There’s a common misconception that X and Y chromosomes determine whether you develop as male or female. In fact, all they do is determine is whether you develop ovaries or testicles, and the actual process of male or female development appears to be entirely driven by hormones, with genes playing no role whatsoever apart from determining whether you develop ovaries or testicles. We know this, because there are certain conditions which either cause the process of gonadal development to go wrong, or prevent that person’s body from responding to the hormones they produce. In that situation, you end up with people who are genetically male, but have developed as female, who look and behave just like ordinary women (to the point where the condition often isn’t spotted until they reach their teens, and fail to start menstruating).
This dependence on hormones has an important consequence: it’s possible to get into a situation where you had hormone levels intermediate between male and female, or typical f your genetic sex for parts of your prenatal development but closer to those of the opposite genetic sex for other parts. In those situations, you end up as a person who has a mixture of male and female characteristics. Exactly what ends up gender blended depending on how far into your prenatal development your hormones went wrong, and for how long the abnormal hormone situation continued. If the abnormal hormone situation occurs in the first trimester, the main thing affected is your genitals and your physical sex, since that’s the critical period when genital development and reproductive organ development takes place. If the abnormal hormone situation occurs later in the pregnancy, the main effects are on the brain, since brain development is ongoing throughout the pregnancy, and most of the important differences between male and female brains appear to arise during its second half.
For some time, I’ve been trying to draw people’s attention to the fact that doctors appear to be inadvertently creating transgender people, through the use of high dose hormone treatments often given to pregnant women thought to be at risk of miscarrying or going into premature labour. Most (or all) of the exposure to these hormone treatments tends to happen after the end of the first trimester and during the critical period for sex-specific brain development. From my own experiences and from chatting to other hormone-exposed people, this is something that appears to have happened on quite a large scale in the 1950s, 60s and 70s, producing both MTF and FTM transgender people (as well as nonbinaries such as myself), due to the use of an artificial estrogen called DES, and the first generation members of a class of hormones called progestins, which turned out to be powerful androgens in female fetuses. In the one study of DES and gender that’s ever been conducted around a third of the “DES sons” in the study identified as female rather than male. If that carries through to the general population, it means there must be several million of us at least, since DES was used in the region of 10 million pregnancies worldwide, often with progestins prescribed alongside it.
DES and the androgenizing progestins had all been withdrawn from use during pregnancy by about 1980, however the fact that the medical industry have managed to keep the existence of medically induced intersex and transgender from that earlier era completely hidden from the public, gives me no confidence that they’re not continuing to do the same with some of their newer hormone treatments that are still in use.
Also, the hormones used in contraceptive pills and injections are all from that earlier era (or have similar properties). If exposure to them occurs during pregnancy, there’s a high likelihood of producing an intersex or transgender baby. Yet women given hormonal contraception aren’t told of the risk of that happening if they happen to fall pregnant and continue using the contraceptives while pregnant.
I also think it’s important that doctors and the pharmaceutical industry aren’t allowed to get away with wrecking people’s lives on such a scale, and then walking away from it as if nothing happened. It makes me wonder how many more of the mysterious chronic ailments that afflict people in Western countries are actually due to something doctors have done, and then subsequently covered up!