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IQ And Disease: The Curious Case of the Ashkenazi Jews
The slow liberation of the Mainstream Media from the deathgrip of political correctness accelerated last week with startlingly courageous coverage in The Economist and the New York Times of the potentially epochal scientific paper by Gregory Cochran, Henry Harpending, and Jason Hardy entitled The Natural History of Ashkenazi Intelligence [PDF file].
The Economist headlined its anonymous article:
And in "Researchers Say Intelligence and Diseases May Be Linked in Ashkenazic Genes,"[ June 2, 2005] the NYT's redoubtable genetics reporter Nicholas Wade reported
"'It would be hard to overstate how politically incorrect this paper is,' said Steven Pinker, a cognitive scientist at Harvard, noting that it argues for an inherited difference in intelligence between groups. Still, he said, 'it's certainly a thorough and well-argued paper, not one that can easily be dismissed outright.'"
The high average intelligence of the Ashkenazi Jews (essentially, Jews from Northern Europe whose ancestors spoke Yiddish, ancestors of the great majority of Jewish Americans) has had an enormous impact on the modern world.
(Jews from the Muslim world score somewhat lower than Ashkenazis, which leads to a sizable social gap within Israel.)
The Economist reported:
"Ashkenazim generally do well in IQ tests, scoring 12-15 points above the mean value of 100..."
Which is not an enormous gap. Assuming a 12 point difference between Ashkenazis and white gentiles, it suggests that the median Ashkenazi scores somewhere around the 80th percentile among all whites. Many gentiles have higher IQs than many Jews.
But this difference in median intelligence does lead to large differences at the far right edge of the bell curve.
For example, some back-of-an-envelope math suggests that Ashkenazi Jews are roughly an order of magnitude more likely than white gentiles to have IQs above 145. Roughly one in 70 Ashkenazi Jews score above 145 compared to one in 700 white gentiles. There are about 30 times as many white gentile adults as Ashkenazi Jews in the U.S. So that implies one-fourth of white Americans with IQs above 145 are Ashkenazi Jews.
Ashkenazi levels of real world accomplishment are impressive and thus support the IQ studies. Jewish Americans make up no more than three percent of the U.S. adult population. But in the 1995 book Jews and the New American Scene, the prominent social scientist Seymour Martin Lipset, a Senior Scholar of the Wilstein Institute for Jewish Policy Studies, and Earl Raab, Director of the Perlmutter Institute for Jewish Advocacy at Brandeis University, pointed out
"During the last three decades, Jews have made up 50% of the top two hundred intellectuals, 40 percent of American Nobel Prize Winners in science and economics, 20 percent of professors at the leading universities, 21 percent of high level civil servants, 40 percent of partners in the leading law firms in New York and Washington, 26% of the reporters, editors, and executives of the major print and broadcast media, 59 percent of the directors, writers, and producers of the fifty top-grossing motion pictures from 1965 to 1982, and 58 percent of directors, writers, and producers in two or more primetime television series." [pp 26-27]
Interestingly, the Ashkenazi cognitive advantage seems to be mostly in verbal and numeric, rather than visual, skills. For example, in Hollywood, fewer top cinematographers are Jewish compared to screenwriters or agents.
Ashkenazi intelligence is one of those facts that are obvious, important, and interesting, yet, is largely unmentionable in polite society… at least until this week.
The Cochran-Harpending theory may turn out to justify the audacity of The Economist and the NYT in breaking this taboo. If validated, it would prove a landmark in the fields of medicine, population genetics, IQ research, and even history.
Wade reported in the NYT:
"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… Ashkenazic diseases like Tay-Sachs, they say, are a side effect of genes that promote intelligence."
Wade goes on to note that this theory was anticipated by Jared Diamond, the celebrated author of the Pulitzer Prize-winning Guns, Germs, and Steel (here's my review). Diamond pointed out in 1994 that one possible explanation for these Ashkenazi hereditary diseases 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."
In their brilliant cross-disciplinary essay, which will appear soon in the Journal of Biosocial Science, the three University of Utah researchers show that from about 800 to 1700 A.D., Yiddish-speaking Jews were almost completely confined to cognitively-demanding occupations such as finance, fields in which intelligence pays off more than in peasant farming.
They cite records showing that wealthy Jews had more children survive to adulthood than poor Jews. Moreover, medieval Jews were sufficiently endogamous (marrying within the ethnic group) to prevent gene flow from the gentile population, which might have diluted the effects of this selection mechanism.
Contrary to the layman's assumption that Darwinian selection can only putter along at geological speeds, the authors mathematically demonstrate that the 35 generations during these nine centuries offered enough time for mutations conferring greater business acumen to spread widely among the Ashkenazi.
Sadly, however, there haven't been enough generations for natural selection to refine away the downsides to some of these intelligence-boosting mutations.
Cochran, Harpending, and Hardy cite evidence that the victims of three hereditary diseases that primarily afflict Ashkenazis tending to be smarter than even other Ashkenazis. For example, a study of patients with torsion dystonia, which until recently put 10 percent of its victims in wheelchairs, found their average IQ was 121.
Tay-Sachs and several other Ashkenazi sphingolipid neurological diseases could be analogous to sickle cell anemia, which is the snag in nature's initial attempt to provide genetic protection against the horrendous tropical killer, falciparum malaria.
That mosquito-borne disease appears to have only become a devastating threat a few thousand years ago, when agriculture began in Sub-Saharan Africa. Enough generations have since gone by for the sickle cell mutation to emerge and spread in tropical Africa and other warm places ravaged by this most deadly of malarias. If you inherit a copy of the sickle cell gene from one of your parents, you are more likely to survive falciparum malaria. But, unfortunately, if you inherit copies from both of your parents, you will die in infancy—unless you get modern medical care.
The sickle cell gene increases until the benefit it provides in surviving malaria is equaled by the toll it takes in sickle cell anemia.
The Ashkenazi sphingolipid disorders could be similar. In the great tradition of Einstein's paper on the General Theory of Relativity, the Utah authors have proposed a straight-forward test of one part of their theory: people with one copy of the genes that cause the Ashkenazi sphingolipid diseases should have higher IQs than their siblings who have no copies.
If validated, the implications of this discovery would be extraordinarily broad.
With luck, it could lead to better treatments of victims of these diseases.
It could also aid understanding of the genetics of intelligence, which in turn might lead to "smart pills" or genetic engineering to boost IQ.
Whether or not that would be a good thing for the human race is difficult to say at present. But allowing the honest study of the social impact of existing genetic differences would help us make better informed decisions about whether we want to permit bioengineers to create new genetic disparities in the lab.
The savage persecutions suffered by Jews suggest that high intelligence can generate resentment among the masses. No doubt there will be some who will suggest that the Cochran-Harpending paper should have been suppressed to prevent awareness of the secret of Ashkenazi intelligence from seeping out.
But you have to be a true-blue intellectual to assume that the only way anybody would ever notice anything as obvious as Jewish brainpower is if it gets mentioned in the New York Times. Political correctness doesn't keep facts from being talked about—just from being written about in an intelligent, constructive manner.
On the other hand, the happier experience of another ethnic minority that may also have evolved stronger intellectual capacities under similar urban conditions—the prosperous Parsis of Bombay—may offer clues to mitigating envy.
In any case, the Cochran-Harpending paper offers a fairly new but crucial perspective on the old nature and nurture question. The researchers have demonstrated that it's quite possible for nurture to change nature. Culture can drive heredity. Economics and social customs alter gene frequencies.
Of course, we already knew that from examples such as lactose intolerance. Once, virtually no adult could easily digest milk. But after some tribes started herding and milking dairy livestock, one or more mutations providing lactose tolerance popped up and spread among them. Thus today, only two percent of Danes are lactose intolerant, compared to 90 percent of Asian Americans.
There may be many more examples of the environment molding genes. For instance, I recently described how the economics of tropical agriculture, in which mothers could frequently raise enough food to feed their children without much help from the fathers, tend to differ from the economics of temperate agriculture, where the labor of fathers often made the difference between their kids' survival or starvation. This leads to different family structures and different behavioral tendencies between tropical and Eurasian men -- what Harpending calls the "Cad vs. Dad" pattern of low vs. high paternal investment.
Are those disparities, which appear to manifest themselves in the large racial inequality in illegitimacy rates seen in modern America, cultural or innate?
Certainly they started out being cultural. But it's possible that selection made them partially inborn over time.
Finally, it's not surprising that Henry Harpending and Gregory Cochran came up with such a stunning paper.
Harpending, who is with the University of Utah's outstanding anthropology department, is one of the leading population geneticists. Unusually for such a mathematically-oriented scientist, he has also lived for 42 months in the field with African tribes. Indeed, his love of Africa is so great that he almost left academia at one point to become a safari guide.
I stay in touch with some quite smart people, but even among them, Gregory Cochran is legendary for the ferocity of his scientific originality.
The Economist describes Gregory Cochran as:
"… a noted scientific iconoclast... He is that rare bird, a scientist who works independently of any institution. He helped popularize the idea that some diseases not previously thought to have a bacterial cause were actually infections, which ruffled many scientific feathers when it was first suggested. And more controversially still, he has suggested that homosexuality is caused by an infection."
The Atlantic Monthly's February 1999 cover story by Judith Hooper, "A New Germ Theory," was about Cochran and another of his research partners, Paul Ewald, and their Darwinian theory for why more diseases will turn out to be caused by infections that doctors then expected. This year, the American Academy of Microbiology endorsed liberalizing Koch's Postulates, which have been the basis for determining if a disease is infectious since the 19th Century, along the lines Cochran and Ewald proposed.
The Atlantic noted:
"Cochran is a solo player, with an encyclopedic mind (he is a former College Bowl contestant) and a manner that verges on edginess."
I can attest that, although a physicist by education and the leading theorist of evolutionary medicine by avocation, Cochran also has memorized almost the entire political and military history of the human race. (Here's an amusing piece by him in The American Conservative showing the similarities between Bush's Iraq adventure and Napoleon's invasion of Spain.)
When I'm reviewing a historical film such as Master and Commander or Hero and I need to pretend to actually know something about the Age of Nelson or China's Warring States era, a call to Cochran will not only fill me in on what happened, but, more importantly, why it happened.
All the evidence isn't in yet. But it could be that Cochran and Harpending have opened the door to explaining why some of history's most important developments happened—and that, finally, the political culture is beginning to listen.