The idea of identifying a genetic basis for homosexuality has sparked debate for more than a quarter of a century and recent findings, cautiously presented by a team of geneticists from Harvard University at the annual meeting of the American Society of Human Genetics on 19 October in San Diego, California, are no exception (1). The major difference is that this new research was based on a much larger dataset ― both DNA and behavioural information for hundreds of thousands of people provided by the massive UK Biobank, a long-term study to assess the genetics of disease, and 23andMe, a privately-held personal genomics and biotechnology company ― compared to previous studies.
Some question the relevance of even asking such questions but most of the controversy tied to this type of research lies in the fact that some sexual behaviours are still illegal in many countries and sadly, could lead to a “witch hunt” in more conservative communities. To avoid potential misuse of the results, the team of behavioural scientists from the US, UK, and Sweden claims to have been extremely careful in the wording their research questions. What they refer to as “non-heterosexual behaviour” includes “a large spectrum of sexual experiences, that go from people who engage exclusively in same-sex behaviour to those who might have experimented once or twice.”
The researchers searched for specific variations in DNA that were more common in people who reported at least one same-sex sexual experience based on a genome-wide association study (GWAS) and identified four variants on chromosomes seven, 11, 12, and 15. Two variants of those variants were shown to be specific to men who reported same-sex sexual experiences and the other variant is located on chromosome 11 in a region with an abundance of olfactory receptors. Interestingly, olfaction ― which is responsible for our sense of smell ― is also thought to play a large role in sexual attraction.
Lead researcher Andrea Ganna, a research fellow with the Broad Institute in Cambridge, Massachusetts and Harvard Medical School emphases that the work does not identify a ‘gay gene’ but rather, highlights the complexity of sexual behaviour which cannot be tied to a specific sequence of DNA and is more likely to be the result of numerous genetic traits and environmental factors are even more likely to play a significant role in which traits wind up correlating with sexual orientation, according to Science magazine. In fact, the recent results disprove a previous much smaller study that suggested a segment of DNA on the X chromosome is linked to inherited homosexuality.
The findings are being hailed by some geneticists as a significant step in understanding the role of genes in sexuality. However, others are asking a possibly more poignant question: why do we need to this research in the first place? Critics argue the study has not done enough to “explore the nuances of how one’s sexual identity differs from sexual behavior” and worry that the study could be used to “stigmatize members of the LGBTQ community.”
Such a contentious topic of research may be better off shelved since perhaps the risks outweigh the benefits of deciphering the genetic code of human sexuality. Unfortunately, the results could end up causing more harm than good.
(1) Ganna, A. et al. PgmNr 278: Large genome-wide analysis of sexual orientation identifies for the first time variants associated with non-heterosexual behavior and reveals overlap with heterosexual reproductive traits. Proceedings of the American Society of Human Genetics annual meeting (2018).
(2) Hamer, D.H.. et al. A linkage between DNA markers on the X chromosome and male sexual orientation. Science (1993). DOI: 10.1126/science.8332896