Gay monkies

In a study published Monday (July 10) in the journal Nature Ecology and Evolution, researchers were looking at same-sex behavior among males on the island — and found it was extremely common among. During mate guarding, a male will monopolize any mating that occurs with a female, which limits different-sex encounters for other males.

In the study, Vincent Savolainen, a professor of organismic biology and director of the Georgina Mace Center for the Living Planet at Imperial College London, and his colleagues tracked the social behavior of male rhesus macaques during a three-year period on Cayo Santiago , a acre island off the coast of Puerto Rico.

Same-sex sexual behavior (SSB) in rhesus macaques appears to be. Humans are the sole living members of the genus Homo, and researchers often use primate models to get at the evolutionary origins of human behaviors. A previously offered explanation for these same-sex behaviors in primates is that they are a way to establish or maintain a dominance hierarchy.

When it came to whether time spent on these same-sex doings had reproductive or fitness costs, the results suggested the reverse. The animals that engaged in same-sex sociosexual behavior seemed to have slightly better reproductive success. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Savolainen does not disagree. Typically, behaviors that give an edge for survival and reproduction and persist across generations have genetic roots. Does the prevalence of same-sex encounters in a group of Puerto Rican monkeys enhance their ability to pass along their genes?

These animals have been observed practicing homosexual courtship, sexual behavior, affection, pair bonding, or parenting. Since then scientists have collected abundant multigenerational data about the monkeys, all of whom live in well-established social groups on the island.

Complex social behaviors exist for many reasons and are shaped by environmental inputs. What remained unknown was what evolutionary benefit, if any, they derived from these encounters. By Emily Willingham edited by Gary Stix. But how findings for another species meaningfully convey information about humans is unclear.

The never-replicated findings have been controversial, and the quest for genes linked to same-sex behaviors in humans and other primate species continues to this day. The conundrum boils down to the fact that some animals expend energy on nonreproductive sexual behavior that does not seem to contribute to passing along genes to later generations, a concept known as evolutionary fitness.

Savolainen took advantage of the carefully tracked family trees of the Cayo Santiago monkeys and their genetic data to evaluate the role of inheritance in their same-sex sociosexual behaviors. If that hypothesis holds up for the macaques, that does not mean it can be assumed to hold for other primates, including humans.

Male monkeys frequently engage in same-sex mounting, and in some cases, more frequently than they have sex with females. The monkeys that do so on Cayo Santiago tend to form more well-developed social ties with other males with whom they have sex and also experience greater reproductive success.

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. It eventually became clear that these primates and many others commonly engage in same-sex sociosexual behaviors whether humans are around or not. Homosexual behaviour appears to be widespread among male macaque monkeys in the wild and the trait may be at least partially passed down in genes from father to son.

The results challenge a so-called Darwinian paradox that expresses a sense of perplexity about the prevalence of same-sex sexual behaviors in many species. Casting macaques as a potential explanatory model for human behavior requires caution, Rodrigues says. That advantage implies an evolutionary payoff to the activity although the researchers noted that this trend was nonsignificant.

They found that 72 percent of males engaged in same-sex behavior, compared with 46 percent that opted for liaisons with the opposite sex. Males engaging in the same-sex sociosexual behaviors were more likely to back each other up in disputes with other monkeys, which gave them a winning edge.

Membership in strong male coalitions has been linked to greater reproductive success in macaques. The latest results pose a challenge to the paradox by suggesting that social benefits accrue from same-sex encounters, including improved evolutionary fitness for animals that engage in it.

Savolainen and his co-authors say that they considered mate guarding and discussed it in their study. Six decades ago researchers documented same-sex sociosexual behavior between male macaques on Cayo Santiago and described it as almost as common as similar behaviors between two different sexes.

The researchers sorted out a small genetic contribution—about 6 percent of the same-sex behavior can be explained by genetics, which is a roughly similar heritability percentage to that of other common complex primate activities, such as grooming. As a counterpoint to these critiques, researchers who pursued these studies emphasized that a biological cause of same-sex sexual behaviors could offer a defense against persecution arising from culture-based moral claims.