New research links homosexual behavior in non-human primates to the evolution of complex social structures
By Jackie Flynn Mogensen edited by Claire Cameron

Tom Applegate/Getty Images
Homosexual behavior is common throughout the animal kingdom: more than 1,500 species are it is estimated that it was observed engaging in homosexual behavior, from spiders and nematodes to bonobos and fish. However, scientists suspect that such behavior are massively underestimated and therefore much less understood than others presented by animals.
A new study by researchers at Imperial College London and published Monday in Ecology and evolution of nature could help shed light. The research focuses on homosexual behavior in non-human primates and describes how it may have evolved to empower these species. nuanced social systems.
“If we want to understand the behavior of wild and complex animals, we must take homosexual behavior into account. [behavior]”, says Vincent Savolainen, professor at Imperial College London and lead author of the paper. “It is, I believe, as important as reproductive sex, caring for children, fighting, eating, etc.”
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In other words, homosexual behaviors in these animals are part of a “behavior repertoire” that helps nonhuman primates navigate their societies, Savolainen explains.
The research adds to a growing body of evidence This suggests that homosexual behavior in non-human primates builds and strengthens social bonds, meaning these behaviors are likely evolutionarily beneficial, Savolainen says. Importantly, in the new study, the authors emphasize that their findings should not be applied to humans or used to interpret LGBTQ+ experiences.
Savolainen and his colleagues analyzed more than 1,700 previous research publications to search for data on homosexual behavior in non-human primates. They identified 59 species with documented evidence of mounting, ejaculation, genital stimulation or other sexual behaviors between individuals of the same sex.
They also looked at where these species lived, taking into account climate, the number of predators in the area and other environmental factors. Certain conditions – severe weather and a higher likelihood of predation, for example – appeared to be associated with homosexual behavior in non-human primates. Animals with longer lifespans were also more likely to engage in such behaviors, as were members of species in which males and females were very different.
The study takes a “very rigorous analytical approach” to determine which traits can directly influence homosexual behavior, says José María Gómez, a professor in the ecology department at the University of Granada, who was not involved in the research. The results suggest that species that live in dry environments show greater sexual dimorphism and that species with greater sexual dimorphism tend to live in larger groups with more complex social structures, where same-sex behaviors might be most beneficial, he says.
Savolainen hopes the research will encourage more studies of how homosexual behaviors arise in nonhuman primates and the role they play in these animals’ lives.
“There was a time when people thought this only happened when you put two baboons in a zoo that can’t do anything else,” Savolainen says. “So yes, things are changing.”
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