Quote from: rachel89 on October 08, 2015, 03:54:49 PM
Is "trans-ness" partly genetic? I know a trans-person and their child (young adult) is also trans. I am being as nonspecific as possible for privacy reasons.
The answer is, it can be. Certain genetic conditions can cause your prenatal hormone production to go wrong, which can affect both your physical sexual development and also prevent masculinization of the brain from taking place (or, in the case of FTMs, cause it to happen inappropriately). Some examples of genetic conditions that can interfere with normal sexual development are: having an XXY karyotype (which can produce male-assigned people with an incompletely masculinized brain); and congenital adrenal hyperplasia (CAH), in which genetically female people can end up with a masculinized brain). Because they all tend to act throughout the pregnancy, in these and other genetic intersex conditions, usually there'll be signs of a physical intersex condition along with the discordant gender identity. I don't know whether it's definitely the case, but the impression I've gained is that with both XXY and CAH, you're more likely to end up with a nonbinary identity rather than a fully transgender one. XXY is a known cause of being trans though, for instance Caroline Cossey is a famous transgender icon who is XXXY (being XXXY has similar effects to XXY, except it causes even greater feminization).
Another thing that can cause the process of sexual development to go wrong is exposure to external hormones. Some examples of this are xenoestrogens in the environment (which can cause male fish and amphibians to end up intersexed or even completely female); and progestin-induced virilization, in which certain artificial hormones used as medicines in the 1960s and 70s turned out to have androgenic effects on female fetuses, and caused baby girls to be born with genitals that had undergone varying degrees of male development.
In general, hormones and chemicals with estrogenic properties cause female development in biologically male fetuses, while those with androgenic properties cause male development in biological females.
A couple of people have already mentioned DES, which is a powerful artificial estrogen that, between 1940 and about 1980, was widely used as a treatment for preventing miscarriages. The official line has always been that the male assigned children who were exposed to DES in the womb suffered virtually no ill effects as a result of their exposure, however, from what I've seen, that's a total lie, and it's caused very high rates of intersex-related abnormalities (with is of course, exactly what you'd expect to happen, considering that estrogens are known to cause female development in biological males across most of the animal kingdom). It's just that so many people were exposed to it, and the public at large regards intersex conditions with such horror, that nobody wants to admit to it and the whole thing has been swept under the carpet.
Due to the way DES was typically prescribed, by far the heaviest exposure tended to happen during the later stages of the pregnancy, after genital development has finished and when the main thing still ongoing is brain development. The result, at least from what I've seen, is that it's generally produced people with a relatively normal male appearance, but whose brains have predominantly developed as female instead of male. Considering how many people were exposed to DES and how few know about it, I think it could well be the main thing causing MTF transsexuality in the over 40s age group. Laura Amato of Laura's Playground is a DES babe, as is Dr Dana Beyer (who blogs on transgender issues for the Huffington Post, and was one of the researchers involved in the one study of DES and gender that's ever been conducted). There's quite a few people with known or suspected DES exposure here at Susan's too.
A number of studies show that DES exposure has transgenerational effects, i.e. not only the children who were exposed to it in the womb have problems, but their own children have unusually high rates of similar abnormalities too. There's various theories as to why this happens, but I don't think any clear answer has been identified as yet. It might well result in families where you have both children and grandchildren who are transgender though.
