Same-sex sexual behaviour among non-human primates may help reinforce social bonds and maintain group cohesion during environmental or social stress, researchers suggest. A study published in Nature Ecology & Evolution by scientists including Prof Vincent Savolainen of Imperial College London analysed reports across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas. The findings indicate such behaviour is widespread and either evolved early in primate history or emerged independently multiple times.
The research found same-sex behaviour was more common in species living in harsh, dry environments with scarce resources and higher predation risk. It was also associated with longer lifespans, pronounced size differences between sexes and complex social hierarchies, all factors linked to intense social competition. Lead author Chloe Coxshall noted that while there may be a heritable component, environmental pressures play a significant and often overlooked role.
Researchers suggest the behaviour can reduce tension, lower aggression and strengthen affiliative bonds, helping groups navigate challenges. While cautioning against direct comparisons with humans, the authors noted parallels with pressures faced by early human species. External experts said the study highlights how common same-sex behaviour is in primate societies, while warning against oversimplifying or directly mapping animal behaviour onto human sexuality.
