Born and Made to Live this Way: Part 3, Dad It’s All Your Fault
An understandably confusing aspect of LGBTQIA genetics is how LGBTQIA genes are passed from generation to generation if LGBTQIA people are less likely to have biological children. This confusion may lead an individual to dismiss born this way sentiments or feel affirmed in their understanding that people choose to be LGBTQIA. Any genetics unit in a general biology course touches on simple, dominant and recessive genes. Anyone with that background already knows having a gene doesn’t mean it’s expressed. The ways in which having genetic material that you don’t use, but your children do, expands once complex traits are introduced. One can absolutely inherent genes that increases the likelihood of developing a LGBTQIA identity, given the right environmental conditions, from straight cisgender parents, and vice versa.
My perspective, as a person with both a science education and lived experience in the LGBTQIA community, is that a heterosexual cisgender state is not a genetic default that is overridden by the expression of a single or multiple gay gene(s). Sexual attraction, romantic attraction, gender identity, or lack thereof, are complex traits that for the perceivable majority of the population shake out along a small stretch of a spectrum of genetic possibilities.
Giorgi Chaladze used a mathematical model to explore mechanisms of inheritance that might explain straight parents birthing gay boys in the Archives of Sexual Behavior in 2016. Chaladze looks at the X-linked inheritance model to explain the paradox of inherited homosexuality in men with a single X and a single Y chromosome. When there is a variation in a gene on the X chromosome, women may express a more commonly expressed version gene on their second (or rarely third) X chromosome and not be affected by the varied gene, but men are stuck with it, for better or worse. Women can have varied genes for the same trait on all copies of their X chromosome, but this is statistically less likely to occur. This inheritance model is used to explain red-green color blindness, which occurs far more frequently in XY men.
If this model also explains XY male homosexuality, one interpretation is that XX female homosexuality occurs far less frequently. Multiple surveys, censuses, and academic studies have found that is not true. Chaladze’s models also do not support an X-linked mechanism for gay inheritance alone. Men would also have to be carriers for the trait, in other words have the gay gene, but not be gay and then reproduce, in order to bring necessary statistical power to the model. I think trying to untangle questions about a single mechanism illuminates the larger LGBTQIA identity inheritance puzzle and encourages us to look for a few more pieces.
How many Americans are Gay:
Born and Made to Live this Way, Part One: “Baby We Were Born this Way”
I don’t think anyone outside of the more clueless science writers really believe in single-gene traits anymore. People who only remember Gregor Mendel from High School Bio still might.
Like most things it’s multi-factorial. One population genetics explanation that seems to me to make some sense is that a child with childless Aunts & Uncles has an advantage. This is pretty much impossible to test rigorously but it does make a nice just-so story.