New research suggests that the sexual orientation of a man can be found in his DNA markers.
Through the leadership of UCLA’s Tuck Ngun, he and his team found that there are epigenetic markers, trait variations that occur due to environmental factors, that differentiate a homosexual and heterosexual male. His research included 47 pairs of identical twin males and he has found that nine parts of the genome can predict homosexuality. The accuracy of the prediction of forseeing one’s sexual orientation using these epigenetic markers is about 70 percent.
The findings were presented to the American Society of Human Genetics. The conculsions of Ngun’s team suggests that external influences can affect a man’s sexual orientation.
“To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers,” said Tuck Ngun, a researcher at the David Geffen School of Medicine at the University of California, Los Angeles, who led the study.
Those who are working in the study of epigenetics believe that the epigenome is created by external influences, and know that it is constantly changing over time. The present idea is that a person is shaped both by genetics and external influences, meaning that there is an interaction between nature and nurture. The fact that a huge number of sets of twins, of which one male was heterosexual and one was homosexual, suggests that there are environmental factors that influence a man’s sexual orientation.
“The relative contributions of biology vs. culture and experience in shaping sexual orientation in humans continues to be debated,” said University of Maryland pharmacology professor Margaret M. McCarthy, who was not involved in the current study, according to the LA Times. “But regardless of when, or even how, these epigenetic changes occur,” she added, the new research “demonstrates a biological basis to partner preference.”
Still, there is more work that needs to be done. Geneticists are still trying to find out what creates an epigenome, as well as the environmental factors of sexual orientation. Also, this research suggests a link, not a causation, which is significant when looking at the research. This could be a correlation, but not the actual reason for a male’s sexual orientation to be homosexual or heterosexual.
“Previous studies had identified broader regions of chromosomes that were involved in sexual orientation,” Ngun said. “But we were able to define these areas down to the base pair level with our approach.”
Further research needs to be done to know exactly what biological factors and epigenetics influence sexual orientation. Because this research is only with a small group of individuals, a more thorough study would require a much larger pool of people.
“To replicate and verify, you need a sturdy preliminary finding upon which to build and expand – and that’s not the case here,” wrote Ed Yong in his critique of the research for the Atlantic. He added that in Ngun’s situation, it may have been best if the research had not been pursued at all.
“Sexual attraction is such a fundamental part of life, but it’s not something we know a lot about at the genetic and molecular level,” Ngun said in an interview with NBC News. “I hope that this research helps us understand ourselves better and why we are the way we are.”