Genetic links found to same-sex sexuality
Research ‘provides the clearest glimpse yet,’ co-author says
The largest study of its kind found new evidence that genes contribute to samesex sexual behaviour, but it echoes research that says there are no specific genes that make people gay.
The genome-wide research on DNA from nearly half a million U.S. and U.K. adults identified five genetic variants not previously linked with gay or lesbian sexuality. The variants were more common in people who reported ever having had a same-sex sexual partner. That includes people whose partners were exclusively of the same sex and those who mostly reported heterosexual behaviour.
The researchers said thousands more genetic variants likely are involved and interact with factors that aren’t inherited, but that none of them cause the behaviour nor can predict whether someone will be gay.
The research “provides the clearest glimpse yet into the genetic underpinnings of samesex sexual behaviour,” said coauthor Benjamin Neale, a psychiatric geneticist at the Broad Institute in Cambridge, Mass.
“We also found that it’s effectively impossible to predict an individual’s sexual behaviour from their genome. Genetics is less than half of this story for sexual behaviour but it’s still a very important contributing factor,” Neale said.
The study was released Thursday by the journal Science. Results are based on genetic testing and survey responses.
Some of the genetic variants found were present in both men and women. Two in men were located near genes involved in male-pattern baldness and sense of smell, raising intriguing questions about how regulation of sex hormones and smell may influence same-sex behaviour. Importantly, most participants were asked about frequency of same-sex sexual behaviour but not if they selfidentified as gay or lesbian. Fewer than 5 per cent of U.K. participants and about 19 per cent of U.S. participants reported ever having a same-sex sexual experience.
The researchers acknowledged that limitation and emphasized that the study’s focus was on behaviour, not sexual identity or orientation. They also note that the study only involved people of European ancestry and can’t answer whether similar results would be found in other groups.
Origins of same-sex behaviour are uncertain. Some of the strongest evidence of a genetic link comes from studies in identical twins. Many scientists believe that social, cultural, family and other biological factors are also involved, while some religious groups and skeptics consider it a choice or behaviour that can be changed.