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Smart people got no babies.... (?)

By razib on August 25, 2006.

RPM comments on some issues relating to human genetics. First, he points to the article about how conservatives are going to outbreed liberals, etc. etc. etc. The problem with this article is that the Left & the Right have been around since the late 18th century and history marches Leftward even though one assumes the Right has been breeding at a higher clip for the past 8+ generations. What gives?

First, there is a heritable component to political orientation. That is, a proportion (around 0.5) of the variation in of conservatism or liberalism within the population is attributable to genes. Additionally, obviously politics is vertically transmitted and horizontally propogated (i.e., parent to child, activist to sheep). But there's a problem with these simple assertions: liberal & conservative are contextual. What is liberal in one environment may not be liberal in another (it maybe conservative). If one holds that a "liberal" or "conservative" tendency is determined by relation to the center of the given distribution, then so long as there is variation within the population due to a variety of factors liberals and conservatives will always hang around, even if the median value shifts greatly. We know from long term breeding experiments that genetic variation often takes a long time to exhaust itself, and certainly if there is a genetic element to political preference and fitness is correlated with the Right end of the spectrum (because of higher birthrates) I suspect that a lot of latent variation will remain for many generations to drive a dynamic political tension within our culture. This isn't even taking into account that fitness varies dependent on the particular circumstances within which genes are expressed.

But there's a bigger more interesting issue which RPM moots:

Regardless of the political direction you'd like to see our country take, however, I think we can all agree that we'd like to see intelligent people spreading their seed.

I prodded RPM to elaborate, and he stated in the comments:

But, if I must: if smart people make babies maybe society as a whole will become smarter. I'm not advocating planned breeding, but it's probably not a good idea for smart people to be put in situations where they don't have the time or means to reproduce.

This is a commons sentiment. I say common because probably every other graduate or undergraduate who has pursued studies in biology has mentioned this sort of thing to me offhand. I've even heard velnerable scientists who are members of the National Academy of Sciences moot this point after a few beers. The logic is simple, intelligence is heritable, and if selection favors the less intelligent then the less intelligent will proliferate and dominate. If you take the motto "Nothing makes sense in biology except in the light of evolution" as your banner, to some extent it isn't that difficult to take the next step and apply it to your own life. In any case, the dumbing down of the world is the premise behind the upcoming film Idiocracy, a man from the present wakes up in a future where the morons find that he is a genius (it is going straight to video, ironically, it wasn't a smart idea I suppose). R. A. Fisher spent some time in The Genetical Theory on this topic, and he practiced positive eugenics in his own life, having a large family. But of course, the e word is terrifying to us today and that is why the sentiment among the intellectual elites never really crystallizes into any plan of action, the sentiment to build a better baby is not a new one, and it ushered in the horrors of the 20th century. Though the British tended to focus on positive eugenics, encouraging the judged to be fit to proliferate, the United States, along with other countries in northern Europe (e.g., Sweden as late as the 1970s) engaged in a massive program of sterilization of the "feeble minded" (see Carrie Buck). This laid the seeds for the abomination which was the Nazi program. No great elaboration is needed here.

The reality is that the fitness implications of high intelligence are equivocal. Otherwise, we'd all be very smart. Bell curved traits which arise out of quantitative loci of small effect, as well as a large environmental component of variation, suggest that the trait under consideration has not been under powerful directional selection consistently. If directional selection was powerful it would have swept away all the variation on that trait. The stupid are our future,* just as they were our past, and likely there is some frequency dependent dynamic which will result in the boomerang back of the eternal recurrence.

* If you view intelligence as purely a relative measure, like "liberal" or "conservative," as opposed to some absolute trait, then we won't get less intelligence is the distribution will just shift to the left or right. The same percentage will remain north of two standard deviations as today, that territory will just be a bit different....

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In any case, the dumbing down of the world is the premise behind the upcoming film Idiocracy, a man from the present wakes up in a future where the morons find that he is a genius (it is going straight to video, ironically, it wasn't a smart idea I suppose).

C. M. Kornbluth's estate should sue.

The thing is that a powerfull intellect is not a preponderant trait in human breeding. I live in a college town, in a neighbourhood populated by many of the profs, and I see little evidence that they have had much success transmitting their intelligence to their prodigy.

I live in a college town, in a neighbourhood populated by many of the profs, and I see little evidence that they have had much success transmitting their intelligence to their prodigy.

assume 0.5 heritability and the offspring will regress half way back to the population mean. i.e., if you assume midparent IQ is 130 (not implausible for professors), you'd expect the children to have IQs of 115, about 1 standard deviation below them. of course, heritability is a bit higher at high SES than low, but still, there is expected regression. nevertheless, crank out the probability distributions and there is a big diff. in the expected distribution of college towns and non-college towns.

If the highest IQ types don't breed, then high IQ is disfunctional, then that explains why hi IQ is rare. By definition you'd expect the best survival at the peak of the bellcurve.

Maybe there's a slightly higher breeding rate lower down to compensate for the higher deathrate.

By definition you'd expect the best survival at the peak of the bellcurve.

only if the population isn't undergoing any directional evolution. fit phenotypes might be at less than modal frequency. also, stochasticity of the "fittest phenotype" over time might be an issue.

"I'm not advocating planned breeding, but it's probably not a good idea for smart people to be put in situations where they don't have the time or means to reproduce."

With due respect to RPM, this statement seems confused. Smart people do not have a problem when it comes to time and means; they have more time and means than stupid people, on average. So why do they have less kids? Simple: because their time and effort is worth more than that of stupid people. They can get more gain out of working than stupid people can, hence the opportunity cost of having a child for them is a lot greater than it is for a stupid person. So they have fewer kids. Basic economics is to blame for this, and there really is no easy solution that doesn't involve at least passive eugenics on the part of the government. Unless you're willing to introduce a stupid tax and subsidize brainy offspring, get used to this pattern.

By definition you'd expect the best survival at the peak of the bellcurve.

This is a complicated issue. It can be shown that stabilizing selection will exhaust quantitative genetic variation given no further mutation, just as will directional selection. What about selection for an oscillating mean, i.e., in one generation it's best to have an IQ of 98, in the next 107, in the next 101, and so on? Kimura argued that the genetic variation could not be maintained in this scenario either, although I've heard one geneticist say that he doesn't agree with this model. I don't think there is a canonical explanation for how quantitative variation is maintained in general that the textbooks agree on.

Slight quibble w/ what Matt said -- the opportunity cost is huge for the mother, not really the father, as dads don't parent nearly as much as moms. In order for the mom also to not parent much, then the kid basically gets raised by nannies of some kind or other: at school until 3, babysitter until 6 or 7, a little time w/ parents, then bed. More parent-kid time on weekends. It's not so bad: kids mostly want to hang out w/ other kids, not what they consider their dopey parents. And the kids of smarties won't live in the same neighborhood as bad influence peers.

So the trick is to help out smarty families financially -- help move into safe, "good school" neighborhoods, help w/ babysitting costs, etc. Also would cost less if illegal immigration weren't shooting housing costs through the roof.

From all reports, the upper classes in Classical times had few kids, while the opposite was the case for Europe in 1700.

Economics?

"The reality is that the fitness implications of high intelligence are equivocal. Otherwise, we'd all be very smart."

I think we all are very smart. I always wonder what was forcing this when we became smart since it seems to have been fairly quick. I have no idea of how to measure the magnitude of intelligence difference in current humans, but relative to everything else it seems trivial.
I've helped people with very low measured intelligence learn to read in literacy centers for example, not good, but they could do it.
Would that mean that there are relatively few traits that cause intelligence? It seems like if there were many they could all vary causing more variation. Or is there some kind of flattening or forcing still happening?

I always wonder what was forcing this when we became smart since it seems to have been fairly quick.

the hominin crania went through a gradual 2 million year evolution until approximately its modern volume around 200 K BP. but modern behavior seems to arrived on the scene between that period and around 30 K.

Agnostic -- Right, I was thinking primarily of mothers but didn't make that explicit. But wrong (or at least incomplete) on the just-so story about housing and immigration: AFAIK, the rate of immigration hasn't changed very much over the past 20 years. Why is housing only getting noticeably more expensive now? Have we suddenly stared running out of space to build? I can definitely imagine plausible scenarios in which there is a connection, but none in which it's the whole story, and you haven't argued the point sufficiently.

Greg -- Probably. Would have to know more about the different periods to make any confident statements.

I call BS on terms like fitness and survival in reference to domestic animals like cattle, sheep and humans. Just because humans are the "most equal" in the barnyard doesn't change that breeding controls our evolution, not survival.

As long as a significant fraction of females in the bell curve hump find smart males attractive (witty, funny, or talented), the IQ gene is safe.

but modern behavior seems to arrived on the scene between that period and around 30 K

Sounds about right for the changeover.

One important reason that genius-types breed less is because many of them can be completely unbearable--few people are willing to put up with their miserable moods and emotional absence.

My ex is a 100% genius/nerd/logician/philosopher--can't be trusted with a simple household tool or kitchen implement (might hurt himself, as he's done); he zones out in public gatherings (contemplating the finer points of Bayes' theorem), and never had a paying job *once* in the (ulp) 11 years we were together. (I know, I know--my bad too)

Yes, I am aware of the dangers of extreme induction, but I think there really is a spectrum at work here. I would never date an extreme logician/philosopher again--much less *breed* with one. Men in the hard sciences are more practical, more down-to-earth (and, as per your "nerdy" post, I bet their nerd score is far lower).

I missed this post the first time around. Perhaps I didn't have my tongue planted firmly enough in my cheek when I wrote that entry. As I said in the comments, I was just looking for a reason to quote the article I quoted because I thought it was clever. Don't look into it more than that.