title: Oxytocin reactivity during intergroup conflict in wild chimpanzees.
abstract: Intergroup conflict is evident throughout the history of our species, ubiquitous across human societies, and considered crucial for the evolution of humans' large-scale cooperative nature. Like humans, chimpanzee societies exhibit intragroup coordination and coalitionary support during violent intergroup conflicts. In both species, cooperation among group members is essential for individuals to gain access to benefits from engaging in intergroup conflict. Studies suggest that a contributive mechanism regulating in-group cooperation during intergroup conflicts in humans involves the neuropeptide hormone oxytocin, known to influence trust, coordination, and social cognition, although evidence from natural settings is lacking. Here, applying a noninvasive method, we investigate oxytocinergic system involvement during natural intergroup conflicts in wild chimpanzees. We found that chimpanzees of both sexes had significantly higher urinary oxytocin levels immediately before and during intergroup conflict compared with controls. Also, elevated hormone levels were linked with greater cohesion during intergroup conflicts, rather than with the level of potential threat posed by rival groups, intragroup affiliative social interactions, or coordinated behavior alone. Thus, the oxytocinergic system, potentially engendering cohesion and cooperation when facing an out-group threat, may not be uniquely human but rather a mechanism with evolutionary roots shared by our last common ancestor with chimpanzees, likely expediting fitness gains during intergroup conflict.
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany; liransamuni@gmail.com wittig@eva.mpg.de.|Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan 01, Ivory Coast.
authors.forename: Liran
authors.initials: L
authors.lastname: Samuni
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.|Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan 01, Ivory Coast.
authors.forename: Anna
authors.initials: A
authors.lastname: Preis
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.
authors.forename: Roger
authors.initials: R
authors.lastname: Mundry
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Deschner
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.|Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan 01, Ivory Coast.
authors.forename: Catherine
authors.initials: C
authors.lastname: Crockford
authors.affiliation: Department of Primatology, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany; liransamuni@gmail.com wittig@eva.mpg.de.|Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan 01, Ivory Coast.
authors.forename: Roman M
authors.initials: RM
authors.lastname: Wittig
mesh_terms: D000374:Aggression / Q000523:psychology; D000533:Altruism; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D003220:Conflict, Psychological; D003299:Cooperative Behavior; D005260:Female; D006126:Group Processes; D007398:Interpersonal Relations; D008297:Male; D010121:Oxytocin / Q000652:urine*; D002679:Pan troglodytes / Q000523:psychology* / Q000652:urine*; D012919:Social Behavior; D035502:Trust / Q000523:psychology
chemical_list: D010121:Oxytocin
keywords: Pan troglodytes; cooperation; group cohesion; neuropeptide; parochial altruism