From grooming to giving blood: The origins of human altruism

Cooperation plays an important role in the lives of most primates, including ourselves. However, the magnitude and scope of cooperation varies considerably across taxa: callitrichids pool efforts to rear a pairs' offspring, male langurs jointly challenge resident males for access to groups of females, female baboons groom one another equitably, and male chimpanzees exchange support for mating opportunities. All of these forms of cooperation have analogs in human societies, but humans cooperate in more diverse contexts, with a wider range of partners, and at larger scales than other primates. The evolutionary foundations of cooperation in nonhuman primates - kinship, reciprocity, and mutualism - also generate cooperation in human societies, but cooperation in human societies may also be supported by group-level processes that do not exist in other primate species. The human capacities for culture may have created novel evolutionary forces that altered the selective benefits derived from cooperation.