This suggests that testosterone is needed to “masculinize” a prenatal brain if that doesn’t happen, the child will grow up to desire men. Males with a genetic condition called androgen insensitivity syndrome can develop female genitalia and are usually brought up as girls, despite being genetically male – with an X and Y chromosome – and they are attracted to men. Ganna’s group found other gene variants that may be linked with sex hormone regulation, which other scientists have previously suggested plays a large role in shaping the brain in ways that influence sexual behavior.Ĭonditions in the uterus during pregnancy are thought to influence the sexual preferences of the child. I find it intriguing that some of the genes from men identified in Ganna’s study are associated with olfactory systems, a finding that has parallels to the work in mice. How might these genes influence same-sex behavior? This idea is further supported by the new study, which identified five new genetic loci (fixed positions on chromosomes) correlating with same-sex activity: two that appeared in men and women, two only in men, and one only in women. With multiple gene candidates being linked to homosexuality, it seemed highly unlikely that a single “gay” gene exists. Expressed in the brain, TRPC2 functions in the recognition of pheromones, chemicals that are released by one member of a species to elicit a response in another.
Male mice lacking TRPC2 no longer display male-male aggression, and they initiate sexual behaviors toward both males and females. Other studies have shown that disruption of a gene called TRPC2 can cause female mice to act like males. When the gene was deleted in female mice, they were attracted to female odors and preferred to mount females rather than males. A 2010 study linked sexual preference to a gene called fucose mutarotase. Genetic studies in mice have uncovered additional gene candidates that could influence sexual preference. So-called genome-wide association studies identified a gene called SLITRK6, which is active in a brain region called the diencephalon that differs in size between people who are homosexual or heterosexual. As the ease and affordability of genome sequencing increased, additional gene candidates have emerged with potential links to homosexual behavior. The 2019 study is the latest in a hunt for “gay genes” that began in 1993, when Dean Hamer linked male homosexuality to a section of the X chromosome. As the author of the book, “Pleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are,” I have done extensive research into the biological forces that conspire to shape human personality and behavior, including the factors influencing sexual attraction.Ī new study suggests that genes are responsible for between 8% and 25% of same-sex preference. I am a molecular biologist and am interested in this new study as it further illuminates the genetic contribution to human behavior. Nonetheless, misconceptions persist that same-sex attraction is a choice that warrants condemnation or conversion, and leads to discrimination and persecution. Rather, it is a continuum that emerges from a person’s genetic makeup.
Numerous studies have established that sex is not just male or female. and the U.K., they concluded that genes account for between 8% and 25% of same-sex behavior. By analyzing the DNA of nearly half a million people from the U.S. In a 2019 issue of Science magazine, geneticist Andrea Ganna at the Broad Institute of MIT and Harvard, and colleagues, described the largest survey to date for genes associated with same-sex behavior. However, biologists have documented homosexual behavior in more than 450 species, arguing that same-sex behavior is not an unnatural choice, and may in fact play a vital role within populations. Despite these numbers, many people still consider homosexual behavior to be an anomalous choice. In the U.S., 1% to 2.2% of women and men, respectively, identify as gay. Across cultures, 2% to 10% of people report having same-sex relations.