Same-sex sexual behaviour among non-human primates may help reinforce social bonds and maintain group stability during environmental or social stress, researchers suggest. Writing in Nature Ecology & Evolution, scientists led by Prof Vincent Savolainen of Imperial College London analysed reports across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas. They found the behaviour to be widespread, indicating either a deep evolutionary origin or repeated independent evolution.
The study found same-sex sexual behaviour was more common in species living in harsh, dry environments with scarce resources and higher predation risk. It was also linked to longer lifespans, pronounced size differences between sexes, and complex social hierarchies, all factors associated with intense social competition. First author Chloe Coxshall noted that while genetics play a role, environmental influences have been underestimated.
Researchers argue the behaviour likely reduces tension, strengthens affiliative bonds and helps groups navigate challenges. While cautioning against direct comparisons with humans, the authors suggest early human species may have shown similar patterns. External experts welcomed the findings as evidence that same-sex behaviour is a normal and adaptive part of primate social life, while also warning against oversimplifying its relevance to modern human sexuality.
