Joan Silk: UCLA Department of Anthropology

Humans differ from most other animals, and from virtually all other primates, in the extent of our dependence on cooperation. In humans, altruism seems to be at least partly based on empathy and genuine concern for the welfare of others (Batson and Powell 1998; Fehr and Fischbacher 2003). We may also be motivated by a concern for reputation (Haley and Fessler 2005), that makes us want others to think that we are generous, fair, or charitable. Nonhuman primates also act altruistically, but the extent and deployment of altruism in primate groups is much more limited than it is in human societies. Altruistic interactions usually involve very small numbers of individuals (usually dyads) and is strongly biased by kinship. There is some evidence for reciprocity among unrelated individuals, but these exchanges are generally restricted to short-term exchanges of low-cost commodities. It is not clear what limits altruism in nonhuman primate groups. New work suggests, however, that differences in the deployment of altruism in human and nonhuman primate may be linked to differences in the capacity for empathy, the existence of moral sentiments, and the concern for the welfare of others.