+Anyway, that's some background about where I was at, personally and ideologically, _before_ I fell in with this robot cult.
+
+My ideological committment to psychological-sex-differences denialism made me uncomfortable when the topic of sex differences happened to come up on the blog—which wasn't particularly often at all, but in such a _vast_ body of work as the Sequences, it did happen to come up a few times (and those few times are the subject of this blog post).
+
+For example, as part of [an early explanation of why the values we would want to program into an artificial superintelligence don't reduce to any one simple principle](https://www.lesswrong.com/posts/NnohDYHNnKDtbiMyp/fake-utility-functions), Yudkowsky remarks that "the love of a man for a woman, and the love of a woman for a man, have not been cognitively derived from each other or from any other value."
+
+From the perspective of axiomatic antisexism that I held at the time, this assertion is cringe-inducing. Of course most people are straight, but is it not all the _same love_?
+
+I wasn't ready to hear it then, but—I mean, probably not? So, for the _most_ part, all humans are extremely similar: [as Yudkowsky would soon write about](https://www.lesswrong.com/posts/Cyj6wQLW6SeF6aGLy/the-psychological-unity-of-humankind) [(following Leda Cosmides and John Tooby)](https://www.cep.ucsb.edu/papers/pfc92.pdf), complex functional adaptations have to be species-universal in order to not get scrambled during meiosis. As a toy example, if some organelle gets assembled from ten genes, those ten alleles _all_ have to be nearly universal in the population—if each only has a frequency of 0.9, then the probability of getting them all right would only be 0.9<sup>10</sup> ≈ 0.349. If allele H [epistatically](https://en.wikipedia.org/wiki/Epistasis) only confers a fitness advantage when allele G at some other locus is already present, then G has to already be well on its way to fixation in order for there to be appreciable selective pressure for H. Evolution, feeding on variation, uses it up. Complicated functionality that requires multiple genes working in concert can only accrete gradually as each individual piece reaches fixation in the entire population, resulting in an intricate species-universal _design_: just about everyone has 206 bones, a liver, a parietal cortex, _&c_.
+
+In this way (contrary to the uninformed suspicions of those still faithful to the blank slate), evolutionary psychology actually turns out to be impressively antiracist discipline: maybe individual humans and ancestry-groups of humans can differ in small ways like personality or skin color, but these are, and _have_ to be, "shallow" low-complexity variations on the same basic human design; new _complex_ functionality would require speciation.
+
+This luck does not extend to antisexism. If the genome were a computer program, it would have `if female { /* ... */ } else if male { /* ... */ }` conditional blocks, and inside those blocks, you can have complex sex-specific functionality. By default, selection pressures on one sex tend to drag the other along for the ride—men have nipples because there's no particular reason for them not to—but in those cases where it was advantageous in the environment of evolutionary adaptedness for females and males to do things _differently_, sexual dimorphism can evolve (slowly—[more than one and half orders of magnitude slower than monomorphic adaptations](/papers/rogers-mukherjee-quantitative_genetics_of_sexual_dimorphism.pdf), in fact).
+
+Robert Trivers wrote, "One can, in effect, treat the sexes as if they were different species, the opposite sex being a resource relevant to producing maximum surviving offspring" (!!). There actually isn't one species-universal design—it's _two_ designs.
+
+If you're willing to admit to the possibility of psychological sex differences _at all_, you have to admit that sex differences in the parts of the mind that are _specifically about mating_ are going to be a prime candidate. (But by no means the only one—different means of reproductive have different implications for [life-history strategies](TODO: linky) far beyond the act of mating itself.) Even if there's a lot of "shared code" in how love-and-attachment works in general, there are also going to be specific differences that were [optimized for](https://www.lesswrong.com/posts/8vpf46nLMDYPC6wA4/optimization-and-the-intelligence-explosion) facilitating males impregnating females. In that sense, the claim that "the love of a man for a woman, and the love of a woman for a man, have not been cognitively derived from each other" just seems commonsensically _true_.
+
+I guess if you _didn't_ grow up with a quasi-religious fervor for psychological sex differences denialism, this theoretical line of argument about evolutionary psychology doesn't seem world-shatteringly impactful?—maybe it just looks like supplementary Science Details brushed over some basic facts of human existence that everyone knows. But if you _have_ built your identity around quasi-religious _denial_ of certain basic facts of human existence that everyone knows (if not everyone [knows that they know](https://www.lesswrong.com/posts/CqyJzDZWvGhhFJ7dY/belief-in-belief)), getting forced out of it by sufficient weight of Science Details [can be a pretty rough experience](https://www.greaterwrong.com/posts/XM9SwdBGn8ATf8kq3/c/comment/Zv5mrMThBkkjDAqv9).
+
+[TODO: this denial was in the background in "The Opposite Sex" and the metaethics sequence, men should think of themselves as men]
+
+Sex differences would come up a couple more times in Yudkowsky's Sequence on Fun Theory—