Movie S1. Experiment 1 Procedure from Bonobos voluntarily hand food to others but not toys or tools Christopher Krupenye Jingzhi Tan Brian Hare 10.6084/m9.figshare.7017281.v1 https://rs.figshare.com/articles/media/Movie_S1_Experiment_1_Procedure_from_Bonobos_voluntarily_hand_food_to_others_but_not_toys_or_tools/7017281 A key feature of human prosociality is <i>direct transfers</i>, the most active form of sharing in which donors voluntarily hand over resources <i>in their possession</i>. Direct transfers buffer hunter-gatherers against foraging shortfalls. The emergence and elaboration of this behaviour thus likely played a key role in human evolution, by promoting cooperative interdependence and ensuring that humans' growing energetic needs (e.g. for increasing brain size) were more reliably met. According to the <i>strong prosociality hypothesis</i>, among great apes only humans exhibit sufficiently strong prosocial motivations to directly transfer food. The <i>versatile prosociality hypothesis</i> suggests instead that while other apes may make transfers in constrained settings, only humans share flexibly across food and non-food contexts. In controlled experiments, chimpanzees typically transfer objects but not food, supporting both hypotheses. Here we show in two experiments that bonobos directly transfer food but not non-food items. These findings show that, in some contexts, bonobos exhibit a human-like motivation for direct food transfer. However, humans share across a far wider range of contexts, lending support to the versatile prosociality hypothesis. Our species' unusual prosocial flexibility is likely built on a prosocial foundation we share through common descent with the other apes. 2018-08-28 14:45:53 bonobo chimpanzee prosociality cooperation sharing human evolution