New research: The "gay gene" does not exist

It's been more than a quarter of a century since a piece of the human X chromosome called Xq28 created headlines that scientists finally found the "gay gene". But that message was false.

- In fact, the connections between genes and behaviors are extremely complicated, and that seems to apply to sexuality as well, says Niklas Långström, psychiatrist and researcher at the Karolinska Institute.

He is part of an international research group that has been looking for inheritance linked to same-sex sex in genetic databases that comprise almost half a million people - about 100 times more than previous studies of the same.

The researchers used genetic information from UK Biobank in the UK and from the genetic test company 23andMe in the US. Participants in the study stated, among other things, whether they had had sex with someone with the same sex.

The results show that five gene variants have a statistically reliable link to same-sex sex. Two of them are found in both men and women. Two exist only in men, and one exists only in women.

These gene variants have very little effect. Together, they account for less than one percent of the differences in human behavior in the issue of same-sex sex, according to a report in the journal Science.

Probably there are many more genes with a link to the differences - each of which has an extremely small effect.

- This means that a genetic test for same-sex sex is an impossibility. It is very clear. So that idea can be buried, says Niklas Långström.

He is well aware that the new findings can awaken strong emotions and be interpreted incorrectly. Same sex sex has previously been classified as a disease that should be cured and is still criminalized in more than 70 countries. This is the reason why the researchers made the extremely unusual decision to supplement their report with a fact box about what the results do not mean.

They state that: "Our results leave no room for discrimination based on sexual identity or attraction, nor do our results lead to any definitive information about the extent to which inheritance or the environment affects sexual preferences."

The new results are published in this week's issue of the scientific journal Science.