Have you ever wondered why some people are gay or trans? I went down that rabbit hole a while ago and here is what I learned - Although no one knows for sure the reason, researchers believe that it stems from “a biological imprint of the brain that is established during fetal development and is immutable.” In other words, it's not a choice... and the field of study relating to this is commonly revered to as “Epigenetics”.
For most of my life, I was taught that being gay was a choice and that there was no scientific proof of a "gay gene." In fact, for many years it was believed that gayness was attributed to bad parenting (so sad and so wrong!!)
In 1958 someone observed that homosexual men tended to have a greater number of older siblings. It wasn’t until nearly 40 years later that researchers Ray Blanchard and Anthony Bogaert studied a “very large and historically significant data base” and found that each older brother increased the odds of homosexuality in a later-born brother by 38 to 48%. This suggested that a prenatal mechanism was the cause of increased homosexuality. Interestingly, subsequent research has found that the affect does not apply to left-handed men, nor does it apply to women.
In 2018 Jacque Balthazart tied the effect to a chemical called Neuroligin which is a protein found in the NLOGN4Y chromosome which is believed to be tied to both homosexuality and autism in male offspring. Long story short, it seems there IS a gay gene and it governs a lot more than just sexual attraction. (Seriously, Google it...) Some have postulated that this is a product of evolution. If a woman bore enough male children to perpetuate the species, then that same mother would need a tender, sensitive child to care for her later in life. Biology stepped up and produced homosexual children as a solution.
It is not known if this effect applies to transgender persons but the science leans in that direction. Brain scans of cis-gendered women and trans-women are virtually identical and very different from brain scans of heterosexual men. I am the oldest of five siblings, so I clearly do not owe my trans-ness to the fraternal birth-order effect. In fact, only about 15% of gay men do, but its existence is the catalyst for the research that I’m confident will eventually lead to more answers.