A Fertility Story: (Warning, image heavy)

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Tuesday’s post took longer to write than expected, so today’s post is being told entirely in images:

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cnn-trap-income dating

 

inflation-and-cost-of-goods

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intelligence vs desired number of children, from Cognitive dysgenics in the OKCupid dataset: a few simple analyses by Emil O. W. Kirkegaard http://emilkirkegaard.dk/en/?p=5942
intelligence vs desired number of children, from Cognitive dysgenics in the OKCupid dataset: a few simple analyses by Emil O. W. Kirkegaard — there are several other graphs in the post so be sure to check them out.
From Selection against variants in the genome associated with educational attainment (PDF)
From Selection against variants in the genome associated
with educational attainment
(PDF)

age-specific-fertilitty

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Source: CDC data, I believe

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Increased gender dimorphism = lower IQ?

The short version of this is if you could measure the relative gender dimorphism of people–say, by comparing siblings–and compare that to their IQ, I wager the more androgynous people would come out smarter.

This began with Jayman’s Pioneer Hypothesis, which basically posits that frontier or pioneer environments will select for a certain suite of traits like aggressiveness and early menarche–that is, traits that allow them to quickly take over and fill up the land.

Based on this initial theory, I hypothesized that East Germany was settled later than West Germany–which turns out to be actually true. I was pretty stoked about that.

Anyway, earlier menarche => lower IQ, (I’m pretty sure this is well-documented) as shortening childhood = shortening the period of time your brain has to develop.

Raising the age of menarche gives your brain more time to develop. In environments where family formation has historically been difficult, ie, very densely populated areas with little free land available where people might have to wait for their relatives to die before they can get their own farm, have likely evolved people who hit menarche later (after all, there’s no need for early menarche in such an environment. See also: cave fish losing pigment because it’s not useful.) The opposite side of this coin is later menopause, but since these folks have lower fertility overall, I don’t think that’s a big factor.

Anyway, later menarche => more time for brains to develop => higher IQ.

I suppose the speculative part here is that late menarche populations are more androgynous and early menarche populations are less androgynous. This probably wouldn’t hold for all populations, but anecdotal experience with Americans seems consistent–eg, MIT students seem highly androgynous, while dumb people from elsewhere seem much more dimorphic. Actually, many of the extremely high-IQ people I’ve known have been trans*, as opposed to none of the dumb ones. Among dumb people, it seems perfectly normal for women to socialize in all-female groups, especially for activities like shopping and discussing celebrity gossip, while men find it normal to socialize in all-male groups, especially for activities like watching other grown men play keep-away (sports), drinking beer, and playing poker. (To be fair, though, I don’t have a lot of first-hand experience in the world of the dumb.)

Historically pioneer and historically densely settled populations probably end up with different notions of what is “normal” dimorphism, leading to lots of disputes as each side claims that their experiences are normal, and not realizing that the other sides’ experiences are normal for them, too.