How quirk of primate evolution gave humans the voice apes lack

 

SimplificationTofTlarynxTletThumansThaveTexcellentTpitchTcontrolTwithTlongTandTstableTspeechTsounds

ScientistsThaveTidentifiedTevolutionaryTmodificationsTinTtheTvoiceTboxTdistinguishingTpeopleTfromTotherTprimatesTthatTmayTunderpinTaTcapabilityTindispensableTtoThumankind:Tspeaking.

ResearchersTsaidTonTThursdayTthatTanTexaminationTofTtheTvoiceTbox,TorTlarynx,TinT43TspeciesTofTprimatesTshowedTthatThumansTdifferTfromTapesTandTmonkeysTinTlackingTanTanatomicalTstructureTcalledTaTvocalTmembrane:Tsmall,Tribbon-likeTextensionsTofTtheTvocalTcords.

HumansTalsoTlackTballoon-likeTlaryngealTstructuresTcalledTairTsacsTthatTmayThelpTsomeTapesTandTmonkeysTproduceTloudTandTresonantTcalls,TandTavoidThyperventilating,TtheyTfound.

TheTlossTofTtheseTtissues,TaccordingTtoTtheTresearchers,TresultedTinTaTstableTvocalTsourceTinThumansTthatTwasTcriticalTtoTtheTevolutionTofTspeechT–TtheTabilityTtoTexpressTthoughtsTandTfeelingsTusingTarticulateTsounds.

ThisTsimplificationTofTtheTlarynxTenabledThumansTtoThaveTexcellentTpitchTcontrolTwithTlongTandTstableTspeechTsounds,TtheyTsaid.

“WeTargueTthatTtheTmoreTcomplicatedTvocalTstructuresTinTnonhumanTprimatesTcanTmakeTitTdifficultTtoTcontrolTvibrationsTwithTprecision,”TsaidTprimatologistTTakeshiTNishimuraTofTKyotoTUniversity’sTCentreTforTtheTEvolutionaryTOriginsTofTHumanTBehaviourTinTJapan,TleadTauthorTofTtheTresearchTpublishedTinTtheTjournalTScience.



“VocalTmembranesTallowTotherTprimatesTtoTmakeTlouder,Thigher-pitchedTcallsTthanThumansT–TbutTtheyTmakeTvoiceTbreaksTandTnoisyTvocalTirregularityTmoreTcommon,”TsaidTevolutionaryTbiologistTandTstudyTco-authorTWTTecumsehTFitchTofTtheTUniversityTofTVienna.

TheTlarynx,TaThollowTtubeTinTtheTthroatTthatTisTconnectedTtoTtheTtopTofTtheTwindpipeTandTcontainsTtheTvocalTcords,TisTusedTforTtalking,TbreathingTandTswallowing.

“TheTlarynxTisTtheTorganTofTvoice,TwhichTcreatesTtheTsignalTweTuseTtoTsingTandTspeak,”TFitchTsaid.

HumansTareTprimates,TasTareTmonkeysTandTapes.TTheTevolutionaryTlineageTthatTledTtoTourTspecies,THomoTsapiens,TsplitTfromTtheToneTthatTledTtoTourTclosestTlivingTrelatives,Tchimpanzees,TroughlyT6mTtoT7mTyearsTago,TwithTtheTlaryngealTchangesToccurringTsometimeTafterTthat.

OnlyTlivingTspeciesTwereTincludedTinTtheTstudyTbecauseTtheseTsoftTtissuesTareTnotTaptTtoTbeTpreservedTinTfossils.TThisTalsoTmeansTitTisTunclearTwhenTtheTchangesTtookTplace.

FitchTsaidTitTisTpossibleTtheTlaryngealTsimplificationTaroseTinTaThumanTforerunnerTcalledTAustralopithecus,TwhichTcombinedTape-likeTandThuman-likeTtraitsTandTfirstTappearedTinTAfricaTroughlyT3.85mTyearsTago,TorTlaterTinTourTgenusTHomo,TwhichTfirstTappearedTinTAfricaTaboutT2.4mTyearsTago.THomoTsapiensToriginatedTmoreTthanT300,000TyearsTagoTinTAfrica.

TheTresearchersTstudiedTlaryngealTanatomyTinTapesTincludingTchimpanzees,Tgorillas,TorangutansTandTgibbons,TasTwellTasTOldTWorldTmonkeysTincludingTmacaques,Tguenons,TbaboonsTandTmandrillsTandTNewTWorldTmonkeysTincludingTcapuchins,Ttamarins,TmarmosetsTandTtitis.

WhileTthisTevolutionaryTsimplificationTofTtheTlarynxTwasTpivotal,TitT“didTnotTgiveTusTspeechTbyTitself”,TFitchTnoted,TpointingToutTthatTotherTanatomicalTtraitsTmatteredTforTspeechToverTtime,TincludingTaTchangeTinTtheTpositionTofTtheTlarynx.

SoundTproductionTmechanismsTinTpeopleTandTnonhumanTprimatesTareTsimilar,TwithTairTfromTtheTlungsTdrivingToscillationsTofTtheTvocalTcords.TAcousticalTenergyTgeneratedTthisTwayTthenTpassesTthroughTtheTpharyngeal,ToralTandTnasalTcavitiesTandTemergesTinTaTformTgovernedTbyTtheTfilteringTofTspecificTfrequenciesTdictatedTbyTtheTvocalTtract



                                  

“SpeechTandTlanguageTareTcriticallyTrelated,TbutTnotTsynonymous,”TsaidTprimatologistTandTpsychologistTHaroldTGouzoulesTofTEmoryTUniversityTinTAtlanta,TwhoTwroteTaTcommentaryTinTScienceTaccompanyingTtheTstudy.

“SpeechTisTtheTaudibleTsound-basedTmannerTofTlanguageTexpressionT–TandThumans,TaloneTamongTtheTprimates,TcanTproduceTit.”

Paradoxically,TtheTincreasedTcomplexityTofThumanTspokenTlanguageTfollowedTanTevolutionaryTsimplification.

“ITthinkTit’sTprettyTinterestingTthatTsometimesTinTevolutionT‘lessTisTmore’T–TthatTbyTlosingTaTtraitTyouTmightTopenTtheTdoorTtoTsomeTnewTadaptations,”TFitchTsaid.

…TweThaveTaTsmallTfavourTtoTask.TMillionsTareTturningTtoTtheTGuardianTforTopen,Tindependent,TqualityTnewsTeveryTday,TandTreadersTinT180TcountriesTaroundTtheTworldTnowTsupportTusTfinancially.

WeTbelieveTeveryoneTdeservesTaccessTtoTinformationTthat’sTgroundedTinTscienceTandTtruth,TandTanalysisTrootedTinTauthorityTandTintegrity.TThat’sTwhyTweTmadeTaTdifferentTchoice:TtoTkeepTourTreportingTopenTforTallTreaders,TregardlessTofTwhereTtheyTliveTorTwhatTtheyTcanTaffordTtoTpay.TThisTmeansTmoreTpeopleTcanTbeTbetterTinformed,Tunited,TandTinspiredTtoTtakeTmeaningfulTaction.

InTtheseTperilousTtimes,TaTtruth-seekingTglobalTnewsTorganisationTlikeTtheTGuardianTisTessential.TWeThaveTnoTshareholdersTorTbillionaireTowner,TmeaningTourTjournalismTisTfreeTfromTcommercialTandTpoliticalTinfluenceT–TthisTmakesTusTdifferent.TWhenTit’sTneverTbeenTmoreTimportant,TourTindependenceTallowsTusTtoTfearlesslyTinvestigate,TchallengeTandTexposeTthoseTinTpower.