Same-sex behaviors in nonhuman primates may support social bonds.

Researchers reviewed more than 1,700 studies and identified 59 primate species with documented same-sex sexual behaviors, and found links between these behaviors and environmental and life-history traits.

A new study from Imperial College London, published in Nature Ecology & Evolution, examines same-sex behavior in nonhuman primates. Researchers reviewed more than 1,700 previous publications and identified 59 species with documented sexual actions between same-sex individuals, including mounting, ejaculation, and genital stimulation. They analyzed species' environments and traits such as climate, predation risk, lifespan and sexual dimorphism to look for patterns. The authors describe same-sex behaviors as part of primates' behavioral repertoires that may help animals navigate complex social systems. Key findings: - The review identified 59 primate species with documented same-sex sexual behaviors drawn from more than 1,700 past publications. - The study reports associations between same-sex behavior and factors such as harsher climates, higher predation risk, longer lifespans and greater sexual dimorphism. - José María Gómez, who was not involved in the research, described the analytical approach as rigorous and noted links among dry environments, sexual dimorphism and larger, more complex social groups. - The authors and quoted researchers frame same-sex behaviors as reinforcing social connections and stress that the results should not be applied to interpret human LGBTQ+ experiences. Summary: The findings indicate that same-sex behaviors are present across a number of primate species and are associated with ecological and social traits, which the authors interpret as potentially reinforcing social bonds. The paper is presented as a step toward broader study of how these behaviors arise and what roles they play in primate societies; further research directions are suggested by the authors and not yet determined at this time.