Study Suggests Same-Sex Sexual Behaviour Helps Primates Cope With Stress and Scarcity

Same-sex sexual behaviour in non-human primates may help reinforce social bonds and maintain group cohesion during periods of environmental or social stress, according to new research. Writing in Nature Ecology & Evolution, scientists led by Prof Vincent Savolainen of Imperial College London analysed documented cases across primate species and found the behaviour to be widespread, recorded in 59 species including chimpanzees, Barbary macaques and mountain gorillas. The findings suggest either a deep evolutionary origin or repeated independent evolution of the behaviour. The study found same-sex sexual behaviour was more common in species living in harsh, dry environments with scarce resources and higher predation risk, as well as in long-lived species with complex social hierarchies and intense competition. Lead author Chloe Coxshall said environmental influences had been underestimated alongside genetic factors. Researchers propose the behaviour helps reduce tension, strengthen bonds and stabilise societies under pressure. While cautioning against direct comparisons with humans, the team noted early human species likely faced similar challenges. Prof Zanna Clay of Durham University said the research shows such behaviour is a normal and adaptive part of primate social life, though others stressed that human sexuality remains far more complex and should not be oversimplified.