Chimpanzees unite against a common enemy

In the face of threats from other groups, people are becoming more cohesive and collaborative with their own, an association suggested by Charles Darwin could be a developing ability. Now, for the first time, a research group at the University of Kyoto has proven experimentally that this tendency is shared with chimpanzees, one of our closest family members.

“Despite the importance of understanding how people work with their groups and can still carry out acts of extreme aggression outside the group, little research has been done so far on whether the link between these behaviors in non-human primates applies,” says the first author James Brooks.

Based on field research that suggested chimpanzees were more cohesive in days and months when they had out-of-group encounters, the team tested the direct link between out-of-group threat and in-group cohesion by simulating an out-of-group encounter. and to observe the subjects. behavior.

Five groups of chimpanzees listened to vocalization of unknown individuals, along with a control over crow vocalization. The team found that subjects heard by the outside groups became more alert and stressed, but instead of translating it into group tenses, the chimpanzees got closer to each other, had more affiliative behaviors, and were less aggressive than they were. received limited food. compared to the control group.

This suggests that competition between groups promotes cohesion in chimpanzees as well as in humans, and that intergroup competition in human evolution may have led to our ability to maintain cooperation and tolerant relations in large groups in the presence of a common enemy.

“This is the first experimental evidence that humans share this tendency with chimpanzees,” explains study leader Shinya Yamamoto, “but it remains to be seen whether this is due to the strong evolutionary history of both species of intergroup competition or a more common trait shared with other great apes. ‘

The team is currently studying whether the same pattern is observed in bonobos – people’s other close relatives – who are known for not committing deadly aggression outside the group.

The paper “Unity Against a Common Enemy: Outreach Threat Promotes Cohesion in Chimpanzees” appeared in the journal on February 24, 2021 PLOS ONE.