By examining just a handful of sites along the genome and determining whether they are methylated, scientists can peg sexual orientation with nearly 70 percent accuracy. That’s according to data presented today (October 8) at the American Society of Human Genetics meeting.
“People have been looking for gay genes for 20 years and haven’t been really able to identify them, in spite of the fact that there’s interest,” Sergey Gavrilets, a professor of evolutionary biology at the University of Tennessee in Knoxville who was not involved in the study, told BuzzFeed News. “The existing evidence that we have now does point very strongly towards the significant role of epigenetics in homosexual orientation.”
Gavrilets and a pair of colleagues proposed the idea of epigenetics influencing sexual orientation several years ago. In the latest work, Eric Vilain, a neuroscientist at the University of California, Los Angeles, postdoc Tuk Ngun, and their colleagues scanned through the genomes of 47 male twin pairs. In 37 pairs, one of the brothers was gay and in 10 pairs, both brothers were gay. The researchers found that the methylation status of nine regions in the genome could identify sexual orientation with 70 percent accuracy.
“This study provides a major step forward in our understanding of how the brain can be affected by factors outside of the genome. It is also possible that the experience of being a homosexual or a heterosexual has itself impacted the epigenetic profile,” Margaret McCarthy, who studies sex differences in the brain at the University of Maryland School of Medicine, said in a statement. “But regardless of when, or even how, these epigenetic changes occur, their findings demonstrate a biological basis to partner preference.”