Class, Caste, and Genes

An article by Sabrina Tavernise appeared in the New York Times a few days ago describing increasing perceptions of class conflict in America, and there is a lot of recent commentary in the press about this report from the Pew Charitable Trust that claims there is less class mobility here than in several other northern countries.   It is not very clear to me what the complaints really are or what alternatives exist. If there is any substantial heritability of merit, where merit is whatever leads to class mobility, then mobility ought to turn classes into hereditary castes surprisingly rapidly.

A start at looking into genetic consequences of meritocracy is to create the simplest possible model and follow its implications. Consider free meritocracy in a two class system, meaning that each generation anyone in the lower class who has greater merit than someone in the upper class immediately swaps class with them. Mating then occurs at random within class. There are no fitness differences, no selection at all, everything is neutral. It is convenient to discuss what happens in terms of IQ because IQ is familiar and, in northern industrial nations, closely related to merit. On the other hand we have to keep in mind that our focus on IQ is like that of the drunk searching for his keys under the lamppost: we can measure IQ but have no good way to measure honesty nor time preference nor conscientiousness and so on.

initial change

This figure shows an initial population with normally distributed merit. A new merit based class system is imposed such that the two new classes are of equal size. In this free meritocracy everyone with merit exceeding the population mean moves into the upper class and everyone with merit less than the average moves into the lower class. The second panel of the figure shows the resulting merit distributions by class before reproduction and the bottom panel shows the distributions after endogamous reproduction. This model assumes that the reshuffling of genes during reproduction leads to normal distributions in the next generation within classes.

The process continues for several generations. By analogy with IQ the additive heritability of merit is set to 0.6 so there are substantial random environmental effects. The second figure shows the evolution of class differences over four generations or about 100 years in human terms.

merit distributions over four generations

Class mobility after the first generation is 30% while after four generations it has declined to 10% and continues to decline after that.  The average merit in the two classes is about -1SD in the lower and +1SD in the upper on the original scale, corresponding to IQs of 85 and 115.

Recall that there are no fitness differences in this model. Still, after four generations, about 70% of the variance is between classes, which can be compared to  about 35% of the variance among continental human groups for random genetic markers, i.e. colloquially class differences are twice neutral race differences. (The familiar among-population figure of 15% made famous by Lewontin refers to gene differences while here we are comparing genotype differences of diploids, hence the difference between 15 and 35.)

A surprise to me from this model was the rapidity with which classes turn into castes: most of the action is in the first generation or so. In retrospect this seems so obvious that it is hardly worth saying but it wasn’t so obvious to me when I started toying with it.

Even though everything here is selectively neutral, I wonder about the extent to which this free meritocracy mimics selection. Any mutant that boosts merit in carriers will be concentrated in the upper class and vice versa. Greg and I discuss in our book how environmental change initially selects for dinged genes that are “quick fixes” in carriers but detrimental in homozygotes, citing sickle cell in humans, broken myostatin in beef cattle, and numerous others. Does this social system mimic selection?

A correlate of IQ in humans is myopia, one idea being that IQ boosters relax early developmental constraints on CNS growth resulting in eyeballs too big for the socket, leading to myopia. I have read somewhere that myopia is positively related to income in the US. Time to try to find that literature.

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73 Responses to Class, Caste, and Genes

  1. dearieme says:

    Have you tried variants on your simple model e.g. a lower class person replaces an upper class person only if the IQ of the former exceeds that of the latter by (say) 5 points?

    • Anonymous says:

      I haven’t but I ought to. I have been trying to come up with a general purpose algorithm that will do this with arbitrary exchange rules, class sizes, and number of classes.

  2. dave chamberlin says:

    “A suprise to me from this model was the rapidity with which classes turned into castes: most of the action in the first generation or so.”

    Maybe that first generation starts after World War Two, when board scores replaced economic class for those who got into the most prestigious universities. My cynical imagination wanders to what the results will be like after the fourth generation.. “Damnit Honey, how can our children focus on their studies when those idiot security gaurds can’t keep the homeless out of our gated community.”

  3. Henry Harpending says:

    I don’t know the data very well but a lot of anecdotal information supports you. The GI Bill was a mechanism for letting a lot of bright folks into universities as was IQ testing in the military during WWII. Bright farm boys got high scores, pushed into OCS, etc.

    Then the flood of money into STEM education after Sputnik also helped the process.

  4. Jason Malloy says:

    Gregory Clark’s next book is a more empirical treatment of this. He seems to find that social classes, unlike ethnic groups, dissolve quickly, and don’t readily form into genetic castes:

    “In England, where we can trace social mobility back to 1066 using surnames, there were never any long persistent ruling and lower classes for the indigenous population: not in medieval England, and not now. About 5-6 generations were, and are, enough to erase most echoes of initial advantage or want. For the English class is, and always was, an illusion. Histories such as those of the Stanley family turn out to be rare exceptions, not the rule.”

    • Jason Malloy says:

      I hope Clark’s book references Nathaniel Weyl, who discovered much the same thing 50 years ago in the Mankind Quarterly:

      “1. The performance coefficients of bearers of royal names are markedly higher than those of non-royal names among Irish-Americans.

      4. English names denoting personal characteristics rank higher than occupational names and the latter are higher than names derived from patronymics.

      6. Absolutely no association was found, within the general group of English occupational surnames, between performance coefficient and original class status

    • Henry Harpending says:

      Thanks Jason: I am not sure there is much contradiction between those data and this model but there may be. If we pick someone from the upper class, then watch his descendants diffuse around in the merit space, what will we see? By using surnames we would be restricted to the male line, I suppose, ought not to be difficult to compute that.

    • FredR says:

      Here’s an updated version, where he looks at a few more societies:

    • Henry Harpending says:

      It is not very clear, thinking about it, what Clark is actually saying. How can, say, “super rich” dissolve quickly? If he is looking at surnames then after five generations, if everyone has two kids, he is looking at 1/32 of someone’s descendants. Or am I not understanding something.

      Another simple shot is my correlation with my child is 1/2, grandchild 1/4, down to 1/32 or about .03 after five generations. But this says nothing about whether the class persists.

    • Skimming Clark’s manuscript, I think he hits the nail right on the head when he says that the right criterion is whether groups regress to the same mean or to different means. He shows that the English were and are regressing to the same mean essentially, i.e. that there is one distribution, not many.

      He identifies US Blacks, Ashkenazi Jews, and recent third-world immigrants to the UK as groups that regress to their own means, not the general mean. Clever. He points out that genetic separation is required to maintain such groups. That is of course exactly what happens in my toy model: classes regress to their own means not the overall mean.

      What about genetic separation. Both Jews and Blacks are admixed populations. Ashkenazi, from Hapmap data mostly, are about half middle-eastern and half Roman. If Greg and I are right about IQ evolution in Ashkenazi, it happened after the population mixing occurred. Best guess is that since the fall of the Roman Empire there has been almost no gene flow into the Ashkenazi population.

      US Blacks are more difficult to understand. They are by most accounts 20-25% European, 75-80% African. Why hasn’t gene flow overcome initial differeneces in, say, IQ? It depends of course not on the color of the ancestry but the IQ of the ancestry. What is the source of European genes in the US Black population and what was its IQ?

      One stereotype is that it was Jefferson and other Massah’s exploiting slave women. At the other end of possibilities we have Linda Burton’s descriptions of underclass Black girls in (Altoona?) Pennsylvania seducing homeless men in order to have light skinned babies.

      My best bet is that most of it is from captives from Catholic armies that Cromwell sold in Carolina. If so, what on earth do we know about mean IQ of renaissance armies? Maybe Peter Frost knows more about this.

      At any rate this provides us a usable definition of whether or not a society is burdened with diversity or not, i.e. do all groups regress to the same mean?

      • saintonge235 says:

        On the question of gene flow for intelligence, you have to take the time factor into account. From what I’ve heard, average West African IQ is about 70, two or more standard deviations below white Americans. With African Americans, the average is 85, one to one and a quarter SDs below white Americans (black Americans have an SD of 12 IQ test points, iirc, whites of 15). So, African Americans have presumably had a one SD increase in intelligence in the U.S. And while I’m not going to exaggerate the slavery-and-discrimination factor, how much selective advantage was there for children of field hands with high IQs?

        To me, that suggests the answer to your question is “Not enough time yet.”

    • Ariadne says:

      As of 2016, it looks like Clarke’s next book was “The Son Also Rises”, which seems to have found a lower rate of social mobility. Though where the boundary is between “class-bound” and “mobile” lies is a matter of definition — even if people with wealthy ancestors 300 years ago are wealthier today, that doesn’t mean that there is a ruling class that is sealed off from the rest of the population.

  5. dearieme says:

    My first reaction to Clark’s stuff is to laugh. Not to laugh at it, but rather to laugh at its implication. The world is over-provided with Faculties of Social Science – staffed, in large proportion, with rather dim people floundering around in a morass of lousy data, trying desperately to impose onto them interpretations consistent with their quasi-religious political doctrines. And then Clark says look at what I have learned from surnames. Really, you’ve got to laugh.

    • Ian says:

      Clark isn’t the first to have investigated social mobility in medieval England, nor he is the only one investigating social mobility in more recent times. In Britain, it’s been well established that social mobility has decreased in recent decades.

      Click to access IntergenerationalMobility.pdf

      Clark also reported that people with Norman surnames such as Percy and Glanville still tended to enjoy slightly greater wealth (10%) and life expectancy (3 years) in present-day Britain, although the differences were less extreme than those in the 1850s.

    • Anonymous coward says:

      The world is over-provided with Faculties of Social Science – staffed, in large proportion, with rather dim people floundering around in a morass of lousy data, trying desperately to impose onto them interpretations consistent with their quasi-religious political doctrines.

  6. says:

    This reminds me that David C Rowe had a paper on Herrnstein’s syllogism.

    Click to access Rowe1999.pdf

  7. j says:

    (1) Ashkenazim have higher proportion of shortsighted and very shortsighted people. It is linked to that thingie you call merit. We need another word for it.
    (2) Merit conveys the wrong idea so we need another world for it. I propose mereor (deserving, in Latin), dignitas (merit in Latin), virtus (the quality of being a man ie human), élan, cachet, character, binah (בינה from Hebrew, wisdom), baquía (the gaucho ability to adapt instantly one’s behaviour in an unexpected situation).
    (3) In real life, castes have very short duration (except in India). Further playing around aka research is required.

    • Henry Harpending says:

      You are right, we should have another word for it. I find myself not paying much attention to words but others do. I am happy to stick with X and Y.

      “Merit” is not so bad if it is defined as the direction in high dimensional space that is measured to impose class mobility. Fat chance of getting that past the thought police.

      How do castes have short duration? Wealthy and poor have been around a long time. They aren’t closed but maybe are getting more and more closed.

      • j says:

        As Jesus said, the poor will be with you forever but are the poor a caste?

        X and Y will not do because traditionally, X are female and Y, male.

        Neither will “class mobility” work for IQ. Maybe we should rank people by H (for Human). 1.0 H = IQ 140. In that scale, 0.5 H refers to IQ 70.

  8. Matt says:


    This model is based on two classes. The more classes you add and the closer they are together, the more you will approximate a normal distribution(?). If every occupation is a class and they aren’t distributed very far apart, you won’t have anything that looks very different from a single normal distribution(?).

    Recall that there are no fitness differences in this model.

    Downward mobility seems key. If there is a fitness gradiant following merit such that high merit individuals are always fitter, then the descendents of the high merit group will continuously replace the low merit group.

    Perhaps in some societies with Castes, chiefly India (but perhaps true to a lesser extent elsewhere, for instance with the Burakumin and slave populations in the New World), the defining factor is not so much more or less meritocracy as lack of downward mobility – i.e. there is a strong social stigma against downward mobility, or there hasn’t a single “merit” that has a linear (or at least mostly linearly positive) relationship with fitness in general.

    A surprise to me from this model was the rapidity with which classes turn into castes: most of the action is in the first generation or so.

    Henry, how quickly would you imagine that the classes would collapse their genetic difference if they were subsequently then reified into legal castes without any upwards or downwards mobility? Probably not quite at a comparable speed, but any estimates?

    • Henry Harpending says:

      If the model had a large number of (graded) classes then an overall histogram might start looking normal. I suppose it depends on what size is imposed on each class in this kind of model.
      I expect you are right on the money with your idea that closure to downward mobility is important in preserving the identity of groups like Burakumin.

      If classes were sealed into legal castes, as you suggest, then genetic differences would not collapse, they would just sit there unchanging. Remember that all the regression to the mean happens in one generation.

  9. Deckin says:

    Do I have it right to assume that mating, in the model, occurs exclusively within class? I imagine you’d get basically the same result, albeit requiring longer generational iteration, if you allowed for a mating differential between classes. I.e., 70% or so of mating is intra class but the remainder is inter class. That would probably model the actual situation better, generating a more powerful conclusion, without hopelessly mucking up the model.

    • Henry Harpending says:

      Right, I changed my typo to read “within” rather than “with”
      My intuition is that allowing that much interclass mating would stop the process in its tracks very fast, but we have to do the numbers. As j says above “further playing around aka research is needed”

      • gcochran9 says:

        Stops it cold and greatly limits the final difference between classes. In words, the same amount of interbreeding pulls down the upper group more and more as the intergroup difference grows.

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  11. Deckin says:

    Thanks for the responses; much appreciated. I guess then we’d need some models/data on actual assortive mating. I’d imagine things could get real complicated because to the extent that there is inter non-assortive mating, it wouldn’t likely be random from either side, at least in real life. It would be structured in that it would occur more frequently within +- 1SD of the mean, and so on. Also, thanks FredR for the link to Clark’s new precis. Super interesting stuff.

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  13. dearieme says:

    ““Merit” is not so bad”: nor so good. If you are thinking of an individual advancing in a society whose demands are set irrespective of that particular individual, “value” might be preferable. And it doesn’t contain the moralising implication of “merit” while also carrying less of the implication of patting oneself on the back implied by some of j’s suggestions.

  14. bob sykes says:

    Excuse me, but there is very strong selection here, and there is a tacit fitness component, otherwise the sorting would not occur.

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  16. Luke Lea says:

    The best hope for democracy, in my opinion, lies in creating a new counter-elite whose interests are closely tied to the interests of labor, to counterbalance our current elite tied to capital. Both elites would be brains-based, to be sure, thus tending towards cast, but between them would represent the interests of the two main productive classes in society.

    To pull off such a thing would probably involve founding a new set of elite colleges and universities for recruitment and training, not unlike what happened when religious dissenters in 17th century Britain, Scotland especially, set up the University of Edinburgh (followed by Harvard, Yale, and Princeton) as the equal of Oxford and Cambridge. Natural selection would be by self-selection and escape from population sinks, which is already happening to a certain extent.

    Here I imagine such a development in concrete terms: God knows if it’s not crazy.

  17. Abelard Lindsey says:

    The best hope for democracy, in my opinion, lies in creating a new counter-elite whose interests are closely tied to the interests of labor, to counterbalance our current elite tied to capital.

    Better yet would be the development of some kind of manufacturing technology that breaks the trend towards capital intensiveness (i.e. semiconductor manufacturing) in manufacturing and productive accomplishment, in general. The less capital required to do things, the less relevant the elite based on such capital is to productive accomplishment. 3-D fabbers, biotech, and perhaps some kind of molecular manufacturing come to mind. I do not believe any kind of political or social solution exists for this problem.

    About “merit”, we need a new term to defined a combination of traits including IQ, conscientiousness, future time orientation, honesty, and focus; that correlate with “success”. Executive Function includes some (but not all) of these traits.

    • Ian says:

      Any single word is likely to be woefully inadequate since so many different abilities can play a part in successfully climbing the social ladder. No one has yet mentioned ambition, Machiavellianism, dominance, extraversion, energy, or even height. In other times and places, fighting ability has played a significant role as well.

      • Practical selection says:

        Nice. I my opinion, high intelligence is correlated with many of the traits that you mention. Fighting ability is very interesting. I believe it is extremely important and is hardwired trait of the “ideal”, classic, Cro-Magnon man. I mean there is a number of indispensable traits for a full functioning individual and fighting ability is one of them.
        Modern “merit” may be disproportionally linked to ability to sit diligently and solve standard problems. Problems that are not too hard, do not required too much creativity.
        Modern Homo Meritus is thus not the “ideal” human, that combines intelligence with many other traits.
        My general comment on theme is that the casts exist already. For instance, marriage is now reserved to couples where both parents have high intelligence and eduction. For the rest of the population (in black and whites, in US and in UK), traditional family is not available.
        My second general comment is that the natural selection today is back and it is at extreme intensity. The less intelligent cast, as presented here, is decimated by drugs (the war to protect them is lost), by homosexuality propaganda, by propaganda of antisocial behavior and resulting sexually transmitted diseases (genital herpes, HIV). The more intelligent cast is decimated by low birth rates.
        Thus, for both less and more intelligent casts, their lifetime is one or two generation, before they are replaced by migrants that do reproduce in large enough numbers. It is the extinction of Native Americans, but repeated at almost every generation.

  18. Luke Lea says:

    If you select just for smarts and not also for looks, you end up with a smart class composed of a lot of less-than-good-looking females. Males however will always be attracted by above average looks, which would lead to a lot of inter-class breeding.

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  21. Benk says:

    What happens when ‘castes’ sort along more than one axis? I’m thinking that the castes in India, and the classes in pre-revolutionary France, had more distinguishing them than simply income and IQ.

    • harpend says:

      Very interesting question. As @J says above, “further playing around aka research is needed”

      If there is some kind of single dimension that we can construct, if for example using IQ we found that time preference and problem solving and ambition were positively related then this would let us estimate a single number, “merit”, and nothing much changes.

      But what if there is a “mobility landscape” with lumps. In a high dimensional space one peak might be our merit, another might be charisma or salesmanship or something like that, another might be management ability. Hard to imagine the high dimensional coalescence into castes that this could lead to, although Greg tells me that in India several years ago there were two incipient castes, VHS repairmen and Beta repairmen, that have since dissipated.

  22. steve says:

    My personal opinion is that you are largely correct, but that it is mostly learned and not hereditary. In other words, I think hard work, honesty, concientiousness etc. is largely learned from ones parents and not inherited. This would still result in the class divide you indicate. Although, it would be a matter of free will that any individual family could break the cycle.

    • LemmusLemmus says:

      That’s not a matter of opinion. If you simply type some appropriate search terms into Google Scholar –

      – you’ll find studies that say otherwise. Here’s from the first three abstracts that Google Scholar coughs up:

      “Estimates of genetic and environmental effects for Openness and Conscientiousness were similar to those found in other studies of personality: Genetic influence was substantial and there was little evidence of shared rearing environment.”

      “Broad genetic influence on the five dimensions of Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness was estimated at 41%, 53%, 61%, 41%, and 44%, respectively. (…) Shared environmental influences accounted for a negligible proportion of the variance in most scales, whereas nonshared environmental influences accounted for the majority of the environmental variance in all scales.”

      “Behavior-genetic models were fit to what the three measures had in common, and to the variance distinctive to each. The results of the model fitting agreed with other recent studies in showing the Big Five dimensions to be substantially and about equally heritable, with little or no contribution of shared family environment. Heritabilities for males and females did not differ significantly. For Agreeableness and Conscientiousness, some effect of shared environment was found for measure-specific variance on the personality inventory”

    • Ariadne says:

      Steven Pinker notes that the vast majority of people are raised by their biological parents, so in practice the difference between genetic inheritance and social inheritance (from one’s parents) is very small. There is, of course, data on this, but when dealing with the public, it’s best to avoid the nature vs. nurture debate as much as possible.

  23. steve says:

    Another point that occured to me is that if it is hereditary then there should be at least one strong countervailing tendency to this class system. Specifically, people can and do marry for looks regardless of IQ. Would this tendency be just as strong resulting in the beautiful cast and the ugly cast or even four castes? Pity the ugly and stupid. Or does this just draw the two castes closer together due to mixing.

  24. TallDave says:

    “Mobility” is the wrong word because it elides the problem of choice.

    What “mobility” surveys tend to measure is the tendency, not the ability, to move between classes. Most Americans who are poor have consciously made choices that resulted in them being poor, and are generally happier that way. Hard work is… hard. And when the bottom 5% of Americans live better than the top 5% of people in India, can we really say theirs is the less rational choice?

    If you want to see mobility, look at American immigrants. Many, especially Asians/Indians, come here and earn 10-100x what their parents did, often despite not even having English as a first language. It’s a choice!

    • Noumenon says:

      I believe you because I chose to work where I don’t have to shave or wear a suit. But what does it mean then if Europe has less income mobility? That the poor life is less attractive there?

    • thrasymachus33308 says:

      LIfe is more complicated than that. Libertarians vastly overestimate to what extent a person has free will.

  25. ad*m says:

    Here is some literature:

    Myopia is associated with IQ and with educational level, for example in Danish conscripts:
    and in Singaporean children

    Retinal detachment is positively associated with affluence, for example in Scotland

    Click to access 1591.full.pdf

    Myopia is associated with retinal detachment, for example in Sweden:

    Openness is associated with myopia, for example in Australia

    There is a lot of evidence for A->B->C, not so much A->C

  26. TallDave says:

    BTW, re myopia — there was a fascinating study in Australia suggesting being indoors more at young ages is also correlated to myopia (which might explain the IQ correlation: higher-IQ kids are reading more). Their theory is that exposure to sunlight causes changes in the shape of the developing eye.

  27. Bryan Willman says:

    One difference between this model and the real world is that in the real world there are many simultaneous definitions of merit, and they change over time.

    For example, in the modern era, the ability to be a great player in the NFL will, at least for a while, grant relative high status, very high earnings, and so on. Likewise, the ability to effectively use and develop computers, robots, and so forth. Neither of those merits had any great or broad value before, say, 1900.

    Historical studies suffer from the problem that, by definition, only a small part of the population are elites, and in a growing population an elite person might have 10 children for 2 elite slots. The other 8 will “fall”, or move to help found America, etc.

  28. Justin H says:

    I love the effort to describe a social problem with a simple quantitative model. It really sharpens our thinking about the issue.

    However, I argue that the proposed model is based on questionable assumptions. The model divides society into precisely two classes without intermarriage. This is an assumption of the model and not a conclusion. If one accepts the assumptions, the model implies that the classes will diverge in “IQ” until the inter-class differences are larger than intra-class differences. But the assumptions are very strong and have a questionable basis in real social situations. My experience suggests that class is better approximated by a continuous gradient. In historical cases where sharp class distinctions existed, traditional castes in Indian, or nobility/commoners in Medieval Europe), those classes were maintained by a strong social rules, and not by other natural mechanisms. Consequently, I would argue the “two class” assumption only holds in societies that have a strong culture tradition of such. The model cannot explain the origin of a two class system. Rather, it only argues for a divergence of IQ if the two class system, along with class mobility, is assumed

    I suggest a different model without predefined classes. In this model, Individuals tend to mate with others of similar IQ, but a strict partition does not exist. Under these relaxed assumptions, castes do not appear spontaneously. Rather, our descendants drift slowly through IQ space, much like diffusing particle.

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  31. As long as there is variation, heritability of variation, and differential perpetuation of that variation, there will be no end to evolution.

  32. Konkvistador says:

    Considering this sorting produces more variance overall, shouldn’t we according to Fisher’s fundamental theorem of natural selection expect evolution to proceed at a faster pace than usual?

    Either left or right depending on the selective pressures…

  33. > Maybe that first generation starts after World War Two, when board scores replaced economic class for those who got into the most prestigious universities.

    Each generation believes that it invented sex, and each generation believes that meritocracy started with it. Reading old books, selection by entry score was dominant in 1900, and affirmative action for women was starting around 1910. Back in 1870, they used less formal indicators of merit, but I find it plausible to believe that academic selection was highly meritocratic at least as early as the late nineteenth century, and has been getting less meritocratic ever since as college entrance became more political – and by 1910, it was already rather political.

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  35. Turning up very late to this, but something close to this argument was made by Michael Young in his satire “The Rise of the Meritocracy” in 1958. I think he invented the word meritocracy, by the way.

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  37. Patrick Boyle says:

    Speaking of myopia. I ran into some interesting effects of the genetics of myopia in my research for my little video on the Tuskegee Airmen. Ashkenazi Jews, East Asians an other high IQ peoples have bad eyes. But blacks have myopia rates among young males that are just about half that of the majority white population. All other things being equal the black fighter pilots of the Tuskegee Airmen should have been better pilots because eyesight is one of the most important qualities you want in a fighter pilot. It is much more important than IQ for example.

    But of course other things are seldom equal. The very real differences that the black pilots exhibited were from other factors.


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  39. infowarrior1 says:

    Certainly high rates of Myopia is Dysgenic is it not? And certainly there are plenty of high IQ types without myopia. Surely IQ need not come at the cost of other dysgenic physiologically detrimental effects.

  40. anon says:

    Class is the “ultimate” genetic metric and means of human evolution. IQ is just a genetic black box trying to predict economic potential that is a loose correlate. Therefore, your aristocratic class in a free market society will be a reservoir of the best genetic stock (intelligence, personality and physical complement). In ancient continuous societies like England, with 1000 year old aristocratic classes, you’ll see a huge dimorphism. In the 19th century the upper class in the UK was 5 inches taller.

    In ancient Egypt’s 3000 year old civilization, you see a similar situation. The upper glass literally did look like gods. Upper class beauty and “divine right” went hand in hand. They were bred over thousands of years to look like gods so that the pharoah could command obedience.

    Askinazi jewish intelligence almost certainly evolved in a similar manner where established dynastic rabbinical lines were reservoirs of high IQ and fecundity over centuries.

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  43. Abraham Lincoln says:

    In a population of 315 million people, once the dumb half has a mean -1SD and the smart half has a mean +1SD, doesn’t the “smart fraction” (say, +2SD) of the overall population increase from ~6 million to ~19 million people?

  44. Ariadne says:

    I ran a simulation of the situation described in the post, where, in the initial population, 60% of variance was due to inheritable factors and 40% was “random”. What I saw was that after many generations, the distribution of “merit” across the whole population was broader than a normal distribution but not bimodal, and the class mobility (the chance that an individual would be in a class different than the class of his parents) was around 20%. The difference of the means of the classes was less than twice the population s.d.

    So I think the results you’d see in a human society would be less shocking than what is presented in the original posting. I suspect that’s because the o.p. focuses the distribution of genotypes in the population, which even with 60% heritability, is much more segregated than the distribution of phenotypes (which is what will cause social friction).

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