There’s a lively chat going on over at Mangan’s about how people react to the growing body of data about the diversity of various human groups with regard to IQ and general intelligence. That such differences actually do exist is at this point uncontroversial amongst those who study psychometrics, but it is of course a radioactive topic in public discourse; in Guns, Germs, and Steel, for example, Jared Diamond ruled it off-limits as a “loathsome” explanation for the differential success of various groups. That human groups vary in conspicuous ways is a plain fact — nobody would have any trouble, say, sorting out a mixed group of Afars and Inuits, no matter how thoroughly you jumbled them up — but to suggest that long-separated populations, developing in very different environments, may have systematic cognitive differences as well is to violate a strongly defended taboo. And by making such a suggestion, no matter how sensible it may be, or how well supported by evidence, one invites the nastiest sort of opprobrium. (Indeed, I have no doubt that some of you are forming dark, excommunicatory thoughts about me as you read this.)
Even highly acute minds can shut right down when this topic comes up. Because such diversity would be, for many, an intolerable fact, a common move is to deny the impartiality of the measurement, or — in an even more audacious rejection of reality, and of the evidence of our own experience — to deny that the concept of “intelligence” actually corresponds to anything real in the first place. As an example of this, here’s a column by David Brooks from a few years back. Read it first, and then read this point-by-point demolition of it by Alex B. over at Gene Expression.
As for why there should be such diversity of IQ amongst various groups, various suggestions have been put forward; perhaps the most compelling is the idea, presented with clarity and rigor in Michael Hart’s Understanding Human History, that adaptation to agricultural life in temperate zones — which requires careful planning and technical innovation in order to survive cold winters — creates a selection pressure in the direction of higher intelligence.
Critics of such views often insist that group differences in average intelligence, to the extent that they are real, must be the result of cultural influences: poverty, racism, and so on. There is no doubt whatsoever that these are important factors, that exert a significant influence. What is often overlooked, however, is that biological and cultural evolution are far from separate processes, and that they are often tightly connected.
In his book Apes or Angels?, Cornelius Troost cites the Ashkenazi Jews as a particularly instructive example of this. The Ashkenazis have among the highest IQs of any human population, and the reason appears to be due to a process of cultural pressure that in turn led to selection at the biological level. We read [p. 146];
Gregory Cochran, Henry Harpending, and Jason Hardy found that Yiddish-speaking Jews from Germany, France, and Poland were discouraged from any occupations except money-lending and tax collection. These occupations required high intelligence, especially in mathematics. From 800 A.D. to 1700 A.D. they served as the financial experts in these societies. Since they were also a self-contained population reproductively, they were subject to … selection which removed genes detrimental to success in those restricted jobs.
There is no doubt about the superiority of Ashkenazim in IQ. They are 3 percent of the US population but have won 27 percent of its Nobel prizes. They account for half the world’s chess champions. They are 20 percent of the professors at our major universities. The Ashkenazim are greatly overrepresented in the winner’s circle of the esteemed Fields Medal in mathematics.
On IQ tests the Ashkenazim score some 12-15 points above the white mean of 100 in the US. While this difference is impressive, at the upper end of the bell curve one out of 70 Ashenazim score above 145 while only one out of 700 white gentiles do so. About one-fourth of all white Americans above 145 are Ashkenazi Jews.
This is a remarkably salient result, made so in particular by the high reproductive isolation of the Jewish people.* If you had wanted to design an experiment to try to cultivate high intelligence, you could hardly have concocted a better one. And note that although the shaping influence was entirely cultural throughout — restriction of Jews to particular occupations, together with self-imposed reproductive isolation — the effect, after centuries, is now innate: Ashkenazi babies are born smart.
“Well,” you may object, “even if all of this may be true, why bring it up? It serves no purpose but to further divide and stratify an already tense and factious society. There’s nothing you can do with this knowledge, after all, other than to discriminate against people.”
The answer to that is that as matters stand, we do not proceed from an agnostic stance on this topic. We have already staked out a position — that all human groups are necessarily exactly identical as regards cognitive faculties — and it is one that entails enormous costs, in particular with respect to stubborn “achievement gaps” that we insist must be closed no matter how vain the effort, or ruinous the expense. It is increasingly clear, however, that this position appears to be at odds with reality — so the only recourse is either to perform ever-more-painful social and intellectual contortions to defend it (including harsher and harsher censure of those who insist on looking at the facts), or else to do the hard work of accommodating this knowledge in a just and compassionate way, by realizing that the aim of a just society simply ought to be the fair and equal treatment of all, as individuals, under the law: a goal that should in no way require the political suppression of facts, however unwelcome they may be. As Steven Pinker wrote in The Blank Slate, such thinking “elevates sappy dogmas above the search for workable solutions.”
Well, it appears that some of my more liberal-minded Park Slope neighbors have already gathered outside with a cauldron of pitch and a bushel of feathers, so that probably ought to be all for now, I think. Somebody’s at the door.
* Note: In the original version of this post, I quoted an erroneous statistic that said the current rate of Jewish intermarriage was 0.5%. This appears, clearly, to have been quite wrong. I apologize for my carelessness.