KinSelection Definition Otherwiseknownasinclusivefitnesstheory,kinselectionreferstothetheorythatpeople haveevolvedtofavorotherswhoaregeneticallyrelatedtothem.Thelogicofthetheoryisthata genecanpropagateitselfthroughtworoutes.Thefirstisbyincreasingthelikelihoodthatbody inwhichitresides(theself)willsurviveandreproduce(e.g.,byleadingtotheselectionof nutritiousfoodsandfertilemates).Thesecondisbyincreasingthereproductionofclose relatives(kin)whoalsopossesscopiesofthesamegene(e.g.,byleadingtheselftohelpkinin waysthatincreasethechancesthattheywillreproduceandthegenewillbepassedon).Someof yourkinaremorecloselyrelatedtoyouthanothersandthereforearemorelikelytocarryyour genes.Thus,becauseyoushare50%ofyourgeneswithyoursiblingsbutonly12.5%withyour cousins,youshouldbemuchmorelikelytohelpsiblingsthancousins.Accordingtothetheory ofinclusivefitness,parentalcareforoffspringisaspecialcaseofkinselection,asitisyet anothercaseofpeople(oranimals)providingcareforcloselyrelatedkinwhocarryshared geneticmaterial. HistoryandModernUsage Thetheoryofkinselectioniswidelyregardedasthemostimportanttheoreticaldevelopment inevolutionarythinkingsinceDarwin,asitproposesamechanismthatexplainswhyindividuals wouldaltruisticallyhelpothers(thatis,whytheywouldprovideresourcestosomeoneelseata costtothemselves).Theideaofaltruismseemscounter-intuitivefromaDarwinianperspective, asanybehaviorthatincreasesthelikelihoodthatanotherindividualwillsurviveorreproduceat acosttoone’sownsurvivalorreproductionshouldbeselectedagainst.Butifthisaltruistic behaviorenhancesthesurvivalorreproductionofarelatedindividualtoagreaterdegreethanit diminishesone’sownchances,thenthetheoryproposesthatsuchbehaviorwouldbeselected for.Togiveaconcreteexample,Imaybewillingtoendangermyselfbyalertingmysiblings whenthereisapredatorafoot,evenifmyownshoutingmakesthepredatormorelikelytosee me.Althoughthisbehaviorputsmeatrisk,ithasthepotentialtoresultingreaterreplicationof thegenesthatIcarrythanifIkeptquietandoneormoreofmysiblingswerekilled. WilliamvonHippel&MartieG.Haselton Seealso:ReciprocalAltruism Furtherreadings:AlthoughWilliamD.Hamiltonoriginatedthetheoryofinclusivefitness,his articlesarehighlymathematicalandcomplex.Forthisreason,secondarysourcesareusually moresuitableforthoseinterestedinfurtherreading.Thefollowingareexcellentsources. Daly,M ., Salmon,C.,&Wilson,M.(1997).Kinship:Theconceptualholeinpsychological studiesofsocialcognitionandcloserelationships.InJ.Simpson&D.T.Kenrick(Eds). Evolutionarysocialpsychology .(pp.265-296).Mahwah,N.J.:LawrenceErlbaum. Buss,D.M.(2004). Evolutionarypsychology:Thenewscienceofthemind .2 nd Edition. Boston:Allyn&Bacon.(Anwide-rangingvolume,ofwhichchapter8isconcernedwith inclusivefitness).