A new study has found further evidence that there is a link between a gay man’s genetic makeup and his sexual orientation. According to researchers at Northwestern University, gay men are likely to share genetic signatures on part of the X chromosome – Xq28. This is not as simple as a gay gene, they warn, but another significant indicator that there are biological factors influencing sexual orientation. Dr. Michael Bailey explains the results:
BAILEY: Sexual orientation has nothing to do with choice. Our findings suggest there may be genes at play – we found evidence for two sets that affect whether a man is gay or straight. But it is not completely determinative; there are certainly other environmental factors involved. The study shows that there are genes involved in male sexual orientation. [...]
We don’t think genetics is the whole story. It’s not. We have a gene that contributes to homosexuality but you could say it is linked to heterosexuality. It is the variation.
This jibes with other research that found environmental factors in the womb likely also have an effect on sexual orientation. For example, a Canadian study found that men with older brothers are more likely to be gay, which suggests maternal biological changes that happen with each additional son. Another study identified sex-specific genetic markers called “epi-marks” that can be triggered during fetal development, causing fluctuations in the DNA expression that impacts sexual development.
It’s becoming increasingly clear that there is not a precise answer to what causes a person to have a particular sexual orientation, but there are a variety of biological functions at work, most of which seem to play out before an individual is even born.