Study Suggests Same-Sex Behaviour in Primates Helps Strengthen Social Bonds Under Stress

Same-sex sexual behaviour in non-human primates may play an important role in reinforcing social bonds and maintaining group stability during environmental or social stress, according to a new study. Researchers from Imperial College London analysed reports across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas, and found such behaviour to be widespread. Writing in Nature Ecology & Evolution, the authors suggest the behaviour either evolved early in primate history or emerged independently multiple times. The analysis found it was more common in species living in harsh, dry environments with scarce resources and higher predation risk, as well as in longer-living species with complex social hierarchies. Researchers propose that same-sex behaviour can reduce tension, lower aggression and strengthen bonds, helping groups navigate challenges. While cautioning against direct comparisons with humans, the team noted the findings raise questions about how social pressures influence behaviour across species. Independent experts welcomed the study for highlighting the adaptive role of same-sex behaviour in primate societies, while warning against oversimplifying its relevance to human sexuality.