Homosexual behaviors in species other than humans are considered an evolutionary enigma because they do not directly contribute to reproduction, but they are neither an aberration nor a mistake of nature. They are quite common and have an explanation. According to a study led by the Experimental Station for Arid Zones (EEZA), institute of the Higher Council for Scientific Research (CSIC) in Almería, occur especially among social animals that interact within a group, such as primates. The objective? Probably strengthen the bonds between its members and avoid conflicts, especially between males.
The researchers turned to scientific literature to examine sexual behavior in more than 1,200 species of mammals and found that homosexual practices are common. They were found in more than 200 species, distributed in 50% of the families. And there are probably more, since not all species have been studied. Furthermore, it is practiced by males and females alike. According to currently available data, it tends to be particularly prevalent in some lineages, especially among primates, where it has been observed in at least 51 species, from lemurs to apes, such as our closest relatives: chimpanzees, bonobos, gorillas and orangutans.
«When we talk about homosexual behavior we are referring to a sexual interaction between individuals of the same sex that is usually momentary and transitory. The behavior is the same as that they have with individuals of the other sex, from copulation to courtship,” José María Gómez, main author of the study and researcher at the Department of Functional and Evolutionary Ecology of the EEZA-CSIC, explains to this newspaper. Only in some cases do couples form, “like two female chimpanzees to take care of their young that they have had with other males.”
Researchers have detected that social species are the ones most likely to exhibit this type of homosexual interactions. These results, say in the magazine ‘Nature Communications’, support the hypothesis that this sexual behavior has been evolutionarily favored as a way to establish, maintain and reinforce social relationships that can increase ties and alliances between members of the same group.
«There are two types of hypotheses to explain these behaviors. The non-adaptive ones consider that they are a consequence of a poor gender identification or they consider them aberrant for not having been able to practice it with individuals of the other sex. However, adaptive ones consider that they fulfill a function. It benefits the individual who practices it because it increases social ties with dominant individuals, increases their positive social interactions and prevents aggression, especially among males,” explains Gómez.
The new study reinforces the adaptive hypotheses. «If homosexual behavior contributes to increasing positive social interactions, it would be expected that they would be more frequent in social species than in solitary ones. And that’s what we saw », he points out. “It is not an aberrant trait, but an adaptation,” concludes the evolutionary biologist.
This comparative phylogenetic analysis has also found a relationship between this sexual behavior and intrasexual violence, in this case only for males. Species whose males are more violent are more likely to exhibit this sexual behavior at some point in their lives.
“As is the case for most traits, evolution has left us a trace of incalculable value to understand this behavior in nature,” says Miguel Verdú, from the Desertification Research Center (CSIC-University of Valencia-Generalitat Valenciana). .
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