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RobinZ comments on The Nature of Offense - Less Wrong
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And you know this how?
Okay, I don't want to argue from anecdotal evidence and stereotypes, so I will admit I don't really know it. But gender and sex differences are possibilities which we can't just ignore - Of Gender and Rationality points (4), (5), (6), (7).
"Gender differences", where "gender" means the social construct of gender identity, are almost certainly relevant; I don't think anyone would claim that different genders aren't socialized differently starting from a young age. Genetic sex differences have a much higher burden of proof, because there has to be some evolutionary benefit to such differences developing.
That said, it would still be nice if you had direct evidence for your particular assertion ("women prefer practical stuff"), because I've seen this assertion before but don't find it persuasive. It doesn't match my own anecdotal experience, and it sounds a lot like other hypotheses on systematic differences between superficially obvious groups that haven't panned out (cf. this post and related posts on Language Log about gender speech differences).
This is known to be false. Many differences are purely random.
It is known that many differences between related species are due to genetic drift rather than selection. Is it known that differences between males and females within a species are due to genetic drift?
There is as much genetic drift on the X and Y chromosomes as on any of the other chromosomes, so at least some of the differences between sexes must be caused by it.
The Y chromosome is physically much smaller than all the other chromosomes. In particular, it's not an equal partner to the X chromosome. From Wikipedia, I learned that the human Y chromosome contains 86 genes, which code for only 23 distinct proteins.
One example of a sex-linked trait that's wasn't due to selection is colorblindness, which is common only in males because the relevant genes are recessive and located on the X chromosome.
At some point, a population of organisms developed some sex determination genes. Over time, this system developed into the XY sex determination system: sexual dimorphism due to the segregation of sex-determining genetic information onto a single highly degenerate chromosome. I think it's very implausible that this segregation is without evolutionary benefit. The occurence of sex-linked monogenic traits like the example you give here are a side effect whose evolutionary cost was outweighed by the benefit of the development of the XY system. So I don't think this is a good example for the claim you are trying to defend.
Random differences still need to be roughly fitness-neutral, else they will be selected against.
Given the stunted nature of the Y chromosome, as Cyan notes, and the fact that all other genetic material is shared, this still means the burden of proof is stacked against the idea of non-obviously essential sexual dimorphism, and strongly so in the case of proposed differences that are large compared to intra-sex individual variation.
I don't think simply counting genes tells us much of anything about the amount of sexual dimorphism in a species, one way or the other. The vast majority of genetic material is shared between sexes in any species, and some species don't even use genes to determine sex. If the fact that most genetic material is shared between sexes really did stack the deck against large sex differences, then we would never see large sex differences anywhere.
Futhermore, I'm not sure what you mean by "non-obviously essential." Obvious to whom? It's not at all obvious to me why (say) it would be adaptive for human males to have so much facial hair compared to human females, and yet human males really do have a lot of facial hair.
The discussion here was about behavior, not physical differences. My apologies if I was unclear about that. Furthermore, you seem to be reading "stack the deck against" as referring to likelihood of differences arising, I meant it more in the sense of "here is an observed behavioral difference between human sexes, is it due to 1) statistical noise 2) learned social behaviors 3) intrinsic genetic differences, &c." It seems reasonable to have a fairly low prior for #3 vs. #2.
Also, "obviously essential" in the the sense of "the whole point of sexual dimorphism". Suckling an infant is pretty clearly essential behavior. "Women are more practical", not so much.
I agree that in the case of behavioral differences, we have a prominent "learned social behavior" hypothesis that we do not have in the case of physiological differences, but it's not because of the number of genes shared between sexes; it's because of the common-sense intuition that culture influences behavior in a dramatic way that it doesn't influence physiology.
I agree here. (In particular, "Women are more practical" is vague to the point of not-even-wrong-ness.) However, it does seem worth noting that if there are non-obviously-essential physiological differences (such as male facial hair), then it's at least not implausible that there might also be non-obviously-essential brain development differences that manifest as behavioral differences.
Well, in a counterfactual world where somehow genetic differences between the sexes were much larger, comparable to the genetic differences between humans and other primates, genetic reasons for behavior differences would be a lot more plausible, just as genetic differences explain behavioral differences between us and other primates now. That this is not the case in reality is why "learned behavior" is a stronger, common-sense hypothesis.
Of course. In fact, there are probably quite a few. But for any given observed behavioral difference, it's sensible to assume it's a learned behavior lacking strong evidence otherwise (such as consistent observation of the same difference in multiple unrelated cultures).
I think we're arguing 95% terminology and 5% substance here.
I suspect there is a substantive disagreement lurking here. Specifically, as much as it hurts my liberal feminist heart to say it (or it did hurt, before I got jaded), I'm going to have to deny this:
Maybe we're tripping over this word genetic? When I say that the number of shared genes doesn't matter, what I'm getting at is that while SRY may "just" be "one gene," it triggers this entire masculinizing developmental process, and while I haven't studied the details (yet), it doesn't look trivial. Obviously culture exists, but the capacity to generate and transmit culture is a specific ability of human brains that happens in a specific manner, and if there are innate sex differences in human brains, then we are not justified in assuming that a given behavioral sex difference is a strictly cultural artifact that could have just as easily gone the other way. Culture is---I don't have the word for it---informed, constrained?---by human nature. We have to reason these things out on a case-by-case basis. Suppose---suppose American males score better than females on a test of mental rotation by eight-tenths of a standard deviation, and suppose we don't have any cross-cultural data, however dearly we might wish for it. I can't bring myself to presume a social explanation.
Another data point for contextualism in epistemology!
ETA: (to self) confirmation bias much?