Max Planck Institute. In violent intergroup conflicts between chimpanzee groups the hormone oxytocin enhances the social affiliation among members of the same group.
The high costs of individuals going to war is perplexing. Individuals are willing to suffer costs in order to benefit their own group, through cooperating and supporting their fellow group members and acting with hostility towards the out-group. Although aggressive, these conflicts are also known to enhance the sense of group belonging and promote social cohesion and affiliation among group members, essential aspects of successful competition with out-groups. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have measured the concentration of the hormone oxytocin in the urine of wild chimpanzees before and during intergroup conflicts and found that their social affiliations enable chimpanzees, too, to stand by each other against rivals.
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