(Washington) Researchers have identified for the first time genetic variations specifically linked to bisexuality, while reminding us that non-genetic factors still prevail in determining sexual orientation.
This study, published Wednesday in the journal Science Advancesseeks to provide a new element of response to the biological question aimed at understanding why natural selection has not gradually ruled out the genetic elements favoring homosexuality, which leads to fewer offspring.
Researchers have found that genetic elements linked to bisexuality, more specifically, are also linked to a more favorable attitude towards risk-taking and a tendency to have more children.
The study follows in particular the major one of 2019 concluding that homosexuality, if it is not defined by a single gene, is explained both by multiple regions of the genome and, like any complex human character, by elusive non-genetic factors.
“We realized that before, people lumped together all homosexual behaviors under one category, but it is a broad spectrum,” Jianzhi Zhang, co-lead author of the paper, told AFP. study, to explain the purpose of this research.
They were based on the British database UK Biobank, which includes more than 450,000 people of European origin.
By cross-referencing their genetic data with their responses to questionnaires, the authors concluded that the genetic signatures linked to homosexuality and bisexuality were in fact distinct.
“Historical persistence”
Genetic markers linked to bisexuality, they determined, are also linked in male carriers to a strong appetite for risk, which seems to favor unprotected sex, because this same genetic marker is also linked to greater number of children.
The results of the study “suggest” that these genetic markers (alleles) “probably represent a reproductive advantage, which could explain their historical persistence and future maintenance” within natural selection, the authors wrote. .
This is explained by the fact that the same gene can carry several different characteristics. “Here we are talking about three traits: number of children, risk taking, and bisexual behavior: they all share (the same) genetic elements,” explains Jianzhi Zhang.
Conversely, genetic markers linked to homosexuality in men who say they have not had a homosexual relationship are correlated with a lower number of children, thus suggesting a possible gradual disappearance of these characteristics.
Data from UK Biobank, however, shows the growth, over decades, in the number of people declaring themselves bisexual or homosexual, undoubtedly due to greater openness in modern societies to these questions.
The authors thus estimate that an individual’s bisexuality is determined 40% by genetic factors and 60% by the environment.
“We want to emphasize the fact that our results contribute above all to better understanding the diversity and richness of human sexuality,” the authors wrote. “They are not, in any way, intended to suggest or support any discrimination based on sexuality.”