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 analysed reports across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas, finding the behaviour to be widespread. The research was co-authored by Prof Vincent Savolainen of Imperial College London, who said the findings may also have relevance for early human species facing similar pressures.
The analysis found same-sex sexual 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, strong size differences between sexes, and complex social hierarchies, all factors linked to intense social competition. Lead author Chloe Coxshall said both genetic and environmental influences appeared important. The researchers suggest the behaviour can reduce tension, increase affiliation and help groups navigate challenges. While cautioning against direct comparisons with humans, the team said the findings raise broader questions about how social pressures shape behaviour. Independent experts welcomed the study’s contribution but warned against oversimplifying or directly mapping animal behaviour onto human sexuality.
