RR ,_, eustatic_JJ changes_NN2 in_II non-glacial_JJ periods_NN2 can_VM be_VBI produced_VVN by_II changes_NN2 in_II the_AT cumulative_JJ length_NN1 of_IO active_JJ spreading_JJ ridges_NN2 ,_, which_DDQ will_VM obviously_RR relate_VVI to_II changes_NN2 in_II plate_NN1 patterns_NN2 (_( Hallam_NP1 ,_, 1977_MC )_) ._. 
Epicontinental_JJ seas_NN2 have_VH0 been_VBN biologically_RR significant_JJ for_IF several_DA2 reasons_NN2 ._. 
They_PPHS2 were_VBDR the_AT site_NN1 of_IO habitation_NN1 of_IO a_AT1 very_RG large_JJ proportion_NN1 of_IO all_DB adult_JJ aquatic_JJ organisms_NN2 ,_, and_CC ,_, because_II21 of_II22 their_APPGE overall_JJ shallowness_NN1 generally_RR less_DAR than_CSN (_( and_CC often_RR much_DA1 less_DAR than_CSN )_) 200_MC m_NNO quite_RR modest_JJ eustatic_JJ and_CC other_JJ physical_JJ changes_NN2 may_VM have_VHI had_VHN disproportionately_RR large_JJ environmental_JJ consequences_NN2 compared_VVN with_IW the_AT open_JJ ocean_NN1 ._. 
Furthermore_RR ,_, extensive_JJ spreads_NN2 of_IO such_DA seas_NN2 can_VM as_CSA effectively_RR isolate_VV0 pieces_NN2 of_IO emergent_JJ continent_NN1 as_CSA spreading_JJ ocean_NN1 floor_NN1 ,_, thereby_RR creating_VVG barriers_NN2 to_II migration_NN1 of_IO terrestrial_JJ organisms_NN2 ,_, and_CC should_VM also_RR promote_VVI equability_NN1 of_IO the_AT continental_JJ climate_NN1 ._. 
It_PPH1 has_VHZ recently_RR been_VBN proposed_VVN that_CST variations_NN2 in_II albedo_NN1 with_II31 respect_II32 to_II33 latitude_NN1 (_( with_IW considerable_JJ consequences_NN2 for_IF global_JJ climate_NN1 )_) are_VBR a_AT1 result_NN1 of_IO both_DB2 the_AT changing_JJ distribution_NN1 of_IO continents_NN2 and_CC sea-level_JJ oscillations_NN2 ._. 
The_AT latter_DA ,_, causing_VVG a_AT1 change_NN1 in_II land-sea_JJ proportions_NN2 ,_, is_VBZ apparently_RR the_AT more_RGR important_JJ (_( Barron_NP1 ,_, Sloan_NP1 &amp;_CC Harrison_NP1 ,_, 1980_MC )_) ._. 
The_AT organic_JJ response_NN1 For_IF the_AT purposes_NN2 of_IO a_AT1 general_JJ survey_NN1 ,_, changes_NN2 in_II various_JJ biological_JJ groups_NN2 through_II time_NNT1 are_VBR most_RGT usefully_RR analysed_VVN in_II31 terms_II32 of_II33 diversity_NN1 (_( or_CC ,_, more_RGR strictly_RR ,_, taxonomic_JJ richness_NN1 )_) ,_, and_CC changes_NN2 in_II spatial_JJ distribution_NN1 by_II the_AT amount_NN1 of_IO provinciality_NN1 or_CC endemism_NN1 ._. 
Obviously_RR ,_, significant_JJ radiations_NN2 will_VM appear_VVI as_RG marked_JJ increases_NN2 ,_, and_CC extinctions_NN2 as_CSA decreases_VVZ of_IO diversity_NN1 ,_, while_CS the_AT degree_NN1 to_II which_DDQ free_JJ migration_NN1 is_VBZ inhibited_VVN by_II geographic_JJ barriers_NN2 ,_, thereby_RR promoting_VVG genetic_JJ isolation_NN1 according_II21 to_II22 the_AT classic_JJ model_NN1 (_( Mayr_NP1 ,_, 1963_MC )_) ,_, should_VM be_VBI expressed_VVN by_II the_AT ratio_NN1 of_IO endemic_JJ to_II pandemic_JJ organisms_NN2 ._. 
Pioneer_NN1 attempts_NN2 to_TO relate_VVI temporal_JJ diversity_NN1 changes_NN2 to_II plate_NN1 tectonics_NN2 were_VBDR undertaken_VVN by_II Valentine_NP1 &amp;_CC Moores_NP1 (_( 1972_MC )_) and_CC Flessa_NP1 &amp;_CC Imbrie_NP1 (_( 1973_MC )_) ,_, while_CS the_AT relationship_NN1 of_IO changing_JJ patterns_NN2 of_IO endemism_NN1 through_II time_NNT1 in_II31 relation_II32 to_II33 plate_NN1 movements_NN2 was_VBDZ outlined_VVN by_II Hallam_NP1 (_( 1974_MC )_) ._. 
For_IF more_RGR up-to-date_JJ palaeobiogeographic_JJ reviews_NN2 see_VV0 Gray_NP1 &amp;_CC Boucot_NP1 (_( 1979_MC )_) and_CC Hallam_NP1 (_( 1981a_FO ,_, b_ZZ1 )_) ._. 
The_AT organic_JJ response_NN1 to_II the_AT changes_NN2 in_II the_AT physical_JJ environment_NN1 induced_VVN by_II plate_NN1 tectonics_NN2 can_VM be_VBI considered_VVN under_RG three_MC headings_NN2 ._. 
Migrating_VVG continents_NN2 I_PPIS1 have_VH0 proposed_VVN four_MC simple_JJ distributional_JJ patterns_NN2 for_IF both_DB2 marine_JJ and_CC terrestrial_JJ animals_NN2 which_DDQ involve_VV0 changes_NN2 in_II time_NNT1 ._. 
Convergence_NN1 (_( not_XX to_TO be_VBI confused_VVN with_IW phyletic_JJ convergence_NN1 )_) refers_VVZ to_II the_AT degree_NN1 of_IO resemblance_NN1 of_IO faunas_NN2 in_II different_JJ regions_NN2 increasing_VVG from_II an_AT1 earlier_JJR to_II a_AT1 later_JJR period_NN1 ,_, and_CC divergence_NN1 refers_VVZ to_II the_AT reverse_JJ phenomenon_NN1 (_( Fig._NN1 18._MC 3_MC )_) ._. 
Disjunct_JJ endemism_NN1 refers_VVZ to_II a_AT1 type_NN1 of_IO regionally_RR restricted_JJ distribution_NN1 of_IO a_AT1 fossil_NN1 taxon_NN1 in_II which_DDQ two_MC or_CC more_RGR component_JJ parts_NN2 are_VBR separated_VVN by_II a_AT1 major_JJ physical_JJ barrier_NN1 and_CC hence_RR is_VBZ not_XX readily_RR explicable_JJ in_II31 terms_II32 of_II33 present-day_JJ geography_NN1 ._. 
Complementarity_NN1 in_II the_AT distributional_JJ changes_NN2 of_IO contiguous_JJ marine_JJ and_CC terrestrial_JJ animals_NN2 is_VBZ recognisable_JJ when_CS one_MC1 group_NN1 exhibits_VVZ convergence_NN1 and_CC the_AT other_JJ divergence_NN1 (_( Fig._NN1 18.4_MC )_) ._. 
This_DD1 happens_VVZ ,_, for_REX21 example_REX22 ,_, when_CS a_AT1 land_NN1 connection_NN1 is_VBZ created_VVN between_II two_MC hitherto_RT isolated_JJ areas_NN2 of_IO continent_NN1 ,_, so_RR allowing_VVG convergence_NN1 of_IO the_AT terrestrial_JJ faunas_NN2 to_TO take_VVI place_NN1 ,_, while_CS severing_VVG of_IO a_AT1 once-continuous_JJ landmass_NN1 gives_VVZ rise_NN1 to_II divergence_NN1 as_II a_AT1 result_NN1 of_IO genetic_JJ isolation_NN1 ._. 
Pliocene_NP1 uplift_NN1 of_IO the_AT isthmus_NN1 linking_VVG North_ND1 and_CC South_ND1 America_NP1 ,_, apparently_RR related_VVN to_II movement_NN1 of_IO the_AT Cocos_NP2 Plate_NN1 in_II the_AT East_ND1 Pacific_NP1 ,_, is_VBZ a_AT1 classic_JJ example_NN1 of_IO complementarity_NN1 and_CC is_VBZ also_RR significant_JJ from_II a_AT1 Darwinian_JJ point_NN1 of_IO view_NN1 ._. 
Substantial_JJ cross-migration_NN1 of_IO terrestrial_JJ mammal_NN1 faunas_NN2 coincided_VVD with_IW mass_JJ extinction_NN1 of_IO the_AT endemic_JJ South_NP1 American_JJ mammals_NN2 which_DDQ had_VHD been_VBN isolated_VVN by_II sea_NN1 through_II Tertiary_JJ times_NNT2 ._. 
This_DD1 has_VHZ generally_RR been_VBN assumed_VVN to_TO have_VHI been_VBN the_AT result_NN1 of_IO competition_NN1 from_II the_AT adaptively_RR superior_JJ North_NP1 American_JJ mammals_NN2 ,_, but_CCB Marshall_NP1 (_( 1981_MC )_) has_VHZ recently_RR argued_VVN that_CST at_RR21 least_RR22 some_DD of_IO the_AT extinction_NN1 was_VBDZ caused_VVN by_II changes_NN2 in_II the_AT physical_JJ environment_NN1 ._. 
In_II contrast_NN1 ,_, the_AT Australian_JJ marsupial_NN1 fauna_NN has_VHZ remained_VVN isolated_VVN by_II sea_NN1 and_CC not_XX until_CS late_RR Tertiary_JJ times_NNT2 ,_, when_RRQ Australia-New_JJ Guinea_NP1 had_VHD moved_VVN close_RR to_II the_AT Indonesian_JJ islands_NN2 ,_, was_VBDZ even_RR limited_VVN and_CC chance_NN1 colonisation_NN1 possible_JJ of_IO Asian_JJ placentals_NN2 across_II small_JJ water_NN1 barriers_NN2 (_( Whitmore_NP1 ,_, 1981_MC )_) ._. 
More_RGR generally_RR ,_, the_AT substantial_JJ diversity_NN1 increase_NN1 of_IO faunas_NN2 through_II the_AT Mesozoic_JJ and_CC Cainozoic_JJ ,_, accelerating_VVG from_II mid-Cretaceous_JJ times_NNT2 onwards_RL ,_, which_DDQ has_VHZ recently_RR been_VBN confirmed_VVN statistically_RR (_( Sepkoski_NP1 ,_, Bambach_NP1 ,_, Raup_NP1 &amp;_CC Valentine_NP1 ,_, 198_MC 1_MC1 )_) ,_, is_VBZ evidently_RR related_VVN in_II substantial_JJ part_NN1 to_II the_AT progressive_JJ break-up_NN1 of_IO the_AT late_JJ Palaeozoic-early_JJ Mesozoic_JJ supercontinent_NN1 known_VVN as_II Pangaea_NP1 ,_, with_IW the_AT consequent_JJ increase_NN1 in_II endemism_NN1 of_IO both_DB2 terrestrial_JJ and_CC neritic_JJ groups_NN2 (_( Valentine_NP1 ,_, 1973_MC )_) ._. 
Sea-level_JJ changes_NN2 Among_II the_AT multiplicity_NN1 of_IO causes_NN2 proposed_VVN to_TO account_VVI for_IF mass_JJ extinction_NN1 events_NN2 ,_, both_RR terrestrial_JJ and_CC extra-terrestrial_NN1 ,_, strong_JJ supporting_JJ evidence_NN1 for_IF a_AT1 succession_NN1 of_IO such_DA events_NN2 is_VBZ available_JJ for_IF only_RR one_MC1 ,_, related_VVN to_II eustatic_JJ changes_NN2 of_IO sea_NN1 level_NN1 (_( Fig._NN1 18.5_MC )_) ._. 
Whether_CSW the_AT extinctions_NN2 among_II neritic_JJ organisms_NN2 were_VBDR the_AT consequence_NN1 of_IO regression_NN1 of_IO epicontinental_JJ seas_NN2 (_( Newell_NP1 ,_, 1967_MC )_) or_CC the_AT widespread_JJ bottom-water_JJ anoxia_NN1 characteristic_NN1 of_IO the_AT initial_JJ phase_NN1 of_IO subsequent_JJ transgression_NN1 (_( Hallam_NP1 ,_, 1981c_FO )_) a_AT1 significant_JJ reduction_NN1 of_IO habitat_NN1 area_NN1 and_CC hence_RR deterioration_NN1 of_IO the_AT environment_NN1 would_VM have_VHI been_VBN produced_VVN by_II either_DD1 phenomenon_NN1 ._. 
By_RR21 far_RR22 the_AT most_RGT important_JJ episode_NN1 of_IO mass_JJ extinction_NN1 took_VVD place_NN1 at_II the_AT end_NN1 of_IO the_AT Permian_NP1 period_NN1 (_( Sepkoski_NP1 et_RA21 al._RA22 ,_, 1981_MC )_) ,_, when_CS it_PPH1 is_VBZ estimated_VVN that_CST as_RG many_DA2 as_CSA 96%_NNU of_IO all_DB marine_JJ species_NN died_VVD out_RP (_( Raup_NP1 ,_, 1979_MC )_) ._. 
Schopf_NP1 (_( 1974_MC )_) and_CC Simberloff_NP1 (_( 1974_MC )_) have_VH0 demonstrated_VVN that_DD1 diversity_NN1 changes_NN2 of_IO marine_JJ invertebrates_NN2 across_II the_AT Permian-Triassic_NP1 boundary_NN1 correlate_VV0 closely_RR with_IW areas_NN2 of_IO epicontinental_JJ sea_NN1 ,_, in_II fact_NN1 seem_VV0 to_TO obey_VVI rather_RG well_RR the_AT ecologists_NN2 '_GE well_RR known_JJ '_GE species-area_NN1 '_GE relationship_NN1 ._. 
The_AT even_RR more_RGR familiar_JJ end-Cretaceous_JJ mass_JJ extinction_NN1 event_NN1 is_VBZ also_RR associated_VVN with_IW substantial_JJ regression_NN1 (_( Fig._NN1 18.5_MC )_) ,_, as_CSA are_VBR the_AT equally_RR striking_JJ events_NN2 in_II the_AT marine_JJ realm_NN1 at_II or_CC near_II the_AT end_NN1 of_IO the_AT Ordovician_JJ and_CC Triassic_NP1 ,_, and_CC to_II a_AT1 lesser_JJ extent_NN1 the_AT Devonian_NP1 (_( Raup_NP1 &amp;_CC Sepkoski_NP1 ,_, 1982_MC ,_, and_CC Fig._NN1 18.6_MC )_) ._. 
It_PPH1 is_VBZ by_RR31 no_RR32 means_RR33 clear_JJ ,_, however_RR ,_, with_IW what_DDQ particular_JJ plate_NN1 tectonic_JJ events_NN2 they_PPHS2 may_VM have_VHI been_VBN associated_VVN ,_, either_RR directly_RR or_CC indirectly_RR ._. 
The_AT end-Ordovician_JJ regression_NN1 is_VBZ indeed_RR widely_RR thought_VVN to_TO be_VBI the_AT result_NN1 of_IO the_AT growth_NN1 of_IO a_AT1 Saharan_NN1 ice_NN1 sheet_NN1 ._. 
The_AT question_NN1 may_VM be_VBI raised_VVN :_: to_II what_DDQ extent_NN1 were_VBDR the_AT extinctions_NN2 selective_JJ or_CC random_JJ ?_? 
Computer_NN1 mode_NN1 fling_NN1 exercises_NN2 have_VH0 persuaded_VVN Raup_NP1 (_( 1981_MC )_) that_CST for_IF the_AT important_JJ group_NN1 of_IO trilobites_NN2 it_PPH1 was_VBDZ more_RRR a_AT1 matter_NN1 of_IO '_GE bad_JJ genes_NN2 '_GE than_CSN '_GE bad_JJ luck_NN1 '_GE ._. 
On_II the_AT other_JJ hand_NN1 ,_, a_AT1 species_NN extinction_NN1 rate_NN1 for_IF the_AT end_NN1 of_IO the_AT Permian_NP1 as_RG high_JJ as_CSA 96%_NNU implies_VVZ that_CST the_AT role_NN1 of_IO chance_NN1 may_VM in_II extreme_JJ cases_NN2 have_VH0 been_VBN dominant_JJ (_( Raup_NP1 ,_, 1979_MC )_) ._. 
Generally_RR speaking_VVG ,_, organisms_NN2 in_II warm_JJ ,_, shallow_JJ seas_NN2 that_CST either_RR build_VV0 or_CC are_VBR closely_RR associated_VVN with_IW reefs_NN2 have_VH0 been_VBN relatively_RR vulnerable_JJ to_II extinction_NN1 ,_, as_CSA have_VH0 planktonic_JJ foraminifera_NN1 and_CC ammonites_NN2 ,_, which_DDQ have_VH0 undergone_VVN a_AT1 succession_NN1 of_IO '_GE boom_NN1 and_CC bust_NN1 '_GE cycles_NN2 (_( Vermeij_NP1 ,_, 1978_MC ;_; Haliam_NP1 ,_, 1981c_FO )_) ._. 
Among_II terrestrial_JJ vertebrates_NN2 (_( as_II31 well_II32 as_II33 at_RR21 least_RR22 some_DD marine_JJ invertebrates_NN2 )_) large_JJ organisms_NN2 have_VH0 been_VBN more_RGR vulnerable_JJ (_( Bakker_NP1 ,_, 1977_MC )_) ._. 
With_II31 regard_II32 to_II33 phases_NN2 of_IO spectacular_JJ radiation_NN1 ,_, the_AT two_MC most_RGT important_JJ in_II the_AT Phanerozoic_JJ record_NN1 ,_, affecting_VVG a_AT1 large_JJ variety_NN1 of_IO organisms_NN2 ,_, correlate_VV0 closely_RR with_IW major_JJ physical_JJ events_NN2 that_CST appear_VV0 ultimately_RR to_TO be_VBI bound_VVN up_RP with_IW plate_NN1 tectonics_NN2 ._. 
The_AT radiation_NN1 of_IO marine_JJ faunas_NN2 following_VVG the_AT massive_JJ end-Palaeozoic_JJ extinctions_NN2 was_VBDZ a_AT1 long-continuing_JJ ,_, progressive_JJ phenomenon_NN1 ,_, but_CCB was_VBDZ marked_VVN by_II a_AT1 pulse_NN1 of_IO acceleration_NN1 and_CC replacement_NN1 in_II the_AT mid-Cretaceous_JJ ,_, with_IW diversity_NN1 increase_NN1 continuing_VVG into_II the_AT Cainozoic_JJ (_( Fig._NN1 18.6_MC )_) ._. 
The_AT better_RRR known_VVN end-Cretaceous_JJ extinction_NN1 event_NN1 can_VM in_II many_DA2 respects_NN2 be_VBI considered_VVN as_II a_AT1 mere_JJ temporary_JJ setback_NN1 in_II this_DD1 very_RG dramatic_JJ faunal_JJ change_NN1 ._. 
The_AT more-or-less_JJR coincident_NN1 ,_, spectacular_JJ mid-Cretaceous_JJ radiations_NN2 included_VVD teleost_NN1 fish_NN ,_, infaunal_JJ veneroid_JJ bivalves_NN2 ,_, carnivorous_JJ neogastropods_NN2 and_CC crabs_NN2 (_( Vermeij_NP1 ,_, 1977_MC ;_; Stanley_NP1 ,_, 1977_MC )_) ._. 
There_EX were_VBDR contemporary_JJ radiations_NN2 of_IO plankton_NN1 ,_, including_II coccolithophores_NN2 ,_, foraminifera_NN1 ,_, diatoms_NN2 and_CC dinoflagellates_NN2 (_( Lipps_NP1 ,_, 1970_MC )_) and_CC deep-sea_JJ ichnofauna_NN1 (_( Frey_NP1 7and_FO ;_; Seilacher_NP1 ,_, 19801_MC ,_, while_CS on_II land_NN1 the_AT angiosperms_NN2 rapidly_RR replaced_VVN the_AT gymnosperms_NN2 as_II the_AT dominant_JJ plants_NN2 (_( Doyle_NP1 ,_, 1977_MC )_) ._. 
It_PPH1 can_VM hardly_RR be_VBI coincidental_JJ that_CST these_DD2 remarkable_JJ evolutionary_JJ events_NN2 ,_, taking_VVG place_NN1 within_II only_RR a_AT1 few_DA2 million_NNO years_NNT2 ,_, correspond_VV0 so_RG closely_RR in_II time_NNT1 with_IW an_AT1 episode_NN1 of_IO exceptional_JJ igneous_JJ and_CC urogenic_JJ activity_NN1 (_( Larsen_NP1 &amp;_CC Pitman_NP1 ,_, 1972_MC )_) ,_, the_AT rapid_JJ disintegration_NN1 of_IO Pangaea_NP1 (_( Hallam_NP1 ,_, 1980_MC )_) and_CC the_AT biggest_JJT marine_JJ transgression_NN1 since_CS the_AT mid-Palaeozoic_JJ ,_, apparently_RR produced_VVN either_RR by_II a_AT1 phase_NN1 of_IO accelerated_JJ sea-floor_NN1 spreading_NN1 or_CC by_II a_AT1 dramatic_JJ increase_NN1 in_II the_AT length_NN1 of_IO the_AT ocean_NN1 ridge_NN1 system_NN1 ._. 
In_RR21 particular_RR22 ,_, plankton_NN1 evolution_NN1 could_VM perhaps_RR have_VHI been_VBN stimulated_VVN by_II a_AT1 drastic_JJ change_NN1 in_II ocean_NN1 current_JJ systems_NN2 consequent_JJ upon_II Pangaea_NP1 breakup_NN1 ,_, but_CCB the_AT sea-level_JJ rise_NN1 might_VM have_VHI been_VBN just_RR as_RG significant_JJ ._. 
Thus_RR Hart_NP1 (_( 1980_MC )_) has_VHZ put_VVN forward_RL a_AT1 factually_RR well-supported_JJ model_NN1 relating_VVG the_AT explosive_JJ diversification_NN1 of_IO late_RR Cretaceous_JJ planktonic_JJ foraminifera_NN1 to_II increasing_JJ depth_NN1 of_IO epicontinental_JJ seas_NN2 ._. 
This_DD1 is_VBZ a_AT1 surprising_JJ conclusion_NN1 with_IW intriguing_JJ implications_NN2 ,_, bearing_VVG in_II mind_NN1 the_AT problem_NN1 of_IO near_JJ total_JJ extinction_NN1 of_IO this_DD1 group_NN1 at_II the_AT end_NN1 of_IO the_AT Cretaceous_JJ ,_, which_DDQ has_VHZ appeared_VVN to_TO be_VBI an_AT1 even_RR greater_JJR enigma_NN1 than_CSN the_AT contemporary_JJ extinction_NN1 of_IO the_AT dinosaurs_NN2 ._. 
The_AT latter_DA might_VM well_RR have_VHI suffered_VVN from_II an_AT1 increase_NN1 in_II continentality_NN1 of_IO climate_NN1 following_VVG regression_NN1 ,_, but_CCB it_PPH1 has_VHZ not_XX unreasonably_RR been_VBN assumed_VVN by_II most_DAT palaeontologists_NN2 that_CST a_AT1 planktonic_JJ group_NN1 such_II21 as_II22 the_AT globigerinid_JJ foraminifera_NN1 should_VM have_VHI been_VBN indifferent_JJ to_II what_DDQ was_VBDZ happening_VVG to_II epicontinental_JJ seas_NN2 ._. 
Darwin_NP1 was_VBDZ troubled_VVN by_II the_AT sudden_JJ appearance_NN1 of_IO a_AT1 wide_JJ diversity_NN1 of_IO fossils_NN2 in_II the_AT Cambrian_JJ ,_, and_CC tentatively_RR suggested_VVN that_CST there_EX might_VM have_VHI been_VBN a_AT1 long_JJ interval_NN1 prior_II21 to_II22 this_DD1 period_NN1 when_RRQ no_AT stratal_JJ record_NN1 was_VBDZ preserved_VVN on_II the_AT continents_NN2 ._. 
For_IF a_AT1 variety_NN1 of_IO reasons_NN2 this_DD1 type_NN1 of_IO explanation_NN1 must_VM be_VBI rejected_VVN today_RT and_CC the_AT explosive_JJ diversification_NN1 of_IO Metazoa_NP1 across_II the_AT Precambrian-Cambrian_JJ boundary_NN1 ,_, as_CSA recorded_VVN in_II the_AT strata_NN2 ,_, is_VBZ now_RT generally_RR accepted_VVN as_CSA being_VBG a_AT1 true_JJ reflection_NN1 of_IO what_DDQ actually_RR happened_VVN (_( Stanley_NP1 ,_, 1976_MC ;_; Seilacher_NP1 ,_, 1977_MC )_) ._. 
This_DD1 diversification_NN1 has_VHZ been_VBN shown_VVN to_TO correspond_VVI closely_RR to_II a_AT1 simple_JJ exponential_NN1 growth_NN1 model_NN1 ._. 
As_II the_AT number_NN1 of_IO taxa_NN2 increased_VVD the_AT rate_NN1 of_IO diversification_NN1 seems_VVZ to_TO have_VHI become_VVN diversity-dependent_JJ (_( Sepkoski_NP1 ,_, 1978_MC )_) ._. 
The_AT close_JJ correspondence_NN1 of_IO diversity_NN1 increase_NN1 with_IW rise_NN1 of_IO sea_NN1 level_NN1 in_II the_AT Cambrian_JJ suggests_VVZ the_AT possibility_NN1 of_IO a_AT1 causal_JJ correlation_NN1 (_( Brasier_NP1 ,_, 1979_MC )_) ._. 
We_PPIS2 lack_VV0 the_AT information_NN1 necessary_JJ to_TO relate_VVI it_PPH1 with_IW confidence_NN1 to_II specific_JJ plate_NN1 tectonic_JJ events_NN2 ,_, as_CSA is_VBZ possible_JJ for_IF the_AT Cretaceous_JJ ,_, but_CCB the_AT Cambrian_JJ sea-level_JJ rise_NN1 might_VM well_RR have_VHI been_VBN a_AT1 consequence_NN1 of_IO opening_NN1 of_IO the_AT Iapetus_NP1 Ocean_NNL1 ,_, with_IW the_AT growth_NN1 of_IO a_AT1 spreading_JJ ridge_NN1 (_( Anderton_NP1 ,_, 1980_MC ,_, 1982_MC )_) ._. 
Climatic_JJ change_NN1 The_AT pronounced_JJ increase_NN1 in_II latitudinal_JJ temperature_NN1 zonation_NN1 through_II the_AT course_NN1 of_IO the_AT Cainozoic_JJ ,_, as_CSA the_AT world_NN1 altered_VVD progressively_RR from_II its_APPGE Mesozoic_JJ condition_NN1 of_IO equability_NN1 ,_, must_VM have_VHI had_VHN the_AT effect_NN1 of_IO creating_VVG a_AT1 great_JJ number_NN1 of_IO ecological_JJ niches_NN2 ._. 
This_DD1 is_VBZ seen_VVN as_II a_AT1 major_JJ factor_NN1 contributing_VVG towards_II the_AT marked_JJ increase_NN1 in_II faunal_JJ diversity_NN1 (_( Valentine_NP1 ,_, 1973_MC )_) ._. 
Increase_VV0 in_II annual_JJ temperature_NN1 range_NN1 on_II the_AT continents_NN2 as_II a_AT1 consequence_NN1 of_IO regression_NN1 of_IO epicontinental_JJ seas_NN2 might_VM well_RR have_VHI played_VVN a_AT1 significant_JJ role_NN1 in_II the_AT mass_JJ extinctions_NN2 of_IO large_JJ reptiles_NN2 at_II the_AT end_NN1 of_IO the_AT Palaeozoic_JJ and_CC Mesozoic_JJ ._. 
Pangaea_NN1 at_II the_AT end_NN1 of_IO the_AT Palaeozoic_JJ must_VM have_VHI experienced_VVN a_AT1 climate_NN1 of_IO extreme_JJ continentality_NN1 ,_, not_XX only_RR because_II21 of_II22 its_APPGE coherence_NN1 (_( Valentine_NP1 &amp;_CC Moores_NP1 ,_, 1972_MC )_) but_CCB because_II21 of_II22 the_AT high_JJ albedo_NN1 of_IO extensive_JJ low-latitude_JJ deserts_NN2 (_( Barron_NP1 et_RA21 al._RA22 ,_, 1980_MC )_) ._. 
The_AT extinction_NN1 of_IO many_DA2 marine_JJ foraminiferal_NN1 and_CC ostracode_VV0 species_NN at_II or_CC close_RR to_II the_AT Eocene-Oligocene_NP1 boundary_NN1 could_VM be_VBI bound_VVN up_RP with_IW the_AT establishment_NN1 of_IO the_AT layer_NN1 of_IO cold_NN1 ,_, deep_JJ water_NN1 in_II the_AT oceans_NN2 known_VVN as_II the_AT psychrosphere_NN1 ._. 
This_DD1 in_II turn_NN1 relates_VVZ to_II the_AT establishment_NN1 of_IO the_AT Circum-Antarctic_JJ current_JJ as_CSA first_MD Australia_NP1 and_CC then_JJ South_ND1 America_NP1 broke_VVD away_II21 from_II22 that_DD1 continent_NN1 ,_, and_CC to_II the_AT formation_NN1 of_IO south_ND1 polar_JJ sea_NN1 ice_NN1 (_( Hallam_NP1 ,_, 1981c_FO )_) ._. 
Discussion_NN1 I_PPIS1 should_VM now_RT like_VVI to_TO broaden_VVI the_AT scope_NN1 of_IO this_DD1 essay_NN1 by_II discussing_VVG the_AT relative_JJ importance_NN1 of_IO stochastic_JJ and_CC deterministic_JJ ,_, as_II31 well_II32 as_II33 biotic_JJ and_CC physical_JJ ,_, factors_NN2 as_CSA promoters_NN2 of_IO evolution_NN1 ._. 
In_II recent_JJ years_NNT2 there_EX has_VHZ been_VBN an_AT1 increasing_JJ tendency_NN1 in_II some_DD circles_NN2 to_TO investigate_VVI the_AT evolutionary_JJ record_NN1 of_IO fossils_NN2 in_II31 terms_II32 of_II33 general_JJ rules_NN2 and_CC processes_NN2 without_IW regard_NN1 to_II specific_JJ causes_NN2 operating_VVG on_II specific_JJ taxa_NN2 ._. 
Thus_RR Van_NP1 Valen_NP1 (_( 1973_MC )_) applied_VVD the_AT survivorship_NN1 curve_NN1 technique_NN1 of_IO population_NN1 biologists_NN2 to_II the_AT study_NN1 of_IO extinction_NN1 rates_NN2 for_IF numerous_JJ fossil_NN1 taxa_NN2 ,_, and_CC claimed_VVD to_TO demonstrate_VVI a_AT1 general_JJ approximation_NN1 to_II linearity_NN1 in_II his_APPGE curves_NN2 ,_, which_DDQ are_VBR cumulative_JJ frequency_NN1 distributions_NN2 of_IO taxonomic_JJ durations_NN2 with_IW logarithmic_JJ ordinates_NN2 ._. 
This_DD1 led_VVD him_PPHO1 to_TO propose_VVI a_AT1 new_JJ evolutionary_JJ '_GE law_NN1 '_GE ,_, which_DDQ ,_, in_RR21 brief_RR22 ,_, states_VVZ that_CST within_II a_AT1 relatively_RR homogeneous_JJ higher_JJR taxon_NN1 ,_, subtaxa_NN1 tend_VV0 to_TO become_VVI extinct_JJ at_II a_AT1 stochastically_RR constant_JJ rate_NN1 ._. 
In_II explanation_NN1 Van_NP1 Valen_NP1 put_VVD forward_RL what_DDQ he_PPHS1 termed_VVD the_AT Red_JJ Queen_NN1 's_GE hypothesis_NN1 ,_, named_VVN after_II the_AT Lewis_NP1 Carroll_NP1 character_NN1 who_PNQS found_VVD it_PPH1 took_VVD all_DB the_AT running_JJ one_PN1 can_VM do_VDI to_TO keep_VVI in_II the_AT same_DA place_NN1 ._. 
It_PPH1 is_VBZ thoroughly_RR Darwinian_JJ in_II its_APPGE stress_NN1 on_II the_AT paramount_JJ importance_NN1 of_IO biotic_JJ interactions_NN2 ._. 
All_DB species_NN within_II a_AT1 given_JJ adaptive_JJ zone_NN1 compete_VV0 intensively_RR ._. 
A_AT1 successful_JJ adaptive_JJ response_NN1 by_II one_MC1 species_NN is_VBZ assumed_VVN to_TO occur_VVI at_II the_AT expense_NN1 of_IO other_JJ species_NN ,_, which_DDQ must_VM either_RR adapt_VVI by_II themselves_PPX2 speciating_VVG or_CC become_VV0 extinct_JJ ,_, as_CSA the_AT '_GE quality_NN1 '_GE of_IO their_APPGE environment_NN1 is_VBZ reduced_VVN ._. 
This_DD1 phenomenon_NN1 leads_VVZ to_II an_AT1 endless_JJ chain_NN1 of_IO adaptive_JJ responses_NN2 and_CC in_II the_AT long_JJ run_NN1 means_VVZ that_DD1 fitness_NN1 and_CC rate_NN1 of_IO extinction_NN1 remain_VV0 constant_JJ ._. 
The_AT high_JJ rate_NN1 of_IO diversification_NN1 and_CC evolutionary_JJ turnover_NN1 in_II mammals_NN2 is_VBZ thought_VVN likely_JJ to_TO be_VBI the_AT result_NN1 of_IO a_AT1 variety_NN1 of_IO factors_NN2 ,_, such_II21 as_II22 strong_JJ competitive_JJ interactions_NN2 leading_VVG to_II specialisation_NN1 in_II feeding_VVG methods_NN2 ,_, limitations_NN2 on_II food_NN1 supply_NN1 ,_, high_JJ mobility_NN1 and_CC energy_NN1 use_NN1 ,_, interspecific_JJ aggression_NN1 and_CC territoriality_NN1 ._. 
Such_DA factors_NN2 will_VM conspire_VVI to_TO lower_VVI the_AT '_GE resource_NN1 threshold_NN1 '_GE needed_JJ to_TO prevent_VVI extinction_NN1 ,_, compared_VVN with_IW other_JJ animals_NN2 ._. 
Epistandard_NN1 rates_NN2 of_IO evolution_NN1 are_VBR required_VVN to_TO make_VVI up_RP the_AT loss_NN1 through_II extinction_NN1 ._. 
Though_CS the_AT Red_JJ Queen_NN1 model_NN1 could_VM conceivably_RR apply_VVI to_II mammals_NN2 ,_, there_EX are_VBR doubts_NN2 about_II its_APPGE more_RGR general_JJ validity_NN1 ._. 
Thus_RR Stanley_NP1 (_( 1973_MC )_) analyses_VVZ the_AT effect_NN1 of_IO competition_NN1 on_II evolutionary_JJ rates_NN2 by_II comparing_VVG mammals_NN2 with_IW bivalve_NN1 molluscs_NN2 ._. 
In_II sharp_JJ contrast_NN1 to_II mammals_NN2 ,_, bivalves_NN2 are_VBR nearly_RR all_DB benthic_JJ suspension_NN1 feeders_NN2 which_DDQ appear_VV0 to_TO mind_VVI their_APPGE own_DA business_NN1 ,_, being_VBG characterized_VVN by_II weak_JJ interactions_NN2 with_IW other_JJ species_NN ,_, primitive_JJ inflexible_JJ behaviour_NN1 ,_, uncrowded_JJ ,_, largely_RR sedentary_JJ mode_NN1 of_IO life_NN1 and_CC generalised_JJ feeding_JJ habits_NN2 ._. 
Limits_NN2 on_II bivalve_NN1 populations_NN2 are_VBR imposed_VVN more_RRR by_II predation_NN1 and_CC fluctuations_NN2 in_II the_AT physical_JJ environment_NN1 than_CSN by_II food_NN1 resources_NN2 ,_, and_CC biotic_JJ competition_NN1 is_VBZ minimal_JJ ._. 
As_CSA Stanley_NP1 remarks_VVZ laconically_RR ,_, '_GE Interspecific_JJ aggression_NN1 is_VBZ not_XX characteristic_JJ of_IO bivalve_NN1 behaviour_NN1 '_GE ._. 
What_DDQ is_VBZ true_JJ of_IO bivalves_NN2 is_VBZ without_IW much_DA1 doubt_NN1 true_NN1 of_IO the_AT majority_NN1 of_IO benthic_JJ invertebrates_NN2 ._. 
More_RGR general_JJ criticisms_NN2 of_IO the_AT Red_JJ Queen_NN1 hypothesis_NN1 have_VH0 been_VBN voiced_VVN by_II Foin_NP1 ,_, Valentine_NP1 &amp;_CC Ayala_NP1 (_( 1975_MC )_) ,_, Raup_NP1 (_( 1975_MC )_) ,_, Salthe_NP1 (_( 1975_MC )_) and_CC Sepkoski_NP1 (_( 1975_MC )_) ._. 
In_II a_AT1 nutshell_NN1 ,_, it_PPH1 is_VBZ argued_VVN that_CST either_DD1 Van_NP1 Valen_NP1 's_GE results_NN2 show_VV0 linearity_NN1 with_IW time_NNT1 ,_, which_DDQ is_VBZ held_VVN to_TO be_VBI biologically_RR without_IW significance_NN1 ,_, or_CC most_DAT do_VD0 not_XX ,_, in_II which_DDQ case_NN1 Van_NP1 Valen_NP1 's_GE '_GE law_NN1 '_GE breaks_NN2 down_RP ._. 
Other_JJ stochastic_JJ models_NN2 have_VH0 been_VBN explored_VVN by_II the_AT computer_NN1 generation_NN1 of_IO phylogenetic_JJ diagrams_NN2 (_( cladograms_VVZ )_) ,_, with_IW termination_NN1 and_CC branching_JJ events_NN2 being_VBG controlled_VVN using_VVG random_JJ numbers_NN2 (_( Raup_NP1 et_RA21 al._RA22 ,_, 1973_MC ;_; Gould_NP1 et_RA21 al._RA22 ,_, 1977_MC )_) ._. 
Part_NN1 of_IO the_AT input_NN1 dealt_VVN with_IW the_AT required_JJ establishment_NN1 of_IO an_AT1 equilibrium_NN1 diversity_NN1 ._. 
The_AT cladograms_NN2 so_RR produced_VVN displayed_VVD a_AT1 variety_NN1 of_IO patterns_NN2 ,_, many_DA2 of_IO which_DDQ appear_VV0 to_TO simulate_VVI temporal_JJ diversity_NN1 changes_NN2 in_II well-studied_JJ fossil_NN1 groups_NN2 ._. 
It_PPH1 does_VDZ not_XX ,_, of_RR21 course_RR22 ,_, follow_VV0 that_CST the_AT radiation_NN1 and_CC extinction_NN1 of_IO the_AT monophyletic_JJ units_NN2 known_VVN as_II clades_NN2 do_VD0 not_XX have_VHI deterministic_JJ explanations_NN2 ._. 
Stanley_NP1 ,_, Signor_NN1 ,_, Lidgard_NP1 &amp;_CC Karr_NP1 (_( 1981_MC )_) present_VV0 some_DD cogent_JJ criticism_NN1 of_IO the_AT work_NN1 of_IO Raup_NP1 and_CC his_APPGE associates_NN2 and_CC establish_VV0 that_DD1 chance_NN1 factors_NN2 have_VH0 not_XX played_VVN a_AT1 dominant_JJ role_NN1 in_II producing_VVG dramatic_JJ changes_NN2 in_II diversity_NN1 ._. 
Hoffman_NP1 (_( 1981_MC )_) gives_VVZ a_AT1 sophisticated_JJ critique_NN1 both_RR of_IO stochastic_JJ modelling_NN1 and_CC the_AT application_NN1 of_IO equilibrium_NN1 theory_NN1 in_II palaeontology_NN1 ._. 
The_AT most_RGT powerful_JJ case_NN1 against_II randomness_NN1 is_VBZ that_CST afforded_VVD by_II mass_JJ extinction_NN1 and_CC radiation_NN1 events_NN2 ,_, whereby_RRQ a_AT1 wide_JJ variety_NN1 of_IO taxonomic_JJ groups_NN2 with_IW different_JJ modes_NN2 of_IO life_NN1 ,_, and_CC effective_JJ biological_JJ independence_NN1 ,_, have_VH0 experienced_VVN synchronised_JJ diversity_NN1 reduction_NN1 or_CC increase_NN1 ._. 
This_DD1 strongly_RR implies_VVZ the_AT operation_NN1 of_IO some_DD form_NN1 of_IO control_NN1 by_II the_AT physical_JJ environment_NN1 ,_, and_CC some_DD likely_JJ examples_NN2 of_IO an_AT1 ultimate_JJ link_NN1 with_IW plate_NN1 tectonics_NN2 have_VH0 been_VBN presented_VVN above_RL ._. 
The_AT interesting_JJ question_NN1 arises_VVZ :_: were_VBDR the_AT several_DA2 widely_RR acknowledged_VVN major_JJ episodes_NN2 of_IO mass_JJ extinction_NN1 in_II the_AT Phanerozoic_NN1 caused_VVN by_II exceptional_JJ events_NN2 different_JJ in_II kind_NN1 from_II what_DDQ occurred_VVD in_II the_AT much_RR lengthier_JJR intervening_JJ periods_NN2 ,_, or_CC are_VBR they_PPHS2 merely_RR the_AT spectacular_JJ end-members_NN2 of_IO a_AT1 whole_JJ series_NN ?_? 
Those_DD2 who_PNQS have_VH0 recourse_NN1 to_II the_AT deus_NN131 ex_NN132 machina_NN133 of_IO lethal_JJ rays_NN2 or_CC thunderbolts_NN2 from_II outer_JJ space_NN1 may_VM incline_NN1 to_II the_AT former_DA view_NN1 ,_, but_CCB only_RR at_II the_AT expense_NN1 of_IO disregarding_VVG the_AT abundant_JJ evidence_NN1 in_II the_AT stratigraphic_JJ record_NN1 of_IO a_AT1 correlation_NN1 between_II mass_JJ extinctions_NN2 and_CC physical_JJ events_NN2 on_II earth_NN1 (_( Hallam_NP1 ,_, 1981c_FO )_) ._. 
Even_RR in_II the_AT one_MC1 case_NN1 where_CS independent_JJ evidence_NN1 is_VBZ claimed_VVN in_II the_AT form_NN1 of_IO an_AT1 abnormal_JJ enrichment_NN1 in_II thin_JJ sedimentary_JJ layers_NN2 of_IO iridium_NN1 and_CC other_JJ platinum_NN1 group_NN1 metals_NN2 ,_, namely_REX the_AT much-publicized_JJ asteroid_NN1 impact_NN1 hypothesis_NN1 for_IF the_AT end-Cretaceous_JJ extinctions_NN2 (_( Alvarez_NP1 ,_, Alvarez_NP1 ,_, Asaro_NP1 &amp;_CC Michel_NP1 ,_, 1980_MC )_) serious_JJ doubts_NN2 have_VH0 been_VBN raised_VVN by_II a_AT1 careful_JJ analysis_NN1 of_IO some_DD key_JJ palaeontological_JJ evidence_NN1 (_( Clemens_NP1 ,_, Archibald_NP1 &amp;_CC Hickey_NP1 ,_, 1981_MC )_) ._. 
There_EX is_VBZ in_II fact_NN1 evidence_NN1 to_TO indicate_VVI that_CST regressions_NN2 at_II intermediate_JJ and_CC small_JJ scales_NN2 correlate_VV0 with_IW coordinated_JJ extinction_NN1 events_NN2 in_II particular_JJ fossil_NN1 groups_NN2 (_( e.g._REX Hallam_NP1 ,_, 1978_MC ;_; Williamson_NP1 ,_, 1981_MC )_) but_CCB much_DA1 more_DAR work_NN1 is_VBZ required_VVN to_TO establish_VVI how_RGQ generally_RR such_DA a_AT1 relationship_NN1 holds_VVZ ._. 
If_CS it_PPH1 does_VDZ turn_VVI out_RP to_TO be_VBI of_IO general_JJ significance_NN1 at_II a_AT1 variety_NN1 of_IO scales_NN2 it_PPH1 will_VM imply_VVI that_CST the_AT increased_JJ environmental_JJ stress_NN1 associated_VVN in_II some_DD way_NN1 with_IW regressions_NN2 promotes_VVZ an_AT1 increase_NN1 in_II extinction_NN1 rate_NN1 and_CC corresponding_JJ vacation_NN1 of_IO ecological_JJ niches_NN2 ,_, with_IW a_AT1 consequent_JJ opportunity_NN1 for_IF new_JJ species_NN to_TO establish_VVI themselves_PPX2 ._. 
Alternatively_RR ,_, or_CC in_II association_NN1 ,_, it_PPH1 could_VM be_VBI that_CST the_AT pronounced_JJ environmental_JJ changes_NN2 associated_VVN with_IW the_AT regression_NN1 events_NN2 act_VV0 to_TO destabilize_VVI intraspecific_JJ selection_NN1 pressures_NN2 and_CC hence_RR promote_VV0 speciation_NN1 ._. 
The_AT comparatively_RR long_JJ time_NNT1 intervals_NN2 between_II such_DA environmental_JJ vicissitudes_NN2 may_VM be_VBI characterized_VVN by_II stasis_NN1 in_II ecosystems_NN2 as_II31 well_II32 as_II33 the_AT component_NN1 species_NN ._. 
A_AT1 brief_JJ consideration_NN1 of_IO the_AT well-documented_JJ Pleistocene_JJ sea-level_JJ oscillations_NN2 caused_VVN by_II glaciation_NN1 and_CC deglaciation_NN1 suggests_VVZ an_AT1 apparent_JJ problem_NN1 ,_, because_CS these_DD2 events_NN2 do_VD0 not_XX ,_, by_RR31 and_RR32 large_RR33 ,_, correlate_VV0 with_IW episodes_NN2 of_IO pronounced_JJ extinction_NN1 or_CC speciation_NN1 ._. 
Indeed_RR ,_, the_AT characteristic_JJ response_NN1 of_IO both_DB2 terrestrial_JJ and_CC marine_JJ organisms_NN2 to_II the_AT pronounced_JJ climatic_JJ changes_NN2 of_IO the_AT Pleistocene_JJ has_VHZ been_VBN to_TO migrate_VVI to_II ecological_JJ refuges_NN2 ,_, in_II effect_NN1 to_TO track_VVI their_APPGE environment_NN1 ._. 
Without_IW such_DA a_AT1 phenomenon_NN1 ,_, in_II fact_NN1 ,_, stratigraphic_JJ correlation_NN1 would_VM operate_VVI under_II a_AT1 crippling_JJ handicap_NN1 ._. 
Why_RRQ therefore_RR did_VDD not_XX organisms_NN2 respond_VVI in_II a_AT1 similar_JJ way_NN1 to_II the_AT much_RR slower_JJR changes_NN2 of_IO sea_NN1 level_NN1 in_II the_AT lengthy_JJ periods_NN2 of_IO climatic_JJ equability_NN1 ?_? 
At_RR21 least_RR22 two_MC possibilities_NN2 readily_RR suggest_VV0 themselves_PPX2 ._. 
Perhaps_RR the_AT Pleistocene_JJ sea-level_JJ falls_NN2 ,_, though_CS dramatically_RR rapid_JJ in_II geological_JJ terms_NN2 ,_, were_VBDR too_RG short-lived_JJ to_TO have_VHI the_AT kind_NN1 of_IO environmental_JJ impact_NN1 required_VVN to_TO cause_VVI extinction_NN1 ._. 
Or_CC perhaps_RR the_AT increasingly_RR unstable_JJ environments_NN2 of_IO the_AT late_JJ Cainozoic_JJ associated_JJ with_IW climatic_JJ deterioration_NN1 caused_VVD a_AT1 selection_NN1 for_IF eurytopic_JJ organisms_NN2 well_RR adapted_VVN to_TO withstand_VVI environmental_JJ instability_NN1 ._. 
In_II contrast_NN1 ,_, the_AT comparative_JJ stability_NN1 of_IO ,_, for_REX21 instance_REX22 ,_, Mesozoic_JJ environments_NN2 might_VM have_VHI allowed_VVN the_AT establishment_NN1 of_IO complex_JJ ecosystems_NN2 characterized_VVN by_II comparatively_RR stenotopic_JJ organisms_NN2 ,_, which_DDQ would_VM have_VHI been_VBN vulnerable_JJ to_TO even_RR modest_JJ environmental_JJ vicissitudes_NN2 ._. 
Such_DA ideas_NN2 need_VV0 to_TO be_VBI tested_VVN ,_, and_CC further_JJR studies_NN2 made_VVN on_II the_AT relative_JJ susceptibility_NN1 of_IO different_JJ fossil_NN1 groups_NN2 to_II extinction_NN1 as_II a_AT1 result_NN1 of_IO particular_JJ environmental_JJ events_NN2 ._. 
Furthermore_RR ,_, we_PPIS2 need_VV0 to_TO enquire_VVI further_RRR into_II the_AT factors_NN2 governing_VVG the_AT response_NN1 of_IO organisms_NN2 to_II given_JJ disturbances_NN2 of_IO their_APPGE environment_NN1 ,_, whether_CSW it_PPH1 involves_VVZ migration_NN1 to_II refuges_NN2 or_CC extinction_NN1 and_CC speciation_NN1 ._. 
There_EX is_VBZ clearly_RR a_AT1 rich_JJ field_NN1 for_IF future_JJ investigation_NN1 into_II matters_NN2 of_IO such_DA major_JJ importance_NN1 ._. 
Though_CS I_PPIS1 believe_VV0 that_CST Darwin_NP1 laid_VVD too_RG much_DA1 stress_NN1 on_II biotic_JJ interactions_NN2 as_II a_AT1 promoter_NN1 of_IO evolution_NN1 and_CC extinction_NN1 ,_, to_II the_AT extent_NN1 of_IO substantially_RR dismissing_VVG changes_NN2 in_II the_AT physical_JJ environment_NN1 ,_, there_EX is_VBZ no_AT justification_NN1 for_IF going_VVG to_II the_AT other_JJ extreme_JJ ,_, as_CSA several_DA2 examples_NN2 will_VM illustrate_VVI ._. 
That_CST the_AT South_NP1 American_JJ mammals_NN2 might_VM have_VHI gone_VVN extinct_JJ in_II the_AT early_JJ Pleistocene_JJ as_II a_AT1 consequence_NN1 of_IO competition_NN1 from_II the_AT North_NP1 American_JJ invaders_NN2 has_VHZ already_RR been_VBN noted_VVN ,_, though_CS we_PPIS2 should_VM take_VVI due_JJ account_NN1 of_IO the_AT caveats_NN2 of_IO Marshall_NP1 (_( 1981_MC )_) ._. 
With_II31 regard_II32 to_II33 marine_JJ benthic_JJ communities_NN2 ,_, the_AT expansion_NN1 of_IO mobile_NN1 ,_, infaunal_JJ deposit-_NN1 and_CC suspension-feeding_JJ populations_NN2 in_II the_AT Mesozoic_JJ correlates_NN2 with_IW a_AT1 decline_NN1 of_IO immobile_JJ suspension_NN1 feeders_NN2 on_II soft_JJ substrates_NN2 (_( Thayer_NP1 ,_, 1979_MC )_) ._. 
Some_DD of_IO the_AT groups_NN2 in_II decline_NN1 ,_, such_II21 as_II22 stalked_JJ crinoids_NN2 ,_, cidaroid_JJ echinoids_NN2 (_( Kier_NP1 ,_, 1974_MC )_) and_CC brachiopods_NN2 ,_, apparently_RR sought_VVN refuge_NN1 in_II the_AT deep_JJ sea_NN1 ._. 
The_AT late_JJ Mesozoic_JJ radiation_NN1 of_IO predatory_JJ crabs_NN2 ,_, neogastropods_NN2 and_CC teleosts_NN2 correlates_VVZ with_IW an_AT1 increase_NN1 in_II resistance_NN1 to_II destruction_NN1 of_IO the_AT shells_NN2 of_IO their_APPGE molluscan_JJ prey_NN1 (_( Vermeij_NP1 ,_, 1977_MC ;_; Ward_NP1 ,_, 1981_MC )_) ._. 
Further_RRR likely_JJ examples_NN2 of_IO coevolution_NN1 concern_NN1 the_AT rise_NN1 of_IO the_AT angiosperms_NN2 ._. 
From_II the_AT late_JJ Cretaceous_JJ onwards_RR the_AT new_JJ sea-grass_JJ communities_NN2 transformed_VVD the_AT shallow_JJ neritic_JJ environment_NN1 and_CC seem_VV0 to_TO have_VHI promoted_VVN the_AT contemporary_JJ radiation_NN1 of_IO deposit-feeding_NN1 and_CC epiphytic_JJ gastropods_NN2 and_CC miliolid_JJ foraminifera_NN1 (_( Brasier_NP1 ,_, 1975_MC )_) ._. 
Although_CS the_AT fossil_NN1 record_NN1 is_VBZ much_RR poorer_JJR ,_, coevolution_NN1 with_IW the_AT terrestrial_JJ angiosperms_NN2 probably_RR accounts_VVZ for_IF a_AT1 major_JJ component_NN1 of_IO the_AT radiation_NN1 of_IO insects_NN2 and_CC birds_NN2 ._. 
In_II all_DB these_DD2 cases_NN2 ,_, however_RR ,_, the_AT initial_JJ trigger_NN1 to_TO change_VVI might_VM have_VHI been_VBN physical_JJ rather_II21 than_II22 biotic_JJ ._. 
A_AT1 final_JJ intriguing_JJ example_NN1 involves_VVZ a_AT1 subtle_JJ interplay_NN1 between_II biotic_JJ and_CC physical_JJ factors_NN2 ,_, and_CC concerns_VVZ the_AT common_JJ phyletic_JJ trend_NN1 towards_II size_NN1 increase_NN1 known_VVN as_II Cope_NP1 's_GE Rule_NN1 ,_, which_DDQ I_PPIS1 suspect_VV0 may_VM be_VBI the_AT only_JJ important_JJ gradualistic_JJ exception_NN1 to_II punctuated_JJ equilibria_NN2 (_( Hallam_NP1 ,_, 1978_MC )_) ._. 
There_EX is_VBZ no_AT shortage_NN1 of_IO adaptive_JJ explanations_NN2 for_IF size_NN1 increase_NN1 ,_, but_CCB Darwin_NP1 is_VBZ one_MC1 of_IO the_AT few_DA2 to_TO have_VHI pointed_VVN out_RP that_DD1 large_JJ organisms_NN2 such_II21 as_II22 mastodonts_NN2 and_CC dinosaurs_NN2 would_VM have_VHI been_VBN more_RGR vulnerable_JJ to_II extinction_NN1 because_II21 of_II22 the_AT limitations_NN2 of_IO food_NN1 resources_NN2 ._. 
I_PPIS1 have_VH0 proposed_VVN that_CST ,_, on_II the_AT reasonable_JJ assumption_NN1 that_CST resources_NN2 remained_VVD more_RGR or_CC less_RGR constant_JJ for_IF the_AT time_NNT1 in_II question_NN1 ,_, the_AT price_NN1 exacted_VVN for_IF (_( phyletically_RR )_) growing_VVG larger_JJR was_VBDZ to_TO become_VVI rarer_JJR ,_, thereby_RR increasing_VVG the_AT probability_NN1 of_IO extinction_NN1 (_( Hallam_NP1 ,_, 1975_MC )_) ._. 
Whether_CSW one_PN1 applies_VVZ the_AT older_JJR notion_NN1 of_IO a_AT1 trend_NN1 from_II less_DAR to_II more_RGR specialized_JJ or_CC the_AT newer_JJR concept_NN1 of_IO a_AT1 trend_NN1 from_II an_AT1 r-to_ZZ1 a_AT1 K-selected_JJ adaptive_JJ strategy_NN1 (_( ecologists_NN2 seem_VV0 to_TO have_VHI a_AT1 love-hate_JJ relationship_NN1 towards_II r_ZZ1 and_CC K_ZZ1 selection_NN1 (_( Dawkins_NP1 ,_, 1981_MC )_) )_) ,_, the_AT phyletically_RR younger_JJR organisms_NN2 would_VM have_VHI become_VVN progressively_RR more_RGR vulnerable_JJ to_II environmental_JJ disturbance_NN1 ._. 
The_AT stratigraphic_JJ record_NN1 has_VHZ been_VBN compared_VVN to_II the_AT traditional_JJ life_NN1 of_IO a_AT1 soldier_NN1 long_JJ periods_NN2 of_IO boredom_NN1 interrupted_VVN by_II moments_NN2 of_IO terror_NN1 (_( Ager_NP1 ,_, 1973_MC )_) ._. 
The_AT fossil_NN1 record_NN1 suggests_VVZ that_CST the_AT largest_JJT members_NN2 of_IO a_AT1 phyletic_JJ series_NN usually_RR had_VHD the_AT most_RRT reason_VV0 to_TO be_VBI apprehensive_JJ of_IO the_AT future_NN1 ._. 
&lsqb;_( &rsqb;_) SELECTION_NN1 IN_II31 RELATION_II32 TO_II33 SEX_NN1 T.H._NP1 CLUTTON-BROCK_NP1 In_II many_DA2 animal_NN1 species_NN ,_, differences_NN2 between_II the_AT sexes_NN2 are_VBR pronounced_VVN ._. 
In_II fact_NN1 ,_, there_EX are_VBR relatively_RR few_DA2 morphological_JJ ,_, physiological_JJ or_CC behavioural_JJ characteristics_NN2 that_CST do_VD0 not_XX differ_VVI to_II some_DD extent_NN1 between_II males_NN2 and_CC females_NN2 (_( see_VV0 Glucksman_NP1 ,_, 1974_MC )_) and_CC the_AT extent_NN1 of_IO these_DD2 differences_NN2 varies_VVZ widely_RR between_II species_NN ._. 
For_REX21 example_REX22 ,_, sexual_JJ differences_NN2 in_II body_NN1 size_NN1 range_NN1 from_II species_NN ,_, like_II worms_NN2 of_IO the_AT genus_NN1 Bonnellia_NP1 ,_, where_CS females_NN2 can_VM be_VBI over_RG 25_MC times_NNT2 the_AT length_NN1 of_IO males_NN2 (_( Barnes_NP1 ,_, 1974_MC )_) to_II species_NN like_II the_AT southern_JJ elephant_NN1 seal_NN1 ,_, Mirounga_NP1 leonina_NN1 ,_, where_CS mature_JJ males_NN2 average_VV0 eight_MC times_NNT2 the_AT weight_NN1 of_IO females_NN2 (_( Bryden_NP1 ,_, 1969_MC )_) ._. 
Other_JJ sex_NN1 differences_NN2 are_VBR less_RGR apparent_JJ such_II21 as_II22 those_DD2 in_II fat_JJ deposition_NN1 ,_, in_II haemoglobin_NN1 levels_NN2 and_CC in_II metabolic_JJ rate_NN1 among_II mammals_NN2 (_( see_VV0 Glucksman_NP1 ,_, 1974_MC )_) or_CC those_DD2 in_II auditory_JJ apparatus_NN1 among_II frogs_NN2 (_( Narins_NP1 &amp;_CC Capranica_NP1 ,_, 1976_MC ,_, 1978_MC )_) ._. 
And_CC many_DA2 have_VH0 only_RR recently_RR been_VBN explored_VVN :_: for_REX21 example_REX22 ,_, recent_JJ research_NN1 shows_VVZ that_CST in_II some_DD species_NN there_EX are_VBR pronounced_JJ sex_NN1 differences_NN2 in_II feeding_VVG ecology_NN1 (_( Gautier-Hion_NP1 ,_, 1980_MC )_) as_II31 well_II32 as_II33 in_II the_AT effects_NN2 of_IO starvation_NN1 on_II survival_NN1 (_( Widdowson_NP1 ,_, 1976_MC )_) ._. 
It_PPH1 was_VBDZ to_TO provide_VVI an_AT1 explanation_NN1 for_IF the_AT evolution_NN1 of_IO sex_NN1 differences_NN2 that_CST Charles_NP1 Darwin_NP1 formulated_VVD the_AT theory_NN1 of_IO sexual_JJ selection_NN1 ,_, described_VVN first_MD in_II The_AT Origin_NN1 of_IO Species_NN (_( 1859_MC )_) and_CC later_RRR ,_, in_II greater_JJR depth_NN1 ,_, in_II The_AT Descent_NN1 of_IO Man_NN1 (_( 1871_MC )_) ._. 
In_II this_DD1 chapter_NN1 ,_, I_PPIS1 briefly_RR trace_VV0 the_AT development_NN1 of_IO the_AT theory_NN1 and_CC describe_VV0 recent_JJ attempts_NN2 to_TO measure_VVI variation_NN1 in_II reproductive_JJ success_NN1 in_II males_NN2 and_CC females_NN2 ,_, as_II31 well_II32 as_II33 some_DD of_IO the_AT practical_JJ problems_NN2 involved_VVD ._. 
However_RR ,_, as_CSA I_PPIS1 argue_VV0 in_II the_AT final_JJ section_NN1 ,_, the_AT extent_NN1 of_IO sexual_JJ dimorphism_NN1 will_VM depend_VVI not_XX on_II the_AT extent_NN1 to_II which_DDQ reproductive_JJ success_NN1 varies_VVZ in_II the_AT two_MC sexes_NN2 but_CCB on_II the_AT comparative_JJ effects_NN2 of_IO particular_JJ phenotypic_JJ traits_NN2 on_II the_AT breeding_NN1 success_NN1 of_IO males_NN2 and_CC females_NN2 ._. 
A_AT1 brief_JJ history_NN1 of_IO sexual_JJ selection_NN1 The_AT origin_NN1 of_IO the_AT theory_NN1 of_IO sexual_JJ selection_NN1 can_VM be_VBI traced_VVN to_II a_AT1 peacock_NN1 or_CC ,_, rather_RR ,_, a_AT1 peahen_NN1 owned_VVN by_II Lady_NNB Tynte_NP1 ._. 
This_DD1 bird_NN1 ,_, born_VVN around_RG 1762_MC ,_, lived_VVD in_II such_DA comfortable_JJ circumstances_NN2 that_CST it_PPH1 had_VHD already_RR reared_VVN eight_MC broods_NN2 when_RRQ ,_, to_II the_AT consternation_NN1 of_IO its_APPGE noble_JJ owner_NN1 ,_, it_PPH1 suddenly_RR developed_VVN the_AT plumage_NN1 and_CC spurs_NN2 of_IO a_AT1 male_NN1 and_CC thereafter_RT refused_VVD to_TO lay_VVI another_DD1 egg_NN1 ._. 
No_AT possible_JJ confusion_NN1 of_IO identities_NN2 could_VM have_VHI occurred_VVN since_CS Lady_NNB Tynte_NP1 was_VBDZ able_JK to_TO recognize_VVI her_APPGE favourite_NN1 by_II the_AT nobs_NN2 on_II its_APPGE toes_NN2 ,_, which_DDQ were_VBDR unaffected_JJ by_II its_APPGE change_NN1 in_II appearance_NN1 (_( Hunter_NP1 ,_, 1837_MC )_) ._. 
It_PPH1 is_VBZ not_XX known_VVN whether_CSW Lady_NNB Tynte_NP1 investigated_VVD just_RR what_DDQ had_VHD happened_VVN to_II the_AT bird_NN1 's_GE genitalia_NN1 but_CCB subsequent_JJ studies_NN2 of_IO female_JJ pheasants_NN2 showing_VVG similar_JJ transvestite_JJ tendencies_NN2 revealed_VVD that_CST only_RR sexual_JJ differences_NN2 developing_VVG at_II or_CC after_II puberty_NN1 were_VBDR affected_VVN and_CC that_CST the_AT reproductive_JJ organs_NN2 themselves_PPX2 remained_VVD unaltered_JJ (_( Yarrell_NP1 ,_, 1827_MC )_) ._. 
This_DD1 finally_RR led_VVD John_NP1 Hunter_NP1 ,_, the_AT eminent_JJ surgeon_NN1 ,_, anatomist_NN1 and_CC classifier_NN1 of_IO monsters_NN2 to_TO produce_VVI a_AT1 seminal_JJ paper_NN1 (_( An_AT1 account_NN1 of_IO an_AT1 extraordinary_JJ pheasant_NN1 ,_, Hunter_NP1 ,_, 1837_MC )_) in_II which_DDQ he_PPHS1 proposed_VVD that_CST differences_NN2 between_II the_AT sexes_NN2 were_VBDR of_IO two_MC kinds_NN2 :_: those_DD2 involving_VVG the_AT sexual_JJ organs_NN2 themselves_PPX2 ,_, which_DDQ were_VBDR evident_JJ from_II birth_NN1 and_CC did_VDD not_XX change_VVI during_II an_AT1 individual_NN1 's_GE lifetime_NNT1 ;_; and_CC those_DD2 that_CST did_VDD not_XX develop_VVI until_CS the_AT animal_NN1 approached_VVD breeding_NN1 age_NN1 ,_, such_II21 as_II22 differences_NN2 in_II body_NN1 size_NN1 ,_, plumage_NN1 and_CC in_II the_AT tendency_NN1 to_TO be_VBI fat_JJ which_DDQ he_PPHS1 termed_VVD '_GE secondary_NN1 '_GE marks_NN2 or_CC characters_NN2 of_IO sex_NN1 (_( Hunter_NP1 ,_, 1837_MC ,_, 1861_MC )_) ._. 
Some_DD of_IO these_DD2 ,_, like_II the_AT plumage_NN1 of_IO gallinaceous_JJ birds_NN2 ,_, could_VM change_VVI during_II an_AT1 individual_NN1 's_GE lifetime_NNT1 but_CCB these_DD2 differences_NN2 were_VBDR not_XX evident_JJ at_II birth_NN1 ._. 
Hunter_NP1 realized_VVD both_RR that_DD1 '_VBZ secondary_NN1 '_GE sexual_JJ characters_NN2 were_VBDR functionally_RR related_VVN to_II fighting_VVG or_CC display_NN1 and_CC that_CST their_APPGE extent_NN1 varied_VVN with_IW ecology_NN1 ._. 
Hunter_NP1 's_GE distinction_NN1 between_II primary_NN1 and_CC secondary_JJ sexual_JJ characters_NN2 was_VBDZ adopted_VVN by_II Charles_NP1 Darwin_NP1 (_( 1871_MC )_) with_IW a_AT1 subtle_JJ distinction_NN1 ._. 
Darwin_NP1 was_VBDZ aware_JJ that_CST many_DA2 '_GE secondary_NN1 '_GE sex_NN1 differences_NN2 were_VBDR evident_JJ at_II birth_NN1 (_( or_CC hatching_NN1 )_) and_CC distinguished_JJ between_II the_AT two_MC categories_NN2 on_II functional_JJ rather_II21 than_II22 on_II ontogenetic_JJ grounds_NN2 ._. 
Darwin_NP1 's_GE primary_JJ sexual_JJ characters_NN2 were_VBDR those_DD2 connected_VVN with_IW the_AT act_NN1 of_IO reproduction_NN1 itself_PPX1 while_CS secondary_JJ sexual_JJ characters_NN2 were_VBDR used_VVN in_II acquiring_VVG mating_JJ partners_NN2 ._. 
To_II these_DD2 two_MC categories_NN2 ,_, Darwin_NP1 added_VVD a_AT1 third_MD :_: sex_NN1 differences_NN2 '_GE related_JJ to_II different_JJ habits_NN2 of_IO life_NN1 ,_, and_CC not_XX at_RR21 all_RR22 ,_, or_CC only_RR indirectly_RR ,_, to_II the_AT reproductive_JJ functions_NN2 '_GE ,_, among_II which_DDQ he_PPHS1 included_VVD structures_NN2 associated_VVN with_IW sex_NN1 differences_NN2 in_II feeding_VVG behaviour_NN1 (_( Darwin_NP1 ,_, 1871_MC )_) ._. 
The_AT theory_NN1 of_IO sexual_JJ selection_NN1 was_VBDZ intended_VVN to_TO provide_VVI an_AT1 explanation_NN1 only_RR of_IO secondary_JJ sexual_JJ characteristics_NN2 ._. 
Darwin_NP1 realized_VVD that_CST many_DA2 secondary_JJ sexual_JJ differences_NN2 were_VBDR a_AT1 consequence_NN1 of_IO the_AT greater_JJR intensity_NN1 of_IO competition_NN1 between_II males_NN2 for_IF access_NN1 to_II mates_NN2 and_CC that_CST many_DA2 traits_NN2 were_VBDR more_RGR highly_RR developed_VVN in_II males_NN2 either_RR because_CS they_PPHS2 conferred_VVD an_AT1 advantage_NN1 in_II fights_NN2 or_CC because_CS they_PPHS2 rendered_VVD their_APPGE possessor_NN1 more_RGR attractive_JJ to_II females_NN2 ._. 
He_PPHS1 distinguished_VVD sexual_JJ selection_NN1 from_II natural_JJ selection_NN1 on_II two_MC grounds_NN2 :_: ._. 
first_MD ,_, that_CST it_PPH1 was_VBDZ a_AT1 consequence_NN1 of_IO competition_NN1 between_II members_NN2 of_IO the_AT same_DA sex_NN1 rather_II21 than_II22 between_II members_NN2 of_IO different_JJ sexes_NN2 or_CC species_NN ;_; and_CC ,_, second_NNT1 ,_, that_CST it_PPH1 depended_VVD on_II variation_NN1 in_II reproductive_JJ success_NN1 rather_II21 than_II22 survival_NN1 ._. 
'_" ..._... This_DD1 form_NN1 of_IO selection_NN1 depends_VVZ ,_, not_XX on_II a_AT1 struggle_NN1 for_IF existence_NN1 in_II31 relation_II32 to_II33 other_JJ organic_JJ beings_NN2 or_CC to_II external_JJ conditions_NN2 ,_, but_CCB on_II a_AT1 struggle_NN1 between_II the_AT individuals_NN2 of_IO one_MC1 sex_NN1 ,_, generally_RR the_AT males_NN2 ,_, for_IF the_AT possession_NN1 of_IO the_AT other_JJ sex_NN1 ._. 
The_AT result_NN1 is_VBZ not_XX death_NN1 to_II the_AT unsuccessful_JJ competitor_NN1 but_CCB few_DA2 or_CC no_AT offspring_NN ._. 
'_GE Darwin_NP1 's_GE theory_NN1 of_IO sexual_JJ selection_NN1 was_VBDZ less_RGR readily_RR accepted_VVN by_II scientists_NN2 than_CSN the_AT theory_NN1 of_IO natural_JJ selection_NN1 ._. 
Wallace_NP1 (_( 1889_MC )_) agreed_VVD that_CST combat_VV0 between_II males_NN2 was_VBDZ an_AT1 important_JJ source_NN1 of_IO selection_NN1 pressures_NN2 leading_VVG to_II sexual_JJ dimorphism_NN1 but_CCB regarded_VVN this_DD1 as_II a_AT1 form_NN1 of_IO natural_JJ selection_NN1 on_II the_AT grounds_NN2 that_CST it_PPH1 increased_JJ '_GE the_AT vigour_NN1 and_CC fighting_VVG power_NN1 of_IO the_AT male_JJ animal_NN1 ,_, since_CS ,_, in_II every_AT1 case_NN1 ,_, the_AT weaker_JJR are_VBR either_RR killed_VVN ,_, wounded_JJ or_CC driven_VVN away_RL '_GE ._. 
He_PPHS1 regarded_VVD Darwin_NP1 's_GE second_MD mode_NN1 of_IO sexual_JJ selection_NN1 female_NN1 choice_NN1 of_IO particular_JJ males_NN2 as_CSA unimportant_JJ on_II the_AT grounds_NN2 that_CST any_DD consequences_NN2 which_DDQ female_JJ choice_NN1 might_VM have_VHI would_VM be_VBI annulled_VVN by_II natural_JJ selection_NN1 unless_CS females_NN2 selected_VVN the_AT fittest_JJT males_NN2 ,_, in_II which_DDQ case_VV0 the_AT results_NN2 of_IO sexual_JJ and_CC natural_JJ selection_NN1 would_VM be_VBI inseparable_JJ ._. 
He_PPHS1 also_RR pointed_VVD to_II the_AT lack_NN1 of_IO evidence_NN1 of_IO consistent_JJ female_JJ choice_NN1 for_IF mates_NN2 carrying_VVG particular_JJ characteristics_NN2 ._. 
Some_DD fifty_MC years_NNT2 later_RRR ,_, the_AT same_DA points_NN2 were_VBDR reaffirmed_VVN in_II two_MC influential_JJ papers_NN2 by_II Huxley_NP1 (_( 1938a_FO ,_, b_ZZ1 )_) ._. 
Wallace_NP1 's_GE objection_NN1 that_CST sexual_JJ selection_NN1 is_VBZ a_AT1 form_NN1 of_IO natural_JJ selection_NN1 is_VBZ semantically_RR correct_JJ after_II all_DB ,_, Darwin_NP1 originally_RR coined_VVD the_AT term_NN1 '_GE natural_JJ selection_NN1 '_GE in_BCL21 order_BCL22 to_TO mark_VVI its_APPGE relation_NN1 to_II man_NN1 's_GE power_NN1 of_IO selection_NN1 ,_, and_CC the_AT opposite_NN1 of_IO natural_JJ selection_NN1 is_VBZ not_XX sexual_JJ but_CCB artificial_JJ selection_NN1 (_( see_VV0 Brown_NP1 ,_, 1975_MC ;_; Halliday_NP1 ,_, 1978_MC )_) ._. 
However_RR ,_, his_APPGE insistence_NN1 that_CST the_AT process_NN1 of_IO sexual_JJ selection_NN1 described_VVN by_II Darwin_NP1 could_VM only_RR increase_VVI the_AT average_JJ reproductive_JJ success_NN1 or_CC survival_NN1 of_IO males_NN2 is_VBZ clearly_RR wrong_JJ (_( Lande_NP1 ,_, 1980_MC )_) ._. 
Especially_RR in_II polygynous_JJ species_NN ,_, the_AT costs_NN2 of_IO combat_NN1 are_VBR frequently_RR high_JJ (_( Geist_NN1 ,_, 1971_MC ;_; Clutton-Brock_NP1 ,_, Albon_NP1 ,_, Gibson_NP1 &amp;_CC Guinness_NP1 ,_, 1979_MC )_) and_CC so_RR ,_, too_RR are_VBR the_AT costs_NN2 of_IO many_DA2 sexually_RR dimorphic_JJ characters_NN2 associated_VVN with_IW combat_NN1 ,_, such_II21 as_II22 increased_JJ male_JJ body_NN1 size_NN1 and_CC weapon_NN1 development_NN1 (_( Clutton-Brock_NP1 ,_, Guinness_NP1 &amp;_CC Albon_NP1 ,_, 1982_MC )_) :_: in_II species_NN where_CS males_NN2 are_VBR substantially_RR larger_JJR than_CSN females_NN2 ,_, both_RR growing_JJ and_CC adult_NN1 males_NN2 are_VBR often_RR more_RGR likely_JJ to_TO die_VVI than_CSN females_NN2 (_( Robinette_NP1 ,_, Gashwiler_NP1 ,_, Low_NP1 &amp;_CC Jones_NP1 ,_, 1957_MC ;_; Grubb_NP1 ,_, 1974_MC ;_; Howe_NP1 ,_, 1977_MC )_) and_CC in_II one_MC1 reindeer_NN population_NN1 which_DDQ crashed_VVD from_II 6000_MC to_II 42_MC ,_, only_RR one_MC1 of_IO the_AT remaining_JJ adults_NN2 was_VBDZ a_AT1 male_NN1 (_( Klein_NP1 ,_, 1968_MC )_) ._. 
Sexual_JJ selection_NN1 on_II males_NN2 may_VM also_RR reduce_VVI the_AT average_JJ fitness_NN1 of_IO females_NN2 (_( Lande_NP1 ,_, 1980_MC )_) :_: in_II species_NN where_CS adult_JJ males_NN2 are_VBR substantially_RR larger_JJR than_CSN females_NN2 ,_, producing_VVG sons_NN2 appears_VVZ to_TO depress_VVI the_AT mother_NN1 's_GE subsequent_JJ reproductive_JJ success_NN1 more_RRR than_CSN producing_VVG daughters_NN2 (_( Clutton-Brock_NP1 ,_, Albon_NP1 &amp;_CC Guinness_NP1 ,_, 1981_MC )_) ._. 
Wallace_NP1 's_GE theoretical_JJ objections_NN2 to_II the_AT importance_NN1 of_IO female_JJ choice_NN1 as_II a_AT1 source_NN1 of_IO sexual_JJ selection_NN1 on_II males_NN2 can_VM also_RR be_VBI discounted_VVN ._. 
R._NP1 A._NP1 Fisher_NP1 (_( 1930_MC )_) demonstrated_VVD that_CST female_JJ choice_NN1 for_IF particular_JJ male_JJ characteristics_NN2 (_( such_II21 as_II22 tail_NN1 size_NN1 )_) can_VM cause_VVI them_PPHO2 to_TO develop_VVI to_II a_AT1 point_NN1 at_II which_DDQ they_PPHS2 reduce_VV0 the_AT average_JJ fitness_NN1 of_IO males_NN2 ._. 
Subsequent_JJ treatments_NN2 have_VH0 confirmed_VVN Fisher_NP1 's_GE conclusions_NN2 (_( O'Donald_NP1 ,_, 1980_MC ;_; Lande_NP1 ,_, 1981_MC )_) and_CC shown_VVN that_CST the_AT process_NN1 need_VM not_XX depend_VVI on_II the_AT initial_JJ female_JJ preference_NN1 favouring_VVG more_RGR viable_JJ males_NN2 (_( Kirkpatrick_NP1 ,_, 1982_MC )_) ._. 
However_RR ,_, while_CS there_EX is_VBZ extensive_JJ evidence_NN1 of_IO assortative_JJ mating_NN1 (_( O'Donald_NP1 ,_, 1980_MC )_) ,_, of_IO the_AT importance_NN1 of_IO plumage_NN1 characteristics_NN2 in_II courtship_NN1 (_( Williams_NP1 ,_, 1982_MC )_) and_CC of_IO female_JJ preference_NN1 for_IF males_NN2 who_PNQS can_VM defend_VVI superior_JJ breeding_NN1 territories_NN2 (_( Pleszczynska_NP1 ,_, 1978_MC )_) only_RR very_RG recently_RR has_VHZ it_PPH1 been_VBN demonstrated_VVN that_CST consistent_JJ female_JJ choice_NN1 for_IF any_DD continuous_JJ morphological_JJ character_NN1 in_II males_NN2 is_VBZ an_AT1 important_JJ source_NN1 of_IO variation_NN1 in_II male_JJ reproductive_JJ success_NN1 ._. 
By_II experimental_JJ manipulation_NN1 of_IO tail_NN1 length_NN1 in_II widdow_NN1 birds_NN2 of_IO the_AT African_JJ genus_NN1 Euplectes_NN2 ,_, Andersson_NP1 has_VHZ been_VBN able_JK to_TO alter_VVI both_DB2 the_AT extent_NN1 to_II which_DDQ males_NN2 are_VBR favoured_VVN by_II females_NN2 and_CC their_APPGE mating_JJ success_NN1 (_( Andersson_NP1 ,_, 1982_MC )_) ._. 
This_DD1 scarcity_NN1 of_IO evidence_NN1 does_VDZ not_XX mean_VVI that_CST the_AT evolution_NN1 of_IO secondary_JJ sexual_JJ characters_NN2 through_II female_JJ choice_NN1 is_VBZ uncommon_JJ ,_, for_IF mating_JJ preferences_NN2 are_VBR usually_RR difficult_JJ to_TO demonstrate_VVI ,_, particularly_RR where_CS inter-male_JJ competition_NN1 is_VBZ also_RR involved_VVN ._. 
Nevertheless_RR ,_, the_AT possibility_NN1 remains_VVZ that_CST ,_, as_CSA Wallace_NP1 argued_VVD ,_, many_DA2 of_IO the_AT sex_NN1 differences_NN2 in_II plumage_NN1 and_CC coloration_NN1 ascribed_VVN by_II Darwin_NP1 to_II the_AT action_NN1 of_IO female_JJ choice_NN1 may_VM have_VHI evolved_VVN because_CS they_PPHS2 help_VV0 the_AT sexes_NN2 to_TO recognize_VVI or_CC locate_VVI each_PPX221 other_PPX222 or_CC because_CS they_PPHS2 improve_VV0 male_JJ success_NN1 in_II competitive_JJ interactions_NN2 ._. 
Measures_NN2 of_IO sexual_JJ selection_NN1 Darwin_NP1 was_VBDZ not_XX specific_JJ as_II21 to_II22 why_RRQ males_NN2 should_VM typically_RR compete_VVI more_RGR strongly_RR for_IF access_NN1 to_II breeding_NN1 partners_NN2 than_CSN females_NN2 and_CC it_PPH1 was_VBDZ left_VVN to_II biologists_NN2 of_IO this_DD1 century_NNT1 to_TO provide_VVI the_AT answer_NN1 (_( Fisher_NP1 ,_, 1930_MC ;_; Bateman_NP1 ,_, 1948_MC ;_; Trivers_NP1 ,_, 1972_MC )_) ._. 
The_AT reason_NN1 why_RRQ males_NN2 usually_RR compete_VV0 more_RGR intensely_RR is_VBZ most_RGT easily_RR understood_VVN by_II considering_VVG the_AT energetic_JJ costs_NN2 of_IO reproduction_NN1 to_II each_DD1 sex_NN1 ._. 
In_II most_DAT animals_NN2 ,_, the_AT energetic_JJ costs_NN2 of_IO fertilization_NN1 to_II the_AT male_NN1 are_VBR minimal_JJ whereas_CS the_AT costs_NN2 of_IO reproduction_NN1 to_II the_AT female_NN1 are_VBR substantial_JJ ._. 
Consequently_RR ,_, males_NN2 are_VBR capable_JJ of_IO fathering_VVG more_DAR progeny_NN1 than_CSN females_NN2 can_VM bear_VVI and_CC rear_VVI :_: in_II current_JJ terminology_NN1 (_( Trivers_NP1 ,_, 1972_MC )_) they_PPHS2 invest_VV0 less_RGR heavily_RR in_II their_APPGE offspring_NN than_CSN females_NN2 ._. 
In_II species_NN where_CS successful_JJ males_NN2 can_VM monopolize_VVI breeding_NN1 access_NN1 to_II large_JJ numbers_NN2 of_IO females_NN2 but_CCB similar_JJ numbers_NN2 of_IO males_NN2 and_CC females_NN2 are_VBR recruited_VVN ,_, direct_JJ competition_NN1 between_II males_NN2 is_VBZ likely_JJ to_TO be_VBI intense_JJ ,_, aggressive_JJ interactions_NN2 may_VM be_VBI frequent_JJ and_CC the_AT selective_JJ advantages_NN2 of_IO possessing_VVG traits_NN2 that_CST affect_VV0 success_NN1 in_II combat_NN1 may_VM be_VBI higher_JJR among_II males_NN2 than_CSN among_II females_NN2 ._. 
However_RR ,_, neither_RR Trivers_NP1 '_GE explanation_NN1 of_IO the_AT prevalence_NN1 of_IO increased_JJ competition_NN1 among_II males_NN2 nor_CC Darwin_NP1 's_GE description_NN1 of_IO the_AT theory_NN1 of_IO sexual_JJ selection_NN1 provide_VV0 an_AT1 operational_JJ definition_NN1 of_IO the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 (_( Wade_NP1 ,_, 1979_MC )_) ._. 
Many_DA2 different_JJ definitions_NN2 of_IO sexual_JJ selection_NN1 have_VH0 been_VBN proposed_VVN but_CCB two_MC kinds_NN2 are_VBR in_RR21 common_RR22 use_VV0 ._. 
First_MD ,_, some_DD workers_NN2 argue_VV0 that_CST the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 will_VM depend_VVI on_II the_AT relative_JJ variability_NN1 of_IO reproductive_JJ success_NN1 among_II males_NN2 and_CC females_NN2 ._. 
For_REX21 example_REX22 ,_, Ralls_NP2 (_( 1977_MC )_) argues_VVZ that_DD1 '_VBZ the_AT intensity_NN1 of_IO intrasexual_JJ selection_NN1 in_II a_AT1 species_NN should_VM be_VBI proportional_JJ to_II the_AT ratio_NN1 of_IO the_AT lifetime_NNT1 number_NN1 of_IO offspring_NN sired_VVD by_II a_AT1 highly_RR successful_JJ male_NN1 compared_VVN to_II the_AT number_NN1 born_VVN by_II a_AT1 highly_RR successful_JJ female_NN1 in_II her_APPGE lifetime_NNT1 '_GE while_CS Payne_NP1 (_( 1979_MC )_) suggests_VVZ that_CST the_AT extent_NN1 to_II which_DDQ variance_NN1 in_II breeding_NN1 success_NN1 differs_VVZ between_II the_AT sexes_NN2 is_VBZ important_JJ ._. 
This_DD1 position_NN1 is_VBZ also_RR sometimes_RT mistakenly_RR attributed_VVN to_II Bateman_NP1 (_( see_VV0 Wade_NP1 &amp;_CC Arnold_NP1 ,_, 1980_MC )_) ._. 
In_II contrast_NN1 ,_, other_JJ workers_NN2 use_VV0 measures_NN2 of_IO the_AT extent_NN1 to_II which_DDQ male_JJ breeding_NN1 success_NN1 deviates_VVZ from_II mean_JJ male_JJ success_NN1 as_CSA estimates_NN2 of_IO the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 on_II males_NN2 (_( see_VV0 Wade_NP1 ,_, 1979_MC ;_; Howard_NP1 ,_, 1979_MC ;_; Wade_NP1 &amp;_CC Arnold_NP1 ,_, 1980_MC )_) ._. 
Similarly_RR ,_, the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 in_II females_NN2 can_VM be_VBI estimated_VVN by_II measuring_VVG the_AT extent_NN1 to_II which_DDQ female_JJ breeding_NN1 success_NN1 deviates_VVZ from_II mean_JJ female_JJ success_NN1 ._. 
Several_DA2 statistical_JJ measures_NN2 are_VBR in_II use_NN1 ,_, including_II the_AT coefficient_NN1 of_IO variation_NN1 ,_, Pielou_NP1 's_GE (_( 1969_MC )_) index_NN1 of_IO evenness_NN1 and_CC variance_NN1 in_II breeding_NN1 success_NN1 divided_VVN by_II the_AT square_NN1 of_IO mean_JJ breeding_NN1 success_NN1 a_AT1 measure_NN1 derived_VVN from_II Crow_NP1 's_GE (_( 1958_MC )_) index_NN1 of_IO the_AT intensity_NN1 of_IO selection_NN1 ,_, where_CS V_ZZ1 is_VBZ variance_NN1 in_II fitness_NN1 and_CC W_ZZ1 is_VBZ the_AT mean_JJ fitness_NN1 of_IO the_AT population_NN1 ._. 
This_DD1 can_VM either_RR be_VBI calculated_VVN using_VVG total_JJ variance_NN1 in_II breeding_NN1 success_NN1 or_CC using_VVG only_JJ variance_NN1 attributable_JJ to_II differences_NN2 in_II the_AT number_NN1 of_IO mates_NN2 per_II individual_NN1 (_( see_VV0 Wade_NP1 &amp;_CC Arnold_NP1 ,_, 1980_MC )_) ._. 
Ratios_NN2 of_IO variation_NN1 in_II male_NN1 and_CC female_JJ success_NN1 can_VM be_VBI used_VVN to_TO estimate_VVI the_AT relative_JJ rate_NN1 at_II which_DDQ male_NN1 and_CC female_JJ characteristics_NN2 can_VM change_VVI ._. 
However_RR ,_, since_CS the_AT extent_NN1 of_IO variation_NN1 among_II females_NN2 differs_VVZ widely_RR between_II species_NN (_( see_VV0 below_RL )_) ,_, they_PPHS2 are_VBR of_IO limited_JJ value_NN1 as_CSA measures_NN2 of_IO the_AT comparative_JJ intensity_NN1 of_IO sexual_JJ selection_NN1 (_( see_VV0 Wade_NP1 &amp;_CC Arnold_NP1 ,_, 1980_MC )_) ._. 
The_AT three_MC measures_NN2 of_IO the_AT extent_NN1 to_II which_DDQ reproductive_JJ success_NN1 varies_VVZ within_II each_DD1 sex_NN1 are_VBR fundamentally_RR similar_JJ though_CS the_AT last_MD is_VBZ the_AT most_RGT convenient_JJ since_CS it_PPH1 offers_VVZ a_AT1 measure_NN1 of_IO the_AT potential_JJ change_NN1 in_II fitness_NN1 between_II generations_NN2 ,_, relative_II21 to_II22 the_AT average_NN1 (_( see_VV0 Crow_NP1 ,_, 1958_MC )_) ._. 
It_PPH1 is_VBZ still_RR necessary_JJ to_TO decide_VVI whether_CSW to_TO use_VVI total_JJ variation_NN1 in_II breeding_NN1 success_NN1 in_II any_DD calculation_NN1 or_CC just_JJ variation_NN1 due_II21 to_II22 differences_NN2 in_II mate_NN1 number_NN1 ._. 
Where_CS the_AT aim_NN1 of_IO the_AT calculations_NN2 is_VBZ to_TO estimate_VVI the_AT potential_JJ rate_NN1 of_IO genetic_JJ change_NN1 ,_, total_JJ variance_NN1 in_II breeding_NN1 success_NN1 is_VBZ clearly_RR the_AT relevant_JJ measure_NN1 to_TO use_VVI ._. 
In_II contrast_NN1 ,_, where_CS calculations_NN2 are_VBR carried_VVN out_RP to_TO assess_VVI the_AT comparative_JJ importance_NN1 of_IO differences_NN2 in_II reproductive_JJ success_NN1 versus_II survival_NN1 for_IF each_DD1 sex_NN1 ,_, only_JJ variation_NN1 in_II mate_NN1 number_NN1 may_VM be_VBI included_VVN (_( see_VV0 Wade_NP1 &amp;_CC Arnold_NP1 ,_, 1980_MC )_) though_CS measures_NN2 of_IO the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 as_CSA conceived_VVN by_II Darwin_NP1 should_VM also_RR include_VVI variation_NN1 due_II21 to_II22 differences_NN2 in_II mate_NN1 quality_NN1 ,_, which_DDQ may_VM be_VBI an_AT1 important_JJ cause_NN1 of_IO variation_NN1 in_II lifetime_NNT1 breeding_NN1 success_NN1 both_RR among_II males_NN2 and_CC females_NN2 in_II monogamous_JJ species_NN ._. 
Lastly_RR ,_, where_CS the_AT aim_NN1 is_VBZ to_TO investigate_VVI the_AT functional_JJ significance_NN1 of_IO particular_JJ phenotypic_JJ sex_NN1 differences_NN2 ,_, it_PPH1 may_VM be_VBI necessary_JJ to_TO calculate_VVI selection_NN1 intensities_NN2 for_IF specific_JJ episodes_NN2 of_IO selection_NN1 ,_, such_II21 as_II22 mating_JJ success_NN1 at_II particular_JJ ages_NN2 (_( see_VV0 Arnold_NP1 &amp;_CC Wade_NP1 ,_, 1983_MC )_) for_IF the_AT effect_NN1 of_IO particular_JJ traits_NN2 on_II lifetime_NNT1 reproductive_JJ success_NN1 may_VM often_RR be_VBI obscured_VVN by_II the_AT influence_NN1 of_IO other_JJ variables_NN2 or_CC by_II random_JJ variation_NN1 ._. 
One_MC1 general_JJ point_NN1 concerning_II all_DB indices_NN2 of_IO sexual_JJ selection_NN1 must_VM be_VBI emphasized_VVN ._. 
Since_CS many_DA2 of_IO the_AT traits_NN2 affecting_VVG breeding_NN1 success_NN1 are_VBR strongly_RR influenced_VVN by_II rearing_JJ conditions_NN2 (_( see_VV0 Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) ,_, these_DD2 measures_NN2 reflect_VV0 the_AT potential_JJ rate_NN1 of_IO genetic_JJ change_NN1 and_CC may_VM provide_VVI little_DA1 indication_NN1 of_IO actual_JJ rates_NN2 of_IO change_NN1 in_II established_JJ populations_NN2 ._. 
Practical_JJ problems_NN2 Although_CS it_PPH1 is_VBZ relatively_RR easy_JJ to_TO decide_VVI how_RRQ the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 should_VM be_VBI estimated_VVN ,_, collecting_VVG the_AT relevant_JJ data_NN poses_VVZ a_AT1 variety_NN1 of_IO logistic_JJ problems_NN2 (_( Ralls_NP2 ,_, 1977_MC ;_; Davies_NP1 ,_, 1982_MC )_) ._. 
In_RR21 particular_RR22 ,_, in_II many_DA2 polygynous_JJ species_NN a_AT1 proportion_NN1 of_IO males_NN2 avoid_VV0 competing_VVG directly_RR with_IW larger_JJR or_CC older_JJR animals_NN2 and_CC adopt_VV0 a_AT1 policy_NN1 of_IO surreptitious_JJ fertilization_NN1 or_CC kleptogamy_NN1 (_( e.g._REX Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1977_MC ;_; Wirtz_NP1 ,_, 1982_MC )_) ._. 
As_II a_AT1 result_NN1 ,_, it_PPH1 is_VBZ often_RR difficult_JJ to_TO be_VBI sure_JJ that_CST breeding_NN1 males_NN2 fertilize_VV0 all_DB the_AT females_NN2 in_II the_AT groups_NN2 that_CST they_PPHS2 guard_VV0 :_: for_REX21 example_REX22 ,_, even_CS21 if_CS22 territorial_JJ male_JJ red-winged_JJ blackbirds_NN2 (_( Agelaius_NP1 phoeniceus_NN )_) are_VBR vasectomized_VVN ,_, their_APPGE females_NN2 sometimes_RT lay_VV0 fertile_JJ eggs_NN2 (_( Bray_NP1 ,_, Kennelly_NP1 &amp;_CC Guarino_NP1 ,_, 1975_MC )_) ._. 
Moreover_RR ,_, all_DB indices_NN2 of_IO the_AT intensity_NN1 of_IO sexual_JJ selection_NN1 beg_VV0 a_AT1 problem_NN1 of_IO fundamental_JJ importance_NN1 :_: over_II what_DDQ period_NN1 should_VM reproductive_JJ success_NN1 be_VBI measured_VVN ?_? 
It_PPH1 is_VBZ widely_RR agreed_VVN that_CST the_AT lifetime_NNT1 reproductive_JJ success_NN1 of_IO individuals_NN2 is_VBZ the_AT most_RGT satisfactory_JJ measure_NN1 of_IO fitness_NN1 that_CST it_PPH1 is_VBZ usually_RR possible_JJ to_TO collect_VVI (_( see_VV0 Falconer_NP1 ,_, 1960_MC ;_; Cavalli-Sforza_NP1 &amp;_CC Bodmer_NP1 ,_, 1961_MC ;_; Maynard_NP1 Smith_NP1 ,_, 1969_MC ;_; Grafen_NP1 ,_, 1982_MC )_) ._. 
This_DD1 may_VM not_XX always_RR be_VBI the_AT case_NN1 for_REX21 example_REX22 ,_, in_II rapidly_RR expanding_JJ populations_NN2 ,_, selection_NN1 may_VM favour_VVI reproductive_JJ rate_NN1 at_II the_AT expense_NN1 of_IO lifetime_NNT1 reproductive_JJ success_NN1 (_( see_VV0 Lewontin_NP1 ,_, 1965_MC ;_; Elliot_NP1 ,_, 1975_MC )_) but_CCB exceptions_NN2 are_VBR probably_RR rare_JJ ,_, especially_RR in_II long-lived_JJ species_NN where_CS variation_NN1 in_II longevity_NN1 greatly_RR exceeds_VVZ variation_NN1 in_II age_NN1 at_II first_MD breeding_NN1 ._. 
While_CS many_DA2 studies_NN2 of_IO sexual_JJ selection_NN1 pay_NN1 lip_NN1 service_NN1 to_II the_AT importance_NN1 of_IO basing_VVG calculations_NN2 on_II measures_NN2 of_IO lifetime_NNT1 success_NN1 ,_, most_DAT use_VV0 estimates_NN2 of_IO success_NN1 calculated_VVD over_RP a_AT1 part_NN1 of_IO the_AT animal_NN1 's_GE lifespan_NN1 ._. 
The_AT time_NNT1 dimension_NN1 used_VVN varies_VVZ widely_RR :_: some_DD studies_NN2 use_VV0 measures_NN2 of_IO instantaneous_JJ reproductive_JJ success_NN1 (_( IRS_NN1 )_) calculated_VVD across_II different_JJ classes_NN2 of_IO males_NN2 at_II a_AT1 particular_JJ point_NN1 in_II time_NNT1 (_( e.g._REX Mason_NP1 ,_, 1964_MC ;_; Scheiring_NP1 ,_, 1977_MC ;_; McCauley_NP1 g&amp;_FO ,_, 1980_MC )_) ,_, while_CS others_NN2 measure_VV0 dally_RR reproductive_JJ success_NN1 (_( DRS_NP1 )_) or_CC seasonal_JJ reproductive_JJ success_NN1 (_( SRS_NP1 )_) (_( see_VV0 Howard_NP1 ,_, 1979_MC ;_; Payne_NP1 ,_, 1979_MC )_) ._. 
Very_RG recently_RR ,_, estimates_NN2 of_IO individual_JJ variation_NN1 in_II lifetime_NNT1 reproductive_JJ success_NN1 (_( LRS_NP1 )_) have_VH0 become_VVN available_JJ from_II field_NN1 studies_NN2 of_IO a_AT1 small_JJ number_NN1 of_IO species_NN ,_, including_II a_AT1 territorial_JJ and_CC promiscuous_JJ invertebrate_JJ ,_, the_AT dragonfly_NN1 Erythemis_NN1 simplicicolis_NN1 (_( McVey_NP1 ,_, 1981_MC )_) ,_, two_MC monogamous_JJ birds_NN2 ,_, the_AT great_JJ tit_NN1 ,_, Parus_NP1 major_JJ (_( McGregor_NP1 ,_, Krebs_NP2 &amp;_CC Perrins_NP1 ,_, 1981_MC )_) and_CC the_AT kittiwake_NN1 Rissa_NP1 tridactyla_NN1 (_( J._NP1 Coulson_NP1 &amp;_CC C._NP1 Thomas_NP1 ,_, personal_JJ communication_NN1 )_) ,_, and_CC one_MC1 polygynous_JJ mammal_NN1 ,_, the_AT red_JJ deer_NN ,_, Cervus_NP1 elaphus_NN1 (_( Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) while_CS in_II several_DA2 other_JJ species_NN ,_, including_II sage_NN1 grouse_NN (_( Centrocercus_NP1 urophasianus_NN1 :_: Wiley_NP1 ,_, 1973_MC )_) estimates_NN2 of_IO individual_JJ success_NN1 are_VBR available_JJ which_DDQ span_VV0 several_DA2 breeding_NN1 seasons_NNT2 ._. 
These_DD2 make_VV0 it_PPH1 possible_JJ ,_, for_IF the_AT first_MD time_NNT1 ,_, to_TO test_VVI the_AT extent_NN1 to_II which_DDQ variation_NN1 in_II instantaneous_JJ ,_, dally_RR and_CC seasonal_JJ reproductive_JJ success_NN1 reflect_VV0 variation_NN1 in_II lifetime_NNT1 success_NN1 ._. 
There_EX appears_VVZ to_TO be_VBI no_AT consistent_JJ relationship_NN1 between_II variation_NN1 in_II IRS_NN1 ,_, DRS_NP1 ,_, SRS_NP1 and_CC LRS_NP1 (_( see_VV0 Table_NN1 23._MC 1_MC1 )_) ._. 
There_EX are_VBR several_DA2 reasons_NN2 why_RRQ variation_NN1 in_II daily_JJ reproductive_JJ success_NN1 may_VM not_XX reflect_VVI variation_NN1 in_II either_RR seasonal_JJ or_CC lifetime_NNT1 success_NN1 ._. 
In_II many_DA2 polygynous_JJ species_NN reproductive_JJ success_NN1 varies_VVZ from_II hour_NNT1 to_II hour_NNT1 and_CC day_NNT1 to_II day_NNT1 and_CC this_DD1 may_VM cause_VVI variation_NN1 in_II IRS_NN1 or_CC DRS_NP1 to_TO overestimate_VVI variation_NN1 in_II SRS_NP1 and_CC LRS_NP1 ._. 
For_REX21 example_REX22 ,_, red_JJ deer_NN stags_NN2 which_DDQ hold_VV0 a_AT1 large_JJ harem_NN1 in_II a_AT1 sheltered_JJ site_NN1 on_II one_MC1 day_NNT1 may_VM have_VHI few_DA2 or_CC no_AT hinds_NN2 the_AT next_MD day_NNT1 if_CS the_AT wind_NN1 changes_NN2 (_( see_VV0 Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) ._. 
As_II a_AT1 result_NN1 ,_, measures_NN2 of_IO variation_NN1 in_II DRS_NP1 overestimate_VV0 SRS_NP1 and_CC LRS_NP1 in_II red_JJ deer_NN (_( see_VV0 Table_NN1 23.2_MC )_) ._. 
Estimates_NN2 of_IO variation_NN1 in_II DRS_NP1 and_CC SRS_NP1 in_II sage_NN1 grouse_NN (_( Centrocercus_NP1 urophasianus_NN1 )_) show_VV0 the_AT same_DA trend_NN1 though_CS estimates_NN2 of_IO variation_NN1 in_II DRS_NP1 and_CC LRS_NP1 were_VBDR similar_JJ in_II McVey_NP1 's_GE (_( 1981_MC )_) study_NN1 of_IO dragonflies_NN2 ._. 
In_RR21 addition_RR22 ,_, variation_NN1 in_II SRS_NP1 will_VM not_XX reflect_VVI variation_NN1 in_II LRS_NP1 (_( see_VV0 Gadgil_NP1 ,_, 1972_MC )_) if_CS individuals_NN2 that_CST breed_VV0 successfully_RR show_VV0 reduced_JJ success_NN1 in_II future_NN1 or_CC are_VBR likely_JJ to_TO cease_VVI breeding_NN1 or_CC die_VV0 earlier_RRR than_CSN less_RGR successful_JJ breeders_NN2 ._. 
There_EX is_VBZ evidence_NN1 that_CST successful_JJ reproduction_NN1 reduces_VVZ the_AT future_JJ reproductive_JJ capabilities_NN2 or_CC survival_NN1 of_IO females_NN2 in_II several_DA2 species_NN (_( e.g._REX Wooller_NP1 &amp;_CC Coulson_NP1 ,_, 1977_MC ;_; Altmann_NP1 ,_, Altmann_NP1 &amp;_CC Hausfater_NP1 ,_, 1978_MC ;_; Guinness_NP1 ,_, Albon_NP1 &amp;_CC Clutton-Brock_NP1 ,_, 1978_MC ;_; Bryant_NP1 ,_, 1979_MC )_) and_CC in_II some_DD species_NN successful_JJ males_NN2 are_VBR likely_JJ to_TO die_VVI before_II unsuccessful_JJ ones_NN2 (_( Geist_NN1 ,_, 1971_MC )_) ._. 
However_RR ,_, several_DA2 other_JJ studies_NN2 have_VH0 shown_VVN that_CST successful_JJ breeders_NN2 live_VV0 longer_RRR (_( Drosophila_NP1 melanogaster_NN1 :_: Partridge_NN &amp;_CC Farquhar_NP1 ,_, 198_MC 1_MC1 )_) ._. 
For_REX21 example_REX22 ,_, in_II red_JJ deer_NN stags_NN2 ,_, where_CS harem_NN1 size_NN1 is_VBZ one_MC1 of_IO the_AT principal_JJ determinants_NN2 of_IO reproductive_JJ success_NN1 (_( Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1979_MC ,_, 1982_MC )_) ,_, not_XX only_RR do_VD0 stags_NN2 that_CST hold_VV0 large_JJ harems_NN2 hold_VV0 them_PPHO2 for_IF longer_JJR within_II particular_JJ breeding_NN1 seasons_NNT2 than_CSN those_DD2 which_DDQ hold_VV0 smaller_JJR harems_NN2 (_( Fig._NN1 23._MC 1a_FO )_) ,_, but_CCB individuals_NN2 that_CST are_VBR consistently_RR successful_JJ in_II securing_VVG large_JJ harems_NN2 throughout_II their_APPGE lives_NN2 tend_VV0 to_TO live_VVI longer_RRR than_CSN their_APPGE less_RGR successful_JJ competitors_NN2 (_( Fig._NN1 23.1b_FO )_) ._. 
Trends_NN2 of_IO this_DD1 kind_NN1 will_VM produce_VVI an_AT1 opposite_JJ bias_NN1 and_CC may_VM cause_VVI variation_NN1 in_II SRS_NP1 to_TO underestimate_VVI variation_NN1 in_II LRS_NP1 ._. 
For_REX21 example_REX22 ,_, the_AT fighting_NN1 ability_NN1 and_CC reproductive_JJ success_NN1 of_IO red_JJ deer_NN stags_NN2 shows_VVZ a_AT1 pronounced_JJ peak_NN1 between_II the_AT ages_NN2 of_IO seven_MC and_CC ten_MC years_NNT2 (_( see_VV0 Fig._NN1 23,2_MC )_) ._. 
If_CS variation_NN1 in_II breeding_NN1 success_NN1 is_VBZ calculated_VVN for_IF stags_NN2 of_IO above_II a_AT1 year_NNT1 old_JJ (_( the_AT age_NN1 of_IO sexual_JJ maturity_NN1 )_) ,_, it_PPH1 greatly_RR exceeds_VVZ more_RGR realistic_JJ measures_NN2 of_IO variation_NN1 in_II breeding_NN1 success_NN1 such_II21 as_II22 variation_NN1 in_II seasonal_JJ success_NN1 within_II cohorts_NN2 or_CC lifetime_NNT1 success_NN1 (_( see_VV0 Table_NN1 23.3_MC )_) ._. 
This_DD1 effect_NN1 will_VM also_RR tend_VVI to_TO overestimate_VVI variation_NN1 in_II male_JJ success_NN1 relative_II21 to_II22 variation_NN1 in_II female_JJ success_NN1 (_( see_VV0 Fig._NN1 23.2_MC )_) ._. 
p_ZZ1 465_MC :_: TABLE_NN1 A_ZZ1 final_JJ problem_NN1 is_VBZ that_CST unless_CS breeding_NN1 success_NN1 is_VBZ measured_VVN across_II the_AT lifetime_NNT1 ,_, a_AT1 biased_JJ set_NN1 of_IO males_NN2 may_VM be_VBI sampled_VVN ._. 
Especially_RR in_II polygynous_JJ species_NN ,_, males_NN2 that_CST fail_VV0 to_TO win_VVI a_AT1 breeding_NN1 territory_NN1 spend_VV0 their_APPGE time_NNT1 on_II the_AT fringes_NN2 of_IO the_AT breeding_NN1 population_NN1 and_CC often_RR show_VV0 high_JJ mortality_NN1 ._. 
The_AT field_NN1 observer_NN1 approaching_VVG a_AT1 breeding_NN1 colony_NN1 is_VBZ likely_JJ to_TO see_VVI mostly_RR (_( if_CS not_XX only_RR )_) breeding_NN1 males_NN2 ._. 
If_CS he_PPHS1 calculates_VVZ the_AT extent_NN1 to_II which_DDQ reproductive_JJ success_NN1 varies_VVZ across_II adults_NN2 that_CST have_VH0 managed_VVN to_TO gain_VVI a_AT1 breeding_NN1 territory_NN1 ,_, he_PPHS1 will_VM underestimate_VVI the_AT real_JJ variance_NN1 since_CS he_PPHS1 will_VM exclude_VVI non-breeders_NN2 ._. 
Dividing_VVG by_II the_AT mean_JJ success_NN1 of_IO males_NN2 in_II this_DD1 sample_NN1 will_VM accentuate_VVI this_DD1 error_NN1 since_CS the_AT mean_JJ success_NN1 of_IO the_AT males_NN2 sampled_VVN will_VM be_VBI higher_JJR than_CSN that_DD1 of_IO the_AT male_JJ population_NN1 as_II a_AT1 whole_NN1 ._. 
Table_NN1 23.4_MC shows_NN2 how_RRQ the_AT restriction_NN1 of_IO the_AT sample_NN1 to_II harem_NN1 holding_VVG males_NN2 in_II red_JJ deer_NN reduces_VVZ estimates_NN2 of_IO daily_JJ variation_NN1 in_II the_AT number_NN1 of_IO females_NN2 held_VVD ._. 
Estimates_VVZ that_CST are_VBR probably_RR biased_VVN in_II this_DD1 way_NN1 are_VBR already_RR widespread_JJ in_II the_AT literature_NN1 (_( see_VV0 Trivers_NN2 ,_, 1976_MC ;_; ,_, Arnold_NP1 &amp;_CC Wade_NP1 ,_, 1983_MC )_) ._. 
pp._NNU2 4678_MC :_: TABLES_NN2 None_PN of_IO these_DD2 four_MC biases_NN2 are_VBR likely_JJ to_TO be_VBI consistent_JJ either_RR across_II the_AT two_MC sexes_NN2 or_CC across_II different_JJ species_NN :_: all_DB four_MC are_VBR more_RGR likely_JJ to_TO affect_VVI estimates_NN2 of_IO variation_NN1 in_II male_JJ success_NN1 than_CSN estimates_NN2 of_IO variation_NN1 in_II female_JJ success_NN1 in_II polygynous_JJ species_NN ,_, though_CS in_II contrary_JJ directions_NN2 ._. 
Ignoring_VVG short_JJ term_NN1 variation_NN1 and_CC age_NN1 effects_NN2 will_VM tend_VVI to_TO overestimate_VVI variation_NN1 in_II male_JJ success_NN1 relative_II21 to_II22 variation_NN1 in_II female_JJ success_NN1 ,_, which_DDQ is_VBZ usually_RR less_RGR strongly_RR age-dependent_JJ in_II polygynous_JJ species_NN (_( see_VV0 Fig._NN1 23.2_MC )_) and_CC less_RGR likely_JJ to_TO vary_VVI widely_RR from_II day_NNT1 to_II day_NNT1 ._. 
Conversely_RR ,_, positive_JJ correlations_NN2 between_II seasonal_JJ success_NN1 and_CC longevity_NN1 or_CC sampling_VVG only_RR successful_JJ males_NN2 will_VM lead_VVI to_TO underestimates_VVZ of_IO variation_NN1 in_II male_JJ success_NN1 relative_II21 to_II22 variation_NN1 in_II female_JJ success_NN1 ._. 
That_CST the_AT two_MC sets_NN2 of_IO biases_NN2 oppose_VV0 each_PPX221 other_PPX222 is_VBZ no_AT guarantee_NN1 that_CST short_JJ term_NN1 measures_NN2 of_IO reproductive_JJ success_NN1 will_VM provide_VVI reliable_JJ estimates_NN2 of_IO variation_NN1 in_II lifetime_NNT1 success_NN1 for_IF the_AT comparative_JJ strengths_NN2 of_IO the_AT different_JJ biases_NN2 probably_RR vary_VV0 widely_RR too_RR ._. 
Moreover_RR ,_, sex_NN1 differences_NN2 in_II the_AT length_NN1 of_IO effective_JJ reproductive_JJ lifespans_NN2 and_CC in_II the_AT influence_NN1 of_IO age_NN1 on_II breeding_NN1 success_NN1 are_VBR likely_JJ to_TO be_VBI more_RRR pronounced_VVN in_II polygynous_JJ species_NN than_CSN in_II monogamous_JJ ones_NN2 ._. 
As_II a_AT1 result_NN1 ,_, short-term_JJ estimates_NN2 of_IO variation_NN1 in_II male_JJ breeding_NN1 success_NN1 are_VBR likely_JJ to_TO overestimate_VVI the_AT extent_NN1 to_II which_DDQ male_JJ success_NN1 varies_VVZ in_II polygynous_JJ species_NN relative_II21 to_II22 similar_JJ measures_NN2 for_IF monogamous_JJ ones_NN2 ._. 
Biased_JJ estimates_NN2 of_IO variation_NN1 in_II reproductive_JJ success_NN1 may_VM also_RR cause_VVI the_AT effects_NN2 of_IO particular_JJ phenotypic_JJ traits_NN2 on_II reproductive_JJ success_NN1 to_TO be_VBI overestimated_VVN ._. 
This_DD1 applies_VVZ particularly_RR to_II traits_NN2 ,_, such_II21 as_II22 body_NN1 size_NN1 ,_, which_DDQ are_VBR themselves_PPX2 related_VVN to_TO age_VVI ._. 
For_REX21 example_REX22 ,_, where_CS the_AT body_NN1 size_NN1 and_CC reproductive_JJ success_NN1 of_IO males_NN2 both_RR increase_VV0 with_IW age_NN1 ,_, the_AT effects_NN2 of_IO size_NN1 on_II breeding_NN1 success_NN1 may_VM be_VBI grossly_RR exaggerated_VVN if_CS age_NN1 differences_NN2 in_II size_NN1 are_VBR ignored_VVN ._. 
This_DD1 effect_NN1 is_VBZ again_RT likely_JJ to_TO be_VBI stronger_JJR in_II males_NN2 than_CSN females_NN2 ._. 
The_AT most_RGT obvious_JJ conclusion_NN1 to_TO be_VBI drawn_VVN is_VBZ the_AT need_NN1 for_IF studies_NN2 of_IO the_AT extent_NN1 to_II which_DDQ lifetime_NNT1 success_NN1 varies_VVZ and_CC of_IO the_AT factors_NN2 which_DDQ affect_VV0 it_PPH1 ._. 
Where_CS this_DD1 is_VBZ impossible_JJ ,_, an_AT1 alternative_JJ approach_NN1 is_VBZ to_TO concentrate_VVI on_II studies_NN2 of_IO variation_NN1 in_II breeding_NN1 success_NN1 within_II cohorts_NN2 but_CCB ,_, even_RR here_RL ,_, problems_NN2 will_VM arise_VVI if_CSW breeding_NN1 success_NN1 is_VBZ consistently_RR related_VVN to_II longevity_NN1 ._. 
Polygyny_NN1 ,_, reproductive_JJ success_NN1 and_CC sexual_JJ dimorphism_NN1 The_AT theory_NN1 of_IO sexual_JJ selection_NN1 has_VHZ led_VVN to_II four_MC common_JJ predictions_NN2 about_II the_AT relationship_NN1 between_II breeding_NN1 success_NN1 and_CC sexual_JJ dimorphism_NN1 ._. 
Variation_NN1 in_II reproductive_JJ success_NN1 should_VM be_VBI greater_JJR in_II males_NN2 than_CSN females_NN2 in_II polygynous_JJ species_NN but_CCB similar_JJ in_II the_AT two_MC sexes_NN2 in_II monogamous_JJ ones_NN2 ._. 
Both_RR in_II red_JJ deer_NN and_CC in_II Erythemis_NP1 ,_, variation_NN1 in_II lifetime_NNT1 breeding_NN1 success_NN1 is_VBZ substantially_RR greater_JJR among_II males_NN2 than_CSN females_NN2 whereas_CS ,_, in_II kittiwakes_NN2 ,_, variation_NN1 is_VBZ similar_JJ in_II both_DB2 sexes_NN2 (_( Figs._NN2 23.3_MC ,_, 23.4_MC )_) ._. 
When_CS the_AT red_JJ deer_NN samples_NN2 are_VBR restricted_VVN to_II animals_NN2 that_CST reach_VV0 breeding_NN1 age_NN1 ,_, sex_NN1 differences_NN2 in_II the_AT extent_NN1 to_II which_DDQ breeding_NN1 success_NN1 varies_VVZ are_VBR accentuated_VVN (_( Table_NN1 23.5_MC )_) ._. 
Considering_CS21 that_CS22 male_JJ red_JJ deer_NN can_VM hold_VVI harems_NN2 of_IO over_RG thirty_MC hinds_NN2 ,_, it_PPH1 is_VBZ ,_, perhaps_RR ,_, surprising_JJ that_CST male_JJ success_NN1 does_VDZ not_XX vary_VVI more_RGR widely_RR ._. 
This_DD1 is_VBZ partly_RR because_CS only_RR a_AT1 proportion_NN1 of_IO hinds_NN2 conceive_VV0 in_II a_AT1 given_JJ year_NNT1 and_CC individual_JJ stags_NN2 rarely_RR hold_VV0 harems_NN2 throughout_II the_AT whole_JJ breeding_NN1 season_NNT1 ,_, and_CC partly_RR because_CS few_DA2 stags_NN2 breed_VV0 successfully_RR for_IF more_DAR than_CSN four_MC years_NNT2 ._. 
In_II contrast_NN1 ,_, the_AT range_NN1 of_IO breeding_NN1 success_NN1 among_II hinds_NN2 is_VBZ greater_JJR than_CSN might_VM be_VBI expected_VVN because_CS their_APPGE potential_JJ breeding_NN1 lifespans_NN2 are_VBR long_RR (_( over_RG 12_MC years_NNT2 )_) and_CC individuals_NN2 tend_VV0 to_TO be_VBI either_RR consistently_RR successful_JJ or_CC consistently_RR unsuccessful_JJ breeders_NN2 ._. 
Variation_NN1 in_II reproductive_JJ success_NN1 should_VM be_VBI greater_JJR among_II males_NN2 of_IO polygynous_JJ species_NN than_CSN among_II males_NN2 of_IO monogamous_JJ ones_NN2 ._. 
One_MC1 surprising_JJ result_NN1 of_IO the_AT comparison_NN1 between_II red_JJ deer_NN and_CC kittiwakes_NN2 is_VBZ that_DD1 variation_NN1 in_II lifetime_NNT1 breeding_NN1 success_NN1 is_VBZ little_RR greater_JJR in_II red_JJ deer_NN stags_NN2 than_CSN in_II male_JJ kittiwakes_NN2 (_( see_VV0 Table_NN1 23.5_MC )_) :_: in_II fact_NN1 if_CS all_DB individuals_NN2 born/hatched_VVN are_VBR included_VVN ,_, it_PPH1 is_VBZ slightly_RR (_( though_CS not_XX significantly_RR )_) greater_JJR in_II male_JJ kittiwakes_NN2 ._. 
The_AT comparison_NN1 is_VBZ an_AT1 unsatisfactory_JJ one_PN1 since_CS there_EX are_VBR important_JJ differences_NN2 in_II the_AT life_NN1 histories_NN2 of_IO the_AT two_MC species_NN :_: male_JJ kittiwakes_NN2 can_VM breed_VVI for_IF many_DA2 more_DAR seasons_NNT2 ,_, adult_NN1 mortality_NN1 is_VBZ not_XX so_RG strongly_RR age-dependent_JJ and_CC females_NN2 can_VM fledge_VVI up_RG21 to_RG22 three_MC young_JJ per_II year_NNT1 (_( see_VV0 Coulson_NP1 ,_, 1966_MC ,_, 1968_MC ;_; Coulson_NP1 &amp;_CC Wooller_NP1 ,_, 1976_MC ;_; Wooller_NP1 &amp;_CC Coulson_NP1 ,_, 1977_MC )_) ._. 
However_RR ,_, this_DD1 example_NN1 serves_VVZ to_TO emphasize_VVI how_RGQ misleading_JJ it_PPH1 can_VM be_VBI to_TO assume_VVI that_CST the_AT breeding_NN1 sex_NN1 ratio_NN1 necessarily_RR reflects_VVZ the_AT extent_NN1 to_II which_DDQ male_JJ reproductive_JJ success_NN1 varies_VVZ for_IF ,_, even_RR among_II closely_RR related_JJ species_NN ,_, it_PPH1 is_VBZ likely_JJ to_TO be_VBI the_AT case_NN1 that_CST males_NN2 have_VH0 substantially_RR longer_JJR breeding_NN1 lifespans_NN2 in_II monogamous_JJ species_NN than_CSN in_II polygynous_JJ ones_NN2 (_( see_VV0 Wiley_NP1 ,_, 1974_MC ;_; Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) ._. 
Direct_JJ competition_NN1 for_IF mates_NN2 will_VM be_VBI more_RGR intense_JJ among_II males_NN2 of_IO polygynous_JJ species_NN than_CSN among_II males_NN2 of_IO monogamous_JJ ones_NN2 ._. 
Fights_NN2 between_II males_NN2 can_VM be_VBI common_JJ and_CC dangerous_JJ in_II polygynous_JJ species_NN (_( see_VV0 Geist_NN1 ,_, 1971_MC )_) ._. 
However_RR ,_, competition_NN1 between_II males_NN2 can_VM also_RR be_VBI intense_JJ in_II monogamous_JJ species_NN (_( Lack_NN1 ,_, 1954_MC ;_; Kleiman_NP1 ,_, 1977_MC )_) and_CC data_NN are_VBR not_XX yet_RR available_JJ which_DDQ would_VM permit_VVI a_AT1 meaningful_JJ comparison_NN1 between_II the_AT two_MC groups_NN2 of_IO species_NN ._. 
In_II fact_NN1 ,_, it_PPH1 is_VBZ unsafe_JJ to_TO assume_VVI that_CST the_AT intensity_NN1 of_IO direct_JJ competition_NN1 between_II males_NN2 should_VM necessarily_RR be_VBI reduced_VVN in_II monogamous_JJ species_NN ._. 
Though_CS variation_NN1 in_II male_JJ success_NN1 may_VM be_VBI caused_VVN principally_RR by_II differences_NN2 in_II mate_NN1 or_CC territory_NN1 quality_NN1 (_( whereas_CS ,_, in_II polygynous_JJ species_NN ,_, differences_NN2 in_II mate_NN1 number_NN1 are_VBR the_AT main_JJ cause_NN1 of_IO differences_NN2 in_II success_NN1 :_: Bateman_NP1 ,_, 1948_MC ;_; Wade_NP1 ,_, 1979_MC ;_; Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) ,_, monogamous_JJ males_NN2 might_VM be_VBI expected_VVN to_TO compete_VVI as_RG intensely_RR for_IF the_AT best_JJT mates_NN2 or_CC territories_NN2 as_CSA do_VD0 polygynous_JJ males_NN2 for_IF the_AT biggest_JJT harems_NN2 ._. 
Where_CS this_DD1 is_VBZ not_XX the_AT case_NN1 ,_, it_PPH1 may_VM be_VBI because_CS males_NN2 can_VM not_XX identify_VVI the_AT breeding_NN1 potential_NN1 of_IO young_JJ females_NN2 or_CC because_CS female_JJ choice_NN1 pre-empts_VVZ male_JJ competition_NN1 rather_CS21 than_CS22 because_CS variation_NN1 in_II success_NN1 is_VBZ slight_JJ among_II males_NN2 ._. 
Sexual_JJ dimorphism_NN1 will_VM be_VBI most_RRT developed_VVN among_II strongly_RR polygynous_JJ species_NN and_CC least_RRT developed_VVN among_II monogamous_JJ ones_NN2 ._. 
In_II many_DA2 different_JJ groups_NN2 of_IO animals_NN2 there_EX is_VBZ an_AT1 association_NN1 between_II polygyny_NN1 and_CC sexual_JJ dimorphism_NN1 and_CC Darwin_NP1 himself_PPX1 was_VBDZ well_JJ aware_JJ of_IO the_AT relationship_NN1 ._. 
More_RGR recently_RR ,_, a_AT1 variety_NN1 of_IO studies_NN2 have_VH0 demonstrated_VVN statistical_JJ relationships_NN2 between_II the_AT degree_NN1 of_IO polygyny_NN1 and_CC the_AT development_NN1 of_IO sexual_JJ dimorphism_NN1 ,_, though_CS the_AT relationship_NN1 is_VBZ not_XX always_RR a_AT1 close_JJ one_PN1 (_( Ralls_NP2 ,_, 1977_MC )_) ._. 
Compared_VVN to_II monogamous_JJ species_NN ,_, polygynous_JJ ones_NN2 usually_RR show_VV0 greater_JJR sexual_JJ dimorphism_NN1 in_II body_NN1 size_NN1 (_( Clutton-Brock_NP1 ,_, Harvey_NP1 &amp;_CC Rudder_NP1 ,_, 1977_MC ;_; Shine_VV0 ,_, 1979_MC ;_; Alexander_NP1 et_RA21 al._RA22 ,_, 1979_MC )_) while_CS weapons_NN2 used_VVN in_II intraspecific_JJ combat_NN1 ,_, such_II21 as_II22 the_AT canines_NN2 of_IO primates_NN2 and_CC the_AT antlers_NN2 of_IO deer_NN ,_, are_VBR also_RR more_RRR developed_VVN in_II the_AT males_NN2 of_IO polygynous_JJ species_NN (_( Harvey_NP1 ,_, Kavanagh_NP1 &amp;_CC Clutton-Brock_NP1 ,_, 1978_MC ;_; Clutton-Brock_NP1 ,_, Albon_NP1 &amp;_CC Harvey_NP1 ,_, 1980_MC )_) ._. 
However_RR ,_, there_EX are_VBR many_DA2 exceptions_NN2 (_( Ralls_NP2 ,_, 1977_MC )_) ._. 
In_II some_DD groups_NN2 of_IO animals_NN2 ,_, the_AT relationship_NN1 between_II the_AT extent_NN1 of_IO polygyny_NN1 and_CC the_AT degree_NN1 of_IO sexual_JJ dimorphism_NN1 is_VBZ not_XX a_AT1 close_JJ one_PN1 (_( Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1977_MC )_) ._. 
In_RR21 addition_RR22 ,_, some_DD polygynous_JJ species_NN ,_, like_II Burchell_NP1 's_GE zebra_NN1 (_( Equus_NP1 burchelli_NN2 )_) ,_, show_VV0 little_JJ or_CC no_AT size_NN1 dimorphism_NN1 while_CS others_NN2 ,_, like_II the_AT spotted_JJ hyena_NN1 (_( Crocuta_NP1 crocuta_NN1 )_) and_CC the_AT Weddell_NP1 seal_NN1 (_( Leptonychotes_NP1 weddelli_NN2 )_) ,_, even_RR show_VV0 reversed_JJ dimorphism_NN1 (_( Klingel_NP1 ,_, 1972_MC ;_; Kruuk_NP1 ,_, 1972_MC ;_; Stirling_NP1 ,_, 1969_MC )_) ._. 
While_CS it_PPH1 is_VBZ possible_JJ that_CST some_DD of_IO these_DD2 exceptions_NN2 result_VV0 from_II the_AT differing_JJ energetic_JJ requirements_NN2 of_IO males_NN2 and_CC females_NN2 and_CC attendant_JJ selection_NN1 pressures_NN2 affecting_VVG the_AT relative_JJ size_NN1 of_IO the_AT two_MC sexes_NN2 (_( Selander_NP1 ,_, 1972_MC ;_; Downhower_NP1 ,_, 1976_MC )_) ,_, the_AT common_JJ association_NN1 between_II sex_NN1 differences_NN2 in_II size_NN1 and_CC the_AT development_NN1 of_IO male_JJ weaponry_NN1 suggests_VVZ that_DD1 selection_NN1 pressures_NN2 associated_VVN with_IW breeding_NN1 competition_NN1 are_VBR frequently_RR involved_VVN ._. 
To_TO interpret_VVI exceptions_NN2 to_II the_AT general_JJ rule_NN1 that_CST sexual_JJ dimorphism_NN1 increases_VVZ with_IW the_AT degree_NN1 of_IO polygyny_NN1 ,_, we_PPIS2 need_VV0 to_TO remember_VVI that_CST it_PPH1 is_VBZ the_AT comparative_JJ effects_NN2 of_IO phenotypic_JJ traits_NN2 on_II reproductive_JJ success_NN1 in_II males_NN2 and_CC females_NN2 that_CST will_VM determine_VVI the_AT degree_NN1 of_IO dimorphism_NN1 and_CC not_XX the_AT amount_NN1 of_IO variation_NN1 in_II reproductive_JJ success_NN1 per_RR21 se_RR22 (_( see_VV0 Price_NP1 ,_, 1970_MC ;_; Lande_NP1 ,_, 1980_MC )_) ._. 
For_REX21 example_REX22 ,_, while_CS sexual_JJ dimorphism_NN1 in_II size_NN1 is_VBZ likely_JJ to_TO evolve_VVI where_RRQ variation_NN1 in_II male_JJ success_NN1 is_VBZ greater_JJR than_CSN female_JJ success_NN1 and_CC a_AT1 given_JJ increment_NN1 in_II body_NN1 size_NN1 has_VHZ the_AT same_DA effect_NN1 on_II breeding_NN1 success_NN1 in_II both_DB2 sexes_NN2 ,_, it_PPH1 will_VM also_RR evolve_VVI if_CSW variation_NN1 in_II reproductive_JJ success_NN1 is_VBZ similar_JJ in_II both_DB2 sexes_NN2 but_CCB size_NN1 has_VHZ a_AT1 greater_JJR influence_NN1 on_II success_NN1 in_II males_NN2 or_CC even_CS21 if_CS22 variation_NN1 in_II success_NN1 is_VBZ greater_JJR in_II females_NN2 but_CCB the_AT effects_NN2 of_IO size_NN1 are_VBR greater_JJR among_II males_NN2 ._. 
Conversely_RR ,_, sexual_JJ dimorphism_NN1 in_II size_NN1 is_VBZ unlikely_JJ to_TO evolve_VVI in_II circumstances_NN2 where_RRQ variation_NN1 in_II reproductive_JJ success_NN1 is_VBZ greater_JJR among_II males_NN2 but_CCB the_AT effects_NN2 of_IO size_NN1 on_II reproductive_JJ success_NN1 are_VBR slight_JJ in_II both_DB2 sexes_NN2 ._. 
In_II the_AT simplest_JJT of_IO all_DB possible_JJ worlds_NN2 sexual_JJ dimorphism_NN1 should_VM ,_, perhaps_RR ,_, be_VBI predicted_VVN by_II the_AT relative_JJ slope_NN1 of_IO lifetime_NNT1 reproductive_JJ success_NN1 on_II body_NN1 size_NN1 in_II males_NN2 and_CC females_NN2 ._. 
However_RR ,_, there_EX is_VBZ no_AT reason_NN1 to_TO suppose_VVI that_CST relationships_NN2 between_II size_NN1 and_CC reproductive_JJ success_NN1 will_VM be_VBI linear_JJ or_CC that_CST they_PPHS2 will_VM follow_VVI a_AT1 similar_JJ pattern_NN1 in_II both_DB2 sexes_NN2 ._. 
Indeed_RR ,_, where_CS size_NN1 differences_NN2 are_VBR heritable_JJ and_CC stabilizing_VVG selection_NN1 is_VBZ operating_VVG ,_, there_EX is_VBZ every_AT1 reason_NN1 to_TO suppose_VVI that_CST relationships_NN2 between_II size_NN1 and_CC reproductive_JJ success_NN1 will_VM not_XX be_VBI linear_JJ ._. 
In_RR21 addition_RR22 ,_, even_RR a_AT1 knowledge_NN1 of_IO the_AT relationship_NN1 between_II body_NN1 size_NN1 and_CC lifetime_NNT1 reproductive_JJ success_NN1 in_II the_AT two_MC sexes_NN2 will_VM not_XX answer_VVI whether_CSW the_AT association_NN1 occurs_VVZ for_IF reasons_NN2 connected_VVN with_IW breeding_NN1 competition_NN1 or_CC because_CS the_AT two_MC sexes_NN2 differ_VV0 in_II their_APPGE energy_NN1 requirements_NN2 (_( see_VV0 Downhower_NP1 ,_, 1976_MC )_) ._. 
To_TO sort_VVI out_RP these_DD2 questions_NN2 ,_, it_PPH1 will_VM be_VBI necessary_JJ to_TO identify_VVI the_AT particular_JJ episodes_NN2 of_IO selection_NN1 during_II which_DDQ size_NN1 influences_NN2 breeding_NN1 success_NN1 in_II males_NN2 and_CC females_NN2 (_( see_VV0 Arnold_NP1 &amp;_CC Wade_NP1 ,_, 1983_MC )_) ._. 
This_DD1 argument_NN1 raises_VVZ the_AT question_NN1 of_IO why_RRQ it_PPH1 is_VBZ that_DD1 sexual_JJ dimorphism_NN1 and_CC polygyny_NN1 are_VBR related_VVN at_RR21 all_RR22 ._. 
The_AT most_RGT likely_JJ explanation_NN1 is_VBZ that_CST the_AT factors_NN2 determining_VVG breeding_NN1 success_NN1 in_II males_NN2 and_CC females_NN2 tend_VV0 to_TO be_VBI most_RGT similar_JJ in_II monogamous_JJ species_NN and_CC most_RGT different_JJ in_II highly_RR polygynous_JJ ones_NN2 ._. 
The_AT factors_NN2 affecting_VVG breeding_NN1 success_NN1 in_II males_NN2 and_CC females_NN2 certainly_RR differ_VV0 widely_RR in_II polygynous_JJ species_NN ._. 
For_REX21 example_REX22 ,_, in_II red_JJ deer_NN ,_, longevity_NN1 ,_, offspring_NN survival_NN1 and_CC home_NN1 range_NN1 quality_NN1 have_VH0 a_AT1 greater_JJR effect_NN1 on_II the_AT reproductive_JJ success_NN1 of_IO hinds_NN2 than_CSN on_II that_DD1 of_IO stags_NN2 ._. 
In_II contrast_NN1 ,_, fighting_VVG ability_NN1 ,_, body_NN1 size_NN1 and_CC (_( because_II21 of_II22 its_APPGE effect_NN1 on_II adult_NN1 size_NN1 )_) early_JJ growth_NN1 have_VH0 a_AT1 more_RGR important_JJ effect_NN1 on_II the_AT reproductive_JJ success_NN1 of_IO stags_NN2 than_CSN hinds_NN2 (_( Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) ._. 
The_AT factors_NN2 affecting_VVG lifetime_NNT1 success_NN1 in_II males_NN2 and_CC females_NN2 of_IO monogamous_JJ species_NN have_VH0 yet_RR to_TO be_VBI described_VVN ._. 
While_CS it_PPH1 is_VBZ clear_JJ that_CST they_PPHS2 will_VM not_XX be_VBI identical_JJ (_( see_VV0 McGregor_NP1 et_RA21 al._RA22 ,_, 1981_MC )_) ,_, it_PPH1 is_VBZ reasonable_JJ to_TO suppose_VVI that_DD1 ,_, especially_RR among_II species_NN that_CST pair_NN for_IF life_NN1 ,_, they_PPHS2 are_VBR likely_JJ to_TO be_VBI more_RGR similar_JJ than_CSN in_II polygynous_JJ species_NN ._. 
Selection_NN1 pressures_NN2 on_II males_NN2 and_CC females_NN2 Emphasis_NN1 on_II the_AT importance_NN1 of_IO understanding_VVG the_AT factors_NN2 affecting_VVG breeding_NN1 success_NN1 in_II males_NN2 and_CC females_NN2 has_VHZ the_AT advantage_NN1 that_CST it_PPH1 forces_VVZ us_PPIO2 to_TO ask_VVI specific_JJ comparative_JJ questions_NN2 concerning_II the_AT functional_JJ significance_NN1 of_IO particular_JJ sex_NN1 differences_NN2 ._. 
For_REX21 example_REX22 ,_, does_VDZ body_NN1 size_NN1 have_VH0 a_AT1 less_RGR important_JJ effect_NN1 on_II the_AT reproductive_JJ success_NN1 of_IO male_JJ zebras_NN2 than_CSN male_JJ bovids_NN2 because_CS zebras_NN2 fight_VV0 with_IW their_APPGE teeth_NN2 and_CC hooves_NN2 rather_II21 than_II22 by_II pushing_VVG ?_? 
Similarly_RR ,_, does_VDZ size_NN1 have_VHI a_AT1 greater_JJR effect_NN1 on_II reproductive_JJ success_NN1 in_II female_JJ Weddell_NP1 seals_NN2 compared_VVN to_II land_NN1 or_CC pack-ice_NN1 breeding_NN1 species_NN because_CS they_PPHS2 breed_VV0 on_II fast_JJ ice_NN1 and_CC defend_VV0 access_NN1 to_II water_NN1 holes_NN2 ?_? 
Conversely_RR ,_, is_VBZ body_NN1 size_NN1 less_RGR important_JJ in_II male_JJ Weddells_NP2 compared_VVD to_II other_JJ species_NN because_CS they_PPHS2 defend_VV0 underwater_JJ territories_NN2 where_RRQ success_NN1 depends_VVZ on_II manoeuvrability_NN1 and_CC because_CS females_NN2 are_VBR widely_RR dispersed_VVN ?_? 
Thinking_VVG in_II these_DD2 terms_NN2 may_VM help_VVI us_PPIO2 to_TO understand_VVI the_AT distribution_NN1 of_IO many_DA2 other_JJ sex_NN1 differences_NN2 ._. 
For_REX21 example_REX22 ,_, among_II hermaphroditic_JJ reef_NN1 fish_NN ,_, some_DD species_NN begin_VV0 life_NN1 as_CSA females_NN2 and_CC a_AT1 proportion_NN1 of_IO individuals_NN2 later_RRR become_VV0 males_NN2 (_( protogyny_NN1 )_) (_( Warner_NP1 ,_, Robertson_NP1 &amp;_CC Leigh_NP1 ,_, 1975_MC ;_; Robertson_NP1 &amp;_CC Hoffman_NP1 ,_, 1977_MC )_) ._. 
But_CCB in_II a_AT1 few_DA2 species_NN ,_, such_II21 as_II22 the_AT clown_NN1 fishes_NN2 (_( Amphiprion_NP1 )_) ,_, individuals_NN2 start_VV0 life_NN1 as_CSA males_NN2 and_CC a_AT1 proportion_NN1 later_RRR become_VV0 females_NN2 (_( protandry_NN1 )_) (_( Fricke_NP1 &amp;_CC Fricke_NP1 ,_, 1977_MC )_) ._. 
The_AT females_NN2 of_IO most_DAT protogynous_JJ species_NN spawn_VV0 on_II the_AT edge_NN1 of_IO the_AT reef_NN1 ,_, releasing_VVG their_APPGE eggs_NN2 into_II the_AT plankton_NN1 ,_, and_CC seldom_RR compete_VV0 for_IF spawning_VVG sites_NN2 ._. 
In_II contrast_NN1 ,_, female_JJ clownfish_NN1 lay_VVD their_APPGE eggs_NN2 around_II sea_NN1 anemones_NN2 which_DDQ they_PPHS2 subsequently_RR help_VV0 to_TO defend_VVI ._. 
Does_VDZ resource_VVI defence_NN1 by_II females_NN2 again_RT increase_VV0 the_AT benefits_NN2 of_IO large_JJ body_NN1 size_NN1 to_II female_JJ clownfish_NN1 while_CS reducing_VVG the_AT benefits_NN2 of_IO size_NN1 to_II males_NN2 as_II a_AT1 consequence_NN1 of_IO female_JJ dispersion_NN1 ?_? 
Understanding_VVG the_AT comparative_JJ effects_NN2 of_IO size_NN1 may_VM even_RR help_VVI to_TO explain_VVI variation_NN1 in_II birth_NN1 sex_NN1 ratios_NN2 ._. 
It_PPH1 has_VHZ been_VBN suggested_VVN that_CST in_II species_NN where_CS reproductive_JJ success_NN1 varies_VVZ more_RGR widely_RR among_II males_NN2 than_CSN females_NN2 and_CC is_VBZ influenced_VVN by_II parental_JJ investment_NN1 ,_, parents_NN2 who_PNQS can_VM afford_VVI to_TO invest_VVI heavily_RR in_II their_APPGE offspring_NN should_VM produce_VVI sons_NN2 while_CS those_DD2 that_CST can_VM not_XX do_VDI so_RR should_VM tend_VVI to_TO produce_VVI daughters_NN2 (_( Trivers_NP1 &amp;_CC Willard_NP1 ,_, 1973_MC )_) ._. 
In_II apparent_JJ contradiction_NN1 to_II the_AT theory_NN1 ,_, dominant_JJ female_JJ baboons_NN2 and_CC macaques_NN2 produce_VV0 more_DAR daughters_NN2 than_CSN sons_NN2 while_CS subordinates_NN2 produce_VV0 more_DAR sons_NN2 than_CSN daughters_NN2 (_( Altmann_NP1 ,_, 1980_MC ;_; Simpson_NP1 &amp;_CC Simpson_NP1 ,_, 1982_MC )_) ._. 
One_MC1 possible_JJ explanation_NN1 is_VBZ that_CST even_CS21 though_CS22 reproductive_JJ success_NN1 probably_RR varies_VVZ more_RGR widely_RR among_II males_NN2 in_II these_DD2 species_NN ,_, maternal_JJ rank_NN1 has_VHZ a_AT1 stronger_JJR effect_NN1 on_II the_AT success_NN1 of_IO daughters_NN2 since_CS females_NN2 remain_VV0 in_II their_APPGE mother_NN1 's_GE troop_NN1 and_CC inherit_VV0 her_APPGE rank_NN1 while_CS sons_NN2 disperse_VV0 to_II other_JJ groups_NN2 and_CC may_VM be_VBI unable_JK to_TO benefit_VVI substantially_RR from_II their_APPGE mother_NN1 's_GE rank_NN1 (_( Altmann_NP1 ,_, 1980_MC )_) ._. 
Perhaps_RR most_RGT importantly_RR ,_, emphasis_NN1 on_II examining_VVG the_AT effects_NN2 of_IO particular_JJ traits_NN2 on_II the_AT breeding_NN1 success_NN1 of_IO males_NN2 and_CC females_NN2 should_VM encourage_VVI us_PPIO2 to_TO investigate_VVI the_AT adaptive_JJ significance_NN1 of_IO sex_NN1 differences_NN2 whose_DDQGE functions_NN2 are_VBR not_XX immediately_RR obvious_JJ ._. 
For_REX21 example_REX22 ,_, in_II many_DA2 mammals_NN2 growing_VVG males_NN2 lay_VVD down_RP less_DAR body_NN1 fat_NN1 than_CSN females_NN2 (_( Glucksman_NP1 ,_, 1974_MC )_) and_CC suffer_VV0 heavier_JJR mortality_NN1 during_II periods_NN2 of_IO food_NN1 shortage_NN1 as_II a_AT1 consequence_NN1 (_( Clutton-Brock_NP1 et_RA21 al._RA22 ,_, 1982_MC )_) ._. 
One_MC1 possible_JJ explanation_NN1 is_VBZ that_CST because_CS early_JJ growth_NN1 exerts_VVZ a_AT1 greater_JJR effect_NN1 on_II reproductive_JJ success_NN1 in_II males_NN2 than_CSN females_NN2 (_( see_VV0 above_RL )_) ,_, selection_NN1 favours_VVZ increased_JJ investment_NN1 by_II young_JJ males_NN2 in_II growth_NN1 at_II the_AT expense_NN1 of_IO laying_VVG down_RP body_NN1 fat_NN1 to_TO assure_VVI survival_NN1 during_II periods_NN2 of_IO food_NN1 shortage_NN1 ._. 
This_DD1 prompts_VVZ the_AT question_NN1 as_II21 to_II22 whether_CSW young_JJ females_NN2 lay_VVD down_RP less_DAR fat_NN1 in_II species_NN showing_VVG reversed_JJ size_NN1 dimorphism_NN1 ._. 
Recent_JJ research_NN1 shows_VVZ that_CST this_DD1 is_VBZ the_AT case_NN1 in_II at_RR21 least_RR22 one_MC1 species_NN belonging_VVG to_II this_DD1 category_NN1 (_( the_AT European_JJ sparrow_NN1 hawk_NN1 :_: I._NP1 Newton_NP1 ,_, personal_JJ communication_NN1 )_) ._. 
These_DD2 explanations_NN2 are_VBR cautiously_RR worded_VVN and_CC necessarily_RR so_RR ,_, for_IF our_APPGE current_JJ knowledge_NN1 of_IO the_AT factors_NN2 affecting_VVG reproductive_JJ success_NN1 in_II males_NN2 and_CC females_NN2 is_VBZ rudimentary_JJ ._. 
Nevertheless_RR ,_, the_AT way_NN1 ahead_RL is_VBZ clear_JJ ._. 
If_CS we_PPIS2 wish_VV0 to_TO fulfil_VVI Charles_NP1 Darwin_NP1 's_GE ambition_NN1 of_IO understanding_VVG the_AT reasons_NN2 for_IF the_AT distribution_NN1 of_IO differences_NN2 between_II the_AT sexes_NN2 ,_, we_PPIS2 shall_VM need_VVI to_TO examine_VVI the_AT causes_NN2 of_IO variation_NN1 in_II lifetime_NNT1 breeding_NN1 success_NN1 among_II males_NN2 and_CC females_NN2 in_II natural_JJ populations_NN2 ._. 
RULES_NN2 FOR_IF CHANGING_VVG THE_AT RULES_NN2 PATRICK_NP1 BATESON_NP1 Few_DA2 biologists_NN2 have_VH0 not_XX at_II one_MC1 time_NNT1 or_CC another_DD1 marvelled_VVD at_II the_AT exquisite_JJ fit_JJ that_CST can_VM be_VBI found_VVN between_II the_AT characteristics_NN2 of_IO an_AT1 organism_NN1 and_CC the_AT characteristics_NN2 of_IO its_APPGE environment_NN1 ._. 
Darwin_NP1 was_VBDZ not_XX the_AT first_MD to_II marvel_NN1 but_CCB he_PPHS1 made_VVD the_AT notion_NN1 of_IO such_DA adaptedness_NN1 scientifically_RR respectable_JJ by_II providing_VVG an_AT1 explanation_NN1 of_IO how_RRQ it_PPH1 might_VM have_VHI come_VVN about_RP ._. 
Nowadays_RT ,_, most_DAT discussion_NN1 about_II adaptation_NN1 assumes_VVZ that_CST when_CS it_PPH1 is_VBZ found_VVN ,_, a_AT1 fit_JJ between_II organism_NN1 and_CC environment_NN1 is_VBZ the_AT result_NN1 of_IO evolutionary_JJ selection_NN1 pressures_NN2 and_CC nothing_PN1 else_RR (_( e.g._REX Lewontin_NP1 ,_, 1978_MC )_) ._. 
Furthermore_RR ,_, each_DD1 adaptation_NN1 is_VBZ supposedly_RR transmitted_VVN from_II one_MC1 generation_NN1 to_II the_AT next_MD by_II genetic_JJ means_NN alone_RR ._. 
However_RR ,_, these_DD2 assumptions_NN2 are_VBR manifestly_RR false_JJ when_CS applied_VVN to_II behaviour_NN1 particularly_RR the_AT behaviour_NN1 of_IO complex_JJ animals_NN2 (_( e.g._REX Lorenz_NP1 ,_, 1965_MC ;_; Hinde_NP1 ,_, 1968_MC )_) ._. 
Quite_RG obviously_RR a_AT1 great_JJ many_DA2 animals_NN2 are_VBR able_JK to_TO tune_VVI their_APPGE behaviour_NN1 to_II their_APPGE environments_NN2 by_II learning_NN1 and_CC by_II other_JJ developmental_JJ mechanisms_NN2 which_DDQ rely_VV0 on_II external_JJ triggering_VVG ._. 
When_CS faced_VVN with_IW an_AT1 example_NN1 of_IO adaptedness_NN1 in_II behaviour_NN1 ,_, at_RR21 least_RR22 three_MC explanations_NN2 can_VM be_VBI offered_VVN for_IF the_AT process_NN1 of_IO adaptation_NN1 ._. 
Consider_VV0 an_AT1 actual_JJ case_NN1 ,_, the_AT way_NN1 in_II which_DDQ a_AT1 long-tailed_JJ tit_NN1 makes_VVZ a_AT1 strong_JJ ,_, cryptic_JJ and_CC well-insulated_JJ place_NN1 in_II which_DDQ to_TO lay_VVI eggs_NN2 ._. 
Once_RR a_AT1 site_NN1 in_II a_AT1 bush_NN1 or_CC tree_NN1 has_VHZ been_VBN selected_VVN ,_, the_AT pair_NN of_IO long-ta_UH fled_VVD tits_NN2 search_VV0 for_IF moss_NN1 and_CC bring_VV0 it_PPH1 back_RP to_II the_AT site_NN1 ._. 
When_CS some_DD moss_NN1 has_VHZ stuck_VVN ,_, each_DD1 tit_NN1 collects_VVZ spiders_NN2 '_GE webs_NN2 and_CC stretches_VVZ them_PPHO2 across_II the_AT moss_NN1 ._. 
More_DAR moss_NN1 is_VBZ collected_VVN and_CC then_RT more_DAR spiders_NN2 '_GE webs_NN2 until_CS a_AT1 platform_NN1 has_VHZ been_VBN formed_VVN ._. 
The_AT bird_NN1 that_CST is_VBZ building_NN1 can_VM now_RT place_VVI moss_NN1 and_CC webs_NN2 around_II itself_PPX1 building_VVG up_II the_AT sides_NN2 of_IO the_AT nest_NN1 ._. 
When_CS the_AT nest-cup_NN1 is_VBZ well_RR formed_VVN the_AT bird_NN1 fetches_VVZ lichen_NN1 and_CC weaves_VVZ this_DD1 on_II21 to_II22 the_AT outside_II21 of_II22 the_AT nest_NN1 ._. 
Building_NN1 up_II the_AT sides_NN2 of_IO the_AT nest_NN1 is_VBZ resumed_VVN but_CCB is_VBZ periodically_RR interrupted_VVN so_CS21 that_CS22 more_DAR lichen_NN1 can_VM be_VBI added_VVN to_II the_AT outside_JJ ._. 
Eventually_RR ,_, the_AT bird_NN1 builds_VVZ the_AT walls_NN2 up_RP and_CC over_II itself_PPX1 to_TO form_VVI a_AT1 dome_NN1 ,_, but_CCB leaves_VVZ a_AT1 neat_JJ entrance_NN1 hole_NN1 at_II the_AT side_NN1 ._. 
Finally_RR ,_, the_AT nest_NN1 is_VBZ lined_VVN with_IW a_AT1 large_JJ number_NN1 of_IO feathers_NN2 (_( Tinbergen_NP1 ,_, 1953_MC ,_, cited_VVN in_II Thorpe_NP1 ,_, 1956_MC )_) ._. 
In_II principle_NN1 ,_, the_AT behaviour_NN1 of_IO the_AT tits_NN2 could_VM be_VBI adapted_VVN to_II the_AT job_NN1 of_IO building_VVG a_AT1 safe_JJ ,_, warm_JJ nest_NN1 for_IF offspring_NN in_II three_MC separate_JJ ways_NN2 ._. 
First_MD ,_, birds_NN2 performing_VVG the_AT appropriate_JJ actions_NN2 could_VM have_VHI had_VHN more_DAR surviving_JJ offspring_NN than_CSN those_DD2 making_VVG less_RGR good_JJ nests_NN2 ;_; consequently_RR ,_, in_II the_AT course_NN1 of_IO time_NNT1 ,_, genes_NN2 necessary_JJ for_IF the_AT expression_NN1 of_IO the_AT appropriate_JJ actions_NN2 spread_VVN through_II the_AT long-tailed_JJ tit_NN1 population_NN1 ._. 
Secondly_RR ,_, the_AT bird_NN1 could_VM copy_VVI what_DDQ another_DD1 more_RGR experienced_JJ bird_NN1 had_VHD done_VDN ;_; the_AT process_NN1 of_IO selecting_VVG the_AT actions_NN2 best_RRT adapted_VVN to_II the_AT environment_NN1 had_VHD gone_VVN on_RP in_II previous_JJ generations_NN2 and_CC been_VBN transmitted_VVN socially_RR ._. 
Thirdly_RR ,_, by_II experimenting_VVG on_II its_APPGE own_DA with_IW different_JJ materials_NN2 and_CC different_JJ actions_NN2 ,_, each_DD1 bird_NN1 could_VM assemble_VVI the_AT appropriate_JJ repertoire_NN1 for_IF building_NN1 nests_NN2 ._. 
The_AT three_MC processes_NN2 of_IO adaptation_NN1 and_CC the_AT three_MC sources_NN2 of_IO adaptedness_NN1 for_IF an_AT1 individual_NN1 are_VBR shown_VVN in_II Table_NN1 24.1_MC ._. 
All_DB three_MC processes_NN2 could_VM contribute_VVI to_II the_AT adaptedness_NN1 of_IO the_AT nestbuilding_NN1 ._. 
We_PPIS2 should_VM not_XX expect_VVI three_MC classes_NN2 of_IO behaviour_NN1 corresponding_VVG to_II the_AT three_MC processes_NN2 of_IO adaptation_NN1 ._. 
Furthermore_RR ,_, we_PPIS2 should_VM not_XX be_VBI surprised_VVN by_II the_AT extent_NN1 of_IO learning_NN1 and_CC imitation_NN1 that_CST can_VM be_VBI found_VVN ,_, particularly_RR in_II complex_JJ animals_NN2 ._. 
Cultural_JJ transmission_NN1 of_IO adapted_JJ behaviour_NN1 is_VBZ by_RR31 no_RR32 means_RR33 confined_VVN to_II humans_NN2 (_( see_VV0 Galef_NP1 ,_, 1976_MC ;_; Bonner_NP1 ,_, 1980_MC )_) ._. 
One_MC1 of_IO the_AT first_MD examples_NN2 to_TO be_VBI discovered_VVN in_II animals_NN2 was_VBDZ the_AT opening_NN1 of_IO milk_NN1 bottles_NN2 in_II Britain_NP1 by_II great_JJ tits_NN2 ,_, blue_JJ tits_NN2 and_CC coal_NN1 tits_NN2 ._. 
The_AT spread_NN1 of_IO the_AT habit_NN1 from_II a_AT1 few_DA2 scattered_JJ locations_NN2 before_II 1930_MC to_II a_AT1 great_JJ many_DA2 in_II 1947_MC was_VBDZ well_RR documented_VVN (_( Fisher_NP1 &amp;_CC Hinde_NP1 ,_, 1949_MC ;_; Hinde_NP1 &amp;_CC Fisher_NP1 ,_, 1951_MC )_) ._. 
The_AT animal_NN1 which_DDQ is_VBZ learning_NN1 does_VDZ not_XX operate_VVI like_II an_AT1 idiot_NN1 photographer_NN1 attempting_VVG to_TO take_VVI a_AT1 snap_NN1 of_IO everything_PN1 ._. 
What_DDQ an_AT1 animal_NN1 learns_VVZ is_VBZ highly_RR selective_JJ and_CC highly_RR ordered_VVN ._. 
The_AT instruments_NN2 for_IF changing_JJ behaviour_NN1 show_VV0 an_AT1 adapted_JJ regularity_NN1 which_DDQ suggests_VVZ that_CST they_PPHS2 themselves_PPX2 have_VH0 been_VBN subject_II21 to_II22 natural_JJ selection_NN1 during_II the_AT course_NN1 of_IO evolution_NN1 ._. 
With_IW precisely_RR this_DD1 point_NN1 in_II mind_NN1 ,_, Konrad_NP1 Lorenz_NP1 (_( 1965_MC )_) referred_VVD to_II the_AT '_GE innate_JJ school_NN1 marm_NN1 '_GE who_PNQS ,_, he_PPHS1 imagined_VVD ,_, was_VBDZ busy_JJ directing_VVG the_AT course_NN1 of_IO learning_NN1 ._. 
It_PPH1 is_VBZ worth_II noting_VVG that_DD1 what_DDQ Lorenz_NP1 meant_VVD by_II the_AT memorable_JJ phrase_NN1 was_VBDZ not_XX that_CST there_EX were_VBDR unlearned_JJ instructions_NN2 for_IF learning_NN1 ,_, but_CCB the_AT instructions_NN2 were_VBDR adapted_VVN for_IF their_APPGE present_JJ use_NN1 by_II natural_JJ selection_NN1 ._. 
The_AT importance_NN1 of_IO this_DD1 distinction_NN1 will_VM become_VVI apparent_JJ later_JJR ._. 
It_PPH1 is_VBZ more_RGR usual_JJ nowadays_RT to_TO use_VVI computer_NN1 metaphors_NN2 and_CC refer_VVI to_II the_AT programming_NN1 of_IO learning_NN1 (_( e.g._REX Pulliam_NP1 &amp;_CC Dunford_NP1 ,_, 1980_MC )_) ._. 
I_PPIS1 mildly_RR distrust_VV0 such_DA metaphors_NN2 ._. 
It_PPH1 can_VM be_VBI easily_RR assumed_VVN that_CST because_CS we_PPIS2 know_VV0 how_RRQ computers_NN2 work_VV0 we_PPIS2 therefore_RR know_VV0 how_RRQ learning_NN1 is_VBZ programmed_VVN ._. 
My_APPGE distrust_NN1 turns_VVZ into_II hostility_NN1 when_RRQ phrases_NN2 like_NN1 '_GE genetically_RR programmed_JJ '_GE are_VBR used_VVN instead_RR ._. 
Such_DA phrases_NN2 confuse_VV0 the_AT way_NN1 in_II which_DDQ coded_JJ information_NN1 is_VBZ transmitted_VVN from_II one_MC1 generation_NN1 to_II another_DD1 with_IW the_AT regularities_NN2 of_IO a_AT1 nervous_JJ system_NN1 ,_, which_DDQ itself_PPX1 is_VBZ the_AT outcome_NN1 of_IO an_AT1 ordered_JJ developmental_JJ process_NN1 ._. 
For_IF these_DD2 reasons_NN2 I_PPIS1 prefer_VV0 to_TO use_VVI the_AT phrase_NN1 '_GE rules_NN2 for_IF changing_VVG the_AT rules_NN2 '_GE (_( Bateson_NP1 ,_, 1976_MC )_) ._. 
A_AT1 necessary_JJ preliminary_JJ is_VBZ to_TO clarify_VVI the_AT meaning_NN1 of_IO the_AT term_NN1 '_GE rule_NN1 '_GE ._. 
Behaviour_NN1 is_VBZ very_RG far_RR from_II being_VBG disorderly_JJ ._. 
It_PPH1 may_VM be_VBI complex_JJ but_CCB it_PPH1 is_VBZ certainly_RR not_XX chaotic_JJ ._. 
Something_PN1 provides_VVZ direction_NN1 and_CC keeps_VVZ it_PPH1 in_II order_NN1 ._. 
Something_PN1 is_VBZ responsible_JJ for_IF the_AT regularity_NN1 ._. 
'_GE Rules_NN2 '_GE refer_VV0 to_II these_DD2 consistencies_NN2 of_IO behaviour_NN1 ._. 
In_II more_RGR complex_JJ animals_NN2 ,_, consistencies_NN2 are_VBR not_XX easily_RR found_VVN on_II the_AT surface_NN1 and_CC many_DA2 of_IO us_PPIO2 feel_VV0 the_AT need_NN1 to_TO postulate_VVI structural_JJ regularity_NN1 beneath_II the_AT surface_NN1 if_CS we_PPIS2 are_VBR to_TO make_VVI sense_NN1 of_IO what_DDQ we_PPIS2 see_VV0 ._. 
A_AT1 famous_JJ example_NN1 of_IO this_DD1 theoretical_JJ approach_NN1 is_VBZ Chomsky_NP1 's_GE (_( 1965_MC )_) analysis_NN1 of_IO language_NN1 in_II31 terms_II32 of_II33 underlying_VVG grammatical_JJ rules_NN2 ._. 
Not_XX everybody_PN1 likes_VVZ this_DD1 style_NN1 and_CC ,_, among_II psychologists_NN2 ,_, Skinner_NP1 (_( 1959_MC )_) in_RR21 particular_RR22 has_VHZ derided_VVN the_AT use_NN1 of_IO concepts_NN2 based_VVN on_II inferred_VVD structures_NN2 and_CC processes_NN2 ._. 
It_PPH1 must_VM be_VBI admitted_VVN that_CST concepts_NN2 referring_VVG to_II unseen_JJ processes_NN2 tend_VV0 to_TO acquire_VVI additional_JJ meanings_NN2 that_CST are_VBR not_XX suggested_VVN by_II the_AT evidence_NN1 they_PPHS2 are_VBR intended_VVN to_TO explain_VVI (_( see_VV0 MacCorquodale_NP1 &amp;_CC Meehl_NP1 ,_, 1948_MC )_) ._. 
Muddle_NN1 ensues_VVZ when_RRQ the_AT rules_NN2 are_VBR treated_VVN as_CS21 though_CS22 they_PPHS2 are_VBR tangible_JJ and_CC can_VM be_VBI observed_VVN directly_RR ._. 
But_CCB the_AT confusion_NN1 can_VM be_VBI avoided_VVN if_CS we_PPIS2 treat_VV0 unseen_JJ high-order_JJ rules_NN2 for_IF what_DDQ they_PPHS2 are_VBR ,_, namely_REX ,_, as_CSA explanatory_JJ devices_NN2 ._. 
When_CS that_DD1 is_VBZ done_VDN the_AT thinking_NN1 can_VM be_VBI creative_JJ and_CC rewarding_JJ ._. 
The_AT usage_NN1 of_IO '_GE rule_NN1 '_GE by_II biologists_NN2 is_VBZ clearly_RR different_JJ from_II that_DD1 employed_VVD by_II social_JJ scientists_NN2 when_CS they_PPHS2 talk_VV0 about_II verbally_RR transmitted_JJ instructions_NN2 for_IF what_DDQ humans_NN2 may_VM and_CC may_VM not_XX do_VDI ._. 
It_PPH1 would_VM obviously_RR avoid_VVI punning_VVG and_CC confusion_NN1 if_CS different_JJ terms_NN2 were_VBDR used_VVN ._. 
However_RR ,_, it_PPH1 is_VBZ unlikely_JJ that_CST biologists_NN2 will_VM be_VBI misunderstood_VVN when_CS they_PPHS2 apply_VV0 the_AT term_NN1 to_II animals_NN2 ._. 
In_II this_DD1 chapter_NN1 I_PPIS1 first_MD consider_VV0 the_AT underlying_JJ rules_NN2 for_IF associative_JJ learning_NN1 and_CC suggest_VV0 that_CST some_DD useful_JJ general_JJ principles_NN2 have_VH0 already_RR been_VBN uncovered_VVN ._. 
I_PPIS1 go_VV0 on_RP to_TO argue_VVI that_DD1 ,_, despite_II the_AT underlying_JJ regularities_NN2 ,_, the_AT behaviour_NN1 of_IO an_AT1 individual_JJ animal_NN1 is_VBZ only_RR predictable_JJ when_CS a_AT1 lot_NN1 is_VBZ known_VVN about_II the_AT conditions_NN2 in_II which_DDQ the_AT animal_NN1 has_VHZ grown_VVN up_RP ._. 
In_BCL21 order_BCL22 to_TO emphasize_VVI the_AT importance_NN1 of_IO this_DD1 point_NN1 ,_, I_PPIS1 devote_VV0 the_AT rest_NN1 of_IO the_AT chapter_NN1 to_II a_AT1 discussion_NN1 of_IO the_AT developmental_JJ rules_NN2 that_CST may_VM influence_VVI mate_NN1 choice_NN1 in_II humans_NN2 ._. 
A_AT1 growing_JJ understanding_NN1 of_IO such_DA rules_NN2 has_VHZ tempted_VVN biologists_NN2 into_II making_VVG exaggerated_JJ claims_NN2 about_II the_AT invariance_NN1 of_IO human_JJ mating_JJ preferences_NN2 and_CC also_RR about_II the_AT origins_NN2 of_IO incest_NN1 taboos_NN2 ._. 
I_PPIS1 argue_VV0 that_CST even_CS21 if_CS22 only_RR one_MC1 process_NN1 were_VBDR involved_VVN ,_, the_AT outcome_NN1 would_VM depend_VVI on_II conditions_NN2 and_CC ,_, since_CS conditions_NN2 vary_VV0 ,_, so_RR must_VM the_AT behavioural_JJ outcome_NN1 ._. 
For_IF all_DB that_DD1 ,_, I_PPIS1 conclude_VV0 that_CST the_AT postulated_JJ underlying_JJ rules_NN2 for_IF development_NN1 may_VM usefully_RR account_VVI for_IF some_DD of_IO the_AT variation_NN1 in_II human_JJ sexual_JJ behaviour_NN1 and_CC possibly_RR even_RR the_AT variation_NN1 in_II marriage_NN1 laws_NN2 ._. 
Rules_NN2 for_IF associative_JJ learning_NN1 Any_DD animal_NN1 with_IW even_RR a_AT1 rudimentary_JJ nervous_JJ system_NN1 will_VM be_VBI better_RRR placed_VVN if_CS it_PPH1 can_VM compute_VVI the_AT arrival_NN1 of_IO impending_JJ danger_NN1 or_CC the_AT location_NN1 of_IO valuable_JJ resources_NN2 such_II21 as_II22 food_NN1 or_CC mates_NN2 ._. 
Its_APPGE nervous_JJ system_NN1 does_VDZ not_XX have_VHI to_TO be_VBI modifiable_JJ in_II order_NN1 to_TO work_VVI with_IW reasonable_JJ efficiency_NN1 in_II this_DD1 way_NN1 ._. 
Even_RR21 so_RR22 ,_, the_AT power_NN1 to_TO predict_VVI and_CC control_VVI the_AT environment_NN1 is_VBZ enormously_RR enhanced_VVN by_II a_AT1 capacity_NN1 to_TO associate_VVI neutral_JJ events_NN2 with_IW those_DD2 that_CST already_RR have_VH0 some_DD importance_NN1 for_IF the_AT animal_NN1 ._. 
With_IW such_DA capacity_NN1 ,_, initially_RR meaningless_JJ cues_NN2 and_CC initially_RR haphazard_JJ or_CC exploratory_JJ acts_NN2 can_VM acquire_VVI causal_JJ significance_NN1 ._. 
What_DDQ could_VM be_VBI the_AT rules_NN2 for_IF the_AT necessary_JJ associative_JJ learning_NN1 processes_NN2 ?_? 
One_MC1 very_RG obvious_JJ possibility_NN1 would_VM be_VBI a_AT1 time-window_NN1 preceding_VVG the_AT important_JJ event_NN1 ._. 
If_CS a_AT1 neutral_JJ event_NN1 occurs_VVZ within_II this_DD1 time-window_NN1 then_RT it_PPH1 loses_VVZ its_APPGE neutrality_NN1 ._. 
To_TO give_VVI a_AT1 text-book_NN1 example_NN1 ,_, college_NN1 students_NN2 were_VBDR trained_VVN in_II a_AT1 situation_NN1 in_II which_DDQ a_AT1 buzzer_NN1 was_VBDZ sounded_VVN before_RT ,_, after_CS or_CC together_RL with_IW the_AT delivery_NN1 of_IO a_AT1 mild_JJ electric_JJ shock_NN1 to_II the_AT finger_NN1 (_( Spooner_NP1 &amp;_CC Kellogg_NP1 ,_, 1947_MC )_) ._. 
Periodically_RR ,_, the_AT students_NN2 '_GE responses_NN2 to_II the_AT buzz_FU alone_RR were_VBDR tested_VVN ._. 
The_AT students_NN2 who_PNQS ,_, in_II the_AT training_NN1 trials_NN2 ,_, heard_VVD the_AT buzz_FU half_RR a_AT1 second_NNT1 before_II the_AT shock_NN1 ,_, jerked_VVD their_APPGE finger_NN1 back_NN1 more_RGR consistently_RR than_CSN those_DD2 who_PNQS had_VHD had_VHN a_AT1 longer_JJR gap_NN1 between_II the_AT buzz_FU and_CC the_AT shock_NN1 during_II training_NN1 ,_, and_CC they_PPHS2 did_VDD so_RG much_DA1 more_DAR markedly_RR than_CSN those_DD2 who_PNQS heard_VVD the_AT buzz_FU at_II the_AT time_NNT1 of_IO the_AT shock_NN1 or_CC after_CS it_PPH1 (_( see_VV0 Fig._NN1 24.1_MC )_) ._. 
The_AT brief_JJ interval_NN1 allowed_VVN for_IF the_AT establishment_NN1 of_IO a_AT1 link_NN1 between_II neutral_JJ and_CC significant_JJ events_NN2 was_VBDZ at_II one_MC1 time_NNT1 elevated_VVN into_II a_AT1 general_JJ law_NN1 of_IO associative_JJ learning_NN1 ._. 
Equipped_VVN with_IW this_DD1 rule_NN1 and_CC with_IW knowledge_NN1 of_IO what_DDQ are_VBR important_JJ events_NN2 ,_, the_AT animal_NN1 seems_VVZ to_TO be_VBI well_RR set_VVN up_RP to_TO acquire_VVI the_AT ability_NN1 to_TO use_VVI initially_RR meaningless_JJ environmental_JJ cues_NN2 as_CSA predictors_NN2 of_IO what_DDQ will_VM happen_VVI ,_, and_CC initially_RR haphazard_JJ acts_NN2 as_CSA instruments_NN2 for_IF controlling_VVG the_AT environment_NN1 ._. 
While_CS it_PPH1 might_VM seem_VVI to_TO make_VVI good_JJ intuitive_JJ sense_NN1 that_CST a_AT1 time-window_NN1 should_VM be_VBI small_JJ ,_, substantial_JJ delay_NN1 in_II detectable_JJ effect_NN1 can_VM sometimes_RT follow_VVI the_AT performance_NN1 of_IO an_AT1 activity_NN1 ._. 
If_CS you_PPY eat_VV0 some_DD contaminated_JJ food_NN1 ,_, you_PPY will_VM not_XX necessarily_RR feel_VVI the_AT ill-effects_NN2 immediately_RR ._. 
Indeed_RR ,_, it_PPH1 is_VBZ well_RR known_VVN now_CS21 that_CS22 many_DA2 mammals_NN2 and_CC birds_NN2 can_VM develop_VVI aversions_NN2 to_II novel_JJ foods_NN2 that_CST were_VBDR followed_VVN by_II ill-effects_NN2 hours_NNT2 after_II ingestion_NN1 (_( reviewed_VVN by_II Domjan_NP1 ,_, 1980_MC )_) ._. 
Experiments_NN2 involve_VV0 a_AT1 spurious_JJ association_NN1 between_II the_AT novel_JJ food_NN1 and_CC the_AT illness_NN1 which_DDQ is_VBZ usually_RR induced_VVN chemically_RR or_CC by_II X-rays_NN2 ._. 
Nevertheless_RR ,_, the_AT animals_NN2 subsequently_RR avoid_VV0 the_AT novel_JJ food_NN1 ._. 
They_PPHS2 do_VD0 not_XX avoid_VVI familiar_JJ food_NN1 which_DDQ has_VHZ similarly_RR been_VBN followed_VVN by_II illness_NN1 ,_, and_CC only_RR certain_JJ cues_NN2 such_II21 as_II22 smells_NN2 and_CC tastes_NN2 associated_VVN with_IW the_AT novel_JJ food_NN1 are_VBR attended_VVN to_II ._. 
Others_NN2 ,_, such_II21 as_II22 noise_NN1 ,_, are_VBR treated_VVN as_CSA being_VBG irrelevant_JJ (_( see_VV0 Revusky_NP1 ,_, 1971_MC ;_; LoLordo_NP1 ,_, 1979_MC )_) ._. 
The_AT implication_NN1 is_VBZ that_CST the_AT animal_NN1 is_VBZ able_JK to_TO classify_VVI neutral_JJ events_NN2 prior_II21 to_II22 learning_NN1 and_CC has_VHZ a_AT1 rule_NN1 for_IF what_DDQ classes_NN2 are_VBR relevant_JJ to_II particular_JJ outcomes_NN2 ._. 
The_AT phenomenon_NN1 of_IO modifiable_JJ taste_NN1 aversion_NN1 is_VBZ often_RR taken_VVN as_CSA one_MC1 of_IO the_AT prime_JJ pieces_NN2 of_IO evidence_NN1 for_IF doubting_VVG general_JJ principles_NN2 of_IO associative_JJ learning_NN1 ._. 
It_PPH1 has_VHZ led_VVN some_DD people_NN to_TO argue_VVI that_CST the_AT only_JJ sensible_JJ way_NN1 to_TO study_VVI learning_NN1 is_VBZ by_II examining_VVG it_PPH1 in_II the_AT ecological_JJ conditions_NN2 to_II which_DDQ it_PPH1 is_VBZ adapted_VVN (_( Johnston_NP1 ,_, 1981_MC )_) ._. 
However_RR ,_, common_JJ features_NN2 can_VM be_VBI found_VVN ,_, whether_CSW a_AT1 rat_NN1 is_VBZ learning_VVG to_TO avoid_VVI poison_NN1 or_CC shock_NN1 ._. 
If_CS two_MC neutral_JJ events_NN2 of_IO the_AT same_DA class_NN1 are_VBR used_VVN ,_, the_AT second_MD one_PN1 interferes_VVZ with_IW learning_VVG about_II the_AT first_MD ._. 
For_REX21 instance_REX22 ,_, rats_NN2 were_VBDR given_VVN novel_JJ saccharin_NN1 solution_NN1 and_CC 1_MC1 5_MC min_NNU later_JJR were_VBDR given_VVN novel_JJ vinegar_NN1 solution_NN1 ,_, and_CC finally_RR they_PPHS2 were_VBDR made_VVN ill_JJ with_IW lithium_NN1 chloride_NN1 ._. 
Subsequently_RR ,_, they_PPHS2 were_VBDR much_RR less_RGR likely_JJ to_TO avoid_VVI the_AT saccharin_NN1 solution_NN1 than_CSN rats_NN2 which_DDQ had_VHD been_VBN given_VVN water_NN1 instead_II21 of_II22 vinegar_NN1 (_( Revusky_NP1 ,_, 1971_MC )_) ._. 
The_AT vinegar_NN1 had_VHD over-shadowed_VVN the_AT saccharin_NN1 ._. 
The_AT time-window_JJ idea_NN1 probably_RR has_VHZ to_TO be_VBI retained_VVN in_II a_AT1 watered-down_JJ form_NN1 because_CS if_CS an_AT1 animal_NN1 is_VBZ given_VVN novel_JJ food_NN1 followed_VVN by_II weeks_NNT2 of_IO familiar_JJ food_NN1 and_CC finally_RR made_VVN sick_JJ ,_, it_PPH1 is_VBZ unlikely_JJ that_CST it_PPH1 will_VM avoid_VVI novel_JJ food_NN1 ._. 
Nonetheless_RR ,_, the_AT notion_NN1 of_IO a_AT1 time-window_NN1 is_VBZ not_XX sufficient_JJ to_TO account_VVI for_IF what_DDQ is_VBZ found_VVN ._. 
The_AT rule_NN1 would_VM seem_VVI to_TO need_VVI a_AT1 triple_JJ condition_NN1 attached_VVN to_II it_PPH1 ._. 
If_CS a_AT1 neutral_JJ event_NN1 has_VHZ occurred_VVN within_II a_AT1 certain_JJ time_NNT1 of_IO an_AT1 already_RR important_JJ event_NN1 ,_, if_CS it_PPH1 was_VBDZ of_IO a_AT1 certain_JJ category_NN1 and_CC if_CS another_DD1 of_IO the_AT same_DA category_NN1 had_VHD not_XX been_VBN interposed_VVN between_II it_PPH1 and_CC the_AT important_JJ event_NN1 ,_, then_RT that_DD1 event_NN1 itself_PPX1 acquires_VVZ significance_NN1 for_IF the_AT animal_NN1 ._. 
At_II this_DD1 point_NN1 it_PPH1 would_VM be_VBI fair_JJ to_TO ask_VVI :_: what_DDQ has_VHZ all_DB the_AT work_NN1 on_II the_AT avoidance_NN1 of_IO shock_NN1 and_CC poisons_NN2 got_VVD to_TO do_VDI with_IW social_JJ behaviour_NN1 ?_? 
The_AT answer_NN1 is_VBZ that_DD1 associative_JJ aspects_NN2 of_IO learning_NN1 enable_VV0 the_AT individual_JJ to_TO cope_VVI not_XX only_RR with_IW its_APPGE physical_JJ environment_NN1 but_CCB also_RR with_IW its_APPGE social_JJ environment_NN1 ._. 
Humphrey_NP1 (_( 1976_MC )_) has_VHZ argued_VVN convincingly_RR that_CST animals_NN2 are_VBR in_II many_DA2 ways_NN2 over-equipped_VVN for_IF the_AT inanimate_JJ environment_NN1 ,_, but_CCB the_AT environment_NN1 provided_VVN by_II other_JJ animals_NN2 (_( particularly_RR clever_JJ ones_NN2 )_) is_VBZ especially_RR complex_JJ ,_, difficult_JJ to_TO predict_VVI and_CC difficult_JJ to_TO control_VVI ._. 
Predators_NN2 and_CC prey_NN1 have_VH0 to_TO be_VBI coped_VVN with_IW one_MC1 way_NN1 or_CC the_AT other_JJ ,_, but_CCB strong_JJ pressures_NN2 also_RR come_VV0 from_II social_JJ companions_NN2 ._. 
Social_JJ groups_NN2 are_VBR clearly_RR not_XX just_RR bands_VVZ of_IO competitors_NN2 and_CC individuals_NN2 often_RR need_VV0 each_PPX221 other_PPX222 for_IF survival_NN1 ._. 
Nevertheless_RR ,_, group_NN1 members_NN2 also_RR have_VH0 to_TO compete_VVI with_IW each_PPX221 other_PPX222 for_IF many_DA2 necessary_JJ resources_NN2 ._. 
In_II such_DA competitions_NN2 ,_, it_PPH1 is_VBZ not_XX simply_RR the_AT one_PN1 who_PNQS is_VBZ strongest_JJT who_PNQS wins_VVZ ._. 
It_PPH1 can_VM frequently_RR be_VBI the_AT one_PN1 with_IW the_AT best_JJT abilities_NN2 to_TO make_VVI complex_JJ calculations_NN2 about_II what_DDQ the_AT others_NN2 are_VBR up_II21 to_II22 ._. 
In_II31 terms_II32 of_II33 predicting_VVG and_CC controlling_VVG the_AT social_JJ environment_NN1 ,_, high_JJ technology_NN1 can_VM quite_RG clearly_RR be_VBI every_AT1 bit_NN1 as_RG important_JJ as_CSA brute_NN1 force_NN1 ._. 
It_PPH1 follows_VVZ that_CST in_II complex_JJ animals_NN2 in_RR21 particular_RR22 ,_, the_AT rules_NN2 for_IF learning_VVG the_AT rules_NN2 can_VM be_VBI as_RG much_DA1 to_TO do_VDI with_IW social_JJ interaction_NN1 as_CSA anything_PN1 else_RR ._. 
Development_NN1 of_IO rules_NN2 If_CS we_PPIS2 are_VBR right_JJ in_II our_APPGE inferences_NN2 about_II the_AT rules_NN2 for_IF associative_JJ learning_NN1 ,_, they_PPHS2 clearly_RR do_VD0 seem_VVI to_TO have_VHI adapted_VVN qualities_NN2 ._. 
They_PPHS2 fit_VV0 the_AT animal_NN1 's_GE information-gathering_JJ equipment_NN1 to_II particular_JJ problems_NN2 and_CC ,_, presumably_RR ,_, they_PPHS2 have_VH0 been_VBN subject_II21 to_II22 natural_JJ selection_NN1 during_II evolution_NN1 ._. 
Therefore_RR ,_, they_PPHS2 must_VM be_VBI transmitted_VVN in_II some_DD way_NN1 ,_, usually_RR genetically_RR ,_, from_II one_MC1 generation_NN1 to_II the_AT next_MD ._. 
At_II this_DD1 point_NN1 ,_, though_CS ,_, we_PPIS2 should_VM not_XX forget_VVI the_AT hard-learned_JJ lesson_NN1 that_CST an_AT1 evolutionary_JJ argument_NN1 is_VBZ not_XX the_AT same_DA as_CSA a_AT1 developmental_JJ one_PN1 ._. 
The_AT rules_NN2 for_IF modifying_VVG behaviour_NN1 do_VD0 not_XX spring_VVI fully_RR armed_VVN out_II21 of_II22 the_AT genome_NN1 ._. 
They_PPHS2 themselves_PPX2 have_VH0 to_TO develop_VVI and_CC ,_, clearly_RR ,_, they_PPHS2 represent_VV0 the_AT workings_NN2 of_IO an_AT1 already_RR functional_JJ nervous_JJ system_NN1 and_CC body_NN1 ._. 
The_AT extent_NN1 to_II which_DDQ their_APPGE development_NN1 involves_VVZ various_JJ kinds_NN2 of_IO experience_NN1 raises_VVZ an_AT1 entirely_RR separate_JJ issue_NN1 ._. 
As_II a_AT1 matter_JJ31 of_JJ32 fact_JJ33 we_PPIS2 know_VV0 that_CST ,_, at_RR21 least_RR22 in_II complicated_JJ animals_NN2 ,_, many_DA2 features_NN2 of_IO the_AT rules_NN2 are_VBR profoundly_RR modified_VVN by_II experience_NN1 ._. 
I_PPIS1 discovered_VVD this_DD1 painfully_RR myself_PPX1 when_CS I_PPIS1 went_VVD as_II a_AT1 visitor_NN1 to_II a_AT1 beautifully_RR equipped_VVN laboratory_NN1 to_TO work_VVI on_II learning_VVG in_II rhesus_NN1 monkeys_NN2 ._. 
The_AT laboratory_NN1 had_VHD some_DD elegant_JJ computer-controlled_JJ apparatus_NN1 for_IF teaching_VVG the_AT monkeys_NN2 to_TO discriminate_VVI between_II visual_JJ forms_NN2 such_II21 as_II22 letters_NN2 ._. 
If_CS the_AT monkey_NN1 pressed_VVD the_AT correct_JJ letter_NN1 it_PPH1 was_VBDZ rewarded_VVN with_IW a_AT1 peanut_NN1 by_II a_AT1 mechanical_JJ dispenser_NN1 which_DDQ was_VBDZ specially_RR designed_VVN for_IF this_DD1 kind_NN1 of_IO food_NN1 ._. 
Everything_PN1 was_VBDZ perfect_JJ except_CS21 that_CS22 when_CS I_PPIS1 came_VVD to_TO train_VVI experimentally_RR naive_JJ monkeys_NN2 ,_, I_PPIS1 discovered_VVD that_CST they_PPHS2 did_VDD not_XX like_VVI peanuts_NN2 ._. 
The_AT monkeys_NN2 had_VHD to_TO be_VBI deprived_VVN of_IO their_APPGE regular_JJ food_NN1 and_CC accustomed_JJ to_II the_AT peanuts_NN2 for_IF weeks_NNT2 before_CS they_PPHS2 would_VM take_VVI them_PPHO2 with_IW any_DD readiness_NN1 ,_, let_VVD alone_RR treat_VVI the_AT nuts_NN2 as_CSA rewards_NN2 for_IF appropriate_JJ behaviour_NN1 ._. 
In_II this_DD1 case_NN1 ,_, which_DDQ is_VBZ not_XX exceptional_JJ (_( see_VV0 Weiskrantz_NP1 &amp;_CC Cowey_NP1 ,_, 1963_MC )_) ,_, experience_NN1 expanded_VVD what_DDQ the_AT monkeys_NN2 regarded_VVN as_CSA acceptable_JJ food_NN1 ,_, and_CC at_II an_AT1 earlier_JJR stage_NN1 in_II development_NN1 experience_NN1 had_VHD narrowed_VVN the_AT range_NN1 ._. 
It_PPH1 could_VM be_VBI argued_VVN that_CST in_II such_DA instances_NN2 an_AT1 unlearnt_NN1 program_NN1 could_VM still_RR be_VBI detected_VVN at_II work_NN1 behind_II the_AT scenes_NN2 since_CS the_AT general_JJ category_NN1 of_IO food_NN1 ,_, and_CC its_APPGE effectiveness_NN1 as_II a_AT1 reward_NN1 ,_, was_VBDZ in_II some_DD sense_NN1 built_VVD in_RP ._. 
In_II other_JJ cases_NN2 though_CS ,_, it_PPH1 becomes_VVZ more_RGR difficult_JJ to_TO pinpoint_VVI what_DDQ might_VM or_CC might_VM not_XX act_VVI as_II a_AT1 reward_NN1 without_IW very_RG extensive_JJ knowledge_NN1 of_IO the_AT animal_NN1 's_GE previous_JJ experience_NN1 ._. 
For_REX21 instance_REX22 ,_, the_AT conditions_NN2 in_II which_DDQ it_PPH1 becomes_VVZ possible_JJ for_IF an_AT1 animal_NN1 to_TO perform_VVI an_AT1 act_NN1 that_CST would_VM bring_VVI it_PPH1 food_NN1 become_VV0 rewarding_VVG themselves_PPX2 ._. 
So_RR the_AT animal_NN1 will_VM work_VVI in_BCL21 order_BCL22 to_TO provide_VVI itself_PPX1 with_IW those_DD2 conditions_NN2 ._. 
In_II this_DD1 way_NN1 lengthy_JJ chains_NN2 of_IO behaviour_NN1 can_VM be_VBI developed_VVN with_IW any_DD one_MC1 event_NN1 providing_VVG the_AT terminating_JJ condition_NN1 for_IF one_MC1 action_NN1 and_CC the_AT enabling_JJ condition_NN1 for_IF the_AT next_MD (_( see_VV0 Kelleher_NP1 ,_, 1966_MC )_) ._. 
This_DD1 is_VBZ the_AT basis_NN1 for_IF many_DA2 complex_JJ circus_NN1 acts_NN2 performed_VVN by_II animals_NN2 ._. 
Beyond_II this_DD1 ,_, the_AT knowledge_NN1 of_IO the_AT ways_NN2 in_II which_DDQ initially_RR neutral_JJ cues_NN2 are_VBR treated_VVN as_CSA potentially_RR relevant_JJ or_CC ignored_VVN is_VBZ growing_JJ ,_, and_CC suggests_VVZ once_RR21 again_RR22 that_CST the_AT rules_NN2 for_IF learning_NN1 can_VM be_VBI influenced_VVN by_II the_AT nature_NN1 of_IO prior_JJ experience_NN1 (_( e.g._REX Dickinson_NP1 ,_, 1980_MC )_) ._. 
Presumably_RR ,_, if_CS the_AT rules_NN2 for_IF learning_NN1 are_VBR to_TO have_VHI any_DD universality_NN1 in_II natural_JJ conditions_NN2 ,_, the_AT experience_NN1 which_DDQ affects_VVZ them_PPHO2 must_VM be_VBI a_AT1 common_JJ feature_NN1 of_IO all_DB the_AT animals_NN2 having_VHG the_AT rules_NN2 in_II other_JJ words_NN2 ,_, the_AT variance_NN1 due_II21 to_II22 the_AT environment_NN1 is_VBZ normally_RR small_JJ in_II the_AT environment_NN1 to_II which_DDQ the_AT animal_NN1 is_VBZ adapted_VVN ._. 
Also_RR ,_, when_CS considering_VVG development_NN1 ,_, it_PPH1 must_VM be_VBI stressed_VVN that_CST we_PPIS2 do_VD0 not_XX have_VHI to_TO depend_VVI on_II an_AT1 infinite_JJ regress_NN1 ._. 
Quite_RG clearly_RR learning_NN1 does_VDZ not_XX have_VHI to_TO be_VBI involved_JJ in_II the_AT development_NN1 of_IO the_AT rules_NN2 for_IF learning_NN1 ._. 
For_REX21 instance_REX22 ,_, even_RR very_RG young_JJ rats_NN2 selectively_RR associate_JJ taste_NN1 with_IW poison_NN1 and_CC texture_NN1 with_IW electric_JJ shock_NN1 (_( Gemberling_NP1 ,_, Domjan_NP1 &amp;_CC Amsel_NP1 ,_, 1980_MC ;_; Domjan_NP1 ,_, 1980_MC )_) ._. 
So_RR ,_, in_II this_DD1 case_NN1 ,_, it_PPH1 looks_VVZ as_CS21 though_CS22 the_AT rules_NN2 for_IF forming_VVG some_DD associations_NN2 ,_, but_CCB not_XX others_NN2 ,_, are_VBR not_XX dependent_JJ on_II learning_VVG for_IF their_APPGE development_NN1 ._. 
But_CCB that_DD1 should_VM not_XX make_VVI anybody_PN1 complacent_JJ about_II the_AT developmental_JJ processes_NN2 ._. 
The_AT classic_JJ mistake_NN1 has_VHZ been_VBN to_TO confuse_VVI experiences_NN2 involved_JJ in_II learning_VVG with_IW all_DB other_JJ kinds_NN2 of_IO experience_NN1 which_DDQ the_AT animal_NN1 can_VM have_VHI during_II its_APPGE development_NN1 (_( see_VV0 Lehrman_NP1 ,_, 1970_MC )_) ._. 
All_DB sorts_NN2 of_IO environmental_JJ conditions_NN2 can_VM have_VHI nonspecific_JJ but_CCB profound_JJ influences_NN2 on_II behavioural_JJ development_NN1 without_IW involving_VVG learning_NN1 (_( see_VV0 Bateson_NP1 ,_, 1981_MC )_) ._. 
Change_VV0 the_AT social_JJ or_CC physical_JJ conditions_NN2 in_II which_DDQ the_AT animal_NN1 is_VBZ growing_VVG up_RP and_CC you_PPY may_VM find_VVI it_PPH1 ends_VVZ up_RP with_IW a_AT1 different_JJ set_NN1 of_IO rules_NN2 for_IF learning_NN1 ._. 
It_PPH1 will_VM seem_VVI obvious_JJ ,_, I_PPIS1 hope_VV0 ,_, that_CST a_AT1 rule_NN1 for_IF learning_VVG or_CC for_IF any_DD other_JJ kind_NN1 of_IO developmental_JJ process_NN1 ,_, is_VBZ not_XX a_AT1 gene_NN1 written_VVN large_JJ ._. 
We_PPIS2 have_VH0 no_AT reason_NN1 to_TO suppose_VVI that_CST there_EX is_VBZ any_DD simple_JJ correspondence_NN1 between_II gene_NN1 and_CC rule_NN1 for_IF changing_JJ behaviour_NN1 any_DD more_DAR than_CSN there_EX is_VBZ an_AT1 isomorphic_JJ relationship_NN1 between_II gene_NN1 and_CC behaviour_NN1 ._. 
So_RR why_RRQ make_VVI an_AT1 issue_NN1 out_II21 of_II22 it_PPH1 ?_? 
The_AT reason_NN1 is_VBZ that_CST some_DD of_IO the_AT influential_JJ popularizers_NN2 of_IO modern_JJ evolutionary_JJ theory_NN1 still_RR manage_VV0 to_TO confuse_VVI the_AT developmental_JJ issue_NN1 with_IW the_AT evolutionary_JJ one_PN1 ._. 
Because_CS gene_NN1 frequencies_NN2 are_VBR generally_RR presumed_VVN to_TO change_VVI in_II phylogeny_NN1 ,_, then_RT it_PPH1 is_VBZ suggested_VVN that_CST genes_NN2 must_VM be_VBI doing_VDG the_AT real_JJ work_NN1 in_II ontogeny_NN1 ._. 
As_II a_AT1 result_NN1 of_IO this_DD1 category_NN1 mistake_NN1 ,_, total_JJ noncommunication_NN1 has_VHZ occurred_VVN between_II the_AT sociobiologists_NN2 and_CC their_APPGE critics_NN2 (_( see_VV0 Bateson_NP1 ,_, 1982b_FO )_) ._. 
The_AT distinct_JJ issues_NN2 are_VBR relatively_RR easy_JJ to_TO sort_VVI out_RP in_II the_AT case_NN1 of_IO associative_JJ learning_NN1 but_CCB ,_, as_CSA will_VM become_VVI apparent_JJ in_II the_AT remainder_NN1 of_IO this_DD1 chapter_NN1 ,_, they_PPHS2 are_VBR all_DB too_RG easily_RR muddled_JJ when_CS functional_JJ approaches_NN2 are_VBR brought_VVN to_TO bear_VVI on_II development_NN1 problems_NN2 ._. 
A_AT1 functional_JJ approach_NN1 to_II morality_NN1 I_PPIS1 am_VBM going_VVGK to_TO consider_VVI now_RT a_AT1 famous_JJ case_NN1 in_II which_DDQ the_AT supposed_JJ regularities_NN2 of_IO human_JJ morality_NN1 are_VBR attributed_VVN to_II the_AT workings_NN2 of_IO adaptive_JJ rules_NN2 ,_, so_RR providing_VVG an_AT1 evolutionary_JJ explanation_NN1 for_IF part_NN1 of_IO human_JJ culture_NN1 ._. 
The_AT evolutionary_JJ costs_NN2 in_II this_DD1 case_NN1 are_VBR those_DD2 due_II21 to_II22 inbreeding_NN1 ,_, and_CC the_AT cultural_JJ outcome_NN1 is_VBZ the_AT incest_NN1 taboo_NN1 ._. 
Two_MC quite_RG distinct_JJ arguments_NN2 are_VBR mounted_VVN ._. 
Since_CS these_DD2 are_VBR sometimes_RT confusingly_RR conflated_VVN ,_, it_PPH1 is_VBZ helpful_JJ to_TO keep_VVI them_PPHO2 separate_JJ even_CS21 though_CS22 they_PPHS2 are_VBR not_XX mutually_RR exclusive_JJ (_( see_VV0 Fig._NN1 24.2_MC )_) ._. 
The_AT first_MD argument_NN1 is_VBZ the_AT classical_JJ one_PN1 and_CC runs_VVZ as_CSA follows_VVZ ._. 
Human_JJ beings_NN2 ,_, being_VBG observant_JJ and_CC intelligent_JJ ,_, spot_VV0 the_AT consequences_NN2 of_IO matings_NN2 between_II close_JJ relatives_NN2 and_CC make_VV0 safety_NN1 laws_NN2 about_II them_PPHO2 ._. 
The_AT incest_NN1 taboo_NN1 is_VBZ equivalent_JJ to_II a_AT1 legal_JJ requirement_NN1 to_TO wear_VVI seat_NN1 belts_NN2 or_CC crash_VV0 helmets_NN2 ._. 
It_PPH1 is_VBZ sometimes_RT claimed_VVN that_CST people_NN in_II many_DA2 cultures_NN2 are_VBR aware_JJ of_IO the_AT ill-effects_NN2 of_IO inbreeding_NN1 (_( Lindzey_NP1 ,_, 1967_MC )_) ,_, but_CCB nobody_PN1 ,_, as_CS31 far_CS32 as_CS33 I_PPIS1 know_VV0 ,_, has_VHZ claimed_VVN that_CST such_DA knowledge_NN1 is_VBZ universal_JJ ._. 
Certainly_RR in_II modern_JJ statistical_JJ studies_NN2 ,_, differences_NN2 between_II children_NN2 of_IO inbred_JJ and_CC outbred_VVD marriages_NN2 can_VM be_VBI scarcely_RR detectable_JJ ,_, particularly_RR when_CS the_AT inbred_JJ marriages_NN2 occur_VV0 in_II communities_NN2 where_RRQ spouses_NN2 are_VBR traditionally_RR at_RR21 least_RR22 first-cousins_NN2 (_( e.g._REX Rao_NP1 &amp;_CC Inbaraj_NP1 ,_, 1977_MC )_) ._. 
Even_RR in_II outbred_JJ communities_NN2 it_PPH1 would_VM be_VBI very_RG difficult_JJ to_TO detect_VVI inbreeding_NN1 costs_VVZ when_RRQ infant_NN1 mortality_NN1 was_VBDZ high_JJ and_CC its_APPGE causes_NN2 and_CC those_DD2 of_IO deformities_NN2 in_II offspring_NN were_VBDR numerous_JJ and_CC varied_VVD ._. 
The_AT second_MD argument_NN1 about_II the_AT origins_NN2 of_IO the_AT incest_NN1 taboo_NN1 is_VBZ the_AT one_PN1 that_CST relates_VVZ to_II the_AT major_JJ theme_NN1 of_IO this_DD1 chapter_NN1 and_CC I_PPIS1 shall_VM consider_VVI it_PPH1 at_II some_DD length_NN1 ._. 
I_PPIS1 should_VM emphasize_VVI first_MD ,_, that_CST the_AT two_MC possibilities_NN2 shown_VVN in_II Fig._NN1 24.2_MC are_VBR not_XX the_AT only_JJ explanations_NN2 for_IF the_AT origins_NN2 of_IO the_AT incest_NN1 taboo_NN1 ._. 
Most_DAT anthropologists_NN2 would_VM prefer_VVI to_TO look_VVI elsewhere_RL ,_, partly_RR I_PPIS1 suspect_VV0 because_II21 of_II22 the_AT way_NN1 the_AT biological_JJ arguments_NN2 have_VH0 been_VBN overstated_VVN ._. 
The_AT biological_JJ part_NN1 of_IO the_AT second_MD argument_NN1 shown_VVN in_II Fig._NN1 24.2_MC is_VBZ well-trodden_JJ ground_NN1 and_CC has_VHZ been_VBN reviewed_VVN in_II numerous_JJ places_NN2 recently_RR (_( e.g._REX Alexander_NP1 ,_, 1980_MC ;_; Fox_NP1 ,_, 1980_MC ;_; Thiessen_NP1 &amp;_CC Gregg_NP1 ,_, 1980_MC ;_; Bixler_NP1 ,_, 1981_MC )_) ._. 
Westermarck_NP1 (_( 1891_MC )_) believed_VVD that_CST satisfying_JJ sexual_JJ relationships_NN2 are_VBR not_XX formed_VVN between_II people_NN who_PNQS have_VH0 spent_VVN their_APPGE childhood_NN1 together_RL ._. 
This_DD1 view_NN1 is_VBZ supported_VVN by_II the_AT behaviour_NN1 of_IO members_NN2 of_IO Israeli_JJ kibbutzim_NN1 who_PNQS very_RG rarely_RR marry_VV0 the_AT people_NN they_PPHS2 have_VH0 grown_VVN up_RP with_IW (_( Spiro_NP1 ,_, 1958_MC ;_; Talmon_NP1 ,_, 1964_MC ;_; Shepher_NP1 ,_, 1971_MC )_) ._. 
Other_JJ evidence_NN1 in_II31 support_II32 of_II33 the_AT Westermarck_NN1 hypothesis_NN1 comes_VVZ from_II the_AT work_NN1 of_IO Wolf_NN1 and_CC his_APPGE colleagues_NN2 ,_, summarized_VVN in_II a_AT1 recent_JJ book_NN1 (_( Wolf_NN1 &amp;_CC Huang_NP1 ,_, 1980_MC )_) ._. 
They_PPHS2 have_VH0 analysed_VVN a_AT1 form_NN1 of_IO arranged_JJ marriage_NN1 which_DDQ was_VBDZ practised_VVN in_II Taiwan_NP1 ._. 
The_AT wife-to-be_JJ was_VBDZ adopted_VVN into_II the_AT family_NN1 of_IO the_AT husband-to-be_NN1 when_CS she_PPHS1 was_VBDZ a_AT1 young_JJ girl_NN1 ._. 
The_AT marriage_NN1 was_VBDZ formalized_VVN and_CC consummated_VVN when_RRQ the_AT partners_NN2 were_VBDR adolescent_JJ ._. 
This_DD1 form_NN1 of_IO arranged_JJ marriage_NN1 ,_, the_AT '_GE minor_JJ marriage_NN1 '_GE ,_, could_VM be_VBI compared_VVN with_IW a_AT1 more_RGR common_JJ form_NN1 of_IO arranged_JJ marriage_NN1 ,_, the_AT '_GE major_JJ marriage_NN1 '_GE ,_, in_II which_DDQ the_AT partners_NN2 met_VVD each_PPX221 other_PPX222 for_IF the_AT first_MD time_NNT1 when_RRQ they_PPHS2 were_VBDR adolescents_NN2 ._. 
In_II a_AT1 great_JJ many_DA2 respects_NN2 the_AT minor_JJ marriages_NN2 were_VBDR less_RGR successful_JJ than_CSN the_AT major_JJ marriages_NN2 ._. 
They_PPHS2 generated_VVD fewer_DAR children_NN2 ,_, the_AT rates_NN2 of_IO infidelity_NN1 were_VBDR higher_JJR ,_, and_RR31 so_RR32 forth_RR33 ._. 
For_REX21 instance_REX22 ,_, 15%_NNU of_IO the_AT 1117_MC minor_JJ marriages_NN2 ended_VVN in_II divorce_NN1 whereas_CS only_RR 6%_NNU of_IO the_AT 1651_MC major_JJ marriages_NN2 did_VDD so_RR ._. 
On_II a_AT1 note_NN1 of_IO caution_NN1 ,_, it_PPH1 should_VM be_VBI pointed_VVN out_RP that_CST the_AT people_NN involved_JJ in_II minor_JJ marriages_NN2 were_VBDR considerably_RR younger_JJR at_II the_AT time_NNT1 of_IO the_AT formalization_NN1 of_IO the_AT marriage_NN1 than_CSN those_DD2 involved_JJ in_II the_AT major_JJ marriages_NN2 ._. 
Also_RR a_AT1 minor_JJ marriage_NN1 was_VBDZ a_AT1 much_RR cheaper_JJR option_NN1 for_IF the_AT parents_NN2 than_CSN a_AT1 major_JJ marriage_NN1 and_CC was_VBDZ ,_, therefore_RR ,_, considered_VVN to_TO be_VBI socially_RR disgraceful_JJ ._. 
These_DD2 factors_NN2 may_VM have_VHI contributed_VVN markedly_RR to_II the_AT relative_JJ lack_NN1 of_IO success_NN1 of_IO the_AT minor_JJ marriages_NN2 ._. 
Another_DD1 independent_JJ piece_NN1 of_IO evidence_NN1 corroborating_VVG the_AT Westermarck_NN1 hypothesis_NN1 is_VBZ provided_VVN by_II stable_JJ incestuous_JJ relationships_NN2 (_( Weinberg_NP1 ,_, 1956_MC )_) ._. 
Weinberg_NP1 found_VVD that_CST whereas_CS most_DAT incestuous_JJ relationships_NN2 were_VBDR unstable_JJ and_CC short-lived_JJ ,_, six_MC that_CST he_PPHS1 examined_VVD involved_JJ strong_JJ and_CC lasting_JJ attachments_NN2 between_II the_AT partners_NN2 ._. 
In_II each_DD1 case_NN1 the_AT siblings_NN2 concerned_JJ had_VHD been_VBN separated_VVN from_II each_PPX221 other_PPX222 when_CS they_PPHS2 were_VBDR babies_NN2 ._. 
Three_MC criticisms_NN2 are_VBR commonly_RR directed_VVN at_II the_AT evidence_NN1 for_IF the_AT Westermarck_NN1 hypothesis_NN1 ._. 
First_MD ,_, it_PPH1 is_VBZ pointed_VVN out_RP that_CST a_AT1 most_RGT preferred_JJ sexual_JJ partner_NN1 is_VBZ not_XX necessarily_RR a_AT1 spouse_NN1 (_( e.g._REX Solomon_NP1 ,_, 1978_MC )_) ;_; however_RR ,_, it_PPH1 is_VBZ difficult_JJ to_TO see_VVI how_RRQ this_DD1 perfectly_RR valid_JJ point_NN1 is_VBZ relevant_JJ to_II the_AT evidence_NN1 given_VVN above_RL ._. 
Secondly_RR ,_, overt_JJ sexuality_NN1 is_VBZ found_VVN between_II siblings_NN2 (_( Finkelhor_NP1 ,_, 1980_MC )_) and_CC among_II kibbutz_NN1 members_NN2 of_IO the_AT same_DA age_NN1 (_( Spiro_NP1 ,_, 1958_MC ;_; Kaffmann_NP1 ,_, 1977_MC )_) ._. 
Finally_RR ,_, despite_II supposed_JJ indifference_NN1 to_II familiar_JJ members_NN2 of_IO the_AT opposite_JJ sex_NN1 ,_, incest_NN1 does_VDZ occur_VVI quite_RG frequently_RR (_( Livingstone_NP1 ,_, 1980_MC )_) ._. 
I_PPIS1 shall_VM not_XX ignore_VVI these_DD2 criticisms_NN2 ,_, but_CCB at_II this_DD1 point_NN1 I_PPIS1 think_VV0 it_PPH1 is_VBZ helpful_JJ to_TO consider_VVI the_AT data_NN from_II animals_NN2 ._. 
Apart_II21 from_II22 strengthening_VVG the_AT view_NN1 that_CST reduced_VVD sexual_JJ responsiveness_NN1 to_II familiar_JJ members_NN2 of_IO the_AT opposite_JJ sex_NN1 is_VBZ quite_RG widespread_JJ in_II birds_NN2 and_CC mammals_NN2 ,_, the_AT animal_NN1 studies_NN2 also_RR suggest_VV0 ways_NN2 of_IO dealing_VVG with_IW criticisms_NN2 of_IO the_AT human_JJ evidence_NN1 ._. 
They_PPHS2 also_RR point_VV0 to_II other_JJ sources_NN2 of_IO variation_NN1 in_II mate_NN1 choice_NN1 ._. 
Imprinting_VVG and_CC discrepancy_NN1 hypothesis_NN1 The_AT effect_NN1 of_IO early_JJ experience_NN1 on_II the_AT mating_JJ preferences_NN2 of_IO birds_NN2 and_CC mammals_NN2 has_VHZ been_VBN known_VVN for_IF a_AT1 long_JJ time_NNT1 ._. 
The_AT effect_NN1 of_IO imprinting_VVG on_II the_AT sexual_JJ preferences_NN2 of_IO birds_NN2 was_VBDZ made_VVN famous_JJ many_DA2 years_NNT2 ago_RA by_II Konrad_NP1 Lorenz_NP1 (_( 1935_MC )_) ._. 
Numerous_JJ quantitative_JJ studies_NN2 have_VH0 been_VBN done_VDN on_II both_RR birds_NN2 and_CC mammals_NN2 in_II the_AT last_MD twenty_MC years_NNT2 (_( reviews_VVZ in_II Immelmann_NP1 ,_, 1972_MC ;_; Bateson_NP1 ,_, 1978a_FO )_) and_CC have_VH0 shown_VVN that_RG early_RR experience_VV0 can_VM have_VHI profound_JJ and_CC lasting_JJ effects_NN2 on_II sexual_JJ preferences_NN2 ._. 
Admittedly_RR ,_, imprinting_VVG was_VBDZ usually_RR thought_VVN of_IO as_CSA the_AT process_NN1 by_II which_DDQ animals_NN2 normally_RR learn_VV0 about_II the_AT characteristics_NN2 of_IO their_APPGE species_NN ,_, even_CS21 though_CS22 a_AT1 reference_NN1 was_VBDZ occasionally_RR made_VVN to_II '_GE asexual_JJ imprinting_NN1 '_GE (_( Aberle_NP1 et_RA21 al._RA22 ,_, 1963_MC )_) and_CC a_AT1 number_NN1 of_IO studies_NN2 were_VBDR done_VDN on_II the_AT reduced_JJ sexual_JJ responsiveness_NN1 to_II familiar_JJ members_NN2 of_IO the_AT opposite_JJ sex_NN1 in_II rodents_NN2 (_( reviews_VVZ in_II Dewsbury_NP1 ,_, 1982_MC ;_; D'Udine_NP1 &amp;_CC Alleva_NP1 ,_, 1983_MC )_) ._. 
In_RR21 general_RR22 ,_, though_CS ,_, thinking_NN1 was_VBDZ retarded_JJ by_II the_AT dichotomous_JJ classifications_NN2 that_CST were_VBDR in_II use_NN1 at_II the_AT time_NNT1 ._. 
Assortative_JJ mating_NN1 was_VBDZ either_RR positive_JJ or_CC negative_JJ ._. 
Animals_NN2 ,_, like_II humans_NN2 ,_, were_VBDR either_RR endogamous_JJ or_CC exogamous_JJ ,_, they_PPHS2 preferred_VVD the_AT familiar_JJ or_CC they_PPHS2 preferred_VVD the_AT novel_NN1 ._. 
It_PPH1 is_VBZ possible_JJ to_TO break_VVI out_II21 of_II22 the_AT straight-jacket_NN1 by_II applying_VVG an_AT1 idea_NN1 that_CST had_VHD been_VBN used_VVN for_IF many_DA2 years_NNT2 in_II thinking_VVG about_II the_AT psychology_NN1 of_IO classification_NN1 and_CC aesthetics_NN1 (_( McLlelland_NP1 &amp;_CC Clark_NP1 ,_, 1933_MC ;_; Berlyne_NP1 ,_, 1960_MC )_) ._. 
This_DD1 is_VBZ known_VVN as_II the_AT '_GE discrepancy_NN1 hypothesis_NN1 '_GE ._. 
In_RR21 general_RR22 ,_, what_DDQ people_NN find_VV0 most_RGT stimulating_JJ and_CC most_RGT attractive_JJ is_VBZ a_RR21 bit_RR22 different_JJ but_CCB not_XX too_RG different_JJ from_II what_DDQ they_PPHS2 know_VV0 already_RR ._. 
As_CSA is_VBZ shown_VVN in_II Fig._NN1 24.3_MC ,_, it_PPH1 was_VBDZ a_AT1 simple_JJ step_NN1 to_TO translate_VVI this_DD1 into_II a_AT1 hypothesis_NN1 about_II the_AT effects_NN2 of_IO early_JJ experience_NN1 on_II mating_JJ preferences_NN2 (_( Bischof_NP1 ,_, 1972_MC ;_; Bateson_NP1 ,_, 1978a_FO )_) ._. 
Experimental_JJ studies_NN2 on_II both_RR birds_NN2 and_CC mammals_NN2 followed_VVD quickly_RR (_( Bateson_NP1 ,_, 1978b_FO ;_; Gilder_NP1 &amp;_CC Slater_NP1 ,_, 1978_MC ;_; McGregor_NP1 &amp;_CC Krebs_NP2 ,_, 1982_MC )_) ._. 
However_RR ,_, it_PPH1 was_VBDZ not_XX all_DB plain_JJ sailing_NN1 ._. 
When_CS they_PPHS2 were_VBDR given_VVN a_AT1 choice_NN1 between_II a_AT1 familiar_JJ and_CC a_AT1 novel_JJ member_NN1 of_IO the_AT opposite_JJ sex_NN1 ,_, birds_NN2 might_VM actually_RR choose_VVI the_AT familiar_JJ even_CS21 when_CS22 the_AT novel_NN1 really_RR did_VDD not_XX look_VVI so_RG very_RG different_JJ to_II our_APPGE eyes_NN2 (_( Miller_NP1 ,_, 1979_MC ;_; Bateson_NP1 ,_, 1980_MC ;_; Slater_NP1 &amp;_CC Clements_NP1 ,_, 1981_MC )_) ._. 
The_AT results_NN2 suggested_VVD that_CST the_AT birds_NN2 might_VM have_VHI sharply_RR tuned_VVN preferences_NN2 only_RR slightly_RR displaced_VVN away_II21 from_II22 siblings_NN2 when_CS normally_RR reared_VVN ._. 
The_AT difficulty_NN1 is_VBZ that_CST ,_, if_CS the_AT most_RGT preferred_JJ mate_NN1 is_VBZ slightly_RR different_JJ from_II a_AT1 familiar_JJ member_NN1 of_IO the_AT opposite_JJ sex_NN1 and_CC if_CS we_PPIS2 do_VD0 not_XX know_VVI how_RRQ to_TO measure_VVI the_AT difference_NN1 ,_, we_PPIS2 can_VM unwittingly_RR present_VVI the_AT animal_NN1 with_IW a_AT1 novel_JJ object_NN1 which_DDQ is_VBZ less_RGR attractive_JJ than_CSN the_AT familiar_JJ ._. 
It_PPH1 might_VM seem_VVI as_CS21 though_CS22 the_AT hypothesis_NN1 is_VBZ so_RG slippery_JJ that_CST it_PPH1 can_VM not_XX be_VBI falsified_VVN ._. 
Indeed_RR ,_, this_DD1 point_NN1 has_VHZ been_VBN used_VVN as_II a_AT1 general_JJ criticism_NN1 of_IO the_AT discrepancy_NN1 hypothesis_NN1 (_( Thomas_NP1 ,_, 1971_MC )_) ._. 
However_RR ,_, the_AT issue_NN1 is_VBZ settled_VVN by_II positive_JJ evidence_NN1 not_XX by_II ingenious_JJ explanation_NN1 of_IO the_AT failure_NN1 to_TO confirm_VVI the_AT idea_NN1 ._. 
If_CS members_NN2 of_IO the_AT opposite_JJ sex_NN1 were_VBDR graded_VVN along_II a_AT1 continuum_NN1 from_II familiar_JJ to_II very_RG novel_JJ and_CC the_AT animals_NN2 were_VBDR allowed_VVN to_TO choose_VVI between_II all_DB the_AT possibilities_NN2 ,_, then_RT progress_NN1 can_VM be_VBI made_VVN ._. 
While_CS we_PPIS2 do_VD0 not_XX yet_RR know_VVI what_DDQ cues_VVZ the_AT animals_NN2 might_VM use_VVI ,_, we_PPIS2 can_VM exploit_VVI the_AT likelihood_NN1 that_CST ,_, when_CS other_JJ qualities_NN2 such_II21 as_II22 physical_JJ well-being_NN1 are_VBR equal_JJ ,_, an_AT1 optimal_JJ choice_NN1 of_IO mate_NN1 is_VBZ likely_JJ to_TO be_VBI one_PN1 that_CST minimizes_VVZ the_AT costs_NN2 of_IO both_RR inbreeding_NN1 and_CC outbreeding_VVG (_( Bateson_NP1 ,_, 1980_MC ,_, 1983_MC )_) ._. 
In_II other_JJ words_NN2 ,_, the_AT genetic_JJ relatedness_NN1 of_IO the_AT partner_NN1 is_VBZ likely_JJ to_TO be_VBI important_JJ ._. 
It_PPH1 is_VBZ a_AT1 relatively_RR easy_JJ matter_NN1 ,_, when_CS we_PPIS2 know_VV0 the_AT pedigrees_NN2 of_IO animals_NN2 ,_, to_TO arrange_VVI choices_NN2 between_II members_NN2 of_IO the_AT opposite_JJ sex_NN1 of_IO different_JJ degrees_NN2 of_IO relatedness_NN1 ._. 
I_PPIS1 have_VH0 done_VDN this_DD1 with_IW Japanese_JJ quail_NN ._. 
Birds_NN2 that_CST had_VHD been_VBN reared_VVN with_IW siblings_NN2 were_VBDR tested_VVN in_II apparatus_NN1 that_CST allowed_VVD them_PPHO2 to_TO be_VBI given_VVN up_RG21 to_RG22 six_MC alternatives_NN2 (_( Bateson_NP1 ,_, 1982a_FO )_) ._. 
In_II one_MC1 experiment_NN1 birds_NN2 were_VBDR given_VVN choices_NN2 between_II members_NN2 of_IO the_AT opposite_JJ sex_NN1 that_CST were_VBDR either_RR familiar_JJ siblings_NN2 ,_, novel_JJ siblings_NN2 ,_, novel_JJ first-cousins_NN2 ,_, novel_JJ third-cousins_NN2 ,_, or_CC novel_JJ unrelated_JJ individuals_NN2 ._. 
Fig._NN1 24.4_MC shows_VVZ the_AT mean_JJ percentage_NN1 durations_NN2 spent_VVN in_II31 front_II32 of_II33 each_DD1 category_NN1 of_IO stimulus_NN1 bird_NN1 by_II both_DB2 adult_JJ males_NN2 and_CC females_NN2 ._. 
The_AT time_NNT1 spent_VVN near_II novel_JJ first-cousins_NN2 was_VBDZ significantly_RR greater_JJR than_CSN the_AT time_NNT1 spent_VVN near_II both_DB2 the_AT familiar_JJ and_CC novel_JJ siblings_NN2 and_CC novel_JJ unrelated_JJ individuals_NN2 ._. 
Despite_II the_AT clear_JJ overall_JJ preference_NN1 for_IF first-cousins_NN2 ,_, the_AT data_NN were_VBDR highly_RR variable_JJ ._. 
The_AT variability_NN1 was_VBDZ expected_VVN as_II the_AT degree_NN1 of_IO relationship_NN1 between_II two_MC individuals_NN2 only_RR indicates_VVZ the_AT probability_NN1 that_CST the_AT two_MC share_VV0 heritable_JJ characters_NN2 ._. 
Knowledge_NN1 by_II a_AT1 bird_NN1 of_IO a_AT1 sibling_NN1 's_GE appearance_NN1 must_VM necessarily_RR be_VBI an_AT1 imperfect_JJ guide_NN1 to_II what_DDQ a_AT1 first-cousin_NN1 will_VM look_VVI like_II ._. 
Of_RR21 course_RR22 ,_, remaining_VVG near_II a_AT1 member_NN1 of_IO the_AT opposite_JJ sex_NN1 is_VBZ not_XX the_AT same_DA as_CSA mating_VVG with_IW it_PPH1 ._. 
However_RR ,_, other_JJ experiments_NN2 have_VH0 shown_VVN that_CST ,_, in_II adult_JJ male_JJ Japanese_JJ quail_NN ,_, the_AT time_NNT1 spent_VVN near_II a_AT1 female_NN1 in_II a_AT1 choice_NN1 test_NN1 is_VBZ strongly_RR linked_VVN to_II the_AT copulation_NN1 preference_NN1 (_( Bateson_NP1 ,_, 1978b_FO )_) ._. 
Furthermore_RR ,_, the_AT males_NN2 are_VBR observed_VVN to_II court_NN1 the_AT females_NN2 in_II the_AT choice_NN1 tests_NN2 ._. 
Finally_RR ,_, I_PPIS1 had_VHD found_VVN in_II other_JJ experiments_NN2 that_CST birds_NN2 show_VV0 no_AT consistent_JJ preferences_NN2 for_IF members_NN2 of_IO the_AT same_DA sex_NN1 ._. 
The_AT results_NN2 with_IW quail_NN provide_VV0 direct_JJ support_NN1 for_IF the_AT discrepancy_NN1 hypothesis_NN1 as_CSA applied_VVN to_II sexual_JJ preferences_NN2 and_CC indirect_JJ support_NN1 for_IF the_AT notion_NN1 of_IO optimal_JJ outbreeding_NN1 ._. 
I_PPIS1 have_VH0 written_VVN elsewhere_RL about_II the_AT evolutionary_JJ pressures_NN2 which_DDQ might_VM generate_VVI a_AT1 balance_NN1 between_II inbreeding_NN1 and_CC outbreeding_VVG (_( Bateson_NP1 ,_, 1983_MC )_) ._. 
However_RR ,_, it_PPH1 is_VBZ worth_II emphasizing_VVG here_RL that_CST at_RR21 least_RR22 four_MC costs_NN2 have_VH0 been_VBN proposed_VVN for_IF inbreeding_NN1 ,_, and_CC at_RR21 least_RR22 seven_MC for_IF outbreeding_VVG ._. 
The_AT costs_NN2 of_IO outbreeding_VVG may_VM include_VVI the_AT risks_NN2 of_IO infections_NN2 from_II pathogens_NN2 carried_VVN by_II the_AT partner_NN1 and_CC the_AT breaking_VVG up_RP in_II the_AT offspring_NN of_IO co-adapted_JJ complexes_NN2 of_IO genes_NN2 found_VVN in_II the_AT parents_NN2 ._. 
Not_XX all_DB costs_NN2 can_VM apply_VVI to_II all_DB species_NN and_CC some_DD naturally_RR outbreeding_VVG species_NN may_VM use_VVI other_JJ mechanisms_NN2 for_IF avoiding_VVG the_AT costs_NN2 of_IO inbreeding_NN1 ,_, such_II21 as_II22 dispersal_NN1 away_II21 from_II22 the_AT natal_JJ area_NN1 by_II one_MC1 sex_NN1 (_( reviewed_VVN by_II Greenwood_NP1 ,_, 1980_MC )_) ._. 
Even_RR in_II those_DD2 species_NN that_CST choose_VV0 a_AT1 mate_NN1 that_CST is_VBZ a_RR21 bit_RR22 different_JJ but_CCB not_XX too_RG different_JJ from_II close_JJ kin_NN ,_, other_JJ factors_NN2 are_VBR also_RR important_JJ ._. 
Qualities_NN2 such_II21 as_II22 the_AT physical_JJ condition_NN1 of_IO the_AT member_NN1 of_IO the_AT opposite_JJ sex_NN1 ,_, the_AT resources_NN2 it_PPH1 holds_VVZ and_CC the_AT extent_NN1 to_II which_DDQ it_PPH1 bears_VVZ characters_NN2 that_CST have_VH0 been_VBN subject_II21 to_II22 sexual_JJ selection_NN1 can_VM all_DB affect_VVI whether_CSW31 or_CSW32 not_CSW33 it_PPH1 is_VBZ chosen_VVN (_( see_VV0 Halliday_NP1 ,_, 1983_MC )_) ._. 
It_PPH1 would_VM be_VBI quite_RG wrong_JJ to_TO suggest_VVI that_CST the_AT only_JJ influence_NN1 on_II mate_NN1 choice_NN1 is_VBZ relative_JJ familiarity_NN1 ._. 
Despite_II the_AT variety_NN1 and_CC the_AT complexity_NN1 ,_, the_AT animal_NN1 work_NN1 indicates_VVZ first_MD and_CC foremost_RRT that_DD1 mate_NN1 choice_NN1 can_VM be_VBI profoundly_RR influenced_VVN by_II early_JJ experience_NN1 ._. 
Secondly_RR ,_, in_II some_DD species_NN the_AT choice_NN1 is_VBZ remarkably_RR finely_RR tuned_VVN so_CS21 that_CS22 under_II certain_JJ circumstances_NN2 familiarity_NN1 may_VM be_VBI preferred_VVN over_II novelty_NN1 ._. 
The_AT fine_JJ tuning_NN1 might_VM be_VBI achieved_VVN by_II employing_VVG two_MC well-known_JJ mechanisms_NN2 as_CSA shown_VVN in_II Fig._NN1 24.5_MC ._. 
Filial_JJ imprinting_NN1 is_VBZ known_VVN to_TO restrict_VVI preferences_NN2 to_II the_AT familiar_JJ (_( see_VV0 Bateson_NP1 ,_, 1979_MC )_) ,_, and_CC sexual_JJ imprinting_NN1 could_VM operate_VVI in_RP exactly_RR the_AT same_DA way_NN1 ._. 
Habituation_NN1 ,_, by_II contrast_NN1 ,_, reduces_VVZ responsiveness_NN1 to_II the_AT familiar_JJ ._. 
The_AT net_JJ effect_NN1 of_IO superimposing_VVG habituation_NN1 on_II imprinting_VVG would_VM be_VBI to_TO displace_VVI the_AT preference_NN1 away_II21 from_II22 the_AT familiar_JJ ._. 
The_AT combination_NN1 of_IO the_AT two_MC learning_NN1 processes_NN2 could_VM produce_VVI a_AT1 sharply_RR peaked_VVN preference_NN1 for_IF something_PN1 a_RR21 bit_RR22 different_JJ from_II the_AT familiar_JJ when_CS other_JJ things_NN2 are_VBR equal_JJ ._. 
Mating_JJ preferences_NN2 in_II humans_NN2 The_AT animal_NN1 evidence_NN1 enriches_VVZ the_AT discussion_NN1 of_IO human_JJ mating_JJ preferences_NN2 in_II several_DA2 important_JJ ways_NN2 ._. 
First_MD ,_, by_II emphasizing_VVG that_CST preferences_NN2 are_VBR displaced_VVN away_RL somewhat_RR from_II the_AT familiar_JJ ,_, it_PPH1 is_VBZ possible_JJ to_TO explain_VVI two_MC facets_NN2 of_IO the_AT data_NN from_II humans_NN2 that_CST would_VM otherwise_RR have_VHI seemed_VVN incompatible_JJ ._. 
Apart_II21 from_II22 the_AT evidence_NN1 of_IO reduced_JJ sexual_JJ interest_NN1 in_II familiar_JJ members_NN2 of_IO the_AT opposite_JJ sex_NN1 ,_, which_DDQ I_PPIS1 have_VH0 already_RR mentioned_VVN ,_, the_AT great_JJ mass_NN1 of_IO data_NN shows_VVZ that_CST freely_RR chosen_VVN human_JJ spouses_NN2 are_VBR more_RRR like_II each_PPX221 other_PPX222 than_CSN would_VM be_VBI expected_VVN on_II a_AT1 chance_NN1 basis_NN1 ._. 
Similarities_NN2 are_VBR not_XX only_RR social_JJ and_CC psychological_JJ ,_, but_CCB also_RR found_VVN in_II measures_NN2 of_IO body_NN1 dimensions_NN2 such_II21 as_II22 length_NN1 of_IO earlobe_NN1 (_( e.g._REX Eckland_NP1 ,_, 1968_MC ;_; Lewis_NP1 ,_, 1975_MC ;_; Thiessen_NP1 &amp;_CC Gregg_NP1 ,_, 1980_MC )_) ._. 
A_AT1 second_MD point_NN1 is_VBZ that_CST the_AT method_NN1 of_IO testing_VVG choices_NN2 draws_VVZ attention_NN1 to_II the_AT relative_JJ nature_NN1 of_IO a_AT1 measured_JJ preference_NN1 ._. 
It_PPH1 will_VM rarely_RR be_VBI the_AT case_NN1 that_CST either_RR an_AT1 animal_NN1 or_CC a_AT1 human_NN1 will_VM be_VBI provided_VVN with_IW the_AT opportunity_NN1 to_TO mate_VVI with_IW an_AT1 absolutely_RR ideal_JJ member_NN1 of_IO the_AT opposite_JJ sex_NN1 ._. 
Furthermore_RR ,_, the_AT best_JJT available_JJ mating_NN1 may_VM be_VBI with_IW a_AT1 sibling_NN1 or_CC an_AT1 offspring_NN on_II certain_JJ occasions_NN2 ._. 
Sexual_JJ responsiveness_NN1 to_II a_AT1 familiar_JJ member_NN1 of_IO the_AT opposite_JJ sex_NN1 may_VM not_XX be_VBI zero_MC particularly_RR when_CS the_AT time_NNT1 allotted_VVN to_II searching_VVG for_IF an_AT1 alternative_NN1 has_VHZ run_VVN out_RP ._. 
The_AT conclusion_NN1 is_VBZ ,_, therefore_RR ,_, that_CST when_CS an_AT1 individual_NN1 has_VHZ no_AT choice_NN1 or_CC an_AT1 impoverished_JJ set_NN1 of_IO choices_NN2 ,_, he_PPHS1 or_CC she_PPHS1 may_VM inbreed_VVI ._. 
Finally_RR ,_, the_AT precocious_JJ sexual_JJ behaviour_NN1 ,_, which_DDQ is_VBZ often_RR observed_VVN between_II siblings_NN2 and_CC was_VBDZ the_AT basis_NN1 for_IF Freud_NP1 's_GE (_( 1950_MC )_) thinking_VVG about_II the_AT development_NN1 of_IO sexual_JJ preferences_NN2 ,_, may_VM play_VVI a_AT1 role_NN1 ._. 
If_CS habituation_NN1 is_VBZ involved_JJ in_II displacing_VVG preferences_NN2 away_II21 from_II22 the_AT familiar_JJ to_II individuals_NN2 that_CST are_VBR slightly_RR different_JJ ,_, then_RT the_AT learning_NN1 process_NN1 may_VM be_VBI facilitated_VVN by_II the_AT performance_NN1 of_IO precocious_JJ sexual_JJ behaviour_NN1 which_DDQ is_VBZ common_JJ enough_RR in_II humans_NN2 (_( Finkelhor_NP1 ,_, 1980_MC )_) as_CSA it_PPH1 is_VBZ in_II other_JJ animals_NN2 ._. 
I_PPIS1 am_VBM not_XX convinced_JJ that_CST overt_JJ sexual_JJ behaviour_NN1 is_VBZ essential_JJ for_IF the_AT development_NN1 of_IO indifference_NN1 ,_, even_CS21 though_CS22 it_PPH1 may_VM help_VVI ._. 
But_CCB I_PPIS1 think_VV0 it_PPH1 is_VBZ highly_RR misleading_JJ to_TO suggest_VVI ,_, as_CSA Shepher_NP1 (_( 1971_MC )_) has_VHZ done_VDN ,_, that_DD1 development_NN1 of_IO sexual_JJ preferences_NN2 is_VBZ complete_JJ by_II the_AT age_NN1 of_IO six_MC in_II humans_NN2 ._. 
He_PPHS1 based_VVD this_DD1 conclusion_NN1 on_II a_AT1 very_RG few_DA2 individuals_NN2 who_PNQS married_VVD within_II their_APPGE peer_NN1 group_NN1 in_II the_AT kibbutz_NN1 and_CC were_VBDR found_VVN to_TO have_VHI entered_VVN the_AT kibbutz_NN1 during_II their_APPGE childhood_NN1 and_CC usually_RR after_II the_AT age_NN1 of_IO six_MC ._. 
To_TO demonstrate_VVI a_AT1 sensitive_JJ period_NN1 of_IO the_AT type_NN1 he_PPHS1 was_VBDZ proposing_VVG ,_, it_PPH1 would_VM be_VBI necessary_JJ to_TO show_VVI that_CST adults_NN2 who_PNQS had_VHD left_VVN a_AT1 kibbutz_NN1 at_II the_AT age_NN1 of_IO six_MC were_VBDR not_XX sexually_RR attracted_VVN by_II members_NN2 of_IO the_AT opposite_JJ sex_NN1 whom_PNQO they_PPHS2 had_VHD been_VBN reared_VVN with_IW while_CS still_RR in_II the_AT kibbutz_NN1 ._. 
As_CSA things_NN2 stand_VV0 ,_, the_AT existing_JJ evidence_NN1 has_VHZ been_VBN wildly_RR over-interpreted_VVN both_RR by_II Shepher_NP1 and_CC by_II others_NN2 who_PNQS have_VH0 uncritically_RR accepted_VVN his_APPGE conclusions_NN2 (_( e.g._REX Lumsden_NP1 &amp;_CC Wilson_NP1 ,_, 1981_MC ;_; van_NP1 den_NP1 Berghe_NP1 ,_, 1982_MC )_) ._. 
If_CS we_PPIS2 reject_VV0 the_AT naive_JJ application_NN1 of_IO the_AT sensitive_JJ period_NN1 concept_NN1 and_CC accept_VV0 that_DD1 familiarity_NN1 of_IO a_AT1 certain_JJ kind_NN1 does_VDZ reduce_VVI sexual_JJ attractiveness_NN1 ,_, then_RT it_PPH1 may_VM be_VBI possible_JJ to_TO reconcile_VVI the_AT thinking_NN1 of_IO Freud_NP1 with_IW that_DD1 of_IO Westermarck_NN1 ._. 
The_AT sexual_JJ attraction_NN1 of_IO their_APPGE siblings_NN2 and_CC parents_NN2 ,_, which_DDQ people_NN under_II psychoanalysis_NN1 reported_VVD they_PPHS2 felt_VVD ,_, may_VM have_VHI created_VVN the_AT conditions_NN2 for_IF developing_VVG subsequent_JJ indifference_NN1 ._. 
This_DD1 line_NN1 of_IO thought_NN1 might_VM also_RR be_VBI applied_VVN rewardingly_RR to_TO explain_VVI one_MC1 striking_JJ feature_NN1 of_IO divorce_NN1 statistics_NN ._. 
For_REX21 instance_REX22 ,_, in_II British_JJ women_NN2 who_PNQS married_VVD before_II the_AT age_NN1 of_IO 20_MC ,_, the_AT proportion_NN1 of_IO marriages_NN2 that_CST ended_VVD in_II divorce_NN1 has_VHZ been_VBN approximately_RR double_VV0 that_DD1 of_IO the_AT marriages_NN2 of_IO women_NN2 who_PNQS married_VVD between_II 20_MC and_CC 24_MC (_( Office_NN1 of_IO Population_NN1 Censuses_NN2 and_CC Surveys_NN2 ,_, 1978_MC )_) ._. 
This_DD1 has_VHZ been_VBN true_JJ at_II any_DD time_NNT1 between_II four_MC and_CC 25_MC years_NNT2 after_II marriage_NN1 ._. 
Many_DA2 factors_NN2 ,_, such_II21 as_II22 differences_NN2 between_II social_JJ classes_NN2 in_II attitudes_NN2 to_II marriage_NN1 ,_, could_VM explain_VVI or_CC contribute_VVI to_II explaining_VVG the_AT difference_NN1 ._. 
Clever_JJ research_NN1 design_NN1 could_VM sort_VVI out_RP some_DD of_IO the_AT confounded_JJ variables_NN2 ,_, so_CS I_PPIS1 shall_VM add_VVI to_II the_AT possibilities_NN2 a_AT1 speculation_NN1 arising_VVG from_II my_APPGE point_NN1 about_II habituation_NN1 ._. 
Early_JJ marriages_NN2 may_VM involve_VVI a_AT1 great_JJ deal_NN1 of_IO intimacy_NN1 but_CCB relatively_RR little_RR sexual_JJ satisfaction_NN1 ._. 
Indeed_RR ,_, people_NN often_RR report_VV0 that_CST their_APPGE early_JJ sex_NN1 lives_NN2 were_VBDR relatively_RR unrewarding_JJ ._. 
If_CS the_AT effects_NN2 of_IO habituation_NN1 are_VBR not_XX powerfully_RR offset_VVN by_II rewarding_VVG sexual_JJ experience_NN1 ,_, the_AT partner_NN1 may_VM lose_VVI his_APPGE or_CC her_APPGE attractiveness_NN1 and_CC become_VVI the_AT equivalent_NN1 of_IO a_AT1 sibling_NN1 ._. 
While_CS a_AT1 great_JJ deal_NN1 is_VBZ stili_NN2 unknown_JJ about_II the_AT development_NN1 of_IO sexual_JJ preferences_NN2 in_II both_RR animals_NN2 and_CC humans_NN2 ,_, the_AT similarities_NN2 are_VBR quite_RG striking_JJ ._. 
In_II my_APPGE view_NN1 a_AT1 good_JJ case_NN1 has_VHZ been_VBN made_VVN for_IF the_AT view_NN1 that_CST the_AT learning_NN1 processes_VVZ involved_JJ in_II the_AT formation_NN1 of_IO mating_JJ preference_NN1 of_IO humans_NN2 have_VH0 been_VBN subject_II21 to_II22 natural_JJ selection_NN1 during_II the_AT course_NN1 of_IO evolution_NN1 ._. 
However_RR ,_, acceptance_NN1 of_IO this_DD1 point_NN1 has_VHZ to_TO be_VBI tempered_VVN by_II an_AT1 awareness_NN1 that_CST mate_NN1 choice_NN1 is_VBZ influenced_VVN by_II many_DA2 qualities_NN2 ._. 
Early_JJ experience_NN1 with_IW particular_JJ individuals_NN2 is_VBZ not_XX the_AT only_JJ source_NN1 of_IO variation_NN1 in_II adults_NN2 '_GE mating_JJ preferences_NN2 ._. 
So_RR even_RR if_CS Westermarck_NP1 was_VBDZ right_JJ ,_, as_CSA I_PPIS1 believe_VV0 he_PPHS1 was_VBDZ ,_, it_PPH1 would_VM be_VBI extremely_RR surprising_JJ if_CS his_APPGE hypothesis_NN1 explained_VVD all_DB of_IO what_DDQ humans_NN2 do_VD0 ._. 
Incest_NN1 taboos_NN2 and_CC marriage_NN1 laws_NN2 In_II a_AT1 society_NN1 in_II which_DDQ spouses_NN2 are_VBR freely_RR chosen_VVN ,_, it_PPH1 is_VBZ easy_JJ to_TO confuse_VVI the_AT influences_NN2 on_II sexual_JJ preference_NN1 with_IW those_DD2 on_II marriage_NN1 ._. 
The_AT anthropologists_NN2 have_VH0 to_TO point_VVI again_RT and_CC again_RT to_II the_AT great_JJ many_DA2 societies_NN2 in_II which_DDQ spouses_NN2 are_VBR arranged_VVN and_CC not_XX freely_RR chosen_VVN ._. 
A_AT1 biologist_NN1 who_PNQS was_VBDZ so_RR minded_VVN could_VM counter_VVI by_II arguing_VVG that_CST ,_, if_CS by_RR31 and_RR32 large_RR33 the_AT marriages_NN2 generate_VV0 the_AT children_NN2 ,_, then_RT marriage_NN1 laws_NN2 could_VM still_RR have_VHI been_VBN influenced_VVN by_II evolutionary_JJ pressures_NN2 ._. 
While_CS that_DD1 argument_NN1 would_VM beg_VVI an_AT1 important_JJ question_NN1 ,_, on_II the_AT face_NN1 of_IO it_PPH1 the_AT marriage_NN1 laws_NN2 do_VD0 seem_VVI to_TO promote_VVI the_AT function_NN1 of_IO optimal_JJ outbreeding_NN1 ._. 
Marriage_NN1 with_IW close_JJ kin_NN is_VBZ generally_RR forbidden_VVN in_II most_DAT societies_NN2 and_CC so_RR ,_, commonly_RR ,_, is_VBZ marriage_NN1 with_IW people_NN of_IO dissimilar_JJ culture_NN1 ._. 
A_AT1 general_JJ bias_NN1 in_II31 favour_II32 of_II33 spouses_NN2 who_PNQS come_VV0 from_II nearby_RL both_RR spatially_RR and_CC socially_RR has_VHZ often_RR been_VBN noted_VVN by_II anthropologists_NN2 (_( Fortes_NN2 ,_, 1962_MC )_) ._. 
Charles_NP1 Darwin_NP1 married_VVD a_AT1 cousin_NN1 and_CC ,_, indeed_RR ,_, such_DA marriages_NN2 were_VBDR quite_RG common_JJ in_II nineteenth-century_JJ Europe_NP1 ._. 
It_PPH1 must_VM be_VBI said_VVN that_CST the_AT apparently_RR convincing_JJ evidence_NN1 has_VHZ been_VBN processed_VVN into_II non-significance_NN1 by_II elegant_JJ mathematical_JJ analysis_NN1 (_( Hajnal_NP1 ,_, 1963_MC )_) ._. 
This_DD1 seems_VVZ to_TO have_VHI been_VBN done_VDN in_II the_AT interests_NN2 of_IO retaining_VVG the_AT theoreticians_NN2 '_GE assumption_NN1 of_IO panmixia_NN1 (_( Charlesworth_NP1 ,_, 1980_MC )_) ._. 
But_CCB maybe_RR Darwin_NP1 knew_VVD better_RRR ,_, since_CS the_AT assumption_NN1 of_IO random_JJ mating_NN1 could_VM hardly_RR apply_VVI in_II those_DD2 numerous_JJ societies_NN2 that_CST actually_RR favour_VV0 first-cousin_JJ marriages_NN2 (_( Murdock_NP1 ,_, 1967_MC )_) ._. 
Is_VBZ there_EX some_DD functional_JJ similarity_NN1 with_IW mate_NN1 choice_NN1 in_II quail_NN ?_? 
Two_MC important_JJ and_CC unresolved_JJ problems_NN2 are_VBR raised_VVN by_II this_DD1 line_NN1 of_IO thought_NN1 ._. 
How_RRQ does_VDZ an_AT1 inhibition_NN1 get_VVI translated_VVN into_II a_AT1 prohibition_NN1 ?_? 
And_CC how_RGQ much_DA1 of_IO the_AT variation_NN1 in_II the_AT prohibition_NN1 is_VBZ explained_VVN by_II the_AT character_NN1 of_IO the_AT inhibitions_NN2 ?_? 
Incest_NN1 taboos_NN2 take_VV0 many_DA2 different_JJ shapes_NN2 and_CC forms_NN2 ._. 
They_PPHS2 sometimes_RT include_VV0 certain_JJ types_NN2 of_IO cousin_NN1 and_CC people_NN related_VVN by_II marriage_NN1 only_RR ._. 
Prohibitions_NN2 on_II sexual_JJ relations_NN2 with_IW parents_NN2 ,_, siblings_NN2 or_CC children_NN2 ,_, are_VBR nearly_RR always_RR universal_JJ but_CCB not_XX quite_RR ._. 
Hopkins_NP1 (_( 1980_MC )_) has_VHZ analysed_VVN the_AT marriage_NN1 records_NN2 of_IO Roman_NP1 Egypt_NP1 in_II which_DDQ the_AT census_NN1 data_NN were_VBDR especially_RR complete_JJ ._. 
He_PPHS1 confirmed_VVD the_AT view_NN1 that_CST among_II perfectly_RR ordinary_JJ people_NN ,_, who_PNQS were_VBDR neither_RR Pharaohs_NN2 nor_CC priests_NN2 ,_, full_JJ brother-sister_JJ marriages_NN2 occurred_VVD in_II a_AT1 minimum_NN1 of_IO nine_MC out_II21 of_II22 the_AT 113_MC marriages_NN2 he_PPHS1 analysed_VVD ,_, If_CS the_AT less_RGR certain_JJ cases_NN2 are_VBR also_RR included_VVN along_II21 with_II22 marriages_NN2 between_II half-siblings_NN2 ,_, the_AT proportion_NN1 of_IO incestuous_JJ marriages_NN2 was_VBDZ of_IO the_AT order_NN1 of_IO 20%_NNU ._. 
Whatever_DDQV view_NN1 one_PN1 takes_VVZ of_IO the_AT origins_NN2 of_IO the_AT incest_NN1 taboos_NN2 ,_, it_PPH1 would_VM be_VBI intellectually_RR shoddy_JJ simply_RR to_TO ignore_VVI these_DD2 data_NN ._. 
Can_VM we_PPIS2 find_VVI a_AT1 common_JJ underlying_JJ principle_NN1 that_CST explains_VVZ the_AT variation_NN1 ?_? 
Levi-Strauss_NP1 (_( 1969_MC )_) proposed_VVD that_CST ,_, women_NN2 being_VBG the_AT most_RGT important_JJ resource_NN1 that_CST men_NN2 have_VH0 ,_, a_AT1 system_NN1 for_IF exchanging_VVG women_NN2 always_RR underlies_VVZ the_AT social_JJ control_NN1 of_IO marriage_NN1 ._. 
His_APPGE arguments_NN2 have_VH0 something_PN1 of_IO the_AT character_NN1 of_IO the_AT Ptolemaic_JJ theory_NN1 of_IO the_AT universe_NN1 brilliant_JJ ,_, logical_JJ ,_, grand_JJ ,_, but_CCB despite_II all_DB these_DD2 things_NN2 ,_, extremely_RR complex_JJ ._. 
His_APPGE theory_NN1 is_VBZ in_II stark_JJ contrast_NN1 to_II the_AT biologists_NN2 '_GE attempts_NN2 to_TO find_VVI a_AT1 relationship_NN1 between_II the_AT prohibitions_NN2 on_II certain_JJ types_NN2 of_IO marriage_NN1 partner_NN1 ,_, and_CC the_AT inhibitions_NN2 about_II having_VHG sexual_JJ contact_NN1 with_IW such_DA classes_NN2 of_IO people_NN ._. 
These_DD2 ideas_NN2 are_VBR simple_JJ ._. 
So_RR simple_JJ ,_, indeed_RR ,_, that_DD1 usually_RR the_AT argument_NN1 is_VBZ not_XX stated_VVN at_RR21 all_RR22 ._. 
The_AT correlation_NN1 between_II prohibition_NN1 and_CC inhibition_NN1 is_VBZ offered_VVN as_CS21 though_CS22 it_PPH1 explained_VVD everything_PN1 ,_, or_CC at_RR21 best_RR22 ,_, the_AT prohibition_NN1 is_VBZ held_VVN to_TO have_VHI arisen_VVN by_II '_GE myth_NN1 making_NN1 '_GE or_CC '_GE ritualisation_NN1 '_GE (_( Bischof_NP1 ,_, 1972_MC )_) ._. 
As_CSA Williams_NP1 (_( 1978_MC )_) pointed_VVD out_RP ,_, such_DA statements_NN2 are_VBR nothing_PN1 more_DAR than_CSN promissory_JJ notes_NN2 ._. 
They_PPHS2 do_VD0 not_XX provide_VVI an_AT1 explanation_NN1 of_IO how_RRQ one_PN1 turns_VVZ into_II the_AT other_JJ ._. 
In_II a_AT1 recent_JJ book_NN1 ,_, Lumsden_NP1 &amp;_CC Wilson_NP1 (_( 1981_MC )_) attempted_VVD to_TO deal_VVI with_IW the_AT issue_NN1 mathematically_RR ._. 
However_RR ,_, their_APPGE efforts_NN2 have_VH0 not_XX provided_VVN the_AT explanation_NN1 that_CST we_PPIS2 need_VV0 ._. 
They_PPHS2 merely_RR assumed_VVD that_DD1 inhibition_NN1 generates_VVZ the_AT incest_NN1 taboo_NN1 without_IW pointing_VVG to_II any_DD behavioural_JJ mechanism_NN1 that_CST could_VM translate_VVI one_PN1 into_II the_AT other_JJ ._. 
In_II31 lieu_II32 of_II33 anything_PN1 better_RRR I_PPIS1 shall_VM make_VVI a_AT1 suggestion_NN1 ._. 
Prohibitions_NN2 may_VM have_VHI arisen_VVN from_II the_AT social_JJ pressure_NN1 directed_VVN against_II unorthodox_JJ behaviour_NN1 ._. 
What_DDQ is_VBZ normal_JJ behaviour_NN1 is_VBZ itself_PPX1 influenced_VVN by_II the_AT pattern_NN1 of_IO early_JJ experiences_NN2 which_DDQ are_VBR common_JJ to_II that_DD1 society_NN1 ._. 
The_AT implication_NN1 is_VBZ ,_, therefore_RR ,_, that_CST there_EX will_VM be_VBI some_DD correlation_NN1 between_II child-rearing_NN1 practices_NN2 and_CC taboos_NN2 (_( see_VV0 Fig._NN1 24.6_MC )_) ._. 
People_NN often_RR strongly_RR disapprove_VV0 of_IO others_NN2 who_PNQS behave_VV0 in_II unusual_JJ ways_NN2 ._. 
The_AT most_RGT obvious_JJ example_NN1 is_VBZ the_AT moral_JJ repugnance_NN1 that_CST many_DA2 people_NN show_VV0 for_IF homosexuality_NN1 between_II consenting_JJ adults_NN2 ._. 
Why_RRQ should_VM they_PPHS2 mind_VVI ?_? 
They_PPHS2 are_VBR not_XX harmed_VVN by_II the_AT homosexuality_NN1 ._. 
But_CCB the_AT conventional_JJ response_NN1 is_VBZ nonetheless_RR a_AT1 violent_JJ one_PN1 in_II some_DD societies_NN2 homosexuality_NN1 may_VM be_VBI punished_VVN by_II death_NN1 ._. 
If_CS fear_NN1 of_IO nonconformity_NN1 and_CC the_AT unusual_JJ has_VHZ driven_VVN the_AT cultural_JJ evolution_NN1 of_IO incest_NN1 taboos_NN2 ,_, then_RT a_AT1 comparable_JJ argument_NN1 should_VM apply_VVI to_II taboos_NN2 on_II marriages_NN2 with_IW strangers_NN2 or_CC members_NN2 of_IO other_JJ castes_NN2 and_CC races_NN2 ._. 
Levi-Strauss_NP1 (_( 1969_MC )_) noted_VVD that_CST such_DA taboos_NN2 certainly_RR exist_VV0 and_CC a_AT1 notorious_JJ modern_JJ example_NN1 of_IO it_PPH1 is_VBZ found_VVN in_II the_AT immorality_NN1 laws_NN2 of_IO South_NP1 Africa_NP1 which_DDQ forbid_VV0 sexual_JJ relations_NN2 between_II blacks_NN2 and_CC whites_NN2 ._. 
If_CS this_DD1 approach_NN1 is_VBZ anywhere_RL near_II correct_JJ ,_, we_PPIS2 should_VM expect_VVI a_AT1 correlation_NN1 between_II the_AT class_NN1 of_IO people_NN who_PNQS are_VBR prohibited_VVN as_CSA sexual_JJ partners_NN2 and_CC the_AT likelihood_NN1 that_CST they_PPHS2 will_VM be_VBI familiar_JJ or_CC extremely_RR novel_JJ (_( see_VV0 Fig._NN1 24.6_MC )_) ._. 
Obviously_RR many_DA2 things_NN2 might_VM muddy_JJ the_AT correlation_NN1 between_II social_JJ structure_NN1 and_CC prohibited_JJ partners_NN2 ,_, but_CCB one_MC1 piece_NN1 of_IO existing_JJ evidence_NN1 points_VVZ in_II the_AT right_JJ direction_NN1 ._. 
While_CS first-cousins_NN2 are_VBR often_RR favoured_VVN as_CSA marriage_NN1 partners_NN2 ,_, a_AT1 distinction_NN1 is_VBZ very_RG often_RR made_VVN between_II parallel_NN1 and_CC cross-cousins_NN2 ._. 
The_AT sibling_NN1 parents_NN2 of_IO parallel_JJ cousins_NN2 are_VBR the_AT same_DA sex_NN1 and_CC the_AT sibling_NN1 parents_NN2 of_IO cross-cousins_NN2 are_VBR of_IO the_AT opposite_JJ sex_NN1 ._. 
Sometimes_RT parallel_JJ cousins_NN2 are_VBR forbidden_VVN as_CSA spouses_NN2 and_CC cross-cousins_NN2 are_VBR favoured_VVN ._. 
Alexander_NP1 (_( 1980_MC )_) has_VHZ gone_VVN through_II Murdock_NP1 's_GE (_( 1967_MC )_) ethnographic_JJ atlas_NN1 and_CC found_VVD that_CST this_DD1 asymmetrical_JJ treatment_NN1 of_IO cousins_NN2 is_VBZ strongly_RR associated_VVN with_IW the_AT type_NN1 of_IO marriage_NN1 common_JJ in_II that_DD1 culture_NN1 ._. 
The_AT results_NN2 are_VBR shown_VVN in_II Table_NN1 24.2_MC ._. 
Alexander_NP1 argues_VVZ that_CST because_CS brothers_NN2 may_VM share_VVI wives_NN2 in_II polygynous_JJ societies_NN2 ,_, parallel_JJ cousins_NN2 may_VM in_II fact_NN1 be_VBI half-siblings_NN2 ._. 
He_PPHS1 seems_VVZ ,_, therefore_RR ,_, to_TO be_VBI using_VVG the_AT evidence_NN1 as_II an_AT1 ingenious_JJ updating_NN1 of_IO the_AT classical_JJ safety_NN1 law_NN1 argument_NN1 ._. 
However_RR ,_, parallel_JJ cousins_NN2 who_PNQS may_VM in_II reality_NN1 be_VBI half-siblings_NN2 are_VBR also_RR likely_JJ to_TO have_VHI lived_VVN in_II the_AT same_DA household_NN1 ._. 
Once_RR21 again_RR22 ,_, genetic_JJ relatedness_NN1 is_VBZ confounded_VVN with_IW familiarity_NN1 ._. 
So_RR ,_, another_DD1 possible_JJ explanation_NN1 is_VBZ that_CST in_II a_AT1 polygynous_JJ society_NN1 ,_, the_AT parallel_JJ cousins_NN2 will_VM be_VBI much_RR more_RGR likely_JJ to_TO grow_VVI up_RP together_RL than_CSN the_AT cross-cousins_NN2 ._. 
In_II effect_NN1 ,_, the_AT parallel_JJ cousins_NN2 are_VBR as_RG familiar_JJ as_CSA siblings_NN2 ._. 
It_PPH1 does_VDZ not_XX follow_VVI from_II the_AT argument_NN1 I_PPIS1 have_VH0 mounted_VVN here_RL that_CST the_AT conformism_NN1 generating_VVG prohibitions_NN2 is_VBZ an_AT1 adaptive_JJ response_NN1 that_CST evolved_VVD in_II the_AT service_NN1 of_IO maintaining_VVG optimal_JJ outbreeding_NN1 ._. 
The_AT conformism_NN1 might_VM have_VHI arisen_VVN for_IF quite_RG different_JJ reasons_NN2 and_CC among_II its_APPGE other_JJ consequences_NN2 happened_VVD incidentally_RR to_TO amplify_VVI the_AT beneficial_JJ effects_NN2 of_IO the_AT inhibitions_NN2 ._. 
Certainly_RR ,_, it_PPH1 would_VM be_VBI difficult_JJ to_TO argue_VVI that_CST all_DB the_AT variation_NN1 in_II human_JJ marriage_NN1 laws_NN2 could_VM be_VBI explained_VVN in_II31 terms_II32 of_II33 their_APPGE evolutionary_JJ benefits_NN2 ._. 
The_AT brother-sister_JJ marriages_NN2 of_IO Roman_NP1 Egypt_NP1 probably_RR had_VHD a_RR31 great_RR32 deal_RR33 to_II do_VD0 with_IW the_AT preservation_NN1 of_IO property_NN1 and_CC nothing_PN1 to_TO do_VDI with_IW the_AT preservation_NN1 of_IO genes_NN2 (_( Hopkins_NP1 ,_, 1980_MC )_) ._. 
And_CC similar_JJ explanations_NN2 can_VM account_VVI for_IF a_AT1 lot_NN1 of_IO the_AT variation_NN1 found_VVN in_II human_JJ societies_NN2 (_( Goody_NP1 ,_, 1976_MC )_) ._. 
It_PPH1 would_VM be_VBI absurd_JJ to_TO adopt_VVI a_AT1 rigidly_RR determinist_NN1 view_NN1 of_IO what_DDQ has_VHZ gone_VVN on_RP in_II the_AT formation_NN1 of_IO culturally_RR transmitted_JJ marriage_NN1 laws_NN2 ._. 
To_TO say_VVI the_AT least_RRT ,_, it_PPH1 is_VBZ unfortunate_JJ that_CST a_AT1 multiply_RR influenced_VVN process_NN1 with_IW many_DA2 stages_NN2 in_II it_PPH1 should_VM be_VBI thought_VVN of_IO by_II sociobiological_JJ proponents_NN2 and_CC their_APPGE critics_NN2 alike_RR (_( e.g._REX Solomon_NP1 ,_, 1978_MC )_) as_CSA having_VHG an_AT1 invariant_JJ outcome_NN1 and_CC a_AT1 single_JJ explanation_NN1 ._. 
It_PPH1 is_VBZ a_RR21 bit_RR22 like_II arguing_VVG that_CST if_CS the_AT hypothesis_NN1 that_CST smoking_JJ causes_NN2 lung_NN1 cancer_NN1 is_VBZ to_TO be_VBI believed_VVN ,_, everybody_PN1 who_PNQS smokes_VVZ must_VM get_VVI cancer_NN1 ;_; what_DDQ is_VBZ more_RGR nothing_PN1 else_RR (_( such_II21 as_II22 asbestos_NN1 )_) can_VM be_VBI admitted_VVN as_CSA having_VHG the_AT same_DA effect_NN1 ._. 
The_AT opposed_JJ parties_NN2 in_II such_DA disputes_NN2 ,_, evidently_RR believing_VVG that_DD1 causality_NN1 has_VHZ a_AT1 chain-like_JJ character_NN1 to_II it_PPH1 ,_, have_VH0 an_AT1 impoverished_JJ notion_NN1 of_IO how_RRQ things_NN2 actually_RR work_VV0 ._. 
In_II most_DAT complex_JJ systems_NN2 the_AT sources_NN2 of_IO variation_NN1 are_VBR likely_JJ to_TO be_VBI numerous_JJ ._. 
It_PPH1 follows_VVZ that_CST alternative_JJ explanations_NN2 do_VD0 not_XX have_VHI to_TO be_VBI mutually_RR exclusive_JJ ._. 
The_AT best_RRT that_DD1 can_VM be_VBI said_VVN about_II marriage_NN1 laws_NN2 is_VBZ that_CST some_DD of_IO the_AT variation_NN1 may_VM be_VBI explained_VVN along_II the_AT lines_NN2 proposed_VVN here_RL ._. 
Even_RR within_II this_DD1 explanatory_JJ framework_NN1 ,_, little_RR useful_JJ understanding_NN1 will_VM be_VBI obtained_VVN without_IW first_MD studying_VVG the_AT problem_NN1 at_II many_DA2 different_JJ levels_NN2 ._. 
What_DDQ is_VBZ needed_VVN ,_, therefore_RR ,_, is_VBZ constructive_JJ collaboration_NN1 between_II biologists_NN2 and_CC social_JJ scientists_NN2 and_CC a_AT1 proper_JJ respect_NN1 for_IF the_AT insights_NN2 that_CST the_AT different_JJ disciplines_NN2 can_VM provide_VVI ._. 
Conclusion_NN1 The_AT arguments_NN2 presented_VVN in_II this_DD1 chapter_NN1 do_VD0 not_XX lead_VVI to_II comfortable_JJ conclusions_NN2 that_CST can_VM be_VBI instantly_RR assimilated_VVN ._. 
However_RR ,_, they_PPHS2 are_VBR not_XX ,_, I_PPIS1 trust_VV0 ,_, obscurantist_NN1 and_CC a_AT1 positive_JJ point_NN1 does_VDZ emerge_VVI ._. 
Regularities_NN2 can_VM be_VBI found_VVN in_II the_AT way_NN1 that_CST behaviour_NN1 is_VBZ tuned_VVN to_II the_AT environment_NN1 during_II development_NN1 ._. 
To_TO be_VBI effective_JJ ,_, though_CS ,_, the_AT rules_NN2 have_VH0 a_AT1 conditional_JJ character_NN1 to_II them_PPHO2 which_DDQ means_VVZ ,_, of_RR21 course_RR22 ,_, that_CST they_PPHS2 generate_VV0 variation_NN1 in_II behaviour_NN1 in_II31 response_II32 to_II33 variable_JJ environments_NN2 ._. 
It_PPH1 is_VBZ not_XX inexplicable_JJ variation_NN1 ,_, but_CCB it_PPH1 is_VBZ variation_NN1 nonetheless_RR ._. 
The_AT old_JJ reductionist_NN1 's_GE vision_NN1 was_VBDZ that_CST one_MC1 day_NNT1 when_RRQ we_PPIS2 knew_VVD enough_RR about_II genes_NN2 we_PPIS2 would_VM be_VBI able_JK to_TO predict_VVI every_AT1 detail_NN1 of_IO every_AT1 adult_NN1 's_GE behaviour_NN1 ._. 
It_PPH1 always_RR was_VBDZ a_AT1 pipe-dream_NN1 ._. 
Imagine_VV0 civil_JJ servants_NN2 working_VVG in_II a_AT1 capital_NN1 city_NN1 and_CC trying_VVG to_TO make_VVI all_DB the_AT decisions_NN2 required_VVN for_IF running_VVG a_AT1 large_JJ country_NN1 ._. 
They_PPHS2 Simply_RR would_VM not_XX have_VHI the_AT flexibility_NN1 or_CC the_AT speed_NN1 of_IO reaction_NN1 to_TO cope_VVI with_IW the_AT complexities_NN2 of_IO everyday_JJ life_NN1 ._. 
And_CC so_RR it_PPH1 is_VBZ with_IW the_AT genes_NN2 ,_, the_AT natural_JJ bureaucrats_NN2 ._. 
On_II their_APPGE own_DA they_PPHS2 are_VBR too_RG clumsy_JJ in_II their_APPGE form_NN1 of_IO regulation_NN1 to_TO provide_VVI the_AT necessary_JJ adaptations_NN2 ,_, especially_RR those_DD2 required_VVN for_IF social_JJ living_NN1 ._. 
The_AT genes_NN2 had_VHD to_TO delegate_VVI control_NN1 ._. 
When_CS we_PPIS2 examine_VV0 animals_NN2 with_IW nervous_JJ systems_NN2 that_CST were_VBDR built_VVN with_IW conditional_JJ rules_NN2 for_IF dealing_VVG with_IW the_AT external_JJ environment_NN1 ,_, the_AT business_NN1 of_IO predicting_VVG how_RRQ they_PPHS2 will_VM respond_VVI on_II the_AT basis_NN1 of_IO knowing_VVG how_RRQ they_PPHS2 were_VBDR made_VVN becomes_VVZ impossible_JJ ._. 
It_PPH1 is_VBZ like_II trying_VVG to_TO predict_VVI the_AT outcome_NN1 of_IO a_AT1 game_NN1 of_IO chess_NN1 before_CS anyone_PN1 has_VHZ made_VVN a_AT1 move_NN1 ._. 
What_DDQ we_PPIS2 can_VM do_VDI is_VBZ attempt_NN1 to_TO get_VVI hold_NN1 of_IO the_AT rules_NN2 of_IO the_AT game_NN1 so_CS21 that_CS22 we_PPIS2 can_VM make_VVI sense_NN1 of_IO a_AT1 game_NN1 as_CSA it_PPH1 is_VBZ played_VVN ._. 
At_II that_DD1 stage_NN1 I_PPIS1 concede_VV0 happily_RR that_CST we_PPIS2 may_VM be_VBI able_JK to_TO predict_VVI what_DDQ a_AT1 clever_JJ animal_NN1 will_VM do_VDI in_II a_AT1 particular_JJ set_NN1 of_IO circumstances_NN2 ._. 
In_II the_AT meantime_NNT1 ,_, we_PPIS2 should_VM expect_VVI to_TO be_VBI surprised_VVN very_RG often_RR ._. 
&lsqb;_( &rsqb;_) SOCIOBIOLOGY_NN1 AND_CC THE_AT DARWINIAN_JJ APPROACH_NN1 TO_TO MIND_VVI AND_CC CULTURE_NN1 EDWARD_NP1 O._NP1 WILSON_NP1 On_II 3_MC October_NPM1 1838_MC ,_, Charles_NP1 Darwin_NP1 wrote_VVD in_II his_APPGE N_ZZ1 notebook_NN1 that_DD1 '_VBZ to_TO study_VVI Metaphysics_NN2 ,_, as_CSA they_PPHS2 have_VH0 always_RR been_VBN studied_VVN appears_VVZ to_II me_PPIO1 to_TO be_VBI like_II puzzling_VVG at_II astronomy_NN1 without_IW mechanics_NN2 ..._... 
Experience_NN1 shows_VVZ that_CST the_AT problem_NN1 of_IO the_AT mind_NN1 can_VM not_XX be_VBI solved_VVN by_II attacking_VVG the_AT citadel_NN1 itself_PPX1 ..._... the_AT mind_NN1 is_VBZ function_NN1 of_IO body_NN1 ..._... we_PPIS2 must_VM bring_VVI some_DD stable_JJ foundation_NN1 to_TO argue_VVI from_II ..._... '_GE (_( in_II Barrett_NP1 ,_, 1980_MC )_) ._. 
Although_CS Darwin_NP1 had_VHD turned_VVN in_II the_AT right_JJ direction_NN1 ,_, he_PPHS1 could_VM do_VDI very_RG little_DA1 with_IW mind_NN1 and_CC culture_NN1 during_II his_APPGE lifetime_NNT1 for_IF the_AT same_DA reason_NN1 that_CST he_PPHS1 was_VBDZ helpless_JJ before_II the_AT mysteries_NN2 of_IO heredity_NN1 :_: the_AT basic_JJ information_NN1 and_CC modes_NN2 of_IO thought_NN1 were_VBDR lacking_VVG to_TO produce_VVI the_AT stable_JJ foundation_NN1 which_DDQ he_PPHS1 correctly_RR viewed_VVN as_CSA essential_JJ ._. 
Today_RT ,_, one_MC1 hundred_NNO years_NNT2 after_II his_APPGE death_NN1 ,_, we_PPIS2 may_VM at_RR21 last_RR22 be_VBI approaching_VVG a_AT1 sufficient_JJ understanding_NN1 to_TO bring_VVI to_II fruition_NN1 Darwin_NP1 's_GE proposal_NN1 ._. 
If_CS so_RR ,_, we_PPIS2 can_VM verify_VVI another_DD1 insight_NN1 ,_, which_DDQ was_VBDZ entered_VVN into_II the_AT M_NN1 notebook_NN1 on_II 16_MC August_NPM1 1838_MC :_: '_GE Origin_NN1 of_IO man_NN1 now_RT proved_VVD ..._... 
Metaphysics_NN2 must_VM flourish_VVI ..._... 
He_PPHS1 who_PNQS understand_VV0 baboon_NN1 would_VM do_VDI more_RRR toward_II metaphysics_NN2 than_CSN Locke_NP1 ._. 
'_" What_DDQ will_VM be_VBI the_AT outcome_NN1 of_IO this_DD1 most_RGT problematic_JJ ,_, controversial_JJ extension_NN1 of_IO evolutionary_JJ theory_NN1 ?_? 
It_PPH1 is_VBZ a_AT1 common_JJ perception_NN1 that_CST during_II the_AT 1950s_MC2 biology_NN1 replaced_VVD physics_NN1 as_II the_AT most_RGT exciting_JJ domain_NN1 of_IO science_NN1 ._. 
I_PPIS1 will_VM make_VVI a_AT1 brash_JJ prediction_NN1 :_: that_DD1 by_II the_AT year_NNT1 2000_MC the_AT social_JJ sciences_NN2 ,_, in_II31 conjunction_II32 with_II33 brain_NN1 studies_NN2 ,_, will_VM commence_VVI to_TO replace_VVI biology_NN1 in_II the_AT central_JJ role_NN1 ._. 
If_CS such_DA an_AT1 advance_NN1 is_VBZ realized_VVN ,_, it_PPH1 represents_VVZ one_MC1 more_DAR step_NN1 in_II a_AT1 progression_NN1 in_II which_DDQ the_AT antidiscipline_NN1 ,_, that_REX21 is_REX22 ,_, the_AT field_NN1 treating_VVG the_AT next_MD level_NN1 of_IO organization_NN1 below_II the_AT one_PN1 under_II scrutiny_NN1 ,_, is_VBZ partly_RR replaced_VVN by_II the_AT synthetic_JJ enterprise_NN1 to_II which_DDQ it_PPH1 gave_VVD rigour_NN1 and_CC impetus_NN1 (_( Wilson_NP1 ,_, 1977_MC )_) ._. 
In_II other_JJ words_NN2 ,_, biology_NN1 advances_VVZ the_AT social_JJ sciences_NN2 ._. 
Just_RR as_CSA physics_NN1 and_CC chemistry_NN1 helped_VVD to_TO modernize_VVI biology_NN1 and_CC moved_VVD it_PPH1 to_II centre_NN1 stage_NN1 during_II the_AT past_JJ thirty_MC years_NNT2 ,_, I_PPIS1 believe_VV0 that_DD1 biology_NN1 is_VBZ about_RPK to_TO augment_VVI the_AT social_JJ sciences_NN2 greatly_RR and_CC move_VVI them_PPHO2 to_II centre_NN1 stage_NN1 ._. 
The_AT principal_JJ remaining_JJ obstacle_NN1 in_II this_DD1 enterprise_NN1 is_VBZ the_AT unknown_JJ relation_NN1 between_II genes_NN2 and_CC culture_NN1 ._. 
But_CCB of_RR21 course_RR22 when_CS one_PN1 uses_VVZ the_AT phrase_NN1 '_GE an_AT1 unknown_JJ relation_NN1 '_GE ,_, he_PPHS1 means_VVZ that_CST it_PPH1 is_VBZ a_AT1 puzzle_NN1 to_TO be_VBI solved_VVN ._. 
In_II this_DD1 case_NN1 the_AT problem_NN1 is_VBZ surely_RR one_MC1 of_IO the_AT most_RGT important_JJ in_II all_DB of_IO science_NN1 ,_, not_XX to_TO mention_VVI philosophy_NN1 ,_, as_CSA Darwin_NP1 perceived_VVD 144_MC years_NNT2 ago_RA ._. 
A_AT1 few_DA2 writers_NN2 still_RR speak_VV0 of_IO a_AT1 permanent_JJ discontinuity_NN1 between_II the_AT biological_JJ sciences_NN2 and_CC the_AT social_JJ sciences_NN2 ,_, grounded_VVN in_II epistemology_NN1 (_( Eccles_NP1 ,_, 1980_MC )_) or_CC at_RR21 least_RR22 forced_VVN by_II a_AT1 fundamental_JJ difference_NN1 in_II goals_NN2 (_( Hampshire_NP1 ,_, 1978_MC )_) ._. 
But_CCB others_NN2 ,_, principally_RR in_II cognitive_JJ science_NN1 and_CC evolutionary_JJ biology_NN1 ,_, have_VH0 come_VVN to_TO see_VVI the_AT gap_NN1 as_II a_AT1 largely_RR unknown_JJ evolutionary_JJ process_NN1 ,_, a_AT1 complicated_JJ and_CC fascinating_JJ interaction_NN1 in_II which_DDQ culture_NN1 is_VBZ generated_VVN by_II biological_JJ process_NN1 while_CS biological_JJ traits_NN2 are_VBR simultaneously_RR altered_VVN by_II genetic_JJ evolution_NN1 in_II31 response_II32 to_II33 cultural_JJ innovation_NN1 ._. 
Charles_NP1 J._NP1 Lumsden_NP1 and_CC I_PPIS1 have_VH0 recently_RR studied_VVN this_DD1 dual_JJ evolutionary_JJ process_NN1 ,_, which_DDQ we_PPIS2 call_VV0 gene-culture_JJ coevolution_NN1 (_( Lumsden_NP1 &amp;_CC Wilson_NP1 ,_, 1981_MC )_) ._. 
We_PPIS2 have_VH0 attempted_VVN to_TO align_VVI a_AT1 previously_RR independent_JJ field_NN1 of_IO inquiry_NN1 ,_, cognitive_JJ and_CC developmental_JJ psychology_NN1 ,_, with_IW evolutionary_JJ biology_NN1 and_CC particularly_RR sociobiology_NN1 ,_, and_CC in_II so_RR doing_VDG have_VH0 constructed_VVN an_AT1 ensemble_NN1 of_IO models_NN2 that_CST trace_VV0 ,_, at_II times_NNT2 clumsily_RR and_CC imperfectly_RR ,_, behavioural_JJ development_NN1 from_II the_AT genetic_JJ blueprint_NN1 to_II the_AT assembly_NN1 of_IO the_AT nervous_JJ system_NN1 to_II the_AT learning_NN1 process_NN1 and_CC then_RT back_RP down_RP to_II the_AT alteration_NN1 of_IO gene_NN1 frequencies_NN2 by_II natural_JJ selection_NN1 operating_NN1 within_II the_AT context_NN1 of_IO particular_JJ cultures_NN2 ._. 
The_AT full_JJ sequence_NN1 covered_VVN by_II our_APPGE models_NN2 is_VBZ referred_VVN to_II as_II the_AT circuit_NN1 of_IO gene-culture_JJ coevolution_NN1 ._. 
This_DD1 research_NN1 is_VBZ a_AT1 logical_JJ extension_NN1 of_IO sociobiology_NN1 ,_, the_AT systematic_JJ study_NN1 of_IO the_AT biological_JJ basis_NN1 of_IO social_JJ behaviour_NN1 and_CC a_AT1 growing_JJ division_NN1 of_IO evolutionary_JJ biology_NN1 ._. 
The_AT particular_JJ problem_NN1 addressed_VVN by_II the_AT theory_NN1 is_VBZ the_AT following_JJ ._. 
We_PPIS2 know_VV0 that_CST human_JJ social_JJ behaviour_NN1 is_VBZ extremely_RR variable_JJ ._. 
It_PPH1 is_VBZ also_RR open-ended_JJ ,_, in_II the_AT sense_NN1 of_IO being_VBG always_RR subject_II21 to_II22 rapid_JJ change_NN1 due_II21 to_II22 innovation_NN1 and_CC importation_NN1 ._. 
Cultural_JJ evolution_NN1 is_VBZ often_RR characterized_VVN as_CSA Lamarckian_JJ in_II quality_NN1 ,_, in_II other_JJ words_NN2 ,_, dependent_JJ on_II the_AT transmission_NN1 of_IO acquired_JJ characters_NN2 ,_, and_CC relatively_RR fast_RR ;_; while_CS genetic_JJ evolution_NN1 is_VBZ Darwinian_JJ ,_, that_REX21 is_REX22 ,_, dependent_JJ on_II changes_NN2 in_II gene_NN1 frequencies_NN2 across_II generations_NN2 ,_, and_CC slow_JJ ._. 
But_CCB exactly_RR how_RRQ are_VBR these_DD2 two_MC processes_NN2 coupled_VVN ?_? 
The_AT solution_NN1 to_II the_AT problem_NN1 can_VM be_VBI found_VVN by_II shifting_JJ emphasis_NN1 from_II the_AT terminal_JJ products_NN2 ,_, the_AT genetic_JJ blueprint_NN1 and_CC the_AT final_JJ cultural_JJ product_NN1 ,_, and_CC concentrating_VVG on_II the_AT developmental_JJ procedures_NN2 that_CST connect_VV0 them_PPHO2 ._. 
The_AT reason_NN1 such_DA analysis_NN1 has_VHZ not_XX proceeded_VVN more_RGR vigorously_RR in_II the_AT past_NN1 is_VBZ that_DD1 evolutionary_JJ biologists_NN2 have_VH0 virtually_RR ignored_VVN developmental_JJ psychology_NN1 ,_, now_RT a_AT1 vast_JJ field_NN1 in_II its_APPGE own_DA right_NN1 ,_, while_CS psychologists_NN2 for_IF their_APPGE part_NN1 have_VH0 not_XX appreciated_VVN the_AT great_JJ potential_NN1 of_IO evolutionary_JJ theory_NN1 for_IF their_APPGE own_DA studies._NNU p_ZZ1 547_MC :_: FIGURE_VV0 The_AT theory_NN1 of_IO gene-culture_JJ coevolution_NN1 (_( see_VV0 Fig._NN1 26.1_MC )_) proposes_VVZ the_AT following_JJ process_NN1 ._. 
First_MD ,_, human_JJ genes_NN2 affect_VV0 the_AT way_NN1 that_CST the_AT mind_NN1 is_VBZ formed_VVN which_DDQ stimuli_NN2 we_PPIS2 perceive_VV0 ,_, how_RRQ information_NN1 is_VBZ processed_VVN ,_, the_AT kinds_NN2 of_IO memories_NN2 most_RGT easily_RR stored_VVN and_CC recalled_VVN ,_, the_AT emotions_NN2 they_PPHS2 are_VBR most_RGT likely_JJ to_TO evoke_VVI ,_, and_RR31 so_RR32 on_RR33 ._. 
These_DD2 effects_NN2 ,_, which_DDQ have_VH0 been_VBN well_RR documented_VVN in_II recent_JJ psychological_JJ research_NN1 ,_, are_VBR called_VVN epigenetic_JJ rules_NN2 ._. 
The_AT rules_NN2 are_VBR rooted_VVN in_II the_AT particularities_NN2 of_IO human_JJ biology_NN1 ,_, and_CC they_PPHS2 affect_VV0 the_AT way_NN1 culture_NN1 is_VBZ formed_VVN ._. 
For_REX21 example_REX22 ,_, outbreeding_VVG is_VBZ much_RR more_RGR likely_JJ to_TO occur_VVI than_CSN brother-sister_JJ incest_NN1 because_II21 of_II22 the_AT apparently_RR innate_JJ rule_NN1 that_CST individuals_NN2 raised_VVD closely_RR together_RL during_II the_AT first_MD six_MC years_NNT2 of_IO life_NN1 are_VBR inhibited_VVN from_II full_JJ sexual_JJ intercourse_NN1 at_II maturity_NN1 ._. 
Certain_JJ colour_NN1 vocabularies_NN2 are_VBR more_RGR likely_JJ to_TO be_VBI adopted_VVN than_CSN others_NN2 because_II21 of_II22 another_DD1 rule_NN1 :_: the_AT retinal_JJ colour_NN1 cones_NN2 and_CC certain_JJ interneurons_NN2 within_II the_AT brain_NN1 encode_NN1 light_NN1 into_II four_MC basic_JJ colours_NN2 ,_, even_CS21 when_CS22 the_AT wavelength_NN1 of_IO light_NN1 falling_VVG on_II the_AT eye_NN1 varies_VVZ in_II a_AT1 continuous_JJ manner_NN1 ._. 
The_AT Dani_NN1 of_IO New_NP1 Guinea_NP1 have_VH0 one_MC1 of_IO the_AT poorest_JJT colour_NN1 vocabularies_NN2 in_II the_AT world_NN1 ,_, in_II fact_NN1 consisting_VVG only_RR two_MC terms_NN2 ,_, for_IF '_GE bright_JJ '_GE and_CC '_GE dark_NN1 '_GE respectively_RR ._. 
Eleanor_NP1 Rosch_NP1 (_( 1973_MC )_) took_VVD advantage_NN1 of_IO this_DD1 fact_NN1 to_TO conduct_VVI an_AT1 experiment_NN1 in_II learning_VVG propensity_NN1 ._. 
She_PPHS1 gave_VVD one_MC1 group_NN1 of_IO male_JJ volunteers_NN2 a_AT1 new_JJ colour_NN1 vocabulary_NN1 to_TO learn_VVI in_II which_DDQ the_AT terms_NN2 were_VBDR centred_VVN on_II the_AT four_MC basic_JJ colours_NN2 ._. 
Another_DD1 group_NN1 of_IO men_NN2 received_VVD a_AT1 vocabulary_NN1 centred_VVN on_II the_AT wavelengths_NN2 at_II the_AT margins_NN2 of_IO the_AT basic_JJ colours_NN2 ._. 
Individuals_NN2 in_II the_AT first_MD ,_, '_GE natural_JJ '_GE group_NN1 learned_VVD the_AT words_NN2 twice_RR as_RG quickly_RR and_CC retained_VVD them_PPHO2 longer_RRR ._. 
When_CS given_VVN a_AT1 choice_NN1 between_II the_AT two_MC terminologies_NN2 ,_, Dani_JJ men_NN2 preferred_VVD the_AT natural_JJ vocabulary_NN1 ._. 
Both_DB2 of_IO these_DD2 cases_NN2 ,_, incest_NN1 avoidance_NN1 and_CC the_AT development_NN1 of_IO colour_NN1 vocabularies_NN2 ,_, illustrate_VV0 nicely_RR how_RGQ biological_JJ constraints_NN2 in_II cognition_NN1 ,_, based_VVN on_II specific_JJ genes_NN2 ,_, can_VM influence_VVI the_AT formation_NN1 of_IO culture_NN1 ._. 
Epigenetic_JJ rules_NN2 have_VH0 been_VBN demonstrated_VVN in_II virtually_RR every_AT1 category_NN1 of_IO cognition_NN1 and_CC behaviour_NN1 investigated_VVN in_II such_DA a_AT1 way_NN1 as_CSA to_TO distinguish_VVI choices_NN2 among_II stimuli_NN2 ._. 
Examples_NN2 include_VV0 odour_NN1 and_CC taste_NN1 discrimination_NN1 ,_, with_IW important_JJ effects_NN2 on_II the_AT evolution_NN1 of_IO language_NN1 and_CC cuisine_NN1 ;_; preference_NN1 from_II infancy_NN1 onward_RL for_RR21 certain_RR22 basic_JJ geometric_JJ designs_NN2 over_II others_NN2 ;_; phoneme_NN1 formation_NN1 ;_; rules_NN2 of_IO transformational_JJ grammar_NN1 ;_; the_AT development_NN1 of_IO particular_JJ ,_, species-wide_JJ facial_JJ expressions_NN2 to_TO denote_VVI the_AT emotions_NN2 of_IO fear_NN1 ,_, loathing_NN1 ,_, anger_VV0 ,_, surprise_NN1 ,_, and_CC happiness_NN1 ;_; various_JJ other_JJ forms_NN2 of_IO nonverbal_JJ communication_NN1 ;_; the_AT pattern_NN1 of_IO mother-infant_JJ bonding_NN1 ;_; the_AT method_NN1 of_IO infant_NN1 holding_VVG by_II women_NN2 ;_; fear_NN1 of_IO strangers_NN2 (_( a_AT1 usually_RR strong_JJ response_NN1 that_CST persists_VVZ from_II about_RG six_MC to_II eighteen_MC months_NNT2 )_) ;_; phobias_NN2 ;_; and_CC others_NN2 (_( see_VV0 the_AT review_NN1 by_II Lumsden_NP1 &amp;_CC Wilson_NP1 ,_, 1981_MC )_) ._. 
It_PPH1 is_VBZ clear_JJ that_CST during_II the_AT past_JJ twenty_MC years_NNT2 developmental_JJ psychologists_NN2 have_VH0 come_VVN to_II the_AT edge_NN1 of_IO a_AT1 vast_JJ array_NN1 of_IO structural_JJ processes_NN2 in_II the_AT development_NN1 of_IO the_AT mind_NN1 ,_, and_CC an_AT1 exciting_JJ era_NN1 of_IO experimental_JJ research_NN1 has_VHZ begun_VVN ._. 
Most_DAT of_IO the_AT ontogenetic_JJ patterns_NN2 occur_VV0 early_RR enough_RR in_II life_NN1 and_CC are_VBR sufficiently_RR strongly_RR marked_VVN and_CC stereotyped_JJ to_TO suggest_VVI that_CST they_PPHS2 are_VBR genetically_RR canalized_VVN ._. 
It_PPH1 is_VBZ further_RRR true_JJ that_CST some_DD degree_NN1 of_IO heritability_NN1 has_VHZ been_VBN indicated_VVN by_II twin_NN1 and_CC pedigree_NN1 analysis_NN1 ,_, of_IO varying_JJ degrees_NN2 of_IO sophistication_NN1 and_CC reliability_NN1 ,_, in_II virtually_RR every_AT1 measurable_JJ category_NN1 of_IO cognitive_JJ ability_NN1 and_CC personality_NN1 trait_NN1 thus_RR far_RR studied_VVN ._. 
Many_DA2 of_IO these_DD2 properties_NN2 form_VV0 components_NN2 of_IO the_AT epigenetic_JJ rules_NN2 just_RR cited_VVN (_( Ehrman_NP1 &amp;_CC Parsons_NP1 ,_, 1981_MC )_) ._. 
By_II 1980_MC about_RG 3100_MC human_JJ genes_NN2 had_VHD been_VBN distinguished_VVN ,_, mostly_RR by_II biochemical_JJ techniques_NN2 ._. 
Of_IO these_DD2 ,_, 340_MC were_VBDR pinpointed_VVN to_II a_AT1 particular_JJ chromosome_NN1 ,_, with_IW at_RR21 least_RR22 one_MC1 on_II each_DD1 of_IO the_AT 23_MC pairs_NN2 of_IO chromosomes_NN2 (_( McKusick_NP1 ,_, 1980_MC )_) ._. 
Some_DD of_IO the_AT genes_NN2 and_CC chromosome_NN1 aberrations_NN2 affect_VV0 behaviour_NN1 in_II selective_JJ ways_NN2 ._. 
A_AT1 notable_JJ example_NN1 is_VBZ the_AT major_JJ gene_NN1 recently_RR identified_VVN that_CST reduces_VVZ spatial_JJ ability_NN1 in_II three_MC standard_JJ tests_NN2 but_CCB not_XX in_II twelve_MC others_NN2 (_( Ashton_NP1 ,_, Polovina_NP1 &amp;_CC Vandenberg_NP1 ,_, 1979_MC )_) ._. 
It_PPH1 is_VBZ equally_RR significant_JJ that_CST the_AT analysis_NN1 of_IO complex_NN1 ,_, multiple-locus_JJ systems_NN2 (_( polygenes_NN2 )_) is_VBZ well_RR advanced_VVN ._. 
Recent_JJ advances_NN2 include_VV0 the_AT calculation_NN1 of_IO the_AT numbers_NN2 of_IO chromosomal_JJ loci_NN2 and_CC genes_NN2 involved_JJ in_II such_DA relatively_RR complicated_JJ behaviours_NN2 as_CSA dominance_NN1 and_CC drug_NN1 aversive_JJ behaviour_NN1 in_II mice_NN2 and_CC the_AT epigenetic_JJ rules_NN2 of_IO colour_NN1 preference_NN1 in_II birds_NN2 (_( Thompson_NP1 &amp;_CC Thoday_NP1 ,_, 1979_MC )_) ._. 
An_AT1 important_JJ principle_NN1 of_IO gene_NN1 culture_NN1 coevolutionary_JJ theory_NN1 is_VBZ that_CST a_AT1 tabula_NN121 rasa_NN122 mind_NN1 ,_, open_VV0 to_II all_DB choices_NN2 equally_RR and_CC hence_RR totally_RR dependent_JJ on_II the_AT accidents_NN2 of_IO history_NN1 ,_, must_VM still_RR have_VHI a_AT1 biological_JJ foundation_NN1 and_CC a_AT1 very_RG finely_RR adjusted_VVN one_PN1 at_II that_DD1 ._. 
The_AT sensory_JJ apparatus_NN1 and_CC brain_NN1 have_VH0 to_TO be_VBI tuned_VVN precisely_RR in_BCL21 order_BCL22 to_TO process_VVI all_DB stimuli_NN2 without_IW bias_NN1 ._. 
Such_DA an_AT1 effect_NN1 ,_, which_DDQ Lumsden_NP1 and_CC I_PPIS1 have_VH0 called_VVN the_AT '_GE pure_JJ cultural_JJ transmission_NN1 '_GE of_IO culture_NN1 ,_, can_VM not_XX be_VBI achieved_VVN merely_RR by_II removing_VVG genetic_JJ constraints_NN2 on_II cognition_NN1 and_CC learning_NN1 ._. 
Quite_RR the_AT contrary_NN1 :_: it_PPH1 requires_VVZ a_AT1 formidable_JJ array_NN1 of_IO homeostatic_JJ devices_NN2 ,_, in_BCL21 order_BCL22 to_TO achieve_VVI uniform_JJ information_NN1 processing_NN1 and_CC hence_RR independence_NN1 from_II all_DB but_II the_AT most_RGT generalized_JJ set_NN1 of_IO internal_JJ reinforcement_NN1 mechanisms_NN2 ._. 
And_CC indeed_RR there_EX is_VBZ no_AT evidence_NN1 that_CST the_AT human_JJ brain_NN1 works_VVZ in_II such_DA an_AT1 extreme_JJ behaviourist_NN1 manner_NN1 ._. 
Nor_CC does_VDZ the_AT grain_NN1 mediate_VVI a_AT1 '_GE pure_JJ genetic_JJ transmission_NN1 '_GE of_IO culture_NN1 ,_, in_II which_DDQ (_( like_II the_AT song_NN1 of_IO the_AT white-crowned_JJ sparrow_NN1 )_) only_RR a_AT1 single_JJ form_NN1 of_IO behaviour_NN1 can_VM be_VBI taught_VVN and_CC learned_VVN ._. 
All_DB of_IO the_AT evidence_NN1 from_II cognitive_JJ studies_NN2 thus_RR far_RR indicates_VVZ that_CST human_JJ behaviour_NN1 lies_VVZ in_RL21 between_RL22 these_DD2 two_MC extremes_NN2 ,_, that_REX21 is_REX22 ,_, in_II the_AT category_NN1 we_PPIS2 have_VH0 termed_VVN '_GE gene-culture_JJ transmission_NN1 '_GE of_IO culture_NN1 ._. 
Multiple_JJ choices_NN2 are_VBR learned_VVN and_CC any_DD one_MC1 of_IO them_PPHO2 can_VM be_VBI followed_VVN as_II21 for_II22 example_NN1 incest_NN1 versus_II outbreeding_VVG but_CCB there_EX is_VBZ an_AT1 innate_JJ predisposition_NN1 to_TO learn_VVI certain_JJ ones_NN2 in_II preference_NN1 to_II others_NN2 ,_, or_CC else_RR to_TO choose_VVI them_PPHO2 once_CS they_PPHS2 have_VH0 been_VBN acquired_VVN ._. 
Let_VV0 us_PPIO2 now_RT review_VVI the_AT essential_JJ steps_NN2 in_II the_AT proposed_JJ coevolutionary_JJ circuit_NN1 ._. 
Consider_VV0 for_REX21 example_REX22 the_AT case_NN1 of_IO the_AT avoidance_NN1 of_IO brother-sister_JJ incest_NN1 ,_, which_DDQ is_VBZ based_VVN to_II a_AT1 substantial_JJ degree_NN1 on_II an_AT1 inhibition_NN1 developed_VVN during_II close_JJ domestic_JJ association_NN1 in_II the_AT first_MD six_MC years_NNT2 of_IO life_NN1 ._. 
Because_CS this_DD1 epigenetic_JJ rule_NN1 occurs_VVZ across_II cultures_NN2 and_CC is_VBZ strong_JJ enough_RR to_TO defeat_VVI countervailing_JJ social_JJ pressures_NN2 ,_, it_PPH1 can_VM reasonably_RR be_VBI supposed_JJ to_TO have_VHI a_AT1 genetic_JJ basis_NN1 ._. 
Moreover_RR ,_, those_DD2 who_PNQS follow_VV0 the_AT rule_NN1 benefit_NN1 in_II natural_JJ selection_NN1 ._. 
Incest_NN1 results_NN2 in_II higher_JJR rates_NN2 of_IO homozygosity_NN1 ,_, the_AT more_RGR frequent_JJ expression_NN1 of_IO lethal_JJ or_CC subvital_JJ recessive_JJ genes_NN2 ,_, and_CC hence_RR a_AT1 greater_JJR incidence_NN1 of_IO hereditary_JJ disease_NN1 and_CC early_JJ death_NN1 among_II the_AT offspring_NN ._. 
The_AT epigenetic_JJ rule_NN1 thus_RR directs_VVZ the_AT developing_JJ mind_NN1 to_TO avoid_VVI brother-sister_JJ incest_NN1 ._. 
The_AT summed_JJ preference_NN1 of_IO members_NN2 of_IO the_AT society_NN1 lead_NN1 to_II particular_JJ cultural_JJ patterns_NN2 ,_, including_II reinforcing_VVG taboos_NN2 and_CC laws_NN2 ,_, that_CST prohibit_VV0 incest_NN1 ._. 
However_RR ,_, because_CS the_AT cultural_JJ transmission_NN1 is_VBZ of_IO the_AT intermediate_JJ ,_, '_GE gene-culture_NN1 '_GE form_NN1 ,_, the_AT preference_NN1 is_VBZ not_XX absolute_JJ ,_, and_CC scattered_JJ individuals_NN2 in_II many_DA2 societies_NN2 still_RR prefer_VV0 and_CC may_VM even_RR practise_VVI brother-sister_JJ incest_NN1 ._. 
The_AT result_NN1 is_VBZ some_DD variation_NN1 among_II cultures_NN2 in_II the_AT frequency_NN1 of_IO its_APPGE members_NN2 who_PNQS adopt_VV0 this_DD1 preference_NN1 ._. 
Consider_VV0 ,_, for_REX21 example_REX22 ,_, groups_NN2 of_IO 25_MC individuals_NN2 ._. 
This_DD1 is_VBZ the_AT size_NN1 of_IO many_DA2 hunter-gatherer_JJ bands_NN2 ,_, the_AT social_JJ organization_NN1 in_II which_DDQ mankind_NN1 has_VHZ existed_VVN throughout_II most_DAT of_IO its_APPGE history_NN1 ._. 
At_II any_DD given_JJ moment_NN1 most_DAT such_DA bands_NN2 can_VM be_VBI expected_VVN to_TO contain_VVI no_AT incestuous_JJ members_NN2 ._. 
A_AT1 smaller_JJR percentage_NN1 of_IO the_AT bands_NN2 will_VM contain_VVI one_MC1 such_DA member_NN1 ,_, a_AT1 still_RR smaller_JJR percentage_NN1 will_VM contain_VVI two_MC incestuous_JJ individuals_NN2 ,_, and_RR31 so_RR32 on_RR33 ._. 
The_AT full_JJ array_NN1 of_IO such_DA fractions_NN2 ,_, comprising_VVG a_AT1 frequency_NN1 distribution_NN1 across_II all_DB cultures_NN2 sampled_VVD ,_, is_VBZ called_VVN an_AT1 ethnographic_JJ curve_NN1 ._. 
We_PPIS2 have_VH0 devised_VVN methods_NN2 for_IF predicting_VVG such_DA curves_NN2 from_II a_AT1 knowledge_NN1 of_IO two_MC functions_NN2 :_: the_AT magnitude_NN1 of_IO bias_NN1 in_II the_AT preference_NN1 for_IF one_MC1 cultural_JJ choice_NN1 (_( such_II21 as_II22 incest_NN1 )_) versus_II another_DD1 (_( outbreeding_VVG )_) ,_, and_CC the_AT degree_NN1 to_II which_DDQ the_AT expressed_JJ preference_NN1 of_IO the_AT remainder_NN1 of_IO the_AT group_NN1 affects_VVZ the_AT magnitude_NN1 of_IO the_AT individual_JJ bias_NN1 ._. 
Two_MC results_NN2 of_IO general_JJ interest_NN1 emerge_VV0 from_II this_DD1 preliminary_JJ analysis_NN1 ._. 
First_MD ,_, it_PPH1 is_VBZ technically_RR possible_JJ to_TO predict_VVI patterns_NN2 of_IO cultural_JJ diversity_NN1 ,_, expressed_VVN as_II the_AT ethnographic_JJ curves_NN2 ,_, from_II a_AT1 knowledge_NN1 of_IO individual_JJ cognitive_JJ development_NN1 ,_, and_CC also_RR to_TO perform_VVI the_AT reverse_NN1 :_: to_TO infer_VVI at_RR21 least_RR22 some_DD of_IO the_AT principal_JJ properties_NN2 of_IO cognitive_JJ development_NN1 from_II a_AT1 knowledge_NN1 of_IO the_AT pattern_NN1 of_IO cultural_JJ diversity_NN1 ._. 
The_AT second_MD result_NN1 of_IO broad_JJ interest_NN1 is_VBZ that_DD1 cultural_JJ diversity_NN1 is_VBZ to_TO be_VBI expected_VVN even_CS21 if_CS22 the_AT underlying_JJ cognitive_JJ development_NN1 is_VBZ rigidly_RR programmed_VVN ._. 
Cultural_JJ anthropologists_NN2 have_VH0 commonly_RR argued_VVN that_CST the_AT existence_NN1 of_IO substantial_JJ differences_NN2 among_II cultures_NN2 is_VBZ evidence_NN1 of_IO the_AT absence_NN1 of_IO underlying_JJ biological_JJ influence_NN1 (_( Sahlins_NP2 ,_, 1976_MC ;_; Harris_NP1 ,_, 1981_MC )_) ._. 
But_CCB this_DD1 conclusion_NN1 is_VBZ entirely_RR wrong_JJ ._. 
Cultural_JJ diversity_NN1 per_RR21 se_RR22 is_VBZ evidence_NN1 neither_RR for_IF nor_CC against_II such_DA control_NN1 ._. 
Rather_RR ,_, what_DDQ matters_VVZ is_VBZ the_AT pattern_NN1 of_IO the_AT diversity_NN1 ._. 
As_CSA biological_JJ bias_NN1 is_VBZ increased_VVN toward_II one_MC1 choice_NN1 as_II31 opposed_II32 to_II33 another_DD1 in_II the_AT course_NN1 of_IO genetic_JJ evolution_NN1 ,_, the_AT mode_NN1 of_IO the_AT ethnographic_JJ curve_NN1 can_VM be_VBI expected_VVN to_TO shift_VVI in_II that_DD1 direction_NN1 ._. 
And_CC as_II the_AT influence_NN1 of_IO peer_NN1 activity_NN1 is_VBZ increased_VVN -this_DD1 influence_NN1 itself_PPX1 may_VM well_RR be_VBI biologically_RR determined_VVN there_RL will_VM be_VBI a_AT1 tendency_NN1 for_IF the_AT ethnographic_JJ curve_NN1 to_TO change_VVI from_II a_AT1 unimodal_JJ to_II a_AT1 multimodal_JJ form_NN1 ._. 
By_II examining_VVG the_AT pattern_NN1 of_IO cultural_JJ diversity_NN1 in_II an_AT1 explicit_JJ form_NN1 such_II21 as_II22 the_AT ethnographic_JJ curve_NN1 ,_, the_AT nature_NN1 of_IO the_AT underlying_JJ epigenetic_JJ rules_NN2 can_VM be_VBI partially_RR inferred_VVN ._. 
A_AT1 recurrent_JJ working_JJ hypothesis_NN1 of_IO gene-culture_JJ coevolutionary_JJ theory_NN1 is_VBZ that_CST the_AT epigenetic_JJ rules_NN2 are_VBR shaped_VVN by_II natural_JJ selection_NN1 over_II many_DA2 generations_NN2 ._. 
Returning_VVG to_II the_AT brother-sister_JJ incest_NN1 case_NN1 for_IF illustration_NN1 ,_, we_PPIS2 note_VV0 that_CST individuals_NN2 who_PNQS conform_VV0 to_II the_AT aversion_NN1 leave_VV0 more_DAR offspring_NN ._. 
As_II a_AT1 result_NN1 ,_, genes_NN2 underwriting_VVG the_AT avoidance_NN1 of_IO incest_NN1 remain_VV0 at_II a_AT1 high_JJ level_NN1 in_II the_AT population_NN1 ._. 
Consequently_RR the_AT predisposition_NN1 is_VBZ sustained_VVN as_CSA one_MC1 of_IO the_AT epigenetic_JJ rules_NN2 ._. 
In_RR21 general_RR22 ,_, the_AT rules_NN2 leading_VVG to_II higher_JJR rates_NN2 of_IO survival_NN1 and_CC reproduction_NN1 tend_VV0 to_TO increase_VVI in_II the_AT population_NN1 ._. 
Thus_RR the_AT assembly_NN1 rules_NN2 of_IO the_AT mind_NN1 build_VV0 up_RP during_II evolution_NN1 ,_, element_NN1 by_II element_NN1 ._. 
In_II the_AT genetic_JJ models_NN2 ,_, the_AT tabula_NN121 rasa_NN122 brain_NN1 ,_, in_II which_DDQ the_AT mind_NN1 is_VBZ created_VVN solely_RR by_II the_AT circumstances_NN2 of_IO history_NN1 ,_, proves_VVZ to_TO be_VBI a_AT1 very_RG improbable_JJ outcome_NN1 in_II the_AT evolution_NN1 of_IO any_DD conceivable_JJ intelligent_JJ species_NN ._. 
Even_CS21 if_CS22 a_AT1 species_NN somehow_RR managed_VVN to_TO begin_VVI with_IW such_DA a_AT1 brain_NN1 it_PPH1 would_VM soon_RR evolve_VVI in_II the_AT direction_NN1 of_IO structural_JJ and_CC biased_JJ epigenetic_JJ rules_NN2 ._. 
And_CC as_II the_AT evolution_NN1 proceeds_NN2 ,_, small_JJ changes_NN2 in_II the_AT degree_NN1 of_IO bias_NN1 can_VM be_VBI expected_VVN to_TO result_VVI commonly_RR in_II much_RR greater_JJR changes_NN2 in_II the_AT final_JJ cultural_JJ product_NN1 ._. 
For_REX21 example_REX22 ,_, a_AT1 barely_RR detectable_JJ innate_JJ bias_NN1 toward_II the_AT use_NN1 of_IO body_NN1 adornment_NN1 ,_, if_CS combined_VVN with_IW a_AT1 moderate_JJ sensitivity_NN1 to_TO peer_VVI usage_NN1 ,_, would_VM result_VVI in_II most_DAT or_CC all_DB members_NN2 using_VVG such_DA adornment_NN1 in_II all_DB societies_NN2 ._. 
Finally_RR ,_, a_AT1 detectable_JJ amount_NN1 of_IO genetic_JJ evolution_NN1 in_II the_AT brain_NN1 and_CC mind_NN1 can_VM occur_VVI within_II only_RR thirty_MC or_CC forty_MC generations_NN2 ,_, or_CC very_RG roughly_RR a_AT1 thousand_NNO years_NNT2 ._. 
If_CS correct_JJ ,_, this_DD1 still_RR purely_RR theoretical_JJ conclusion_NN1 implies_VVZ that_CST epigenetic_JJ rules_NN2 and_CC mental_JJ traits_NN2 might_VM have_VHI continued_VVN to_TO evolve_VVI into_II historical_JJ times_NNT2 ._. 
The_AT conventional_JJ view_NN1 ,_, that_DD1 such_DA biological_JJ evolution_NN1 ceased_VVD tens_MC2 of_IO thousands_NNO2 of_IO years_NNT2 ago_RA and_CC human_JJ change_NN1 has_VHZ consisted_VVN entirely_RR of_IO cultural_JJ evolution_NN1 since_II then_RT ,_, may_VM be_VBI incorrect_JJ ._. 
In_II closing_NN1 ,_, I_PPIS1 want_VV0 to_TO take_VVI note_NN1 of_IO the_AT familiar_JJ lament_NN1 that_CST science_NN1 and_CC technology_NN1 have_VH0 created_VVN not_XX just_RR a_AT1 cornucopia_NN1 but_CCB terrible_JJ dangers_NN2 as_RR21 well_RR22 ._. 
What_DDQ is_VBZ meant_VVN by_II science_NN1 in_II this_DD1 case_NN1 is_VBZ of_RR21 course_RR22 the_AT physical_JJ sciences_NN2 and_CC to_II a_AT1 lesser_JJ degree_NN1 the_AT biological_JJ sciences_NN2 ._. 
But_CCB the_AT solution_NN1 is_VBZ not_XX ,_, as_CSA a_AT1 few_DA2 modern_JJ Luddites_NN2 have_VH0 suggested_VVN ,_, the_AT curtailment_NN1 of_IO science_NN1 itself_PPX1 ,_, including_II sociobiology_NN1 and_CC the_AT social_JJ sciences_NN2 ._. 
Quite_RR the_AT opposite_JJ :_: the_AT solution_NN1 is_VBZ to_TO make_VVI every_AT1 effort_NN1 to_TO extend_VVI new_JJ scientific_JJ procedures_NN2 into_II the_AT deeper_JJR reaches_NN2 of_IO human_JJ nature_NN1 in_BCL21 order_BCL22 to_TO provide_VVI solutions_NN2 to_II those_DD2 residual_JJ problems_NN2 that_CST continue_VV0 to_TO defy_VVI simple_JJ economic_JJ and_CC technological_JJ solution_NN1 ._. 
The_AT peculiar_JJ clockwork_NN1 of_IO the_AT human_JJ mind_NN1 ,_, not_XX scientific_JJ knowledge_NN1 itself_PPX1 ,_, is_VBZ the_AT source_NN1 of_IO the_AT danger_NN1 ._. 
If_CS evolutionary_JJ theory_NN1 can_VM be_VBI successfully_RR extended_VVN to_II the_AT assembly_NN1 of_IO the_AT mind_NN1 and_CC the_AT creation_NN1 of_IO cultural_JJ diversity_NN1 ,_, the_AT result_NN1 may_VM well_RR rank_VVI as_II the_AT completion_NN1 of_IO the_AT Darwinian_JJ revolution_NN1 ._. 
Whether_CSW the_AT particular_JJ scheme_NN1 summarized_VVD here_RL can_VM contribute_VVI substantially_RR to_II that_DD1 end_NN1 remains_VVZ to_TO be_VBI seen_VVN ,_, but_CCB I_PPIS1 hope_VV0 at_II the_AT very_RG least_RRT I_PPIS1 have_VH0 been_VBN able_JK to_TO express_VVI why_RRQ I_PPIS1 believe_VV0 that_CST the_AT social_JJ sciences_NN2 will_VM eventually_RR be_VBI fused_VVN with_IW biology_NN1 ._. 
No_AT natural_JJ boundary_NN1 appears_VVZ to_TO exist_VVI between_II the_AT natural_JJ and_CC social_JJ sciences_NN2 ._. 
Their_APPGE blend_NN1 zone_NN1 ,_, a_AT1 mysterious_JJ and_CC sometimes_RT prohibited_JJ domain_NN1 ,_, offers_VVZ a_AT1 great_JJ immediate_JJ potential_NN1 for_IF scientific_JJ discovery_NN1 in_II the_AT postulationaldeductive_JJ and_CC experimental_JJ tradition_NN1 of_IO the_AT natural_JJ sciences_NN2 ._. 
&lsqb;_( &rsqb;_) EVOLUTION_NN1 ,_, ETHICS_NN ,_, AND_CC THE_AT REPRESENTATION_NN1 PROBLEM_NN1 BERNARD_NP1 WILLIAMS_NP1 This_DD1 paper_NN1 is_VBZ concerned_JJ with_IW culture_NN1 and_CC with_IW evolution_NN1 ,_, but_CCB not_XX with_IW cultural_JJ evolution_NN1 ._. 
It_PPH1 discusses_VVZ the_AT relations_NN2 between_II biological_JJ evolution_NN1 and_CC the_AT areas_NN2 of_IO human_JJ culture_NN1 which_DDQ may_VM broadly_RR be_VBI called_VVN '_GE ethical_JJ '_GE ._. 
The_AT concept_NN1 of_IO cultural_JJ evolution_NN1 is_VBZ problematical_JJ ,_, and_CC there_EX are_VBR notorious_JJ difficulties_NN2 about_II applying_VVG the_AT notions_NN2 of_IO evolution_NN1 and_CC natural_JJ selection_NN1 to_II cultural_JJ development_NN1 ;_; in_RR21 particular_RR22 ,_, the_AT ends_NN2 served_VVN by_II various_JJ cultural_JJ developments_NN2 are_VBR themselves_PPX2 defined_VVN by_II culture_NN1 ,_, as_CSA are_VBR the_AT '_GE choices_NN2 '_GE to_II which_DDQ Wilson_NP1 refers_VVZ in_II his_APPGE paper_NN1 (_( this_DD1 volume_NN1 )_) ._. 
That_DD1 area_NN1 ,_, however_RR ,_, is_VBZ not_XX the_AT concern_NN1 of_IO the_AT present_JJ discussion_NN1 ._. 
There_EX are_VBR two_MC kinds_NN2 of_IO connection_NN1 between_II evolutionary_JJ theory_NN1 and_CC ethics_NN :_: one_MC1 normative_JJ ,_, and_CC one_PN1 explanatory_JJ ._. 
There_EX is_VBZ also_RR a_AT1 connection_NN1 between_II these_DD2 two_MC ,_, to_II which_DDQ I_PPIS1 shall_VM come_VVI later_RRR ._. 
The_AT first_MD of_IO these_DD2 is_VBZ older_JJR than_CSN the_AT second_NNT1 ,_, and_CC has_VHZ acquired_VVN a_AT1 bad_JJ name_NN1 ;_; indeed_RR ,_, it_PPH1 acquired_VVD it_PPH1 fairly_RR early_RR ,_, in_II some_DD part_NN1 from_II the_AT monumental_JJ and_CC unappealing_VVG system_NN1 of_IO Herbert_NP1 Spencer_NP1 ._. 
In_II fact_NN1 ,_, as_CSA John_NP1 Burrow_NP1 has_VHZ shown_VVN (_( Burrow_NP1 ,_, 1966_MC )_) a_AT1 lot_NN1 of_IO this_DD1 material_NN1 ante-dated_NN1 The_AT Origin_NN1 of_IO Species_NN ;_; the_AT concept_NN1 of_IO '_GE the_AT survival_NN1 of_IO the_AT fittest_JJT '_GE (_( Spencer_NP1 's_GE own_DA phrase_NN1 )_) was_VBDZ already_RR implicit_JJ in_II earlier_JJR sociological_JJ work_NN1 which_DDQ Spencer_NP1 derived_VVN from_II Malthus_NP1 ._. 
Darwin_NP1 himself_PPX1 had_VHD little_DA1 sympathy_NN1 for_IF these_DD2 ideas_NN2 and_CC not_XX much_RR ,_, personally_RR ,_, for_IF Spencer_NP1 ,_, though_CS he_PPHS1 did_VDD once_RR say_VVI I_PPIS1 quote_VV0 Burrow_NP1 (_( p._NNU 182_MC )_) '_GE in_II a_AT1 moment_NN1 of_IO enthusiasm_NN1 ..._... that_CST Spencer_NP1 's_GE Principles_NN2 of_IO Biology_NN1 made_VVD him_PPHO1 feel_VVI that_CST he_PPHS1 '_VBZ is_VBZ about_RG a_AT1 dozen_NNO times_NNT2 my_APPGE superior_NN1 '_GE ,_, and_CC thought_VVD that_CST Spencer_NP1 might_VM one_MC1 day_NNT1 be_VBI regarded_VVN as_II the_AT equal_JJ of_IO Descartes_NN2 and_CC Leibniz_NP1 ,_, rather_RR spoiling_VVG the_AT effect_NN1 by_II adding_VVG ,_, '_GE about_II whom_PNQO ,_, however_RR ,_, I_PPIS1 know_VV0 very_RG little_DA1 '_" '_GE ._. 
The_AT bad_JJ normative_JJ applications_NN2 of_IO evolutionary_JJ theory_NN1 to_II ethics_NN which_DDQ were_VBDR made_VVN by_II Spencer_NP1 and_CC others_NN2 also_RR ,_, of_RR21 course_RR22 ,_, involved_VVD a_AT1 lot_NN1 of_IO bad_JJ evolutionary_JJ theory_NN1 :_: if_CS normative_JJ lessons_NN2 could_VM be_VBI drawn_VVN from_II Darwinian_JJ theory_NN1 ,_, there_EX is_VBZ certainly_RR no_AT reason_NN1 why_RRQ they_PPHS2 should_VM take_VVI the_AT form_NN1 suggested_VVN by_II Social_JJ Darwinists_NN2 ._. 
However_RR ,_, there_EX is_VBZ in_RR21 addition_RR22 a_AT1 standard_JJ objection_NN1 which_DDQ holds_VVZ that_CST no_AT such_DA lessons_NN2 can_VM be_VBI drawn_VVN at_RR21 all_RR22 ,_, at_RR21 least_RR22 in_II any_DD directly_RR logical_JJ way_NN1 ,_, since_CS any_DD project_NN1 of_IO deriving_VVG ethical_JJ content_NN1 from_II premisses_NN2 of_IO evolutionary_JJ theory_NN1 commits_VVZ the_AT '_GE naturalistic_JJ fallacy_NN1 '_GE ,_, an_AT1 error_NN1 which_DDQ is_VBZ today_RT often_RR equated_VVN with_IW that_DD1 of_IO trying_VVG to_TO derive_VVI ought_VMK from_II is_VBZ ._. 
Interesting_JJ questions_NN2 about_II '_GE naturalism_NN1 '_GE in_II ethics_NN in_II fact_NN1 go_VV0 beyond_II these_DD2 purely_RR logical_JJ issues_NN2 ._. 
Naturalism_NN1 in_II a_AT1 broader_JJR sense_NN1 consists_VVZ in_II the_AT attempt_NN1 to_TO lay_VVI down_RP certain_JJ fundamental_JJ aspects_NN2 of_IO the_AT good_JJ life_NN1 for_IF man_NN1 on_II the_AT basis_NN1 of_IO considerations_NN2 of_IO human_JJ nature_NN1 ._. 
If_CS this_DD1 project_NN1 falls_NN2 ,_, it_PPH1 is_VBZ not_XX for_IF purely_RR logical_JJ reasons_NN2 ;_; it_PPH1 will_VM rather_RR be_VBI for_IF the_AT more_RGR interesting_JJ reason_NN1 that_CST the_AT right_JJ sort_NN1 of_IO truths_NN2 do_VD0 not_XX exist_VVI about_II human_JJ nature_NN1 ._. 
I_PPIS1 shall_VM come_VVI back_RP to_II this_DD1 wider_JJR question_NN1 at_II the_AT end_NN1 of_IO this_DD1 paper_NN1 ._. 
The_AT point_NN1 about_II ought_VMK and_CC is_VBZ ,_, so_RG far_RR as_CSA it_PPH1 goes_VVZ ,_, does_VDZ have_VHI some_DD force_NN1 ._. 
It_PPH1 can_VM be_VBI put_VVN in_II the_AT following_JJ way_NN1 ._. 
Suppose_VV0 that_CST considerations_NN2 of_IO evolutionary_JJ theory_NN1 show_VV0 that_CST certain_JJ behaviour_NN1 is_VBZ in_II some_DD sense_NN1 appropriate_JJ for_IF human_JJ beings_NN2 ._. 
Either_DD1 human_JJ beings_NN2 can_VM diverge_VVI from_II this_DD1 pattern_NN1 ,_, or_CC they_PPHS2 can_VM not_XX ._. 
If_CS they_PPHS2 can_VM ,_, then_RT the_AT biological_JJ considerations_NN2 are_VBR not_XX going_VVGK to_TO show_VVI that_CST they_PPHS2 ought_VMK not_XX to_TO ;_; while_CS ,_, if_CS they_PPHS2 can_VM not_XX so_RR diverge_VVI ,_, then_RT there_EX is_VBZ no_AT question_NN1 of_IO ought_VMK ._. 
This_DD1 argument_NN1 seems_VVZ to_II me_PPIO1 sound_RR so_RG far_RR as_CSA it_PPH1 goes_VVZ ,_, but_CCB it_PPH1 does_VDZ not_XX go_VVI very_RG far_RR ._. 
Implicit_JJ in_II this_DD1 last_MD argument_NN1 is_VBZ another_DD1 logical_JJ relation_NN1 which_DDQ is_VBZ more_RGR interesting_JJ for_IF this_DD1 question_NN1 than_CSN that_DD1 between_II ought_VMK and_CC is_VBZ :_: the_AT relation_NN1 ,_, that_REX41 is_REX42 to_REX43 say_REX44 ,_, between_II ought_VMK and_CC can_VM ._. 
This_DD1 relationship_NN1 underlies_VVZ some_DD important_JJ negative_JJ arguments_NN2 which_DDQ by_II citing_VVG certain_JJ claims_NN2 to_II the_AT effect_NN1 that_CST human_JJ beings_NN2 can_VM not_XX ,_, as_CSA they_PPHS2 may_VM suppose_VVI ,_, live_VV0 in_II a_AT1 certain_JJ way_NN1 ,_, lead_VV0 to_II the_AT conclusion_NN1 that_CST certain_JJ ethical_JJ goals_NN2 or_CC ideals_NN2 are_VBR unrealistic_JJ and_CC should_VM be_VBI revised_VVN ._. 
By_II arguments_NN2 of_IO this_DD1 kind_NN1 ,_, biological_JJ or_CC similar_JJ arguments_NN2 could_VM coherently_RR yield_VVI constraints_NN2 on_II social_JJ goals_NN2 ,_, personal_JJ ideals_NN2 ,_, possible_JJ institutions_NN2 and_RR31 so_RR32 forth_RR33 ._. 
To_TO say_VVI that_DD1 human_JJ beings_NN2 can_VM not_XX do_VDI certain_JJ things_NN2 is_VBZ ,_, of_RR21 course_RR22 ,_, an_AT1 extremely_RR vague_JJ form_NN1 of_IO statement_NN1 ._. 
At_II one_MC1 extreme_JJ ,_, it_PPH1 may_VM mean_VVI that_CST the_AT world_NN1 will_VM not_XX contain_VVI an_AT1 example_NN1 of_IO any_DD single_JJ human_JJ being_NN1 doing_VDG that_DD1 thing_NN1 ;_; at_II the_AT other_JJ end_NN1 ,_, it_PPH1 may_VM merely_RR mean_VVI that_CST if_CS a_AT1 group_NN1 of_IO human_JJ beings_NN2 adopt_VV0 a_AT1 norm_NN1 requiring_VVG that_DD1 behaviour_NN1 ,_, the_AT norm_NN1 will_VM often_RR be_VBI broken_VVN ,_, its_APPGE observance_NN1 will_VM give_VVI rise_NN1 to_II a_AT1 good_JJ deal_NN1 of_IO anxiety_NN1 ,_, those_DD2 who_PNQS comply_VV0 without_IW anxiety_NN1 to_II the_AT norm_NN1 will_VM be_VBI unusual_JJ in_II other_JJ respects_NN2 ,_, and_RR31 so_RR32 forth_RR33 ._. 
This_DD1 vagueness_NN1 will_VM not_XX matter_VVI so_RG long_RR as_CSA one_PN1 is_VBZ clear_JJ about_II the_AT level_NN1 at_II which_DDQ the_AT formula_NN1 of_IO '_" ought_VMK implies_VVZ can_NN1 '_GE is_VBZ being_VBG applied_VVN :_: thus_RR the_AT latter_DA ,_, and_CC weaker_JJR ,_, kind_NN1 of_IO '_" can_VM not_XX '_" would_VM be_VBI enough_DD to_TO provide_VVI a_AT1 strong_JJ argument_NN1 against_II the_AT behaviour_NN1 being_VBG made_VVN into_II a_AT1 norm_NN1 for_IF a_AT1 human_JJ society_NN1 ,_, but_CCB it_PPH1 would_VM not_XX be_VBI enough_RR if_CS the_AT question_NN1 concerned_VVD the_AT adoption_NN1 of_IO a_AT1 personal_JJ ideal_NN1 in_II an_AT1 individual_JJ case_NN1 ._. 
Here_RL ,_, as_CSA so_RG often_RR ,_, it_PPH1 is_VBZ a_AT1 centrally_RR important_JJ question_NN1 ,_, who_PNQS is_VBZ supposedly_RR being_VBG addressed_VVN by_II a_AT1 given_JJ piece_NN1 of_IO ethical_JJ discourse_NN1 ._. 
Granted_VVN that_CST one_PN1 is_VBZ clear_JJ about_II that_DD1 ,_, the_AT fact_NN1 that_CST relevant_JJ statements_NN2 of_IO what_DDQ human_JJ beings_NN2 can_VM and_CC can_VM not_XX do_VDI come_VVI in_II various_JJ strengths_NN2 is_VBZ not_XX so_RG important_JJ ._. 
What_DDQ is_VBZ vitally_RR important_JJ is_VBZ the_AT difficulty_NN1 of_IO knowing_VVG which_DDQ of_IO them_PPHO2 ,_, relevant_JJ to_II difficult_JJ ethical_JJ issues_NN2 ,_, are_VBR on_II biological_JJ grounds_NN2 in_II fact_NN1 true_JJ ._. 
In_II this_DD1 area_NN1 there_EX is_VBZ an_AT1 important_JJ connection_NN1 ,_, which_DDQ I_PPIS1 mentioned_VVD before_RT ,_, between_II what_DDQ I_PPIS1 called_VVD the_AT normative_JJ and_CC the_AT explanatory_JJ interest_NN1 ._. 
If_CS some_DD biological_JJ constraint_NN1 can_VM rule_VVI out_RP ,_, or_CC make_VV0 unrealistic_JJ ,_, some_DD normative_JJ practice_NN1 or_CC institution_NN1 ,_, then_RT knowledge_NN1 of_IO it_PPH1 may_VM not_XX only_RR encourage_VVI us_PPIO2 to_TO decline_VVI that_DD1 practice_NN1 if_CS it_PPH1 is_VBZ suggested_VVN ,_, but_CCB may_VM also_RR contribute_VVI an_AT1 explanation_NN1 of_IO why_RRQ human_JJ communities_NN2 do_VD0 not_XX in_RR21 general_RR22 display_VV0 that_DD1 practice_NN1 or_CC institution_NN1 ._. 
Might_VM biological_JJ considerations_NN2 then_RT go_VV0 further_RRR and_CC explain_VV0 the_AT human_JJ adoption_NN1 of_IO other_JJ practices_NN2 ,_, which_DDQ are_VBR conformable_JJ to_II biological_JJ constraints_NN2 ?_? 
This_DD1 raises_VVZ a_AT1 general_JJ question_NN1 which_DDQ is_VBZ central_JJ to_II these_DD2 areas_NN2 ,_, and_CC which_DDQ I_PPIS1 shall_VM call_VVI the_AT representation_NN1 problem_NN1 ._. 
It_PPH1 is_VBZ a_AT1 problem_NN1 which_DDQ comes_VVZ up_RP at_II various_JJ points_NN2 in_II considering_VVG the_AT relations_NN2 between_II biology_NN1 and_CC human_JJ practices_NN2 ,_, and_CC may_VM be_VBI put_VVN in_II the_AT following_JJ way_NN1 :_: how_RRQ is_VBZ a_AT1 phenotypic_JJ character_NN1 which_DDQ would_VM present_VVI itself_PPX1 in_II other_JJ species_NN as_II a_AT1 behavioural_JJ tendency_NN1 represented_VVN in_II a_AT1 species_NN which_DDQ has_VHZ a_AT1 culture_NN1 ,_, language_NN1 and_CC conceptual_JJ thought_NN1 ?_? 
It_PPH1 may_VM be_VBI said_VVN that_CST in_II some_DD cases_NN2 ,_, at_RR21 least_RR22 ,_, such_DA a_AT1 tendency_NN1 will_VM show_VVI up_RP in_II that_DD1 species_NN merely_RR as_CSA itself_PPX1 that_REX41 is_REX42 to_REX43 say_REX44 ,_, as_CSA a_AT1 merely_RR biological_JJ character_NN1 of_IO that_DD1 species_NN ._. 
But_CCB ,_, in_II fact_NN1 ,_, virtually_RR no_AT behavioural_JJ tendency_NN1 which_DDQ constitutes_VVZ genuine_JJ action_NN1 can_VM just_RR show_VVI up_RP in_II a_AT1 cultural_JJ context_NN1 '_GE as_CSA itself_PPX1 '_GE ._. 
Where_CS there_EX is_VBZ culture_NN1 ,_, it_PPH1 affects_VVZ everything_PN1 ,_, and_CC we_PPIS2 should_VM reject_VVI the_AT crude_JJ view_NN1 that_CST culture_NN1 is_VBZ applied_VVN to_II an_AT1 animal_NN1 in_II a_AT1 way_NN1 which_DDQ leaves_VVZ its_APPGE other_JJ characteristics_NN2 unmodified_JJ ._. 
(_( Related_VVN to_II that_DD1 view_NN1 is_VBZ the_AT naive_JJ assumption_NN1 of_IO certain_JJ sociobiologists_NN2 that_CST sociobiology_NN1 should_VM expect_VVI to_TO be_VBI more_RGR closely_RR related_VVN to_II social_JJ anthropology_NN1 than_CSN to_II other_JJ social_JJ sciences_NN2 ,_, because_CS the_AT '_GE primitive_NN1 '_GE peoples_NN2 studied_VVN by_II social_JJ anthropology_NN1 are_VBR nearer_JJR to_II nature_NN1 than_CSN human_JJ beings_NN2 who_PNQS live_VV0 in_II large_JJ industrialized_JJ societies_NN2 ._. )_) 
None_PN of_IO this_DD1 is_VBZ to_TO deny_VVI that_CST there_EX is_VBZ a_AT1 biological_JJ basis_NN1 for_IF elements_NN2 in_II human_JJ behaviour_NN1 which_DDQ are_VBR culturally_RR affected_VVN ,_, moulded_JJ and_CC elaborated_VVN ._. 
It_PPH1 is_VBZ not_XX to_TO deny_VVI that_CST some_DD culturally_RR elaborated_VVN behaviour_NN1 can_VM usefully_RR be_VBI explained_VVN from_II a_AT1 biological_JJ perspective_NN1 ._. 
It_PPH1 is_VBZ simply_RR to_TO recall_VVI the_AT fact_NN1 that_CST almost_RR all_DB human_JJ behaviour_NN1 ,_, at_RR21 least_RR22 that_DD1 which_DDQ deserves_VVZ the_AT name_NN1 of_IO '_GE action_NN1 '_GE ,_, is_VBZ in_II fact_NN1 culturally_RR moulded_VVN and_CC elaborated_VVN ._. 
In_II accepting_VVG that_CST there_EX is_VBZ a_AT1 representation_NN1 problem_NN1 ,_, I_PPIS1 reject_VV0 two_MC views_NN2 according_II21 to_II22 which_DDQ there_EX would_VM be_VBI no_AT such_DA problem_NN1 ._. 
First_MD is_VBZ a_AT1 simple_JJ reductionist_NN1 view_NN1 ,_, which_DDQ would_VM neglect_VVI the_AT way_NN1 in_II which_DDQ culture_NN1 not_XX only_RR shapes_NN2 but_CCB constitutes_VVZ the_AT vast_JJ mass_NN1 of_IO human_JJ behaviour_NN1 ._. 
When_CS ancient_JJ Greek_NN1 thought_VVD first_MD discovered_VVD the_AT opposition_NN1 of_IO '_GE nature_NN1 '_GE and_CC '_GE convention_NN1 '_GE ,_, it_PPH1 also_RR discovered_VVD that_CST an_AT1 essential_JJ part_NN1 of_IO human_JJ nature_NN1 is_VBZ to_TO live_VVI by_II convention_NN1 ._. 
The_AT study_NN1 of_IO human_JJ nature_NN1 is_VBZ ,_, in_II good_JJ part_NN1 ,_, the_AT study_NN1 of_IO human_JJ conventions_NN2 ,_, and_CC that_DD1 is_VBZ what_DDQ it_PPH1 is_VBZ from_II the_AT strictest_JJT ethological_JJ point_NN1 of_IO view_NN1 ._. 
That_DD1 is_VBZ how_RRQ this_DD1 species_NN is_VBZ ._. 
It_PPH1 is_VBZ a_AT1 claim_NN1 additional_JJ to_II this_DD1 ,_, but_CCB one_PN1 which_DDQ I_PPIS1 also_RR believe_VV0 to_TO be_VBI true_JJ ,_, that_DD1 human_JJ conventions_NN2 ,_, at_RR21 least_RR22 beyond_II a_AT1 certain_JJ state_NN1 of_IO elaboration_NN1 ,_, can_VM be_VBI understood_VVN only_RR with_IW the_AT help_NN1 of_IO history_NN1 ,_, and_CC that_CST the_AT social_JJ sciences_NN2 accordingly_RR have_VH0 an_AT1 essential_JJ historical_JJ base_NN1 ._. 
To_TO pursue_VVI the_AT question_NN1 of_IO whether_CSW that_DD1 is_VBZ so_RR ,_, would_VM go_VVI beyond_II the_AT limits_NN2 of_IO the_AT present_JJ discussion_NN1 ,_, but_CCB it_PPH1 is_VBZ worth_II bearing_VVG in_II mind_NN1 ,_, when_CS the_AT relations_NN2 are_VBR discussed_VVN of_IO biology_NN1 to_II the_AT social_JJ sciences_NN2 ,_, that_CST an_AT1 essential_JJ social_JJ science_NN1 is_VBZ likely_JJ to_TO prove_VVI to_TO be_VBI history_NN1 ._. 
The_AT second_MD point_NN1 of_IO view_NN1 which_DDQ is_VBZ excluded_VVN by_II taking_VVG seriously_RR the_AT representation_NN1 problem_NN1 is_VBZ one_PN1 which_DDQ I_PPIS1 am_VBM disposed_JJ ,_, perhaps_RR unfairly_RR ,_, to_TO call_VVI '_GE the_AT Wittgensteinian_JJ cop-out_NN1 '_GE ._. 
This_DD1 is_VBZ a_AT1 view_NN1 implicit_JJ in_II the_AT idea_NN1 that_CST the_AT central_JJ concept_NN1 for_IF gaining_VVG insight_NN1 into_II human_JJ activities_NN2 is_VBZ that_DD1 of_IO a_AT1 '_GE language_NN1 game_NN1 '_GE ._. 
Since_RR '_GE language_NN1 '_GE in_II this_DD1 formulation_NN1 is_VBZ regarded_VVN both_RR as_II the_AT key_NN1 to_II human_JJ convention_NN1 ,_, and_CC also_RR as_CSA something_PN1 which_DDQ human_JJ beings_NN2 possess_VV0 and_CC animals_NN2 do_VD0 not_XX ,_, the_AT phrase_NN1 itself_PPX1 implies_VVZ the_AT lack_NN1 of_IO interesting_JJ explanatory_JJ or_CC constraining_VVG connections_NN2 between_II human_NN1 and_CC animal_NN1 behaviour_NN1 ._. 
It_PPH1 suggests_VVZ an_AT1 autonomy_NN1 of_IO the_AT human_NN1 ,_, under_II a_AT1 defining_JJ idea_NN1 of_IO linguistic_JJ and_CC conceptual_JJ consciousness_NN1 ,_, which_DDQ tends_VVZ to_TO put_VVI a_AT1 stop_NN1 to_II any_DD interesting_JJ questions_NN2 of_IO the_AT biological_JJ kind_NN1 before_CS they_PPHS2 even_RR start_VV0 ._. 
It_PPH1 therefore_RR does_VDZ not_XX give_VVI any_DD help_NN1 even_RR in_II the_AT areas_NN2 ,_, such_II21 as_II22 sex_NN1 and_CC hunger_NN1 ,_, where_CS we_PPIS2 most_RGT obviously_RR need_VV0 means_NN of_IO describing_VVG the_AT relations_NN2 between_II culture_NN1 and_CC the_AT biological_JJ ._. 
The_AT feature_NN1 of_IO human_JJ culture_NN1 and_CC human_JJ activities_NN2 that_CST gives_VVZ rise_NN1 to_II the_AT representation_NN1 problem_NN1 is_VBZ above_II all_DB that_DD1 human_JJ communities_NN2 embody_VV0 norms_NN2 ,_, and_CC it_PPH1 is_VBZ this_DD1 notion_NN1 that_CST I_PPIS1 shall_VM principally_RR discuss_VVI ._. 
However_RR ,_, there_EX are_VBR other_JJ ways_NN2 ,_, as_RR21 well_RR22 ,_, of_IO picking_VVG out_RP differences_NN2 between_II human_JJ activities_NN2 and_CC those_DD2 of_IO other_JJ animals_NN2 ._. 
One_PN1 is_VBZ the_AT very_JJ general_JJ feature_NN1 that_CST humans_NN2 possess_VV0 conceptual_JJ and_CC reflexive_VV0 consciousness_NN1 ;_; this_DD1 ,_, and_CC the_AT very_RG large_JJ philosophical_JJ problems_NN2 introduced_VVN by_II those_DD2 three_MC terms_NN2 ,_, I_PPIS1 shall_VM happily_RR leave_VVI on_II one_MC1 side_NN1 ._. 
Another_DD1 distinction_NN1 between_II human_NN1 and_CC animal_NN1 behaviour_NN1 is_VBZ that_CST considerations_NN2 of_IO motive_NN1 are_VBR appropriate_JJ to_II the_AT assessment_NN1 of_IO human_JJ action_NN1 ._. 
This_DD1 is_VBZ a_AT1 matter_NN1 that_CST is_VBZ worth_II some_DD brief_JJ discussion_NN1 ,_, since_CS it_PPH1 is_VBZ closely_RR connected_VVN with_IW the_AT fuss_NN1 that_CST has_VHZ been_VBN made_VVN about_II the_AT application_NN1 of_IO the_AT term_NN1 '_GE altruism_NN1 '_GE to_II animal_NN1 as_II21 to_II22 human_JJ behaviour_NN1 ._. 
In_II other_JJ animals_NN2 there_EX is_VBZ behaviour_NN1 which_DDQ benefits_NN2 another_DD1 individual_NN1 ,_, and_CC moreover_RR there_EX is_VBZ behaviour_NN1 the_AT end_NN1 of_IO which_DDQ is_VBZ to_TO benefit_VVI another_DD1 individual_NN1 ,_, in_II a_AT1 sense_NN1 of_IO '_GE end_NN1 '_GE which_DDQ requires_VVZ a_AT1 lot_NN1 of_IO work_NN1 to_TO make_VVI clear_JJ ,_, but_CCB which_DDQ is_VBZ uncontentiously_RR illustrated_VVN by_II behaviour_NN1 the_AT end_NN1 of_IO which_DDQ is_VBZ that_CST the_AT animal_NN1 should_VM take_VVI in_II food_NN1 ._. 
In_II the_AT human_JJ case_NN1 ,_, many_DA2 more_DAR layers_NN2 can_VM be_VBI added_VVN ,_, and_CC other_JJ distinctions_NN2 drawn_VVN ._. 
There_EX are_VBR questions_NN2 of_IO intention_NN1 ,_, where_CS this_DD1 concerns_VVZ what_DDQ thoughts_NN2 produce_VV0 the_AT action_NN1 ,_, and_CC what_DDQ features_NN2 of_IO the_AT action_NN1 are_VBR ,_, relative_II21 to_II22 that_DD1 thought_NN1 ,_, accidental_JJ ._. 
There_EX are_VBR questions_NN2 of_IO underlying_JJ desire_NN1 ._. 
Some_DD actions_NN2 which_DDQ benefit_VV0 others_NN2 come_VV0 from_II the_AT desire_NN1 just_RR to_TO benefit_VVI that_DD1 particular_JJ person_NN1 ,_, while_CS others_NN2 flow_VV0 from_II some_DD more_DAR general_JJ disposition_NN1 ,_, while_CS the_AT desire_NN1 to_TO benefit_VVI a_AT1 particular_JJ person_NN1 or_CC group_NN1 may_VM be_VBI accompanied_VVN by_II a_AT1 variety_NN1 of_IO other_JJ desires_NN2 ,_, for_REX21 instance_REX22 to_TO extract_VVI goodwill_NN1 from_II them_PPHO2 ,_, or_CC the_AT possibility_NN1 of_IO a_AT1 reward_NN1 ._. 
The_AT cultural_JJ and_CC psychological_JJ elaboration_NN1 of_IO these_DD2 various_JJ motives_NN2 of_RR21 course_RR22 raises_VVZ difficulties_NN2 for_IF any_DD simple_JJ relation_NN1 of_IO them_PPHO2 to_II the_AT biological_JJ ._. 
Some_DD of_IO those_DD2 difficulties_NN2 arise_VV0 just_RR from_II the_AT general_JJ problem_NN1 of_IO applying_VVG biological_JJ models_NN2 to_II a_AT1 species_NN which_DDQ engages_VVZ in_II intentional_JJ thought_NN1 ;_; to_II that_DD1 extent_NN1 there_EX is_VBZ no_AT special_JJ problem_NN1 about_II altruism_NN1 and_CC morality_NN1 ._. 
People_NN think_VV0 that_CST there_EX is_VBZ a_AT1 special_JJ barrier_NN1 here_RL to_II the_AT application_NN1 of_IO biological_JJ models_NN2 ,_, I_PPIS1 believe_VV0 ,_, because_CS they_PPHS2 take_VV0 '_GE altruism_NN1 '_GE ,_, in_II a_AT1 '_GE properly_RR moral_JJ '_GE sense_NN1 ,_, to_TO refer_VVI to_II some_DD quite_RG peculiarly_RR pure_JJ motive_NN1 ,_, such_II21 as_II22 the_AT intention_NN1 to_TO benefit_VVI others_NN2 derived_VVN from_II impartial_JJ reflection_NN1 on_II their_APPGE interests_NN2 and_CC associated_VVN with_IW no_AT other_JJ desire_NN1 whatsoever_DDQV ._. 
But_CCB it_PPH1 is_VBZ extremely_RR unreasonable_JJ to_TO suppose_VVI that_CST all_RR (_( perhaps_RR any_DD )_) human_JJ beings_NN2 act_VV0 from_II that_DD1 motivation_NN1 ,_, either_RR ,_, and_CC if_CS morality_NN1 is_VBZ to_TO be_VBI a_AT1 generally_RR human_JJ phenomenon_NN1 ,_, it_PPH1 is_VBZ simply_RR a_AT1 mistake_NN1 to_TO equate_VVI it_PPH1 from_II the_AT beginning_NN1 with_IW such_DA exigently_RR Kantian_JJ formulations_NN2 ,_, and_CC it_PPH1 is_VBZ a_AT1 mistake_NN1 even_RR from_II the_AT point_NN1 of_IO view_NN1 of_IO the_AT human_JJ sciences_NN2 ._. 
It_PPH1 is_VBZ no_RR21 doubt_RR22 true_JJ that_CST a_AT1 biological_JJ perspective_NN1 will_VM make_VVI one_PN1 more_RGR suspicious_JJ of_IO extremely_RR intellectualist_JJ or_CC ,_, again_RT ,_, very_RG purist_JJ views_NN2 of_IO morality_NN1 ;_; but_CCB equally_RR ,_, so_RR will_VM a_AT1 reasonable_JJ historical_JJ and_CC psychological_JJ understanding_NN1 of_IO morality_NN1 ._. 
It_PPH1 is_VBZ the_AT notion_NN1 of_IO a_AT1 norm_NN1 that_CST perhaps_RR gives_VVZ rise_NN1 to_II the_AT central_JJ representation_NN1 problem_NN1 ._. 
The_AT main_JJ point_NN1 is_VBZ condensed_VVN in_II the_AT question_NN1 raised_VVN by_II Pat_NP1 Bateson_NP1 in_II his_APPGE paper_NN1 (_( this_DD1 volume_NN1 )_) ,_, about_II the_AT relation_NN1 between_II an_AT1 inhibition_NN1 and_CC a_AT1 prohibition_NN1 ._. 
The_AT most_RRT ,_, it_PPH1 seems_VVZ ,_, that_CST a_AT1 genetically_RR acquired_VVN character_NN1 could_VM yield_VVI would_VM be_VBI an_AT1 inhibition_NN1 against_II behaviours_NN2 of_IO a_AT1 certain_JJ kind_NN1 ;_; what_DDQ relation_NN1 could_VM that_DD1 have_VHI to_II a_AT1 socially_RR sanctioned_VVN prohibition_NN1 ?_? 
Indeed_RR ,_, if_CS the_AT inhibition_NN1 exists_VVZ ,_, what_DDQ need_VV0 could_VM there_EX be_VBI for_IF such_DA a_AT1 prohibition_NN1 ?_? 
If_CS the_AT prohibitory_JJ norm_NN1 is_VBZ to_TO be_VBI part_NN1 of_IO the_AT '_GE extended_JJ phenotype_NN1 '_GE of_IO the_AT species_NN ,_, how_RRQ could_VM we_PPIS2 conceive_VVI ,_, starting_VVG from_II an_AT1 inhibition_NN1 ,_, that_CST this_DD1 should_VM come_VVI about_RP ?_? 
This_DD1 is_VBZ a_AT1 central_JJ example_NN1 of_IO the_AT problem_NN1 ,_, but_CCB it_PPH1 is_VBZ not_XX the_AT only_JJ example_NN1 even_RR with_II31 respect_II32 to_II33 norms_NN2 ,_, and_CC it_PPH1 will_VM be_VBI helpful_JJ to_TO distinguish_VVI various_JJ things_NN2 that_CST fall_VV0 under_II the_AT general_JJ heading_NN1 of_IO a_AT1 '_GE norm_NN1 '_GE ._. 
Not_XX everything_PN1 that_CST falls_VVZ under_II this_DD1 heading_NN1 is_VBZ a_AT1 sanctioned_JJ prohibition_NN1 ._. 
We_PPIS2 can_VM distinguish_VVI various_JJ items_NN2 ;_; I_PPIS1 will_VM represent_VVI them_PPHO2 as_CSA stacked_VVN ,_, in_II a_AT1 way_NN1 which_DDQ is_VBZ typical_JJ ,_, but_CCB not_XX by_II any_DD means_NN universal._NNU (_( 1_MC1 )_) Behaviour_NN1 which_DDQ is_VBZ normal_JJ ._. 
This_DD1 does_VDZ not_XX just_RR mean_VVI '_GE frequent_JJ '_" :_: exceptions_NN2 are_VBR perceived_VVN as_58 '_GE odd_JJ '_GE ,_, but_CCB are_VBR not_XX necessarily_RR disapproved_VVN of_IO ,_, sanctioned_VVD ,_, etc._RA (_( 2_MC )_) (_( 1_MC1 )_) together_RL with_IW an_AT1 institution_NN1 ._. 
This_DD1 can_VM be_VBI applied_VVN to_II the_AT case_NN1 of_IO marriage_NN1 ,_, where_CS there_EX will_VM of_RR21 course_RR22 be_VBI usually_RR sanctions_NN2 of_IO varying_JJ degrees_NN2 against_II behaviours_NN2 that_CST threaten_VV0 marriage_NN1 ,_, and_CC sexual_JJ activity_NN1 outside_II marriage_NN1 may_VM be_VBI disapproved_VVN of_IO ,_, but_CCB this_DD1 does_VDZ not_XX imply_VVI that_CST merely_RR not_XX engaging_VVG in_II marriage_NN1 is_VBZ disapproved_VVN of_IO ,_, nor_CC that_CST an_AT1 unmarried_JJ condition_NN1 is_VBZ sanctioned._NNU (_( 3_MC )_) Behaviour_NN1 which_DDQ lies_VVZ outside_RL (_( 1_MC1 )_) and_CC (_( 2_MC )_) ,_, and_CC to_II which_DDQ in_RR21 addition_RR22 there_EX may_VM be_VBI strong_JJ personal_JJ disinclination_NN1 :_: e.g._REX homosexuality_NN1 as_CSA regarded_VVN in_II enlightened_JJ circles._NNU (_( 4_MC )_) (_( 3_MC )_) together_RL with_IW rejection_NN1 and_CC disapproval_NN1 of_IO the_AT deviant_JJ behaviour_NN1 :_: e.g._REX homosexuality_NN1 as_CSA regarded_VVN in_II less_RGR enlightened_JJ circles._NNU (_( 5_MC )_) (_( 4_MC )_) together_RL with_IW sanctions_NN2 personal_JJ or_CC legal_JJ :_: e.g._REX homosexuality_NN1 in_II the_AT least_RGT enlightened_JJ circles_NN2 ._. 
Among_II the_AT cases_NN2 in_II which_DDQ the_AT options_NN2 are_VBR not_XX stacked_VVN like_II this_DD1 ,_, is_VBZ that_DD1 in_II which_DDQ the_AT sanctions_NN2 and_CC disapproval_NN1 exist_VV0 against_II behaviour_NN1 which_DDQ is_VBZ in_II fact_NN1 frequent_JJ and_CC not_XX the_AT subject_NN1 ,_, perhaps_RR ,_, of_IO any_DD deep_JJ personal_JJ disinclination_NN1 ;_; this_DD1 ,_, at_II the_AT limit_NN1 ,_, is_VBZ pure_JJ humbug_NN1 ,_, like_II the_AT old_JJ school-master_NN1 's_GE attitude_NN1 to_II masturbation._NNU (_( 1_MC1 )_) to_II (_( 3_MC )_) of_RR21 course_RR22 raise_VV0 some_DD difficulties_NN2 for_IF a_AT1 biological_JJ approach_NN1 ,_, particularly_RR with_II31 regard_II32 to_II33 institutions_NN2 ,_, and_CC an_AT1 adequate_JJ treatment_NN1 of_IO the_AT representation_NN1 problem_NN1 will_VM deal_VVI with_IW all_DB these_DD2 levels_NN2 ._. 
The_AT question_NN1 of_IO inhibitions_NN2 and_CC prohibitions_NN2 arises_VVZ most_RGT clearly_RR at_II levels_NN2 (_( 4_MC )_) and_CC (_( 5_MC )_) ._. 
There_EX is_VBZ ,_, moreover_RR ,_, a_AT1 specially_RR paradoxical_JJ version_NN1 of_IO it_PPH1 which_DDQ arises_VVZ from_II certain_JJ cases_NN2 in_II which_DDQ not_XX only_RR does_VDZ extra_JJ conceptual_JJ content_NN1 have_VH0 to_TO be_VBI introduced_VVN to_TO characterize_VVI the_AT human_JJ prohibition_NN1 ,_, but_CCB also_RR the_AT introduction_NN1 of_IO that_DD1 content_NN1 stands_VVZ in_II conflict_NN1 with_IW the_AT proposed_JJ biological_JJ explanation_NN1 of_IO it_PPH1 ._. 
A_AT1 clear_JJ example_NN1 of_IO this_DD1 arises_VVZ with_IW the_AT famous_JJ example_NN1 of_IO the_AT incest_NN1 taboo_NN1 ,_, which_DDQ has_VHZ been_VBN discussed_VVN by_II Bateson_NP1 (_( this_DD1 volume_NN1 )_) ._. 
There_EX are_VBR of_RR21 course_RR22 many_DA2 incest_NN1 taboos_NN2 ,_, that_REX41 is_REX42 to_REX43 say_REX44 ,_, prohibitions_NN2 on_II sexual_JJ relations_NN2 between_II persons_NN2 of_IO various_JJ degrees_NN2 of_IO familial_JJ relation_NN1 ,_, and_CC some_DD of_IO these_DD2 are_VBR hardly_RR even_RR candidates_NN2 for_IF biological_JJ explanation_NN1 ._. 
Moreover_RR ,_, there_EX may_VM well_RR be_VBI some_DD very_RG severe_JJ doubts_NN2 about_II the_AT application_NN1 of_IO the_AT biological_JJ model_NN1 even_RR to_II the_AT favourite_JJ cases_NN2 ._. 
The_AT present_JJ discussion_NN1 ,_, is_VBZ not_XX ,_, however_RR ,_, concerned_JJ with_IW the_AT factual_JJ merits_NN2 of_IO these_DD2 explanations_NN2 ,_, but_CCB only_RR with_IW the_AT shape_NN1 that_CST they_PPHS2 take_VV0 ._. 
In_II other_JJ species_NN ,_, there_EX are_VBR behavioural_JJ drives_NN2 the_AT function_NN1 of_IO which_DDQ is_VBZ to_TO avoid_VVI inbreeding_NN1 ._. 
Such_DA a_AT1 drive_NN1 ,_, however_RR ,_, has_VHZ to_TO be_VBI operationalized_VVN in_II some_DD other_JJ way_NN1 ,_, since_CS the_AT animals_NN2 do_VD0 not_XX have_VHI any_DD direct_JJ knowledge_NN1 of_IO the_AT matters_NN2 relevant_JJ to_II inbreeding_NN1 :_: the_AT inhibition_NN1 against_II mating_NN1 has_VHZ to_TO be_VBI triggered_VVN by_II the_AT recognition_NN1 of_IO or_CC reaction_NN1 to_II some_DD property_NN1 adequately_RR correlated_VVN with_IW the_AT kin_NN relationship_NN1 ,_, such_II21 as_II22 being_VBG an_AT1 individual_JJ with_IW which_DDQ the_AT animal_NN1 has_VHZ been_VBN brought_VVN up_RP ._. 
It_PPH1 is_VBZ this_DD1 inhibition_NN1 that_CST is_VBZ allegedly_RR displayed_VVN ,_, in_II the_AT well-known_JJ case_NN1 ,_, by_II those_DD2 brought_VVN up_RP in_II the_AT kibbutz_NN1 ._. 
But_CCB we_PPIS2 have_VH0 not_XX yet_RR reached_VVN any_DD incest_NN1 taboo_NN1 ._. 
There_EX are_VBR no_AT sanctions_NN2 against_II marrying_VVG those_DD2 that_CST one_PN1 is_VBZ brought_VVN up_RP with_IW (_( as_CSA such_DA )_) ;_; the_AT sanction_NN1 is_VBZ against_II marriages_NN2 which_DDQ would_VM constitute_VVI close_JJ in-breeding_NN1 ._. 
The_AT conceptual_JJ content_NN1 of_IO the_AT prohibition_NN1 is_VBZ thus_RR different_JJ from_II the_AT content_NN1 that_CST occurs_VVZ in_II the_AT description_NN1 of_IO the_AT inhibition_NN1 ._. 
It_PPH1 indeed_RR relates_VVZ to_II the_AT suggested_JJ function_NN1 of_IO that_DD1 inhibition_NN1 ,_, but_CCB that_DD1 fact_NN1 will_VM not_XX explain_VVI how_RRQ the_AT prohibition_NN1 which_DDQ is_VBZ explicitly_RR against_II in-breeding_NN1 will_VM have_VHI arisen_VVN ._. 
It_PPH1 certainly_RR does_VDZ not_XX represent_VVI a_AT1 mere_JJ '_GE raising_NN1 to_II consciousness_NN1 '_GE of_IO the_AT inhibition_NN1 ._. 
It_PPH1 can_VM have_VHI come_VVN about_RP ,_, in_II fact_NN1 ,_, only_RR given_VVN human_JJ knowledge_NN1 of_IO relevant_JJ facts_NN2 presumably_RR ,_, of_IO the_AT ill-effects_NN2 of_IO in-breeding_NN1 ._. 
But_CCB once_RR that_DD1 is_VBZ an_AT1 essential_JJ step_NN1 in_II the_AT explanation_NN1 ,_, we_PPIS2 no_RR21 longer_RR22 need_VV0 the_AT biological_JJ element_NN1 in_II the_AT explanation_NN1 (_( of_IO the_AT prohibition_NN1 ,_, that_REX41 is_REX42 to_REX43 say_REX44 ,_, rather_CS21 than_CS22 of_IO the_AT inhibition_NN1 )_) ._. 
It_PPH1 turns_VVZ out_RP that_CST we_PPIS2 have_VH0 to_TO appeal_VVI in_II any_DD case_NN1 to_II something_PN1 like_II a_AT1 rational_JJ collective_JJ agency_NN1 ,_, directed_VVN towards_II avoiding_VVG recognized_JJ and_CC agreed_JJ evils_NN2 ,_, and_CC that_CST already_RR provides_VVZ an_AT1 adequate_JJ explanation_NN1 a_AT1 fairly_RR traditional_JJ one_MC1 of_IO the_AT incest_NN1 prohibition_NN1 ._. 
A_AT1 similar_JJ paradox_NN1 can_VM arise_VVI with_IW other_JJ norms_NN2 supposedly_RR based_VVN at_II a_AT1 biological_JJ level_NN1 ,_, but_CCB there_EX are_VBR cases_NN2 that_CST avoid_VV0 it_PPH1 ._. 
Consider_VV0 for_REX21 instance_REX22 the_AT '_GE double_JJ standard_NN1 '_GE in_II sexual_JJ morality_NN1 ,_, traced_VVN by_II Symons_NP1 (_( 1979_MC )_) to_II the_AT disparity_NN1 between_II ovum_NN1 and_CC sperm_NN ._. 
This_DD1 account_NN1 ,_, though_CS it_PPH1 applies_VVZ much_RR more_RGR widely_RR ,_, is_VBZ essentially_RR the_AT same_DA as_CSA an_AT1 explanation_NN1 of_IO these_DD2 social_JJ phenomena_NN2 which_DDQ goes_VVZ back_RP at_RR21 least_RR22 to_II Hume_NP1 ,_, who_PNQS accounted_VVD for_IF '_GE the_AT artificial_JJ virtues_NN2 of_IO chastity_NN1 and_CC modesty_NN1 in_II women_NN2 '_GE by_II referring_VVG to_II the_AT naturally_RR greater_JJR disposition_NN1 of_IO males_NN2 to_TO protect_VVI children_NN2 that_CST they_PPHS2 believe_VV0 to_TO be_VBI their_APPGE own_DA ._. 
Here_RL again_RT ,_, there_EX may_VM be_VBI serious_JJ doubts_NN2 about_II relevant_JJ anthropological_JJ facts_NN2 ,_, but_CCB the_AT present_JJ point_NN1 concerns_VVZ the_AT principle_NN1 of_IO the_AT explanation_NN1 ,_, which_DDQ involves_VVZ an_AT1 important_JJ difference_NN1 from_II the_AT incest_NN1 case_NN1 ._. 
Here_RL ,_, it_PPH1 is_VBZ natural_JJ to_TO think_VVI in_II31 terms_II32 of_II33 the_AT institutionalization_NN1 of_IO a_AT1 disposition_NN1 which_DDQ could_VM be_VBI displayed_VVN in_II a_AT1 simpler_JJR form_NN1 pre-culturally_RR ._. 
The_AT conceptual_JJ content_NN1 required_VVN in_II this_DD1 case_NN1 to_TO describe_VVI the_AT institution_NN1 ,_, though_CS it_PPH1 involves_VVZ a_AT1 great_JJ deal_NN1 of_IO cultural_JJ elaboration_NN1 ,_, does_VDZ not_XX display_VVI the_AT same_DA kind_NN1 of_IO break_NN1 between_II the_AT pre-cultural_JJ and_CC the_AT cultural_JJ as_CSA is_VBZ found_VVN in_II the_AT incest_NN1 case_NN1 ;_; and_CC the_AT biological_JJ pattern_NN1 of_IO explanation_NN1 could_VM recognizably_RR run_VVI through_II such_DA ideas_NN2 as_CSA human_JJ beings_NN2 finding_VVG certain_JJ institutions_NN2 '_GE natural_JJ '_GE ,_, which_DDQ does_VDZ not_XX require_VVI any_DD appeal_NN1 to_II a_AT1 rational_JJ collective_JJ agency_NN1 to_TO understand_VVI the_AT basic_JJ biological_JJ idea_NN1 ,_, as_CSA is_VBZ damagingly_RR the_AT case_NN1 with_IW the_AT incest_NN1 example_NN1 ._. 
In_II fact_NN1 ,_, an_AT1 explanation_NN1 which_DDQ went_VVD back_RP to_II a_AT1 biologically_RR grounded_VVN disposition_NN1 could_VM in_II this_DD1 case_NN1 precisely_RR avoid_VV0 the_AT invocation_NN1 of_IO rational_JJ collective_JJ agency_NN1 ,_, which_DDQ is_VBZ rather_RG an_AT1 intellectualist_NN1 embarrassment_NN1 to_II the_AT story_NN1 as_CSA Hume_NP1 (_( 173840_MC )_) tells_VVZ it_PPH1 ._. 
None_PN of_IO this_DD1 implies_VVZ that_CST even_CS21 if_CS22 such_DA biological_JJ elements_NN2 did_VDD play_VVI some_DD role_NN1 in_II explaining_VVG these_DD2 institutions_NN2 ,_, the_AT institutions_NN2 would_VM then_RT be_VBI necessary_JJ or_CC unchangeable_JJ even_CS21 if_CS22 the_AT explanation_NN1 were_VBDR true_JJ ,_, this_DD1 could_VM still_RR be_VBI a_AT1 case_NN1 in_II which_DDQ becoming_JJ conscious_JJ of_IO their_APPGE rationale_NN1 was_VBDZ a_AT1 help_NN1 in_II changing_VVG them_PPHO2 ._. 
In_II one_MC1 of_IO the_AT two_MC cases_NN2 we_PPIS2 have_VH0 considered_VVN incest_NN1 the_AT prohibition_NN1 is_VBZ paradoxically_RR related_VVN to_II pre-cultural_JJ dispositions_NN2 :_: it_PPH1 expresses_VVZ their_APPGE function_NN1 ,_, but_CCB not_XX their_APPGE content_NN1 ._. 
In_II the_AT case_NN1 just_RR considered_VVN ,_, social_JJ institutions_NN2 could_VM in_II principle_NN1 be_VBI an_AT1 expression_NN1 of_IO a_AT1 pre-cultural_JJ disposition_NN1 ._. 
In_II other_JJ cases_NN2 ,_, again_RT ,_, the_AT existence_NN1 of_IO norms_NN2 seems_VVZ to_TO be_VBI a_AT1 substitute_NN1 for_IF a_AT1 pre-cultural_JJ disposition_NN1 ._. 
This_DD1 might_VM well_RR be_VBI so_RR with_IW the_AT control_NN1 of_IO aggression_NN1 and_CC of_IO self-seeking_JJ behaviour_NN1 ;_; I_PPIS1 shall_VM make_VVI one_MC1 or_CC two_MC remarks_NN2 about_II this_DD1 question_NN1 without_IW pursuing_VVG it_PPH1 at_RR21 length_RR22 ._. 
In_II the_AT work_NN1 of_IO Maynard_NP1 Smith_NP1 and_CC others_NN2 (_( see_VV0 ,_, for_REX21 example_REX22 ,_, Maynard_NP1 Smith_NP1 ,_, this_DD1 volume_NN1 )_) games_NN2 theory_NN1 is_VBZ applied_VVN to_II explaining_VVG selection_NN1 for_RR21 certain_RR22 genetically_RR based_VVN patterns_NN2 of_IO behaviour_NN1 ._. 
Games_NN2 theory_NN1 can_VM equally_RR be_VBI applied_VVN to_II characterizing_VVG human_JJ norms_NN2 which_DDQ are_VBR instituted_VVN against_II aggression_NN1 and_CC other_JJ non-cooperative_JJ behaviour_NN1 ._. 
(_( Ullmann-Margalit_JJ (_( 1977_MC )_) gives_VVZ a_AT1 recent_JJ analysis_NN1 ,_, though_CS the_AT outlines_NN2 of_IO the_AT idea_NN1 that_CST sanctioned_VVD norms_NN2 can_VM represent_VVI a_AT1 solution_NN1 to_II the_AT Prisoners_NN2 '_GE Dilemma_NN1 can_VM be_VBI found_VVN in_II Hobbes_NP1 ._. )_) 
The_AT principles_NN2 of_IO the_AT two_MC applications_NN2 of_IO games_NN2 theory_NN1 are_VBR in_II many_DA2 ways_NN2 the_AT same_DA but_CCB their_APPGE results_NN2 point_VV0 ,_, in_II a_AT1 sense_NN1 ,_, in_II opposite_JJ directions_NN2 ._. 
If_CS sanctioned_JJ norms_NN2 are_VBR necessary_JJ in_II the_AT human_JJ case_NN1 ,_, or_CC socialization_NN1 into_II rule-observing_JJ behaviour_NN1 ,_, this_DD1 must_VM be_VBI because_CS constraints_NN2 on_II human_JJ responses_NN2 in_II these_DD2 areas_NN2 are_VBR not_XX ,_, or_CC not_XX significantly_RR ,_, genetically_RR based_VVN ._. 
Granted_VVN structures_NN2 of_IO the_AT Prisoners_NN2 '_GE Dilemma_NN1 type_NN1 ,_, cooperative_JJ behaviour_NN1 can_VM be_VBI secured_VVN only_RR granted_VVN a_AT1 certain_JJ level_NN1 of_IO assurance_NN1 ,_, and_CC the_AT need_NN1 of_IO norms_NN2 (_( in_RR21 particular_RR22 of_IO sanctioned_JJ norms_NN2 )_) to_TO produce_VVI that_DD1 assurance_NN1 shows_VVZ that_CST the_AT assurance_NN1 can_VM not_XX be_VBI adequately_RR delivered_VVN by_II genetically_RR based_VVN signals_NN2 ._. 
It_PPH1 is_VBZ very_RG tempting_JJ to_TO suppose_VVI that_CST the_AT lack_NN1 of_IO any_DD such_DA reliable_JJ signals_NN2 ,_, and_CC the_AT perilously_RR low_JJ level_NN1 of_IO security_NN1 often_RR reached_VVN in_II human_JJ communities_NN2 ,_, must_VM be_VBI connected_VVN with_IW a_AT1 high_JJ level_NN1 of_IO conceptual_JJ and_CC ,_, in_RR21 particular_RR22 ,_, predictive_JJ thought_NN1 ,_, and_CC also_RR an_AT1 associated_JJ capacity_NN1 for_IF deceit_NN1 ._. 
This_DD1 perhaps_RR gives_VVZ a_AT1 special_JJ force_NN1 to_II the_AT Voltairean_JJ remark_NN1 about_II the_AT function_NN1 of_IO language_NN1 being_VBG to_TO conceal_VVI thought_NN1 ._. 
The_AT previous_JJ remarks_NN2 have_VH0 raised_VVN some_DD questions_NN2 about_II the_AT relations_NN2 between_II human_JJ norms_NN2 and_CC possible_JJ underlying_JJ dispositions_NN2 determined_VVN at_II a_AT1 biological_JJ level_NN1 ._. 
They_PPHS2 represent_VV0 some_DD aspects_NN2 of_IO what_DDQ I_PPIS1 have_VH0 called_VVN the_AT representation_NN1 problem_NN1 ,_, and_CC it_PPH1 is_VBZ only_RR through_II further_JJR investigation_NN1 of_IO that_DD1 problem_NN1 ,_, and_CC by_II becoming_VVG clearer_JJR about_II how_RRQ the_AT various_JJ kinds_NN2 of_IO norm_NN1 could_VM relate_VVI to_II our_APPGE biological_JJ inheritance_NN1 ,_, that_CST we_PPIS2 can_VM come_VVI to_TO see_VVI much_RR about_II what_DDQ biological_JJ constraints_NN2 there_EX might_VM be_VBI ,_, beyond_II the_AT obvious_JJ ones_NN2 ,_, on_II social_JJ and_CC ethical_JJ arrangements_NN2 ._. 
I_PPIS1 do_VD0 not_XX believe_VVI it_PPH1 to_TO be_VBI excluded_VVN a_JJ21 priori_JJ22 that_CST there_EX could_VM be_VBI some_DD ,_, and_CC I_PPIS1 do_VD0 not_XX believe_VVI that_CST very_RG much_DA1 is_VBZ to_TO be_VBI achieved_VVN by_II very_RG general_JJ assertions_NN2 or_CC denials_NN2 of_IO the_AT possibility_NN1 ._. 
What_DDQ is_VBZ needed_VVN is_VBZ more_RGR detailed_JJ analysis_NN1 ,_, not_XX only_RR anthropological_JJ but_CCB philosophical_JJ ,_, of_IO the_AT demands_NN2 that_CST any_DD explanations_NN2 of_IO this_DD1 sort_NN1 would_VM have_VHI to_TO meet_VVI ._. 
It_PPH1 will_VM be_VBI needed_VVN ,_, above_II all_DB ,_, if_CS we_PPIS2 are_VBR to_TO be_VBI able_JK to_TO read_VVI the_AT historical_JJ record_NN1 ._. 
It_PPH1 is_VBZ only_RR if_CS we_PPIS2 can_VM read_VVI that_DD1 record_NN1 that_CST we_PPIS2 can_VM discover_VVI some_DD very_RG important_JJ biological_JJ characteristics_NN2 of_IO human_JJ beings_NN2 ,_, since_CS (_( to_TO repeat_VVI an_AT1 earlier_JJR point_NN1 )_) it_PPH1 is_VBZ through_II convention_NN1 ,_, convention_NN1 that_CST has_VHZ a_AT1 history_NN1 ,_, that_DD1 human_JJ nature_NN1 is_VBZ expressed_VVN ._. 
It_PPH1 is_VBZ not_XX merely_RR that_DD1 without_IW a_AT1 hold_NN1 on_II the_AT representation_NN1 problem_NN1 we_PPIS2 can_VM not_XX discover_VVI the_AT relevant_JJ content_NN1 in_II the_AT historical_JJ record_NN1 ;_; without_IW understanding_VVG that_DD1 problem_NN1 ,_, we_PPIS2 can_VM not_XX adequately_RR control_VVI the_AT idea_NN1 that_CST there_EX is_VBZ any_DD relevant_JJ content_NN1 at_RR21 all_RR22 ._. 
If_CS a_AT1 biologically_RR grounded_VVN disposition_NN1 showed_VVD up_RP simply_RR in_II the_AT form_NN1 of_IO what_DDQ human_JJ beings_NN2 could_VM not_XX or_CC would_VM not_XX do_VDI ,_, then_RT there_EX would_VM be_VBI no_AT real_JJ problem_NN1 of_IO alternative_JJ behaviours_NN2 ._. 
The_AT alternatives_NN2 will_VM simply_RR be_VBI absent_JJ from_II the_AT record_NN1 ,_, and_CC it_PPH1 is_VBZ unlikely_JJ that_CST anyone_PN1 ,_, except_CS as_II the_AT most_RGT extreme_JJ perversity_NN1 ,_, would_VM want_VVI to_TO undertake_VVI them_PPHO2 ._. 
This_DD1 ,_, of_RR21 course_RR22 ,_, is_VBZ the_AT area_NN1 in_II which_DDQ the_AT is/ought_FU argument_NN1 scores_VVZ its_APPGE clear_JJ but_CCB uninteresting_JJ success_NN1 ._. 
What_DDQ is_VBZ much_RR more_RGR interesting_JJ ,_, I_PPIS1 have_VH0 already_RR suggested_VVN ,_, is_VBZ the_AT idea_NN1 that_CST there_EX could_VM be_VBI patterns_NN2 of_IO behaviour_NN1 which_DDQ human_JJ beings_NN2 are_VBR entirely_RR capable_JJ of_IO wanting_JJ and_CC indeed_RR ,_, on_II an_AT1 individual_JJ or_CC limited_JJ scale_NN1 ,_, of_IO achieving_VVG ,_, but_CCB which_DDQ for_IF biological_JJ reasons_NN2 are_VBR bound_VVNK to_TO be_VBI psychologically_RR costly_JJ ,_, or_CC confined_VVN to_II a_AT1 small_JJ group_NN1 of_IO otherwise_RR unusual_JJ individuals_NN2 ,_, or_CC otherwise_RR bound_VVN to_TO fail_VVI as_RG general_JJ social_JJ institutions_NN2 ._. 
To_TO understand_VVI how_RRQ this_DD1 could_VM be_VBI involves_VVZ some_DD understanding_NN1 of_IO the_AT representation_NN1 problem_NN1 ,_, and_CC to_TO decide_VVI that_CST any_DD given_JJ pattern_NN1 of_IO behaviour_NN1 has_VHZ this_DD1 character_NN1 of_IO being_VBG ,_, as_CSA one_PN1 might_VM put_VVI it_PPH1 ,_, '_GE biologically_RR discouraged_VVN '_" requires_VVZ one_PN1 to_TO be_VBI able_JK to_TO read_VVI the_AT historical_JJ record_NN1 ._. 
It_PPH1 hardly_RR needs_VVZ emphasizing_VVG that_CST on_II any_DD question_NN1 that_CST is_VBZ interesting_JJ ,_, such_II21 as_II22 social_JJ roles_NN2 of_IO the_AT sexes_NN2 ,_, we_PPIS2 would_VM have_VHI to_TO be_VBI able_JK to_TO read_VVI the_AT historical_JJ record_NN1 better_RRR than_CSN we_PPIS2 now_RT can_VV0 in_RP order_VVI to_TO arrive_VVI at_II any_DD strong_JJ conclusions_NN2 about_II what_DDQ is_VBZ biologically_RR discouraged_VVN ._. 
I_PPIS1 come_VV0 back_RP finally_RR to_II what_DDQ I_PPIS1 mentioned_VVD at_II the_AT beginning_NN1 of_IO this_DD1 chapter_NN1 as_II the_AT area_NN1 of_IO '_GE naturalism_NN1 '_GE more_RGR broadly_RR conceived_VVD :_: that_REX41 is_REX42 to_REX43 say_REX44 ,_, the_AT question_NN1 of_IO founding_VVG human_JJ ethics_NN on_II considerations_NN2 of_IO human_JJ nature_NN1 ,_, in_II some_DD way_NN1 which_DDQ goes_VVZ beyond_II merely_RR respecting_II the_AT limits_NN2 ,_, biological_JJ or_CC other_JJ ,_, on_II what_DDQ human_JJ beings_NN2 are_VBR able_JK to_TO do_VDI ._. 
This_DD1 is_VBZ the_AT project_NN1 of_IO thinking_VVG out_RP ,_, from_II what_DDQ human_JJ beings_NN2 are_VBR like_II ,_, how_RRQ they_PPHS2 might_VM best_JJT and_CC most_RGT appropriately_RR live_VV0 ._. 
Such_DA a_AT1 project_NN1 continues_VVZ to_TO attract_VVI some_DD philosophers_NN2 ._. 
Its_APPGE attractions_NN2 are_VBR obvious_JJ ._. 
It_PPH1 does_VDZ not_XX ,_, in_II any_DD obvious_JJ way_NN1 ,_, require_VV0 any_DD supernatural_JJ warrant_NN1 ,_, while_CS it_PPH1 is_VBZ less_RGR arbitrary_JJ or_CC relativistic_JJ than_CSN other_JJ secular_JJ ways_NN2 of_IO looking_VVG at_II the_AT content_NN1 of_IO morality_NN1 ._. 
It_PPH1 seems_VVZ to_TO offer_VVI some_DD promise_NN1 of_IO being_VBG both_RR well-founded_JJ and_CC contentful_JJ ._. 
It_PPH1 seems_VVZ to_II me_PPIO1 that_CST a_AT1 correct_JJ understanding_NN1 of_IO human_JJ evolution_NN1 is_VBZ very_RG relevant_JJ to_II projects_NN2 of_IO this_DD1 kind_NN1 ,_, but_CCB that_CST the_AT effect_NN1 of_IO that_DD1 understanding_NN1 is_VBZ largely_RR discouraging_VVG to_II them_PPHO2 ._. 
This_DD1 is_VBZ for_IF two_MC different_JJ kinds_NN2 of_IO reason_NN1 ._. 
The_AT first_MD is_VBZ a_AT1 reason_NN1 at_II a_AT1 more_RGR particular_JJ and_CC factual_JJ level_NN1 and_CC is_VBZ correspondingly_RR more_RGR sensitive_JJ than_CSN the_AT other_JJ to_II changes_NN2 in_II hypotheses_NN2 about_II the_AT emergence_NN1 of_IO human_JJ beings_NN2 ._. 
It_PPH1 is_VBZ simply_RR that_CST the_AT most_RGT plausible_JJ stories_NN2 now_RT available_JJ about_II that_DD1 evolution_NN1 ,_, including_II its_APPGE very_RG recent_JJ date_NN1 and_CC also_RR certain_JJ considerations_NN2 about_II the_AT physical_JJ characteristics_NN2 of_IO the_AT species_NN ,_, suggests_VVZ that_CST human_JJ beings_NN2 are_VBR to_II some_DD degree_NN1 a_AT1 mess_NN1 ,_, and_CC that_CST the_AT rapid_JJ and_CC immense_JJ development_NN1 of_IO symbolic_JJ and_CC cultural_JJ capacities_NN2 has_VHZ left_VVN man_NN1 as_II a_AT1 being_NN1 for_IF which_DDQ no_AT form_NN1 of_IO life_NN1 is_VBZ likely_JJ to_TO prove_VVI entirely_RR satisfactory_JJ ,_, either_RR individually_RR or_CC socially_RR ._. 
Many_DA2 of_RR21 course_RR22 have_VH0 come_VVN to_II that_DD1 conclusion_NN1 before_RT ,_, and_CC those_DD2 who_PNQS have_VH0 tried_VVN to_TO reach_VVI a_AT1 naturalistic_JJ morality_NN1 which_DDQ transcends_VVZ it_PPH1 have_VH0 had_VHN to_TO read_VVI the_AT historical_JJ record_NN1 ,_, or_CC read_VVN beyond_II the_AT historical_JJ record_NN1 ,_, in_II ways_NN2 which_DDQ seek_VV0 to_TO reveal_VVI a_AT1 partly_RR hidden_VVN human_JJ nature_NN1 which_DDQ is_VBZ waiting_VVG to_TO be_VBI realized_VVN or_CC perfected_VVD ._. 
The_AT evolutionary_JJ story_NN1 ,_, to_II the_AT extent_NN1 that_CST it_PPH1 can_VM now_RT be_VBI understood_VVN (_( and_CC to_II the_AT much_RR more_RGR modest_JJ extent_NN1 to_II which_DDQ I_PPIS1 understand_VV0 it_PPH1 myself_PPX1 )_) seems_VVZ to_II me_PPIO1 to_TO give_VVI some_DD support_NN1 to_II the_AT view_NN1 that_CST in_II this_DD1 respect_NN1 the_AT historical_JJ story_NN1 means_VVZ very_RG much_RR what_DDQ it_PPH1 seems_VVZ to_TO mean_VVI ._. 
The_AT second_MD and_CC more_RGR general_JJ reason_NN1 lies_VVZ not_XX in_II the_AT particular_JJ ways_NN2 in_II which_DDQ human_JJ beings_NN2 may_VM have_VHI evolved_VVN ,_, but_CCB simply_RR in_II the_AT fact_NN1 that_CST they_PPHS2 have_VH0 evolved_VVN ,_, and_CC by_II natural_JJ selection_NN1 ._. 
The_AT idea_NN1 of_IO a_AT1 naturalistic_JJ ethics_NN was_VBDZ born_VVN of_IO a_AT1 deeply_RR teleological_JJ outlook_NN1 ,_, and_CC its_APPGE best_JJT expression_NN1 ,_, in_II many_DA2 ways_NN2 ,_, is_VBZ still_JJ to_TO be_VBI found_VVN in_II Aristotle_NP1 's_GE philosophy_NN1 ,_, a_AT1 philosophy_NN1 according_II21 to_II22 which_DDQ there_EX is_VBZ inherent_JJ in_II each_DD1 natural_JJ kind_NN1 of_IO thing_NN1 an_AT1 appropriate_JJ way_NN1 for_IF things_NN2 of_IO that_DD1 kind_NN1 to_TO behave_VVI ._. 
On_II that_DD1 view_NN1 it_PPH1 must_VM be_VBI man_NN1 's_GE deepest_JJT desire_NN1 need_NN1 ?_? purpose_NN1 ?_? satisfaction_NN1 ?_? to_TO live_VVI in_II the_AT way_NN1 that_CST is_VBZ in_II this_DD1 objective_JJ sense_NN1 appropriate_JJ to_II him_PPHO1 (_( the_AT fact_NN1 that_CST modern_JJ words_NN2 break_VV0 up_RP into_II these_DD2 alternatives_NN2 expresses_VVZ the_AT modern_JJ break-up_NN1 of_IO Aristotle_NP1 's_GE view_NN1 )_) ._. 
Other_JJ naturalistic_JJ views_NN2 ,_, Marxist_JJ and_CC some_DD which_DDQ indeed_RR call_VV0 themselves_58 '_GE evolutionary_JJ '_GE ,_, have_VH0 often_RR proclaimed_VVN themselves_PPX2 free_JJ from_II any_DD such_DA picture_NN1 ,_, but_CCB it_PPH1 is_VBZ basically_RR very_RG hard_JJ for_IF them_PPHO2 to_TO avoid_VVI some_DD appeal_NN1 to_II an_AT1 implicit_JJ teleology_NN1 ,_, an_AT1 order_NN1 in_II31 relation_II32 to_II33 which_DDQ there_EX would_VM be_VBI an_AT1 existence_NN1 that_CST would_VM satisfy_VVI all_DB the_AT most_RGT basic_JJ human_NN1 needs_VVZ at_RR21 once_RR22 ._. 
The_AT first_MD and_CC hardest_JJT lesson_NN1 of_IO Darwinism_NN1 ,_, that_CST there_EX is_VBZ no_AT such_DA teleology_NN1 at_RR21 all_RR22 ,_, and_CC that_CST there_EX is_VBZ no_AT orchestral_JJ score_NN1 provided_VVN from_II anywhere_RL according_II21 to_II22 which_DDQ human_JJ beings_NN2 have_VH0 a_AT1 special_JJ part_NN1 to_TO play_VVI ,_, still_RR has_VHZ to_TO find_VVI its_APPGE way_NN1 fully_RR into_II ethical_JJ thought_NN1 ._. 
REFERENCES_NN2 etc._RA &lsqb;_( pp._NNU2 565566_MC &rsqb;_) OMITTED_VVN ;_; p_ZZ1 567_MC :_: EPILOGUE_NP1 ;_; p_ZZ1 568_MC :_: BLANK_JJ 
