Ashkenazi Jews, genetic diseases, and intelligence

As this article appearing in today's NY Times itself mentions, the theory isn't very PC.

I see some possible flaws in the reasoning--at least as it's described in the article. Of course I'm no scientist (obligatory disclaimer), but I do have a bit more than the general reader's knowledge of evolution. Judge for yourself, though, and read the article.

Once again, because of the Times's requirement for registration, I will reproduce more of the original article than is my usual practice:

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...

He and two colleagues at the University of Utah, Gregory Cochran and Jason Hardy, see the pattern of genetic disease among the Ashkenazi Jewish population as reminiscent of blood disorders like sickle cell anemia that occur in populations exposed to malaria, a disease that is only 5,000 years old.

In both cases, the Utah researchers argue, evolution has had to counter a sudden threat by favoring any mutation that protected against it, whatever the side effects. Ashkenazic diseases like Tay-Sachs, they say, are a side effect of genes that promote intelligence.

The explanation that the Ashkenazic disease genes must have some hidden value has long been accepted by other researchers, but no one could find a convincing infectious disease or other threat to which the Ashkenazic genetic ailments might confer protection.

A second suggestion, wrote Dr. Jared Diamond of the University of California, Los Angeles, in a 1994 article, "is selection in Jews for the intelligence putatively required to survive recurrent persecution, and also to make a living by commerce, because Jews were barred from the agricultural jobs available to the non-Jewish population."

The article then goes on to discuss whether the authors are correct in their interpretation of the existence of the genetic diseases and the possible link to intelligence, or whether the existence of the diseases have no connection to intelligence, but can be explained by something called "founder effect," which involves the amplification of random mutations in small populations. I took an entire course in population genetics in college, and so I remember a few basics, but the finer points have long departed my brain. So I have no idea which camp is correct. But the part that interested me most was this:

In describing what they see as the result of the Ashkenazic mutations, the researchers cite the fact that Ashkenazi Jews make up 3 percent of the American population but won 27 percent of its Nobel prizes, and account for more than half of world chess champions. They say that the reason for this unusual record may be that differences in Ashkenazic and northern European I.Q. are not large at the average, where most people fall, but become more noticeable at the extremes; for people with an I.Q. over 140, the proportion is 4 per 1,000 among northern Europeans but 23 per 1,000 with Ashkenazim.

The Utah researchers describe their proposal as a hypothesis. Unlike many speculations, it makes a testable prediction: that people who carry one of the sphingolipid or other Ashkenazic disease mutations should do better than average on I.Q. tests.

Whoa, that's some statistic! What the researchers are saying about the distribution of intelligence in the Ashkenazi Jewish population is very interesting, and it happens to somewhat parallel the argument Larry Summers was making (remember that?) about men vs. women in science--that is, that the major and important difference occurred not near the middle of the scale, but at the far extreme, the "genius" level many standard deviations away from the mean.

But to me, this fact makes the Utah scientists' arguments somewhat puzzling. Why would a selection process (if such a process actually did occur) for smarts that would confer an advantage in business and money-lending and surviving persection end up increasing the numbers of extreme intellectual outliers in a population, rather than just the average IQ of that population? Perhaps there's an explanation in there somewhere, but I don't see it. One would expect an increase in general intelligence, but not necessarily a greater increase in phenomenal intelligence; an increase in the ability to do arithmetic, perhaps, but not entry in such disproportionate numbers into the stratospheric regions of abstract math. I always thought arithmetic and higher math were not all that closely linked. And what about the ability to play chess? Chess is a game of strategy, to be sure, but it's a game of a special kind of strategy--spatial strategy (again, linked to higher math)--and it's hard to see how that ability would have been selected for by the processes these scientists describe, an aptitude for business, or the need to escape the Cossacks or whoever might be the persecutors du jour.

Fascinating, though. I'll be interested to learn whether people who carry these mutations in their benign single-cell form actually are especially smart. Somehow, I doubt it--but I expect we'll see when the results of the proposed research come out.