In 1993, Dean Harmer, a geneticist at the National Cancer Institute in the US, published a paper revealing the discovery of a “gay gene”.
Dean Harmer analysed the genetics of 114 homosexual men and their families. They observed that their maternal cousins and uncles had increased rates of same-sex orientation, but their fathers and paternal family did not. Harmer observed that the X chromosome Xq28 was more prominent in brothers who were both gay. These findings were replicated by researchers at Northwestern University in 2014. The study looked at 409 pairs of homosexual twins and found a significant link between Xq28 and same-sex relationships.
For more than twenty years after the publication of Harmer’s study, research institutions and universities across the world attempted to replicate the findings to no avail. This would suggest that the original study and the subsequent Northwestern University study were outliers. It is also highly unlikely that a single gene could cause a behavioural pattern as complex as same-sex attraction. Complex behavioural phenotypes usually stem from a large number of genes interacting and working together to build a behavioural pattern.
[P1] The Xq28 gene dictates same-sex attraction. [P2] People are either born with the gene or they are not. [P3] Therefore, people are born gay.
Rejecting the premises
[Rejecting P1] A single gene cannot explain as complex a behavioural pattern as same-sex attraction.