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Human-like altruism claimed in chimps

June 26, 2007
World Science staff

Sci­en­tists of­ten as­sume al­tru­ism is ei­ther un­ique to hu­mans, or that at least the hu­man ver­sion dif­fers from that of oth­er an­i­mals in im­por­tant ways. Thus, only hu­mans are sup­posed to act on be­half of oth­ers, even to­ward un­re­lat­ed in­di­vid­u­als, with­out per­son­al gain, at a cost to them­selves. 

Credit: Anne Fischer, Max Plank-Institute for Evolutionary Anthropology

Re­search­ers have tried re­peat­edly to test this as­sump­tion, es­pe­cially stu­dy­ing our close rel­a­tive the chim­pan­zee.

Past work has failed to turn up un­equiv­o­cal ev­i­dence that chim­pan­zees act purely al­tru­is­tic­ally to­ward peers, ex­cept family mem­bers. But in new re­search, Fe­lix War­ne­ken and col­leagues of the Max Planck In­sti­tute for Ev­o­lu­tion­ary An­thro­po­l­ogy in Leip­zig, Ger­ma­ny, re­ported what they called strong ev­i­dence that chimps do so.

Both chim­pan­zees and 18-month-old hu­man in­fants helped al­tru­is­tic­ally re­gard­less of any ex­pecta­t­ion of re­ward, they wrote—e­ven when some ef­fort was re­quired, and even when the re­cip­i­ent was an un­fa­mil­iar per­son. All these fea­tures were pre­vi­ously thought to be un­ique to hu­mans, the re­search­ers said.

“Chim­panzees per­form bas­ic forms of help­ing in the ab­sence of re­wards spon­ta­ne­ously and re­peat­edly,” they wrote in a pa­per on the stu­dy, pub­lished in the July is­sue of the re­search jour­nal P­loS Bi­ol­o­gy. Al­tru­is­m’s ev­o­lu­tion­ary roots may thus go deeper than pre­vi­ously thought, as far back as the last com­mon an­ces­tor of hu­mans and chim­pan­zees, Warneken and col­leagues said.

In one test, a chimp saw a per­son try to reach through bars for a stick on the oth­er side, too far for the per­son, but with­in the ape’s reach. The chimps spon­ta­ne­ously helped the per­son, re­gard­less of wheth­er this yielded a re­ward—and even if they had to climb sev­er­al feet to reach the stick, re­search­ers re­ported.

The in­ves­ti­ga­tors set strict con­di­tions by “hav­ing the apes in­ter­act with hu­mans they barely knew, and on whom they had nev­er de­pended for food or oth­er fa­vors,” wrote Frans B. M. de Waal of the Yer­kes Na­tional Pri­mate Re­search Cen­ter at Em­o­ry Un­ivers­ity, At­lan­ta, Ga., in a com­men­tary al­so pub­lished in the jour­nal.

Apes were al­so found to help each oth­er. One chimp would try to en­ter a locked room with food, with­in sight of anoth­er chimp. The ob­serv­ing chimp would re­liably un­chain the door so that the oth­er chimp could move in, re­search­ers re­ported.

De Waal wrote that out­side of ex­pe­ri­men­tal situa­t­ions, re­search­ers have of­ten seen chimps help­ing each oth­er. The famed Eng­lish pri­ma­tol­o­gist Jane Goodall re­ported see­ing an adult male chimp drown try­ing to res­cue an in­fant chimp, not his own, who had fall­en in­to wa­ter, for ex­am­ple.

But past stud­ies, us­ing dif­fer­ent ex­pe­ri­men­tal se­tups, have not­ed lim­its to chimp help­ful­ness—sug­gest it will take more re­search to de­fine the bound­aries of this be­hav­ior, ac­cord­ing to sci­en­tists.

In a 2005 stu­dy, Jo­an Silk of the Un­ivers­ity of Cal­i­for­nia, Los An­ge­les and col­leagues pre­sented cap­tive chimps with a de­vice that gave them a choice be­tween two op­tions. A chimp could choose to serve it­self with food, and only itself; or, it could pick an op­tion that gave it the same food, but al­so re­sulted in food be­ing de­liv­ered to anoth­er chimp. The ani­mals were no more likely to choose the sec­ond op­tion, even though they could see that it would help a friend at no in­con­ven­ience to them­selves, re­search­ers said.

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Scientists often assume altruism is either unique to humans, or that at least human version differs from that of other animals in important ways. Thus, only humans are supposed to act on behalf of others, even toward unrelated individuals, without personal gain, at a cost to themselves. Researchers have tried repeatedly to test this assumption, especially studying our close relative the chimpanzee. Past work has failed to turn up unequivocal evidence that chimpanzees act purely altruistically toward peers, except family members. But in new research, Felix Warneken and colleagues of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reported what they called strong evidence that chimps do so. Both chimpanzees and 18-month-old human infants helped altruistically regardless of any expectation of reward, they wrote—even when some effort was required, and even when the recipient was an unfamiliar person. All these features were previously thought to be unique to humans, the researchers said. “Chimpanzees perform basic forms of helping in the absence of rewards spontaneously and repeatedly,” they wrote in a paper on the study, published in the July issue of the research journal PloS Biology. Altruism’s evolutionary roots may thus go deeper than previously thought, as far back as the last common ancestor of humans and chimpanzees, Warneken and colleagues said. In one test, a chimp saw a person try to reach through bars for a stick on the other side, too far for the person, but within the ape’s reach. The chimps spontaneously helped the person, regardless of whether this yielded a reward—and even if they had to climb several feet to reach the stick, researchers reported. The investigators set strict conditions by “having the apes interact with humans they barely knew, and on whom they had never depended for food or other favors,” wrote Frans B. M. de Waal of the Yerkes National Primate Research Center in Emory University, Atlanta, Ga., in a commentary also published in the journal. Apes were also found to help each other. One chimp would try to enter a locked room with food, within sight of another chimp. The observing chimp would reliably unchain the door so that the other chimp could move in, researchers reported. De Waal wrote that outside of experimental situations, researchers have often seen chimps helping each other. The famed English primatologist Jane Goodall reported seeing an adult male chimp drown trying to rescue an infant chimp, not his own, who had fallen into water, for example. But past studies, using different experimental setups, have noted limits to chimp helpfulness—suggesting it will take more research to define the boundaries of this behavior, according to scientists. In a 2005 study, Joan Silk of the University of California, Los Angeles and colleagues presented captive chimps with a device that gave them a choice between two options. The chimp could choose to serve only itself with food, or it could select an option that gave it the same food, but also resulted in food being delivered to another chimpanzee. The chimpanzees were no more likely to choose the second option, even though they could see that it would help a friend at no inconvenience to themselves, the researchers said.