Most cells in our body, even during embryo development, don’t behave any different if they have XX or XY. The only exception is germ cells, which become either sperm or egg cells; these influence surrounding cells to produce different sorts of hormones (AMH and testosterone, and later estrogens, which are made from testosterone). These hormones only have relatively modest effects on body tissues: AMH blocks the formation of the uterus and Fallopian tubes in the embryo, and testosterone allows the Wolffian tubes to develop into sperm ducts and the prostate. Other than those “exist/don’t” actions, everything else is just a matter of stimulating or blocking the growth of certain tissues, or distorting their shape.
Nipples and breasts are just modified sweat glands, similar to those in the armpits and groins, but capable of producing a more enriched liquid. As with every other tissue, their development is exactly the same no matter the chromosomes, and their only response is to hormones. Since they must grow in response to estrogen, they don’t behave any differently during fetal development and until puberty. Theoretically, to do so, they should disappear in response to testosterone in the embryo, but obviously that doesn’t carry any benefit and thus there are no genes that perform this selection.
Yes, I’m aware this is satirical. But idk I’m bored and I just think this whole “idc if we are XX or XY, just give me hormones and I’ll do the thing” being canonical human biology is pretty based.
Most cells in our body, even during embryo development, don’t behave any different if they have XX or XY. The only exception is germ cells, which become either sperm or egg cells; these influence surrounding cells to produce different sorts of hormones (AMH and testosterone, and later estrogens, which are made from testosterone). These hormones only have relatively modest effects on body tissues: AMH blocks the formation of the uterus and Fallopian tubes in the embryo, and testosterone allows the Wolffian tubes to develop into sperm ducts and the prostate. Other than those “exist/don’t” actions, everything else is just a matter of stimulating or blocking the growth of certain tissues, or distorting their shape.
Nipples and breasts are just modified sweat glands, similar to those in the armpits and groins, but capable of producing a more enriched liquid. As with every other tissue, their development is exactly the same no matter the chromosomes, and their only response is to hormones. Since they must grow in response to estrogen, they don’t behave any differently during fetal development and until puberty. Theoretically, to do so, they should disappear in response to testosterone in the embryo, but obviously that doesn’t carry any benefit and thus there are no genes that perform this selection.
Yes, I’m aware this is satirical. But idk I’m bored and I just think this whole “idc if we are XX or XY, just give me hormones and I’ll do the thing” being canonical human biology is pretty based.