Same-sex sexual behavior can help primates to survive — and reproduce
*Bonds between same-sex individuals help apes and monkeys to manage conflict and strengthen alliances, especially in dry habitats and predator-rich landscapes.
(My thought... The US is in a predator-rich landscape right now.)
*In golden snub-nosed monkeys, sexual interactions between individuals of the same sex seem to fortify social bonds.
Article...
Same-sex sexual behavior is part of the normal social life of some primates and could play an important part in their long-term success, a survey of nearly 500 species of apes, monkeys and other non-human primates has found.
The study, published on 12 January in Nature Ecology and Evolution, suggests that same-sex sexual behavior in wild populations might be a response to harsh environments, predation and navigating complex social hierarchies1. Observed behaviors included mounting, genital touching and fellatio.
“A lot of people have long regarded same-sex behavior as an accident, or rare, or only in zoo animals,” says co-author Vincent Savolainen, an evolutionary biologist at Imperial College London. But “it’s part of the normal social life of primates”.
Although a staple of wildlife documentaries, same-sex sexual behavior in animals has only begun to receive serious study in the past few years. Explanations range from accident — behavioral spillover when reproduction is dominated by a few individuals — to adaptation, says Isabelle Winder, an evolutionary anthropologist at Bangor University in Wales. “It’s very hard to figure out what the significance is or if there is a significance.”
Strengthening social bonds
Previously, Savolainen’s team followed a colony of rhesus macaques (Macaca mulatta) in Puerto Rico for three years, discovering that same-sex sexual behavior in males was routine and linked to later reproductive success, potentially because it fortifies social alliances2. “They fight together, they have sex together, and maybe later in life they will have access to more females,” he says.
To see if same-sex sexual behavior had benefits in other primates, Savolainen, Chloë Coxshall — a behavioral primatologist at Imperial College London — and their colleagues scoured the scientific literature, identifying instances in 59 species among 491 surveyed, and found evidence for recurring same-sex behavior in 23 of these.
When they compared the prevalence of same-sex sexual behavior with environmental and other variables, the researchers found that it was most likely to occur in dry conditions and in areas where risk of predation was high, and among longer-lived species and those with strong sexual dimorphism — large size differences between males and females. Same-sex sexual behavior was also more common in primates that live in hierarchical groups, in which individuals — especially males — must climb the social ladder to have a chance at reproducing.
Further modelling suggested that ecological and ‘life history’ traits such as lifespan lead to same-sex sexual behavior indirectly — through their influence on social structures. The study found that dry conditions can lead to sexual dimorphism, which in turn was associated with living in hierarchical groups in which same-sex sexual behavior tended to occur. Disentangling these various factors “is the greatest value of this study, in my view”, says José Mariá Gómez, an evolutionary ecologist at the Experimental Station of Arid Zones in Almería, Spain.
For example, in golden snub-nosed monkeys (Rhinopithecus roxellana), which cope with cold climates, same-sex sexual behavior tends to occur alongside bond-strengthening grooming. In long-lived bonobos (Pan paniscus), a chimpanzee relative, the high frequency of same-sex behavior could help to maintain social cohesion over decades, the researchers suggest.
Winder says the research is groundbreaking because it shows how to study seemingly rare behaviors observed in wild animals, and it could be applied to other behaviors such as mourning, tool use and symbolic language, to understand their wider social context. “They’re not one-off occurrences.”
https://www.nature.com/articles/d41586-026-00119-5
Posts
