By Abbas Nazil
Same-sex sexual behaviour among non-human primates may play an important role in maintaining social cohesion and helping groups navigate environmental and social challenges, according to a new study.
Researchers from Imperial College London analysed reports of same-sex sexual behaviour across 59 primate species, including chimpanzees, Barbary macaques, and mountain gorillas, finding that it is widespread and likely to have either evolved early in the primate lineage or developed independently multiple times.
The study suggests that this behaviour helps reduce tensions within groups, strengthens social bonds, and enables species to cope with environmental pressures, particularly in drier habitats where resources are scarce and predation risks are high.
The findings also indicate that species with longer lifespans, pronounced sexual dimorphism, and complex social hierarchies are more likely to exhibit same-sex sexual behaviour.
According to Prof Vincent Savolainen, a co-author of the study, the behaviour functions as an affiliative mechanism, helping primates navigate the challenges of their environment and society.
Chloe Coxshall, the study’s first author, emphasized that both genetic and environmental factors influence the occurrence of same-sex sexual behaviour, with environmental conditions shaping life history traits that affect social systems.
While the research focuses on non-human primates, the authors note that early human species likely faced similar challenges, making it plausible that same-sex behaviour played a role in human evolution as well.
The study cautions against directly mapping these findings onto modern human sexual orientation and identity, which are influenced by far more complex social and psychological factors.
Experts not involved in the research highlighted the study’s significance in showing that same-sex behaviour is a common and adaptive part of primate sociality.
Prof Zanna Clay of Durham University described the research as providing a novel perspective on the evolutionary origins of same-sex behaviour and suggested that future studies could examine similar patterns in other animal groups.
Josh Davis of the Natural History Museum stressed that while same-sex behaviour occurs widely across the animal kingdom, human sexuality is shaped by a much broader range of factors, making direct comparisons challenging.
The study adds to growing evidence that same-sex behaviour in animals is not rare or aberrant but serves important social and adaptive functions across species.