>Bonobos live in a relatively stable ecological environment in Congo, where there is enough food available. Under those circumstances, there is less need for competition with other groups and peaceful interaction with strangers might even be beneficial for the conservation of the species. Early humans, on the other hand, lived in nomadic groups that had to compete with other groups of humans for food. Under such circumstances, it is probably evolutionarily more beneficial to favor individuals from your own group over strangers.'