Comic Discussion > QUESTIONABLE CONTENT
WCDT: 2236-40 (23-27 July 2012) Weekly Comic Discussion Thread
sitnspin:
A monogendered sexually reproducing species exist. Worms are simultaneously hermaphrodtic, they can both impregnate and be impregnated. Then there are sequential hermaphrodites, species that can change sexes, some of them multiple times.
There is a science fiction book by Usula Le Guin called "The Left Hand of Darkness" that deals with a planet inhabited by a humanoid species that are sequential hemaphrodites who go through regular cycles of sex change but spend most of their time neuter with no sexual expression at all, only expressing as male or female a few days per month.
Somebody:
--- Quote from: Boomslang on 27 Jul 2012, 02:11 ---If you're talking about why sexual reproduction occurs, as opposed to parthogenesis, it's pretty clear that the genetic shuffling that occurs introduces greater genetic variability into a species. Which makes it more likely that under changing conditions the species as a whole will survive. Bacteria can do this sort of genetic shuffling without sex, but their method of doing so is if not impossible, at least highly impractical for multicellular organisms like us.
--- End quote ---
That doesn't explain why mammals aren't hermaphrodites, with all members capable of both impregnating and *being* impregnated!
--- Quote from: El_Flesh on 27 Jul 2012, 06:00 ---All you need to make your offspring is to combine the nucleii of two eggs. I don't know if injecting on egg nucleus into another will kickstart it into fetal growth; it might need sperm touching its outer cellular wall to start the chemical changes that commence the process. It might be a process of penetrating the host nucleus as well and combining the two, or, one could remove a nucleus from EACH donor, combine them, and inject the result into another egg that has had its nucleus cleared.
Or, if you remove the nucleus from one egg and inject it into a similarly cleared sperm, then fertilize another egg with it, that might be easiest - however the nucleus of the egg might be too large for the sperm cell; I don't recall their relative sizes.
Another possibility would be to inject one egg nucleus into another egg, then kickstart it with a sperm cell that had its nucleus removed.
I don't know if this degree of microsurgery exists, for sperm cells are a LOT smaller than eggs.
All in all, I'd be pretty surprised to find out that none of this is currently possible. It might be however, that the failure to success ratio would be so high that it simply isn't done at the present time.
--- End quote ---
It's more complicated than that. In sperm, various genes are activated to make the children grow big and healthy while still in the womb. Eggs, OTOH, activate *contrary* genes to keep the foetus small and thus not such a big strain on the mother during pregnancy & childbirth.
Simply fusing the nuclei of two eggs would thus end up with two doses of "small" and no "big", leading to an unviable foetus.
Boomslang:
--- Quote from: Somebody on 27 Jul 2012, 22:34 ---
--- Quote from: Boomslang on 27 Jul 2012, 02:11 ---If you're talking about why sexual reproduction occurs, as opposed to parthogenesis, it's pretty clear that the genetic shuffling that occurs introduces greater genetic variability into a species. Which makes it more likely that under changing conditions the species as a whole will survive. Bacteria can do this sort of genetic shuffling without sex, but their method of doing so is if not impossible, at least highly impractical for multicellular organisms like us.
--- End quote ---
That doesn't explain why mammals aren't hermaphrodites, with all members capable of both impregnating and *being* impregnated!
--- End quote ---
No, but the fact that our lineage is predominantly non-hermaphroditic explains that very easily. It's still possible for hermaphroditism to appear as a mutation, but unless that mutation is also compatible with existing reproduction of the species, it will die off that generation. And beyond that, it would only become dominant if it was positively affecting the survival of the species- I went into why that isn't necessarily the case earlier on in the post you quoted.
Humans, especially, would be negatively affected by being hermaphrodites. Tribal societies use various methods to decrease the amount of children they have so that they don't outstrip their resources. The maximum number of children you can raise to adulthood is far fewer than the maximum number that can be born even with half the tribe not producing them. Furthermore, unlike most animals, pregnant humans are less able to hunt, travel large distances, outrun predators, or fight those predators or another tribe, in addition to the high possibility of dying in childbirth. If mammals were hermaphroditic by default, it would be hard to see how humanity as we know it could have ever come about. It's already kind of shocking we made it to the tool-using phase as things are.
wiserd:
--- Quote from: Somebody on 27 Jul 2012, 22:34 ---
Simply fusing the nuclei of two eggs would thus end up with two doses of "small" and no "big", leading to an unviable unbelievably cute foetus.
--- End quote ---
FTFY.
WAYF:
I think that Marten gave some pretty solid advice there. Cautionary, but not too cautionary. And they both now seem to be approaching it from the frame of mind that Tai said what she said because she meant it and not because she was drunk, which to me is a step forward!
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