Causes of gay and lesbian

By Sara Reardon.

Causes Of Homosexuality: Past And Present Understandings

Controversial results released in suggested a genetic link between bisexuality and risk-takingbut many researchers found flaws in the methodology. Few aspects of human biology are as complex—or politically fraught—as sexual orientation. Now a new study claims to dispel the notion that a single gene or handful of genes make a person prone to same-sex behavior.

The analysis, which examined the genomes of nearly half a million men and women, found that although genetics are certainly involved in who people choose to have sex with, there are no specific genetic predictors. Yet some researchers question whether the analysis, which looked at genes associated with sexual activity rather than attraction, can draw any real conclusions about sexual orientation.

The handful of genetic studies conducted in the past few decades have looked at only a few hundred individuals at most—and almost exclusively men. Other studies have linked sexual orientation with environmental factors such as hormone exposure before birth and having older brothers.

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. In the new study, a team led by Brendan Zietsch of the University of Queensland, Australia, mined several massive genome data banks, including that of 23andMe and the UK Biobank 23andMe did not fund the research.

They asked more thanparticipants whether they had ever had sex with someone of the same sex, and also questions about sexual fantasies and the degree to which they identified as gay or straight. The researchers found five single points in the genome that seemed to be common among people who had had at least one same-sex experience.

Two of these genetic markers sit close to genes linked to sex hormones and to smell—both factors that may play a role in sexual attraction. But taken together, these five markers explained less than 1 percent of the differences in sexual activity among people in the study.

When the researchers looked at the overall genetic similarity of individuals who had had a same-sex experience, genetics seemed to account for between 8 and 25 percent of the behavior. The rest was presumably a result of environmental or other biological influences.

The findings were published August 30,in Science. Despite the associations, the authors say that the genetic similarities still cannot show whether a given individual is gay. The research has limitations: almost all of the participants were from the U. Still, researchers welcome the data.

The study will causes of gay and lesbian be the last word on the vexing question of what causes homosexuality, however. In geneticist Dean Hamer of the U. But Hamer, now retired, disagrees. His study, which analyzed the genomes of 40 pairs of gay brothers, looked exclusively at people who identified as homosexual.

He sees the new paper as an analysis of risky behavior or openness to experience, noting that participants who engaged causes of gay and lesbian at least one same-sex experience were also more likely to report having smoked marijuana and having more sexual partners overall.

Hamer says that the findings do not reveal any biological pathways for sexual orientation. Rice and Vilain agree that the conclusion is unclear. A more detailed questionnaire that looks at more aspects of sexuality and environmental influences would allow the researchers to better pinpoint the roots of attraction.

The authors say that they did see links between sexual orientation and sexual activity, but concede that the genetic links do not predict orientation. Nevertheless, Hamer and others praise the new contribution to a field that suffers from a dearth of good studies.

Subscribe to Scientific American to learn and share the most exciting discoveries, innovations and ideas shaping our world today. August 29, 4 min read. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing.

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