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Reading Week 5 - Caspari - 44 Scientific American August...

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44 Scientific American, August 2011 Photograph by Tktk Tktk
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August 2011, Scientifi cAmerican.com 45 HUMAN ORIGINS the evolution of grandparents Senior citizens may have been the secret of our species’ success By Rachel Caspari
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46 Scientific American, August 2011 D URING ThE ±UMMER of 1963, whEN I w²± ±Ix yE²R± old, My f²MIly TR²vElEd FrOm Our HOme in PHiLaDeLpHia tO ³Os AngeLes tO Visit mY maternaL reLa- tiVes. ´ aLreaDY kneW mY granDmOtHer WeLL: sHe HeLpeD mY mOtHer care FOr mY tWin brOtHers, WHO Were OnLY 18 mOntHs mY juniOr, anD me. µHen sHe Was nOt WitH us, mY granDmOtHer LiVeD WitH Her mOtHer, WHOm ´ met tHat summer FOr tHe first time. ´ cOme FrOm a LOng-LiVeD FamiLY. ¶Y granDmOtH- er Was bOrn in 1895, anD Her mOtHer in tHe 1860s; bOtH LiVeD aLmOst 100 Years. µe staYeD WitH tHe tWO matriarcHs FOr seVeraL Weeks. ·HrOugH tHeir stOries, ´ LearneD abOut mY rOOts anD WHere ´ beLOngeD in a sOciaL netWOrk spanning FOur generatiOns. ·Heir reminiscences persOnaLLY cOnnecteD me tO LiFe at tHe enD OF tHe CiViL µar anD tHe ¸ecOnstruc- tiOn era anD tO tHe cHaLLenges mY ancestOrs FaceD anD tHe WaYs tHeY perseVereD. ¶Y stOrY is nOt unique. ¹LDers pLaY criticaL rOLes in Human sOcieties arOunD tHe gLObe, cOnVeYing WisDOm anD prOViDing sOciaL anD ecOnOmic suppOrt FOr tHe FamiLies OF tHeir cHiLDren anD Larger kin grOups. ´n Our mODern era, peOpLe rOutineLY LiVe LOng enOugH tO becOme granDparents. But tHis Was nOt aLWaYs tHe case. µHen DiD granDparents becOme preVaLent, anD HOW DiD tHeir ubiquitY affect Human eVOLutiOn? ¸esearcH mY cOLLeagues anD ´ HaVe been cOnDucting inDi- cates tHat granDparent-ageD inDiViDuaLs became cOmmOn reLa- tiVeLY recentLY in Human preHistOrY anD tHat tHis cHange came at abOut tHe same time as cuLturaL sHiFts tOWarD DistinctLY mOD- ern beHaViOrs—incLuDing a DepenDence On sOpHisticateD sYm- bOL-baseD cOmmunicatiOn OF tHe kinD tHat unDerpins art anD Language. ·Hese finDings suggest tHat LiVing tO an OLDer age HaD prOFOunD effects On tHe pOpuLatiOn sizes, sOciaL interactiOns anD genetics OF earLY mODern Human grOups anD maY eXpLain WHY tHeY Were mOre successFuL tHan arcHaic Humans, sucH as tHe ºeanDertaLs. LIVE FAST, DIE YOUNG ThE fIR±T ±TE» in figuring Out WHen granDparents became a fiX- ture in sOcietY is assessing tHe tYpicaL age breakDOWn OF past pOpuLatiOns—WHat percent Were cHiLDren, aDuLts OF cHiLDbear- ing age anD parents OF tHOse YOunger aDuLts? ¸ecOnstructing tHe DemOgrapHY OF ancient pOpuLatiOns is trickY business, HOW- eVer. ¼Or One tHing, WHOLe pOpuLatiOns are neVer preserVeD in tHe FOssiL recOrD. ¸atHer paLeOntOLOgists tenD tO recOVer Frag- ments OF inDiViDuaLs. ¼Or anOtHer, earLY Humans DiD nOt neces- sariLY mature at tHe same rate as mODern Humans. ´n Fact, mat- uratiOn rates Differ eVen amOng cOntempOrarY Human pOpuLa- tiOns. But a HanDFuL OF sites HaVe YieLDeD HigH enOugH numbers OF Human FOssiLs in tHe same LaYers OF seDiment tHat scientists can cOnfiDentLY assess tHe age at DeatH OF tHe remains—WHicH is keY tO unDerstanDing tHe makeup OF a preHistOric grOup.
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Reading Week 5 - Caspari - 44 Scientific American August...

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