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High Schools Disrupt Natural Teen Sleep Schedules June 04, 2005 On The Evolution Of Ashkenazi Jewish Intelligence Ashkenazi Jews pose two mysteries for biological science. First, why do they have so many genetic diseases that fall into just a few categories of metabolic function such as the sphingolipd storage diseases Tay-Sachs, Gaucher, Niemann-Pick, and mucolipidosis type IV? The rates of such diseases are so high that their incidence must be the result of either a recent genetic bottleneck where the Ashkenazi population was very small or natural selective pressures aimed at some other phenotype selected for these genotypes due to advantages that those genotypes offer for other functionality. Granted, a lot of Jews want to argue that they are just studious due to their culture. Also, lots of ideologues - particularly on the political Left - stand ready to attack anyone who argues that ethnic and racial groups differ in average intelligence. But the higher average level of Ashkenazi Jewish intelligence is so glaringly obvious that I figure anyone who tries to argue otherwise is either engaged in intellectual con artistry or is ignorant or foolish.
Henry Harpending, Gregory Cochran (a PhD physicist turned genetic theorist), and Jason Hardy put forth a hypothesis that seeks to explain both mysteries simultaneously. Nicholas Wade of the New York Times has written one of the two news stories about it to date.
The proposed hypothesis holds that Jews developed their genetic diseases as a side effect of strong selective pressures for higher intelligence during the Middle Ages as they were forced to work mainly in occupations that required greater cognitive ability.
here) A team of scientists at the University of Utah has proposed that the unusual pattern of genetic diseases seen among Jews of central or northern European origin, or Ashkenazim, is the result of natural selection for enhanced intellectual ability. The selective force was the restriction of Ashkenazim in medieval Europe to occupations that required more than usual mental agility, the researchers say in a paper that has been accepted by the Journal of Biosocial Science, published by Cambridge University Press in England. The Economist has the other article about this research paper.
This concentration of mutations argues for selective pressures as the logical expanation for rate of occurrence of these mutations in Ashkenazi Jews. What can, however, be shown from the historical records is that European Jews at the top of their professions in the Middle Ages raised more children to adulthood than those at the bottom. Of course, that was true of successful gentiles as well. But in the Middle Ages, success in Christian society tended to be violently aristocratic (warfare and land), rather than peacefully meritocratic (banking and trade). Put these two things togethera correlation of intelligence and success, and a correlation of success and fecundityand you have circumstances that favour the spread of genes that enhance intelligence. The questions are, do such genes exist, and what are they if they do? Dr Cochran thinks they do exist, and that they are exactly the genes that cause the inherited diseases which afflict Ashkenazi society. That small, reproductively isolated groups of people are susceptible to genetic disease is well known. Constant mating with even distant relatives reduces genetic diversity, and some disease genes will thus, randomly, become more common. But the very randomness of this process means there should be no discernible pattern about which disease genes increase in frequency. In the case of Ashkenazim, Dr Cochran argues, this is not the case. Most of the dozen or so disease genes that are common in them belong to one of two types: they are involved either in the storage in nerve cells of special fats called sphingolipids, which form part of the insulating outer sheaths that allow nerve cells to transmit electrical signals, or in DNA repair. The former genes cause neurological diseases, such as Tay-Sachs, Gaucher's and Niemann-Pick. And what is even less random is that in several cases the genes for particular diseases come in different varieties, each the result of an independent original mutation. This really does suggest the mutated genes are being preserved by natural selection. But it does not answer the question of how evolution can favour genetic diseases. The analogy is to overclocking computer processors (computer processing units or CPUs). Some hobbyists turn up the clocks on their desktop PCs to them run faster than they were designed to run. In the case of the Ashkenazis in Europe the hypothesis proposes that selective pressures for higher Ashkenazi intelligence were so high that it caused the propagation of mutations that pushed their intelligence up so quickly (evolutonarily speaking) that the selective pressure overrode the reduction in reproductive fitness caused by the deleterious side effects on some of those who received those mutations.
The problem with overclocking is that "Sometimes you get away with it, sometimes you don't." But I'll hazard a guess: the change accelerates some brain system tied to cognitive functioning - nearly redlines it, leaves it vulnerable to common insults in a way that can cause spectacular trouble. More generally, if this is what I think it is, all these Ashkenazi neurological diseases are hints of ways in which one could supercharge intelligence. One, by increasing dendrite growth: two, by fooling with myelin: three, something else, whatever is happening in torsion dystonia. In some cases the difference is probably an aspect of development, not something you can turn on and off. In other cases, the effect might exist when the chemical influence is acting and disappear when the influence does. In either case, it seems likely that we could - if we wanted to - developed pharmaceutical agents that had similar effects. The first kind, those affecting development, would be something that might have to be administered early in life, maybe before birth. while the second kind would be 'smart pills' that one could pop as desired or as needed. Of course, we have to hope that we can find ways of improving safety. Would you take a pill that increased your IQ by 10 or 15 points that also had a 10% chance of putting you in a wheel chair? Looked at from this perspective many Jews have paid and continue to pay a high price from the effects of mutations that "overclock" their brains. This hypothesis cries out to be tested because if it is proven then, as Greg points out, these mutations point in directions for research aimed at raising human intelligence.
one can even put a price tag on the value of higher intelligence. However, such calculations understate the economic value of higher intelligence because most of the value of scientific and technological knowledge produced by high IQ people flows to lower IQ people.
The paper is downloadable as a 40 page PDF (on big PDFs I get better results downloading to a file and then opening rather than running Acrobat Reader from within a browser). This paper elaborates the hypothesis that the unique demography and sociology of Ashkenazim in medieval Europe selected for intelligence. Ashkenazi literacy, economic specialization, and closure to inward gene flow led to a social environment in which there was high fitness payoff to intelligence, specifically verbal and mathematical intelligence but not spatial ability. As with any regime of strong directional selection on a quantitative trait, genetic variants that were otherwise fitness reducing rose in frequency. In particular we propose that the well-known clusters of Ashkenazi genetic diseases, the sphingolipid cluster and the DNA repair cluster in particular, increase intelligence in heterozygotes. Other Ashkenazi disorders are known to increase intelligence. Although these disorders have been attributed to a bottleneck in Ashkenazi history and consequent genetic drift, there is no evidence of any bottleneck. Gene frequencies at a large number of autosomal loci show that if there was a bottleneck then subsequent gene flow from Europea...
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