A website called Hormones Matter have just published this article on my behalf:
https://www.hormonesmatter.com/synthetic-hormones-pregnancy-gendered-brain-development/In it, I talk about the discovery 60 years ago that
a) the brain has a sex that arises during prenatal development and, once set, remains like that for life
and
b) the sex of the brain is determined by hormone levels during prenatal development, not by genetics.
The discovery became known as the organizational-activational hypothesis. I found a pair of slides illustrating one of the early experiments used to demonstrate it, involving manipulating hormone levels during the critical period for rat brain development (through castration or by injecting testosterone). Basically, what those experiments show is that you can produce male rats with female brains through castration at the appropriate time, or females with male brains. Similar experiments with similar results have been carried out on numerous other animal species, including Rhesus monkeys, which are one of the closest animal models to human beings.
Unfortunately, news of that discovery never filtered through to the world of medicine, where doctors have been giving pregnant women synthetic female hormones (estrogens and progestins) ever since WW2 ended, for miscarriage prevention and for various other medical reasons. In adult men, these drugs act as chemical castration agents, and the way they're administered causes the foetus to be exposed during the critical period for sex differences in the brain. Therefore you'd expect them to be producing male bodied people with female brains, which is certainly what seems to have happened with the earliest of them, the artificial estrogen DES. DES is no longer used, however I think there's a very real possibility it could be happening with the drugs that replaced DES, since they also are artificial female hormones, and also have testosterone suppressive properties in adult men.