TY - JOUR

T1 - Uniting against a common enemy

T2 - Perceived outgroup threat elicits ingroup cohesion in chimpanzees

AU - Brooks, James

AU - Onishi, Ena

AU - Clark, Isabelle R.

AU - Bohn, Manuel

AU - Yamamoto, Shinya

N1 - Publisher Copyright: © 2021 Brooks et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

PY - 2021/2/24

Y1 - 2021/2/24

N2 - Outgroup threat has been identified as an important driver of ingroup cohesion in humans, but the evolutionary origin of such a relationship is unclear. Chimpanzees (Pan troglodytes) in the wild are notably aggressive towards outgroup members but coordinate complex behaviors with many individuals in group hunting and border patrols. One hypothesis claims that these behaviors evolve alongside one another, where outgroup threat selects for ingroup cohesion and group coordination. To test this hypothesis, 5 groups of chimpanzees (N = 29 individuals) were observed after hearing either pant-hoots of unfamiliar wild chimpanzees or control crow vocalizations both in their typical daily environment and in a context of induced feeding competition. We observed a behavioral pattern that was consistent both with increased stress and vigilance (self-directed behaviors increased, play decreased, rest decreased) and increased ingroup cohesion (interindividual proximity decreased, aggression over food decreased, and play during feeding competition increased). These results support the hypothesis that outgroup threat elicits ingroup tolerance in chimpanzees. This suggests that in chimpanzees, like humans, competition between groups fosters group cohesion.

AB - Outgroup threat has been identified as an important driver of ingroup cohesion in humans, but the evolutionary origin of such a relationship is unclear. Chimpanzees (Pan troglodytes) in the wild are notably aggressive towards outgroup members but coordinate complex behaviors with many individuals in group hunting and border patrols. One hypothesis claims that these behaviors evolve alongside one another, where outgroup threat selects for ingroup cohesion and group coordination. To test this hypothesis, 5 groups of chimpanzees (N = 29 individuals) were observed after hearing either pant-hoots of unfamiliar wild chimpanzees or control crow vocalizations both in their typical daily environment and in a context of induced feeding competition. We observed a behavioral pattern that was consistent both with increased stress and vigilance (self-directed behaviors increased, play decreased, rest decreased) and increased ingroup cohesion (interindividual proximity decreased, aggression over food decreased, and play during feeding competition increased). These results support the hypothesis that outgroup threat elicits ingroup tolerance in chimpanzees. This suggests that in chimpanzees, like humans, competition between groups fosters group cohesion.

KW - Psychology

KW - chimpanzees

KW - Agression

KW - Vocalization

KW - Animal sociality

KW - Vigilance

KW - Food

KW - Animal behavior

KW - Human evolution

UR - http://www.scopus.com/inward/record.url?scp=85102096425&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/0b8cc0ce-597c-30f5-b746-9da0a4b7ee89/

U2 - 10.1371/journal.pone.0246869

DO - 10.1371/journal.pone.0246869

M3 - Journal articles

C2 - 33626062

AN - SCOPUS:85102096425

VL - 16

JO - PLoS ONE

JF - PLoS ONE

SN - 1932-6203

IS - 2

M1 - e0246869

ER -