Homosexual behavior in macaque monkeys may be the result of evolution and a common feature of primate reproduction, according to a study from Imperial College London, which concluded after observing a wild colony of macaques for three years. .
Based on observations and genetic data, the study published in Nature Ecology and Evolution refutes the belief that homosexual behavior between males of the same species (SSB) is something rare in non-human animals, which is given only when there are unusual conditions.
“Our research therefore shows that same-sex sexual behaviors may be common among animals and may evolve,” the researchers write in their conclusions.
The team studied 236 males from a colony of 1,700 rhesus macaques living in the wild on the tropical island of Cayo Santiago, Puerto Rico. In addition to observing their behavior and conducting genetic analyses, the team had access to each individual’s genealogical and kinship records dating back to 1956.
After recording all the copulations of the 236 males, both males with males (SSB) and males with females (different-sex behavior, DSB), they found that 72% of males had sex with other males compared to 46% of those who did it with individuals of the opposite sex.
This behavior is not new, on the contrary. SSB has been observed in thousands of species, from insects to penguins. And science offers several explanations: dominance in a group, a shortage of partners of different sex or a reduction in tension after an assault, but there is still not enough data to corroborate these theories.
In the case of this colony of macaques, SSB in males was strongly associated with collaborative ‘alliances’, meaning that male pairs who have regular sex are more likely to support each other in conflict, thus helping them provides an advantage in the group.
They also studied the effect of homosexual sex on the number of offspring and found that males who practice it may have more reproductive success, thanks to the benefits of having more ‘alliances’.
They also confirmed that SSB is 6.4% heritable, the first evidence of a genetic link to primate SSB outside of humans. This figure is similar to that of other heritable behaviors in primates, such as grooming and sociability.
For the main researcher, Vincent Savolainen, from Imperial College, “unfortunately some people continue to believe that homosexual behavior is unnatural”, even in some countries homosexuality is prosecuted under penalty of death.
“Our research shows that homosexual behavior is widespread among non-human animals” although “our duty is to advance the scientific understanding of homosexual behavior, and explore the benefits it brings to nature and animal societies,” he concludes.
