🦍 Here's why primates exhibit homosexual behaviors

The observation of homosexual behaviors in animals has long raised questions about their origins and functions. A recent study, focused on primates, shows that these behaviors are not random but are actually associated with specific environmental and social pressures. This research even indicates they could constitute an evolutionary strategy, contributing to group cohesion and resilience.

By analyzing data from nearly 500 non-human primate species, scientists identified same-sex sexual behaviors in 59 of them. This phenomenon appears to have ancient evolutionary roots. The study, published in Nature Ecology & Evolution, attempts to interpret the ecological and social factors that favor the emergence of these behaviors.

An adaptive response to harsh environments

Researchers have established a significant link between the frequency of homosexual behaviors and the difficulty of living conditions. These behaviors appear more often in species evolving in environments where food is scarce or hard to access. This was notably the case with Barbary macaques, which live in an austere habitat. This suggests that these practices could play a role in managing group tensions in the face of adversity.

Another factor is predation pressure. Indeed, species that are constantly threatened by predators, such as vervet monkeys which must constantly avoid snakes and big cats, exhibit more homosexual behaviors. Thus, in the face of constant danger, reinforcing social cohesion becomes a priority for group survival. These interactions could serve as a calming mechanism, reducing internal conflicts and consolidating alliances against external threats.

Finally, the analysis reveals that these behaviors are not the product of chance or constraint. They seem integrated into the natural behavior of the species, influenced by its evolutionary history. Their persistence across many primate lineages, from lemurs to great apes, confirms they are part of a "behavioral toolkit" that can be activated in response to specific needs.

The central role of social complexity

Another determining factor appears to be the social structure of the species. Indeed, homosexual behaviors are more frequently observed in primates living in hierarchical societies, where competition for resources or status is intense. This is notably the case with mountain gorillas, where males are much larger than females. This size difference seems to be a determining point, as the behaviors appear different in monkeys of similar size.

In monkeys with very pronounced hierarchies and violent conflicts, homosexual interactions surprisingly seem to function as a kind of social strategy. They would allow for forming and consolidating alliances, managing conflicts without resorting to violence, and even negotiating one's position within a group. Observations in rhesus macaques have shown that males engaging in such behaviors formed coalitions, subsequently giving them better access to females and thus to offspring.

This social function is particularly valuable for long-lived species, for whom the stability of long-term relationships is beneficial. Researchers conclude that these behaviors are an integral part of the social fabric of many primate species and constitute an adaptation to group living.