- There is certainly no single genetic signature for determining same-sex sexual behavior.
- The conclusion is based on a large study that involved more than 493,000 people.
- Instead, there are a bunch of small genetic factors and environmental influences that affect sexual preference.
In 1993, scientists linked a genetic marker named xq28 to male homosexuality, giving rise to the controversial notion of a ‘gay gene’. However, those findings haven’t been replicated in decades of genetic research.
Numerous twin studies and examinations of inheritance of sexual orientation in humans have suggested that same-sex sexual behavior is associated with a genetic component. But no study has been able to detect particular genetic signatures.
Recently, a massive study on the genetic basis of sexuality revealed 5 genetic variants linked to same-sex sexual behavior. However, none of these variants are reliable enough to predict people’s sexual preference.
There’s No ‘Gay Gene’
The findings are based on a large study that involved more than 493,000 people from the United Kingdom, the United States, and Sweden. The aim was to analyze genes linked with sexual orientation and find whether sexual behavior can be explained by genetics.
Researchers didn’t find any evidence of a single ‘gay gene’. Instead, there are a bunch of small genetic factors and environmental and cultural influences that affect partner choice.
Out of the 5 genetic variants (that are found to be linked with same-sex sexual behavior), two were found in males, one in females, and two in both sexes. These variants are not rare in humans and have small effects. Together, they account for up to 25% of the variation in same-sex sexual behavior.
Reference: ScienceMag | DOI:10.1126/science.aat7693
Moreover, there is no evidence that sexual preference is linked with variants on chromosome X. In fact, same-sex sexual behavior — like other behavioral traits — is very polygenic, which means there are numerous variants that contribute to these traits.
We Need More Data
The findings may not be representative of the worldwide population. The genome data is obtained from the UK Biobank and 23andMe, a privately held personal genomics and biotechnology company based in California.
Their database mostly includes people from European ancestry. The median age of individuals in 23andMe’s database is 51, and UK Biobank participants were 40-70 years old. Moreover, the work doesn’t include gender and sexual minorities, such as intersex people and transgender people.
Although researchers have detected some genetic variants — called single nucleotide polymorphisms — associated with same-sex sexual behavior, they are not sure what these variants actually do.
One gene, for example, is related to smell that plays a role in sexual attraction. Another variant is linked with baldness in males – a trait affected by sex hormone levels.
Many uncertainties remain to be examined, such as how social and cultural factors affect sexual preference might interact with genetic influences.
Overall, human sexuality is a sensitive topic and explaining nuanced findings to the general public would be tricky.