Prosociality among non-kin in bonobos and chimpanzees compared
Models of the origin of human prosociality towards non-kin have been primarily developed from chimpanzee studies. Substantially less effort has been made to consider the prosociality of bonobos. Like chimpanzees, bonobos cooperate with non-kin extensively but, unlike chimpanzees, immigrating members are central to bonobo cooperation. In experiments bonobos are tolerant during encounters with strangers and during co-feeding. They help strangers without immediate tangible reward, and forfeit monopolizable food to facilitate a physical interaction with them. Such prosociality seems proactive as it is not elicited by solicitation. Bonobos also seem to prefer sharing food over non-food objects, while chimpanzees reliably transfer non-food objects rather than food. These findings highlight the possibility that human sharing with strangers might have also evolved as a mutualistic endeavour to initiate a long-term partnership. Future models of human prosociality will need to incorporate findings from both Pan species.
