Louden Wilde
Muse
Sex is also variable. There are configurations of chromosomes like XXY, XXX, X, XYY, and so forth. And other species use completely different non-XY sex-determining systems.
Here's a good video I watched recently explaining it: https://youtu.be/of7vrIIcTa0
Once again the platypus is a freak.![]()
That's true (that there are a small number of people with alternate sex chromosome arrangements), but you're conflating deleterious (harmful) mutants with natural variation. In humans (and most eutherian mammals) those alternate configurations cause other health issues. Note that you can find harmful mutations that eliminate pretty much any human characteristic.
There are a few rodent species that lack a Y chrom, but otherwise they show similar sexual development. Since a definition of sex has to work in a comparative/historical context (since it's clear it's the same process), we use gamete type/organization of the body around producing that gamete as a definition
If a person is fertile at any point in their life, it's because they are able to produce oocytes or sperm. If not, they are not relevant to a definition of sex.
Here's a more long-winded version of the definition I and many biologists use:
Sex is a biological concept. Asexual reproduction (cloning) is routine in microorganisms and some plants, but most vertebrates and all mammals have 2 distinct sexes. Even single-cell organisms have “mating types” to facilitate sexual reproduction. Only cells belonging to different mating types can fuse together to reproduce sexually (2, 3). Sexual reproduction allows for exchange of genetic information and promotes genetic diversity. The classical biological definition of the 2 sexes is that females have ovaries and make larger female gametes (eggs), whereas males have testes and make smaller male gametes (sperm); the 2 gametes fertilize to form the zygote, which has the potential to become a new individual. The advantage of this simple definition is first that it can be applied universally to any species of sexually reproducing organism. Second, it is a bedrock concept of evolution, because selection of traits may differ in the 2 sexes. Thirdly, the definition can be extended to the ovaries and testes, and in this way the categories—female and male—can be applied also to individuals who have gonads but do not make gametes.
Note that there are a lot of differences between the two mammalian gamete types besides size (e.g. many features of chromatin organization and epigenetic marks, stored gene products - the oocyte having all those necessary for the first cell division or two).
So while initiators of sexual development (multiple kinds of genetic and environmental systems) varies across taxa/species, it does not suggest that there are more than two human/mammalian sexes (nor in any vertebrate, I believe)
Apologies to all those who have gotten sick of me reiterating these points. That's how I first became aware of this whole mess - people (whom I didn't realize at the time fancied themselves furthering trans-rights) with a poor understanding of repro/comparative bio posting misleading/false statements.
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