Greg Clark has a new book out, The Son Also Rises. His thesis, in short, is that moxie has high heritability. Most studies show fairly high social mobility from one generation to the next – but Clark finds (using surname analysis) that paternal lineages that were over-represented (or under-represented) in measures of status (such as education or wealth) can be still be over-represented (or under-represented) in high-status groups several hundred years later. Both statements are true. In the short run, from one generation to the next, luck plays a big role. In the longer run, the fact that the subpopulation being examined has a different genotypic average, one more likely to result in high status, means that regression to the mean of the general population is slow for the subgroup, essentially caused by gradual change in its average genotype, change produced by intermarriage with individuals who on average have a less favorable genotype. Other than high heritability, the other prerequisite for this pattern is highly assortative mating for moxie. If two groups have different average amounts of moxie, complete endogamy (as in Indian castes) would ensure that the between-group difference would continue indefinitely, disregarding selection.

We All Are Tall!

Here’s a simple example. Take a group of NBA players – they’re a good deal taller than average. Assume that they all marry WNBA players ( it’s a thought experiment, ok?). The kids will be taller than average, and probably some get into the NBA (far more than average) , but most don’t. There’s a lot of change in status from one generation to the next. Have them continue to marry among themselves: they stay that tall, and each generation is over-represented in the NBA. In any generation, kids in a particular family are gaining or losing NBA status, but people in this clan are regressing to a higher mean.

Now instead, imagine that 10% marry out each generation. The people they marry are probably not as as tall, but even more important, they are, on average, genetically shorter. Keep up this admixture for generations and our NBA/WNBA clan will eventually converge to the population mean.

Where did Clark and his students see this this pattern of slow long-term social mobility?

Everywhere they looked. England, Sweden, Japan, Korea, China, Chile. In England, Norman surnames are still 25% over-represented at Oxford and Cambridge, but then it’s only been 947 years. The Japanese upper class is something like half Samurai (5% of the population when they lost their special privileges, 143 years ag0).

Assuming that is in fact a genetic phenomenon, such slow convergence also requires pretty low paternal uncertainty – but then paternal uncertainty is in fact low, at least in the populations we have looked at. I talked to Clark about this: he hadn’t really looked at it yet and had heard that the rate was around 10%. Where do people get these notions? Now he knows better.

It’s not in the book (ongoing work) but it turns out that the long-term pattern is the same if you look at matrilineal descent. As it should be, if it’s genetic.

It turns out that you can predict a kid’s social status better if you take into account the grandparents as well as the parents – and the nieces/nephews, cousins, etc. Which means that you’re estimating the breeding value for moxie – which means that Clark needs to read Falconer right now. I’d guess that taking into account grandparents that the kids never even met, ones that died before their birth, will improve prediction. Let the sociologists chew on that.

Adoption – turns out most of the kid’s status is due to genetic factors, rather than family environment. At least for reasonably normal environments: this may not be the case if you’re raised in a barrel and fed through the bung-hole.

Often groups with a different average genotypic value are generated by a process of biased leaving and/or joining – like upper and lower classes or the Amish. Natural selection can also do this, in an endogamous group. Of course, you can do the same thing by importing a population that already has a higher or lower average. As long as it doesn’t mix much, it can stay different (higher or lower) for a long time.

If culture was the driver, a group could just adopt a different culture (it happens) and decide to be the new upper class by doing all that shit Amy Chua pushes, or possibly by playing cricket. I don’t believe that this ever actually occurs. Although with genetic engineering on the horizon, it may be possible. Of course that would be cheating.

It is hard to change these patterns very much. Universal public education, fluoridation, democracy, haven’t made much difference. I do think that shooting enough people would. Or a massive application of droit de seigneur, or its opposite.

Clark finds that windfalls don’t make much difference in the long run. Back in 1830, they kicked the Cherokee out of Georgia and distributed the land by lottery in 1832. One-fifth of the adult male white Georgians were winners, with a value of something like $150,000 in 2014 dollars. But by 1880, their descendants were no more literate, their occupational status no higher. Sounds like modern lottery winners, or NBA players, yes? The major exception must be extreme poverty: a windfall that keeps you from starving to death must have long-range effects on your descendants.

If moxie is genetic, most economists must be wrong about human capital formation. Having fewer kids and spending more money on their education has only a modest effect: this must be the case, given slow long-run social mobility. It seems that social status is transmitted within families largely independently of the resources available to parents. Which is why Ashkenazi Jews could show up at Ellis Island flat broke, with no English, and have so many kids in the Ivy League by the 1920s that they imposed quotas. I’ve never understood why economists ever believed in this.

Moxie is not the same thing as IQ, although IQ must be a component. It is also worth remembering that this trait helps you acquire status – it is probably not quite the same thing as being saintly, honest, or incredibly competent at doing your damn job.