let me hear your voice tonight (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
alexseanchai) wrote2014-08-17 06:43 pm
alexseanchai) wrote2014-08-17 06:43 pm
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I can make the math of sex chromosomes work for a two-sex species like humans. I can make the math work for a four-sex species: XXZ and XXW are one sex, YYZ and YYW are another, XYZ is a third, XYW is a fourth. This math also works for a six-sex species, obviously. Three-sex species, which is where I'm trying to make the math go? Not so much.
Halp.
(I am contemplating gender roles for a three-sex species, assuming the vast majority of people of that species, like the vast majority of humans, are cisgender. I keep running into the fact that humans, at least white USAian humans, tend to conceive of gender roles as binaries, not trinaries.)
Halp.
(I am contemplating gender roles for a three-sex species, assuming the vast majority of people of that species, like the vast majority of humans, are cisgender. I keep running into the fact that humans, at least white USAian humans, tend to conceive of gender roles as binaries, not trinaries.)
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Also, are parents of all 3 genders needed for reproduction, or can 2 reproduce possibly with some restriction on possible offspring genders? (Alternately, you could have 2 parents being gamete givers and the 3rd carrying the baby to term, as IIRC is hinted in The Gods Themselves.)
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Just figuring out how to get to three sexes out of combos of sex chromosomes. I thought of another way to manage six--XX, XY, XZ, YY, YZ, ZZ--but that still doesn't get to three.
The way I'm figuring is egg-producer, sperm-producer, gestator; I've never read The Gods Themselves that I recall but I must have encountered the concepts therein at some point.
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ETA: the third sex could also be like worker bees, without a lot of gender markers at all, with the other two sexes being highly feminine (as defined by the society) and highly masculine (as defined by the society).
didn't see your edit at first
Hm, maybe...but one would expect the third sex then to be pretty rare comparatively, like intersex people are in our society, and that doesn't really suit what I'm trying to work out wrt gender relations in this species.
Yeah, I know that, but I'm trying to sort out how this species' societies react to the concept (not the specifics, just the concept) of 'cis gender-A' and 'cis gender-B' and 'cis gender-C' before I get to any permutation of 'trans' or 'genderqueer'. If for no other reason than that how our society reacts to cis women and cis men shapes how it reacts to trans women and trans men and people who defy either of those binaries.
ETA: Truuuue. ponder
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If you really want to do it with three chromosomes, it's not just sex determination that gets weird - presumably cells divide into three instead of two in meiosis and the fundamental genetic structure is triple instead of double stranded and I confuse myself. (]There are lots of ways to have three genetic parents without triple-stranded DNA and triploidy - you could, fr. ex, have two parents who each produce half of the main nuclear DNA, and then a third parent who provides the egg cell and all the other genetic info like mitochondrial genes and cell RNA - this is actually a thing that's been done with human embryos, and you could punch up the contribution of the third parent's DNA). Or you could have a situation where A and B each provide half a cell's DNA, then *that* cell undergoes meiosis, and parent C fertilizes both of those cells. Or you could step away from what DNA/RNA genetics do entirely and have the genetics be divided up some way other than mitosis - maybe something more like three-way bacterial conjugation than meiosis and fertilization. Anyway, the options are there.
With diploid cell but three equal parents, you could do three sex chromosomes X,Y,W that have rock-paper-scissors dominance (so XX and XY are one sex, YY and YW are a second, and WW and WX are a third) and come out with a pretty even sex ratio depending on exactly how the fertilization process worked.
With a three-chromosome system I'd probably go with a system of two sex chromosomes, call them K and J. Your three sexes are KKK, KKJ, and KJJ - the possible remixes of that are also KKK, KKJ, and KJJ. Statistically, you are twice as likely to get a KKJ as a result, but that can be worked around, either culturally or with a biological trick that makes KKJ embryos less likely to mature. (A JJJ, should it be produced somehow, would either be infertile or not viable, like yy or xo gametes in humans.) This is basically going to work the same as your system except that Z and W are the same chromosome, so the XYW and XYZ aren't distinct.
If two sex chromosomes is still too binary, but you still want triploidy with one chromosome from each parent, the simplest system I can think of is an XYW system where an embryo has to have both an X and a Y to be viable, so the three possible sexes are XXY, XYY, and XYW. With that system, from any mating you get odds of 8/27 nonviable, 7/27 XXY, 7/27 XYY, and 5/27 XYW.
(For worldbuilding with trinary culture, I recommend Her Majesty's Bucketeers - it's set on a world with three sexes, and while the worldbuilding has other issues, he was very good at turning *all* the cultural binaries into trinaries. I've spent a lot of time thinking about this because of that book. He doesn't go into any biological detail about reproduction at all, though.)
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*pokes Googles* Their Majesties' Bucketeers, you mean?
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It might be possible, but I can't work out how to make it work with one sex produces eggs, another sperm, and the third gestates the offspring. Which might not be the ideal configuration for where I'm trying to go with this, but it's the one I've got in my head.
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Hm. That could work! (Or XY is infertile or nonviable.)
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Or you could get a chimera where either X or Y dominates in clusters of cells around the body, like happens in XX's now. That would be sort of fun but may not be your goal.
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Deep enough to make the story make sense. Chromosomes make sense. (shrug)
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Are you thinking about more like two sexes contribute genetic material and a third gestates, or more like side-blotched lizards which apparently have 3 male/2 female types?
I always thought the ant thing was interesting too, since that's more about fertilization and also what happens during development. This is such a cool subject and I wish I knew more about it. :/
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two sexes contribute genetic material and a third gestates
That. Though the thing I seem to be writing is one sex of dragon provides ova, another sex provides sperm, the third lays the eggs, and the fourth hatches and raises the nestlings. (I thought it would be funny to split spinning, knitting, crocheting, and weaving into four different gender roles, and then it stuck in my head.)