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Giving among strangers more nurture than nature, study suggests

Oct. 13, 2009
Courtesy National Science Foundation
and World Science staff

So­cially learn­ed be­hav­ior and be­liefs are much bet­ter can­di­dates than ge­net­ics to ex­plain why many peo­ple set aside self-in­ter­est to help strangers, a study sug­gests.

The re­search by Adri­an V. Bell and col­leagues of the Un­ivers­ity of Cal­i­for­nia Da­vis ap­pears in the Oct. 12 edi­tion of the jour­nal Pro­ceed­ings of the Na­tional Acad­e­my of Sci­ences.

Al­tru­ism has long been a sub­ject of in­ter­est to sci­en­tists. Su­per­fi­cially at least, ev­o­lu­tion­ary the­o­ry sug­gests al­tru­ism should­n’t ex­ist. Ev­o­lu­tion oc­curs be­cause some genes in a popula­t­ion are usu­ally more ad­van­ta­geous than oth­ers. The fa­vor­a­ble genes spread through the popula­t­ion be­cause their bear­ers are able to out-reproduce oth­er in­di­vid­u­als, grad­u­ally chang­ing the whole group’s char­ac­ter­is­tics. This does­n’t seem to al­low for al­tru­ism, as pre­sumably only those who help them­selves ul­ti­mately get ahead in the ev­o­lu­tion­ary race.

Sci­en­tists have pro­posed a range of pos­si­ble so­lu­tions to ex­plain why al­tru­ism might arise.

Bel­l’s group used a math­e­mat­i­cal equa­t­ion, called the Price equa­t­ion, that de­scribes con­di­tions un­der which al­tru­ism could evolve. This equa­t­ion prompted the re­search­ers to com­pare the ge­net­ic and the cul­tur­al dif­fer­entia­t­ion be­tween neigh­bor­ing so­cial groups. 

Us­ing pre­vi­ously cal­cu­lat­ed es­ti­mates of ge­net­ic dif­fer­ences, they used the World Val­ues Sur­vey—whose ques­tions are likely to be heavily in­flu­enced by cul­ture in many coun­tries—as a source of da­ta to com­pute the cul­tur­al dif­fer­entia­t­ion be­tween the same neigh­bor­ing groups. They then found that the role of cul­ture had a much great­er scope for ex­plaining giv­ing be­hav­ior than ge­net­ics.

The World Val­ues Sur­vey was less use­ful for ap­ply­ing the re­sults to an­cient his­to­ry, the re­search­ers not­ed. But an­cient prac­tices, such as ex­clu­sion from the mar­riage mar­ket, de­ni­al of the fruits of co­op­er­a­tive ac­ti­vi­ties, ban­ish­ment and ex­e­cu­tion hap­pen now as they did then. These ac­ti­vi­ties would have ex­erted pres­sure against genes tend­ing to­ward an­ti­so­cial be­hav­ior, pre­sumably in fa­vor of genes that pre­dis­posed in­di­vid­u­als to­ward be­ing pro-so­cial rath­er than an­ti-so­cial. This would re­sult in genes inter­act­ing with cul­ture, or “gene-cul­ture co­ev­o­lu­tion,” pro­mot­ing pro-so­cial tend­encies, Bell and col­leagues argue.

Bell is con­tin­u­ing his re­search in Tonga, where he plans to es­ti­mate sta­tis­tic­ally what so­cial learn­ing be­hav­iors peo­ple have in gen­er­al that may ex­plain the dis­tri­bu­tion of cul­tur­al be­liefs across the Tong­an Is­lands.


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Socially learned behavior and beliefs are much better candidates than genetics to explain why many people set aside self-interest to help strangers, a study suggests. The research by Adrian V. Bell and colleagues of the University of California Davis appears in the Oct. 12 edition of Proceedings of the National Academy of Sciences. Altruism has long been a subject of interest to scientists. Superficially at least, evolutionary theory suggests altruism shouldn’t exist. Evolution occurs when some genes in a population are more advantageous than others. The favorable genes spread through the population because their bearers are able to out-reproduce other individuals, gradually changing the whole group’s characteristics. This doesn’t seem to allow for altruism, as presumably only those who help themselves ultimately get ahead in the evolutionary race. Scientists have proposed a range of possible solutions to explain why altruism might arise. Bell’s group used a mathematical equation, called the Price equation, that describes conditions under which altruism could evolve. This equation prompted the researchers to compare the genetic and the cultural differentiation between neighboring social groups. Using previously calculated estimates of genetic differences, they used the World Values Survey—whose questions are likely to be heavily influenced by culture in a large number of countries—as a source of data to compute the cultural differentiation between the same neighboring groups. They then found that the role of culture had a much greater scope for explaining giving behavior than genetics. The World Values Survey was less useful for applying the results to ancient history, the researchers noted. But ancient practices, such as exclusion from the marriage market, denial of the fruits of cooperative activities, banishment and execution happen now as they did then. These activities would have exerted pressure against genes tending toward antisocial behavior, presumably in favor of genes that predisposed individuals toward being pro-social rather than anti-social. This would result in “gene-culture coevolution” of human pro-social propensities, Bell and colleagues proposed. Bell is continuing his research in Tonga, where he plans to estimate statistically what social learning behaviors people have in general that may explain the distribution of cultural beliefs across the Tongan Islands. He is developing a survey instrument to help capture people’s cultural beliefs and measure the effect of migration on the similarities and differences between populations.