Contemporary hunter-gatherers commonly engage in cooperative interactions among unfamiliar individuals, so did early Homo sapiens (e.g.
flexible dispersal, high social fluidity, intergroup alliance and long-distance trade.
However, it remains unclear to what extent this kind of xenophilia evolved once our lineage split with other apes.
One hypothesis proposes that human xenophilia was derived in our lineage, which is supported by the larger pattern of xenophobia in most primates – including chimpanzees.
Modern humans live in an “exploded” network with unusually large circles of trust that form due to prosociality toward unfamiliar people (i.e. 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.
A core prediction of the first impression hypothesis is that social preferences for positive interactions with non-group members (e.g.