Same-Sex Behaviour in Primates May Help Groups Cope With Stress, Study Suggests

Same-sex sexual behaviour among non-human primates may help reinforce social bonds and maintain group stability under environmental and social stress, researchers say. A study published in Nature Ecology & Evolution analysed reports across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas, finding the behaviour widespread among major groups. Scientists from Imperial College London suggest this either points to a deep evolutionary origin or repeated independent evolution. The behaviour was more common in species living in harsher, drier environments with scarce resources and higher predation risk. It was also associated with longer lifespans, pronounced size differences between sexes, and complex social hierarchies. Researchers believe same-sex behaviour may reduce tension, strengthen bonds and help groups navigate competition and stress. While cautioning against direct comparisons with humans, the authors note early human species likely faced similar pressures. Independent experts say the findings highlight same-sex behaviour as a common and adaptive feature of primate social life, though they warn against oversimplifying its relevance to human sexuality.