Primates' same-sex sexual behaviour may reinforce bonds amid environmental stress'

"Same-sex sexual behaviour among non-human primates may arise as a way to reinforce bonds and keep societies together in the face of environmental or social challenges, researchers have suggested. Prof Vincent Savolainen, a co-author of the paper from Imperial College London, added that while the work focused on our living evolutionary cousins, early human species probably experienced similar challenges, raising the likelihood they, too, showed such behaviour."

"Writing in the journal Nature Ecology & Evolution, Savolainen and colleagues reported how they analysed accounts of same-sex sexual behaviour in non-human primates, finding it to be widespread in most major groups, with reports in 59 species including chimpanzees, Barbary macaques and mountain gorillas. That, they added, either suggested an evolutionary origin far back in the primate family tree, or the independent evolution of the behaviour multiple times."

Same-sex sexual behaviour among non-human primates can reinforce social bonds and help maintain group cohesion when facing environmental or social challenges. The behaviour occurs widely across primate lineages, with reports in at least 59 species including chimpanzees, Barbary macaques and mountain gorillas. Patterns suggest either an ancient evolutionary origin or multiple independent evolutions. The behaviour is associated with drier environments, scarce resources, higher predator risk, longer lifespans, sexual size dimorphism linked to intense competition, and complex social systems with hierarchies. Both heritable and environmental influences contribute to the occurrence of same-sex sexual behaviour in primates.

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