To make peace or reduce stress: gorillas also have homosexual sex

BarcelonaHumans are by no means the only animals that practice sex just for pleasure.Nor are those of us who engage in it with individuals of the opposite sex as well as the same. In fact, at least 1,500 animal species have been documented with homosexual behavior. And in some, such as giraffes, males copulate primarily with other males. Others, like albatrosses or penguins, have stable homosexual partners for a significant part of their lives.

However, although recreational sex between individuals of the same sex is widespread in the animal kingdom, the evolutionary origin of this behavior is unknown. To try to shed some light on this, a team from Imperial College London has focused on studying non-human primates, our closest evolutionary relatives. They analyzed nearly 500 species and identified evidence of homosexual behavior in 59, of which 23 occurred frequently.

It should be noted that the team did not conduct fieldwork, but rather used previous research that documented these behaviors—a limitation of the study—because for a long time, animal homosexuality has unfortunately been a taboo subject in science.

The authors of this analysis investigated same-sex pairings in the different contexts in which they occur and found them to be more frequent in long-lived species, such as chimpanzees, and in those with size differences between the sexes, such as double dung mass in mountain gorillas. They also found them in species with highly complex and hierarchical social systems, such as baboons.

Interestingly, they also observe that recreational sex—that which is not aimed at reproduction—appears more frequently when primates live in challenging environments, such as resource scarcity, high predator risk, and ecological stress, for example, during a prolonged drought.

The Many Functions of Sex

To explain this relationship, the authors of the paper, who It is published in Nature Ecology & Evolution, They point to the many functions that sex fulfills, such as strengthening bonds, reinforcing ties between individuals, reducing tension, fostering group cohesion, or establishing alliances.

In this sense, "in situations of scarce food resources or ecological stress, for example, survival is more important than reproduction." points out Montserrat Colell, a researcher in ethology and primatology at the University of Barcelona —and a disciple of primatologist Jordi Sabater Pi, who did not participate in this study.

Living in a complex social group for a long time is potentially stressful and can entail significant energetic and reproductive costs. In this sense, behaviors that can foster, build, and maintain strong relationships between individuals could be an advantage, the authors of the study suggest as a potential explanation.

Recreational sex, Colell reminds us, has been documented to fulfill a wide variety of functions, such as facilitating reconciliation between individuals after a fight to return to an initial state of calm, as occurs with bonobos, "who practice widespread sex to calm the group and return to the initial status," another group. To avoid inbreeding, some primates, upon reaching puberty, leave for another group and, to integrate more quickly, offer themselves to all individuals.

A unique case is that of mountain gorillas, which form groups where several males can live together, one of them the dominant one. "There is often a lot of homosexual behavior, as a way of fostering alliances, similar to grooming"Females have also been observed having sex with other females, although the reasons are unclear. It could be for pleasure, for play," Colell explains.

Evolutionary origin of homosexual sex

Although the analysis was conducted on non-human primates, the conclusions also have implications for a better understanding of the evolutionary origins of modern humans—that is, us. The researchers suggest that hominid species prior to the Homo sapiens They also experienced the same ecological and social pressures as present-day primates, such as resource scarcity, predators, and the inherent challenges of being part of a large, complex, and hierarchical group. Therefore, the authors propose, these factors may also have contributed to the evolution of homosexual behavior in our ancestors. "Perhaps in the case of modern humans, it wouldn't be food scarcity or rigid social hierarchies that explain these behaviors, but rather the pressures of modern social life," they suggest.

The study analyzes same-sex sexual behavior in non-human primates and does not address human sexual orientation, identity, or lived experience. "The aim of the research is to document the factors that explain the diversity of behaviors in the animal world, not to justify or explain human identities; the authors explicitly reject any use of these results to legitimize discrimination or minimize the experiences of the LGBTQ+ community," the researchers clarify.