Same-sex sexual behaviour among non-human primates may help reinforce social bonds and maintain group cohesion during environmental or social stress, according to new research. Writing in Nature Ecology & Evolution, scientists analysed documented cases across 59 primate species, including chimpanzees, Barbary macaques and mountain gorillas, finding the behaviour to be widespread rather than exceptional.
The study, co-authored by Prof Vincent Savolainen of Imperial College London, suggests such behaviour is more common in species living in harsher environments, where food is scarce and predation risk is higher. It was also linked to longer lifespans, pronounced size differences between males and females, and complex social hierarchies, all factors associated with intense competition and social tension. Lead author Chloe Coxshall said the findings highlight that while there may be a heritable component, environmental pressures play a significant and often overlooked role.
Researchers argue that same-sex sexual behaviour can function as an affiliative tool, reducing aggression and strengthening relationships within groups. While cautioning against direct comparisons with humans, the authors note that early human species likely faced similar social pressures. External experts welcomed the study’s contribution to understanding primate sociality, while also warning against oversimplifying or directly mapping animal behaviour onto human sexuality.
