Biology is complex and resistant to neat little boxes with labels. In the debate, i.e. one side spouting unsupportable accusations and the other talking about the medical and biological realities of being trans, the terms biological sex and chromosomal sex are bandied about. Let’s not even start with birth certificates and the issues there.
Supposedly the body is male or female, nothing more complex. Why isn’t this true?
At the eighth week of gestation the gonads, which are coded for in the genes, start producing sex hormones. That production affects the proto reproductive organs, which up to now were neither male nor female (but more like a female than a male), and those organs start to develop. The body itself is quite sensitive to estrogens and androgens and also starts developing differently. Some time later this include the growing brain tissue.
Outside of the gonads, nothing else really knows much of anything of what the encoded sex is. The proof? Consider the intersex conditions complete and partial androgen insensitivity syndrome. These chromosomal males develop with some or all of the external genitalia of a female. Internally the fallopian tubes and ovaries are not present. There can be a vestigial uterus, enough that there are some cases of CAIS males carrying a baby to term.
The resulting children are raised female and the internal issues are only discovered when they never get their period. They live their entire lives as female (barring a transgender issue) and have the body development of a female.
This reality, that the body is responsive to sex hormones and not so much to the chromosomes beyond the creation of gonads, is why cross sex hormone therapy works at all. Without estrogen receptors in the MtF person, breasts would not develop, the skin would not change, and body fat would not redistribute.
Nature is very conservative as well. The same hormonal pathways in the pituitary lead to the production of sperm and eggs. LH and FSH signal the gonads.
There are many intersex conditions as a result of development and sometimes external influences (e.g. DES). Intersex conditions affect about 1% of the population and vary from extremely minor such as my having an undescended testicle that never resolved itself, to conditions like PAIS, CAIS, Mayer-Rokitansky-Küster-Hauser syndrome and Swyers syndrome which are very impactful.
The above just covers what can happen to XX and XY embryos. Unfortunately that isn’t all that makes neat boxes labeled male and female insufficient for some people. There are a number of chromosomal abnormalities including single X, klinefelters, turners, and many more that lead to developmental problems as well as the ability to function without intervention.
Chromosomal sex is often not a constant in the body. Many babies are conceived with a fraternal twin of the opposite sex. Some of those end up with one baby integrating the other one. The result is a chromosomal mosaic where parts of the body are XX and parts XY. The development is still determined by the tissue that develops into the gonads with the caveats under biological sex.
Relationship between genetics and transgenderism
Of identical twins where one twin is trans, around 30% of the other twins are trans as well. I saw another quote of 39%, the first was from my therapist who follows the literature and I tend to trust that.
The correspondence in fraternal twins of the same or opposite sex is basically zero. This clearly says two things. Genetics affects the predisposition to be transgender, and how the children are raised has little to do with it since twins of the same sex are raised together with the same environment.
Why being transgender is not a delusion
Outside of people with genuine issues like schizophrenia, transgender adults have a normal view of the world with the exception of their internal gender. There is a much higher incidence of depression, anxiety and in far too many cases of suicide attempts or, unfortunately, successes.
The other side of this is what happens when someone transitions. Generally they become much happier people and don’t feel the internal struggle anymore.
The flip side of the argument is talking about intersex people and identified gender. Until recently, children born with ambiguous genitalia were simply made into girls, and that because the surgery is simpler. The babies obviously weren’t consulted as to whether they were girls or boys. This practice is ending because the resulting children often were similar to trans children and felt like they were treated, living and had the physicality of the wrong gender.
Another piece of evidence often talked about are the Riemer twins. Identical twin boys were born, but David had a botched circumcision and the decision was made to surgically change him to female and raise him as a female. David later on decided to transition and live as a male. It’s hard to argue he was delusion since he was genetically male and had male gonads and male development.
What you can say to doubters?
Not much because it is rare that these feelings come from a truly rational place. They won’t be swayed by these arguments because they are convinced in their hearts that we are a kind of perversion. It doesn’t have to be religious and frankly both progressives and conservatives can have the issue.
If you run across the rare person who feels like this and actually has an open mind you can talk about the evidence, otherwise just walk away.