In a series of experiments, Jingzhi Tan and Brian Hare of Duke University found that bonobos would voluntarily forego their food and offer it to a stranger in exchange for social interaction.
The authors found that the bonobos' behavior was at least partially driven by unselfish motivations, since the animals helped strangers acquire food that was out of reach even when no social interaction was possible as a result of helping them. However, their generosity had its limits: Animals would not share food in their possession if no social interaction was possible.
Though the study subjects were all bonobos that had been orphaned by the bushmeat trade in Congo, they showed no significant psychological differences from bonobos that had been raised by their mothers. According to the authors, their results reveal the evolution of generosity in these apes, our closest living relatives. They suggest that the behavior may have evolved to allow for the expansion of individual social networks.
Lead author Tan adds, "Our results show that generosity toward strangers is not unique to humans. Like chimpanzees, our species would kill strangers; like bonobos, we could also be very nice to strangers. Our results highlight the importance of studying bonobos to fully understand the origins of such human behaviors."