Scientists discover genetic variations associated with bisexuality

For the first time, scientists have identified genetic variations associated with human bisexual behavior and found that these variations are related to risk taking and greater offspring when the carriers are heterosexual men. The study was published this Wednesday (3) in the journal Science Advances.

Jianzhi “George” Zhang, a professor at the University of Michigan and lead author of the new research, told AFP that the study helps answer the long-standing evolutionary question of why natural selection has not eliminated the genetics that underpin same-sex attraction.

The research was based on data from more than 450,000 people of European descent who signed up to the UK Biobank, a long-term genomics project that has been a great help to health research.

It is based on recent studies, such as an article published in 2019 in Science, which stated that genetic variants somehow influenced homosexual behavior, although environmental factors were more important.

“We realized that in the past, people lumped all homosexual behaviors together… but in reality there is a spectrum,” Zhang said.

By combining participants' genetic data with their questionnaire responses, the authors concluded that the genetic signatures associated with homosexuality and bisexuality were, in fact, different.

– Historical persistence –

The study determined that genetic markers associated with bisexuality are also linked to a greater affinity for risk in male carriers, which probably favors more unprotected sex, since this same genetic marker is associated with a greater number of children .

The results “suggest” that these genetic markers “are likely to be advantageous for reproduction, which may explain their persistence in the past and predict their future prevalence,” the authors wrote.

This is explained by the fact that the same gene can carry several different characteristics. “We are talking about three traits here: number of children, risk taking and bisexual behavior, all of which share genetic elements,” Zhang explained.

On the other hand, genetic markers associated with homosexual behavior were correlated with fewer children when the carriers were heterosexual men, suggesting a gradual disappearance of these traits.

However, data from the UK Biobank also revealed that the number of people reporting both homosexual and bisexual behaviors has increased over the decades, due to increasing social openness.

The authors estimate, for example, that whether a person behaves bisexually or not is influenced by 40% by their genetics and by 60% by their environment.

The study “contributes to the diversity, richness and better understanding of human sexuality”, stated the authors. “It is in no way intended to suggest or support discrimination based on sexual behavior,” they added.