Gay pride, genes and brains

This post is part of the Diversity in Science Pride Blog Carnival: Pride Month 2011 edition.

Having grown up very early on as both an avid student of Darwin’s ideas and an earnest follower of the Roman Catholic faith, puberty posed for me a painfully confounding paradox: how could a nice church-going boy who read biology text books for fun find himself attracted to the same sex, an implausible urge that both my religion and science deemed abnormal and maladaptive? Hormones and peer-pressure can make life a bit problematic for many teenagers, but for a gay one who made sense of his world through the lens of biology and Catholicism, life suddenly became unfathomably perplexing, and quite depressing.

But it was biology that would help rescue me from the emotional tailspin. It was in the early 1990s that two highly publicized studies came out on biology and sexual orientation. These were Simon LeVay’s brain structure studies and Dean Hamer’s genetic linkage studies of gay men.

LeVay published results in 1991 that indicated differences in the structure of a small part of the brain when comparing the brains of homosexual to heterosexual men. The difference was reported to be in the third Intersitial Nucleus of the Anterior Hypothalamus (INAH3). This small bundle of neurons was more than twice as large in heterosexual men as it was in homosexual men. The reduced size of INAH3 was also observed in heterosexual women.

Figure of the INAH3 region of the hypothalamus courtesy of simonlevay.com.


In 1993, Hamer and colleagues published a study of a linkage analysis among gay men. The report indicated that among the gay male subjects, there was a higher frequency of gay male uncles and cousins on the mother’s side than on the father’s side of the family, suggesting there might be maternal inheritance of genetic determinants of homosexuality. The study went on to test for X chromosome linkage among the gay subject, and found a linkage between homosexuality and a stretch of the X chromosome called Xq28.

Figure of the X chromosome and the Xq28 region courtesy of NCBI.

Both these studies resulted in a frenzy of media coverage, with headlines about “the gay brain” and “the gay gene” splashed across magazine covers and newspaper front pages. For a young student of biology, it was always thrilling when science made its way to the top stories in the news. But this time it was personal. These studies told me that there might be a biological basis for the variation in sexual behavior among humans. And that if it was in the genes and in the brain circuitry, and thus not a choice as many proposed, why struggle and suffer needlessly to change it?

Of course, these studies had their critics. The LeVay brain data showed a correlation, but did not clarify if the brain structure variations were the cause or result of homosexual behavior. And the Hamer study never actually pinpointed to a specific gene allele that determined sexual orientation, but to a whole region of the X chromosome, and while some studies recapitulated the results, others did not, as is often the case in studies on the genetic underpinnings of such complex traits as human behavior. Still, the studies came out at the right time for me to come out. Not only did the findings appeal to my scientific way of thinking, but they also brought the talk of sexual orientation out into the open, on the news, on the covers of mainstream magazines, and into the lab and the world of biology.

Of course the coming out process did not magically become a piece of cake for me. But as a young scientist in the making, Dean Hamer and Simon LeVay were heroes to me, and their timely publication of their results made an unintended but hugely positive difference in my life.