• CADmonkey@lemmy.world
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    1 year ago

    Human embryos (and probably others) start out female, and grow the male parts a fee weeks later. There is probably someone lurking who can give better details but that’s the gist of it. Thats why men have nipples.

    • LillyPip@lemmy.ca
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      1 year ago

      You pretty much nailed it.

      Also, it gets much more complicated than that; at least 2% of humans are intersex, meaning they’re a mix of male and female, everywhere from outward presentation (rare) to chromosomal (more common).

      It’s not just gender that’s a spectrum: sex is, too. I said ‘at least’ because it’s possible for people to go their whole lives without realising they’re intersex. 2% is huge: if you know 100 people, statistically 2 of them are intersex. Most of us know more than that.

      The ‘only two genders’ thing is biologically bullshit. Biology is never cut and dried.

      eta: for reference, I have a disorder that’s been in the spotlight lately – Ehlers-Danlos – and you’ve probably at least heard of it. You’ve likely talked to someone who has it recently. It occurs in 1 in 20,000 people. Again, roughly 1 in 50 have intersex traits. I wish this had the visibility it deserves. It’s exceedingly normal.

    • meowMix2525@lemm.ee
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      1 year ago

      Yeah the Y chromosome doesn’t kick in until later in fetal development.

      There’s actually a surprisingly small amount of biological information stored on the Y chromosome, IIRC the vast majority lies on the X.

      • Tlaloc_Temporal@lemmy.ca
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        1 year ago

        There’s only around 700 genes in the Y chromosome, with only about 70 actually making proteins. Compare the X chromosome with about 800 protein-coding genes and 20-25,000 total genes.

    • douz0a0bouz@midwest.social
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      1 year ago

      About the nipples. You’re right in that we all get them by default. As I understand it the only reason males keep them is because evolutionarily it would take more energy to remove them than keep them. Basically we’re all slackers at the genetic level.