Scientists have recently discovered two gene variants that are more common in gay men than straight men, adding to the evidence that homosexuality is, at least, partially genetic. This news may actually sound familiar to you, as studies in the early ‘90s also identified regions on the 8th and X-chromosomes that were correlated with homosexuality. But the genes identified this time are on the 13th and 14th chromosomes, and it’s the first time ever scientists have identified specific genes, not just a region on a chromosome that could be correlated with sexuality.
The genes were found by comparing the DNA of 1077 gay men with the DNA of 1231 straight men, looking for variations as small as a single nucleotide. The gene on chromosome 13, called SLITRK6, is active in a region of the brain called the diencephalon; that same region contains the hypothalamus. The SLITRK6 gene has been shown to be active in the hypothalamus of male mice fetuses days before they’re born, which is thought to be a crucial time for sexual differentiation.
The other gene scientists identified is called TSHR, and it’s mainly active in regulating the thyroid, an endocrine gland in your neck. The thyroid releases hormones that control your metabolism, and there is a thyroid condition where the TSHR gene doesn’t function, leading to an overactive thyroid and weight loss. This condition, called Grave’s disease, is more common among gay men.
So these recently pinpointed genes fit nicely with past research, but it’s possible to have these variants and not be gay. By our current understanding homosexuality is influenced by many genes, each having a small effect. And the environment probably plays a role too.