Same-sex sexual behaviour among non-human primates may help reinforce social bonds and maintain group stability during environmental or social stress, researchers suggest. A study led by scientists including Prof Vincent Savolainen of Imperial College London analysed reports across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas. Published in Nature Ecology & Evolution, the research found such behaviour to be widespread, indicating either deep evolutionary roots or repeated independent evolution.
The analysis showed same-sex behaviour was more common in species living in harsh, dry environments with scarce resources and higher predation risks. It was also linked to longer lifespans, pronounced size differences between males and females, and complex social hierarchies, all factors associated with intense competition. Lead author Chloe Coxshall said environmental influences on this behaviour had often been overlooked.
Researchers argue the behaviour likely serves affiliative functions, reducing tension and aggression while strengthening bonds within groups. While cautioning against direct comparisons with humans, the authors noted early human species may have faced similar pressures. External experts welcomed the findings as evidence that same-sex behaviour is a common and adaptive feature of primate societies, though others warned against drawing simplistic parallels with human sexuality.
