Intergroup Relations in Chimpanzees

TLDR

Since the 1970s, detailed observations of chimpanzee intergroup conflict have prompted comparisons to human warfare, faced with objections about data scarcity, observer influence, and relevance, but recent studies have countered these criticisms and clarified the functional and mechanistic bases of such aggression. Chimpanzee studies illustrate the promise of the behavioral biology approach for understanding and addressing the roots of violence in our own species. Across five long‑term sites, intergroup aggression is pervasive in chimpanzee societies even without artificial feeding, with males contesting territory, food, and females based on numerical strength assessments and striving for dominance, mirroring human male competition over similar resources and a preference for low‑risk attacks.

Abstract

▪ Abstract In the 1970s, researchers provided the first detailed descriptions of intergroup conflict in chimpanzees. These observations stimulated numerous comparisons between chimpanzee violence and human warfare. Such comparisons have attracted three main objections: (a) The data supporting such comparisons are too few, (b) intergroup aggression is the result of artificial feeding by observers, and (c) chimpanzee data are irrelevant to understanding human warfare. Recent studies provide strong evidence against these criticisms. Data from the five long-term sites with neighboring groups show that intergroup aggression is a pervasive feature of chimpanzee societies, including sites where artificial feeding never took place. Recent studies have clarified questions about the functional goals and proximate mechanisms underlying intergroup aggression. Male chimpanzees compete with males in other groups over territory, food, and females, base their decisions to attack strangers on assessments of numerical strength, and strive for dominance over neighboring groups. Human males likewise compete over territory, food, and females and show a preference for low-risk attacks and intergroup dominance. Chimpanzee studies illustrate the promise of the behavioral biology approach for understanding and addressing the roots of violence in our own species.