Re:Mixed up: Biological Gender vs. Feminization
by snowgirl (978879)

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Ah... such a simple world you live in. One baby has a Y, and it's male, and the other has an X, and it's female.

Actually, it's the SRY (sex determining gene) on the Y chromosome that initiates... I said INITIATES sexual distinction in males. Without this gene, the germ cell line "stripe" turns into ovaries. If there is a mutation in this gene, you will get an XY female with ovaries. If this gene is present and there are no mutations in this gene, then the germ cell line "stripe" becomes testicles.

The testicles produce androgen. Androgen drives the external development of the genitalia. If there is insufficient androgens, or insufficient response to androgens then the scrotalabial folds become labia, and the clitoris/penis precursor becomes a clitoris. If there are sufficient androgens, and response, the scrotalabial folds fuse into a scrotum, and the clitoris/penis precursor becomes a penis. The development of the external genitalia can also vary anywhere along a continuum between the two.

Separately, the testicles produce Anti-muellerian hormones, which prevent the development of the muellerian ducts, namely, the upper vagina, cervix, uterus, and fallopian tubes. If there is insufficient AMH, or insufficient response, the fetus will develop such organs regardless of the genetic makeup of the child, regardless of the external appearance of the genitalia. YES, there are MEN with UTERUSES, if they're AMH resistant.

Now... notice that none of this depends upon estrogen levels. That's because the mother floods the bodies of all children with estrogens. However, it's heavily dependent upon hormones that are produced in the testicles. There a number of chemicals that block androgens, and these result in birth defects, which is why you get in ads for things like Rogaine "pregnant women should never even TOUCH these pills."

There a hojillion different ways to define "biological sex" and none of them are conclusive, and none of them are guaranteed. There are women with XY, and men with XX (and they were born that way, and assigned their sex by doctors), there are women with high androgen levels (5-alpha-reductase deficiency) and men with low androgen levels, there are women with testicles, and men with ovaries, there are women without uteruses, and men with uteruses. The only thing left to define men from women biologically, is external genitalia... and that can be surgically altered.

So, seriously... you don't know anything... I hope this short lesson on sexual distinction in humans helps you out.