Same-sex sexual behaviour among non-human primates may have evolved as a strategy to reinforce social bonds and help groups cope with environmental or social challenges, according to a new study published in Nature Ecology & Evolution.
Researchers from Imperial College London analysed accounts of same-sex behaviour across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas. They found the behaviour was more common in species living in drier environments with scarce resources and higher predation risk, as well as in species with longer lifespans, greater size differences between sexes, and complex social hierarchies.
Lead author Chloe Coxshall noted that while same-sex behaviour has a heritable component, environmental factors are often overlooked. Co-author Professor Vincent Savolainen said the behaviour appears to be an affiliative mechanism to reduce tension and aggression, allowing groups to navigate challenges. The team suggested that early human species likely exhibited similar behaviour.
Experts not involved in the study praised the research for demonstrating the widespread and adaptive nature of same-sex behaviour in primates. However, Josh Davis of the Natural History Museum cautioned against directly extrapolating findings to humans, citing the complexity of human sexuality and the contentious nature of such comparisons.
