Bonobos respond prosocially toward members of other groups

Abstract

Modern humans live in an “exploded” network with unusually large circles of trust that form due to prosociality toward unfamiliar people (i.e. xenophilia). In a set of experiments we demonstrate that semi-free ranging bonobos (Pan paniscus) – both juveniles and young adults – also show spontaneous responses consistent with xenophilia. Bonobos voluntarily aided an unfamiliar, non-group member in obtaining food even when he/she did not make overt requests for help. Bonobos also showed evidence for involuntary, contagious yawning in response to videos of yawning conspecifics who were complete strangers. These experiments reveal that xenophilia in bonobos can be unselfish, proactive and automatic. They support the first impression hypothesis that suggests xenophilia can evolve through individual selection in social species whenever the benefits of building new bonds outweigh the costs. Xenophilia likely evolved in bonobos as the risk of intergroup aggression dissipated and the benefits of bonding between immigrating members increased. Our findings also mean the human potential for xenophilia is either evolutionarily shared or convergent with bonobos and not unique to our species as previously proposed.

Attention Towards Emotions is Modulated by Familiarity with the Expressor. A Comparison Between Bonobos and Humans

“…However, this novel finding is in fact in line with previously conducted behavioral studies in bonobos calling attention to their strong xenophilic tendencies and other-regarding preferences (i.e., bonobos voluntarily help non-group members in obtaining food 31 ; bonobos forego their own food in order to facilitate an interaction with a stranger and prefer them over group members, and help strangers acquire food 19 . Emotional attention can be driven by the evolutionary relevance of the emotional signal to the observer 32 .…”

“…It is thought that for bonobos, socializing with unfamiliar conspecifics is beneficial as it helps them extend their social network. In turn, socializing with unfamiliar others may enhance survival by promoting cooperation among individuals 31 conspecifics. Nevertheless, we found no such bias and the results even pointed in the other direction, as was also the case when they observed unfamiliar humans.…”

Oxytocin and vasotocin receptor variation sheds light into the evolution of human prosociality

“…Our results could be used as a springboard for other studies delving into the differences in prosociality between bonobos and chimpanzees, as well as for those studies looking into evidence for convergent evolution in bonobos and modern humans in an attempt to explain their similarities in terms of prosocialit 107, 108 . We found three alleles that bonobos and modern humans share (rs237897(A), rs2228485(G) and rs1042615(A)), while we did not find any for modern humans and chimpanzees.…”

Serotonergic innervation of the human amygdala and evolutionary implications

“…Studies in captive apes have demonstrated that bonobos are more cooperative and perform better at social cognition tasks compared to chimpanzees (Hare, Melis, Woods, Hastings, & Wrangham, ; Herrmann, Hare, Call, & Tomasello, ; Tan, Ariely, & Hare, ). Along a similar vein, a study by Hermann and colleagues (2007) found that human children out‐perform captive chimpanzees in tasks utilizing social cognition, but not physical cognition, leading some to suggest that social cognition represents a particularly important human adaptation (Boyd & Richerson, ; Tomasello, ).…”