Same-sex sexual behaviour among non-human primates may help strengthen social bonds and reduce tension during periods of environmental or social stress, according to new research. Scientists analysing reports across 59 primate species found the behaviour to be widespread, appearing in chimpanzees, Barbary macaques and mountain gorillas, among others. The study, led by researchers including Prof Vincent Savolainen from Imperial College London and published in Nature Ecology & Evolution, suggests the behaviour may either have deep evolutionary roots or have evolved independently multiple times.
The analysis found same-sex 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, larger social groups, strong hierarchies and greater size differences between sexes. Researchers argue these conditions increase social tension, making affiliative behaviours more valuable for group stability. The authors caution against drawing direct parallels with humans, noting the complexity of human sexuality, though they suggest early human species may have faced similar pressures. External experts welcomed the findings as evidence that same-sex behaviour is a natural and adaptive part of primate social life, while others urged care when extending animal research to human behaviour.
