Ashkenazi Jewish intelligence

Whether Ashkenazi Jews tend to have higher intelligence than other ethnic groups has been an occasional subject of scientific controversy. A 2005 scientific paper, "Natural History of Ashkenazi Intelligence", proposed that Ashkenazi Jews as a group inherit higher verbal and mathematical intelligence but lower spatial intelligence than other ethnic groups, on the basis of inherited diseases and the peculiar economic situation of Ashkenazi Jews in medieval Europe. Opposing this hypothesis are explanations for the congenital illnesses in terms of the founder effect, explanations of intellectual successes by reference to Jewish culture's promotion of scholarship and learning, and doubts about whether a group difference in intelligence really exists. However, some believe that the ultimate answer to this question is a combination of both theories, because the two don't exclude each other.

"Natural History of Ashkenazi Intelligence"

"Natural History of Ashkenazi Intelligence", a 2005 paper by Gregory Cochran, Jason Hardy, and Henry Harpending, argued that the unique conditions under which Ashkenazi Jews lived in medieval Europe selected for high verbal and mathematical intelligence but not spatial intelligence. Their argument has four main premises:

1. Today's Ashkenazi Jews have a higher average mathematical and verbal IQ and an unusual cognitive profile compared to other ethnic groups, including Sephardi and Mizrahi Jews.
2. From roughly 800 to 1650 CE, Ashkenazi Jews in Europe were a mostly isolated genetic group. When Ashkenazi Jews married non-Jews, they usually left the Jewish community; few non-Jews married into the Jewish community.
3. During the same period, laws barred Ashkenazi Jews from working most jobs, including farming and crafts, and forced them into finance, management, and international trade. Wealthy Jews had several more children per family than poor Jews. So, genes for cognitive traits such as verbal and mathematical talent, which make a person successful in the few fields where Jews could work, were favored; genes for irrelevant traits, such as spatio-visual abilities, were supported by less selective pressure than in the general population. Furthermore, ostensibly intelligent Rabbis were not barred from reproduction as learned scholars of Christianity were, who were sequestered in monasteries and nunneries.
4. Today's Ashkenazi Jews suffer from a number of congenital diseases and mutations at higher rates than most other ethnic groups; these include Tay-Sachs, Gaucher's disease, Bloom's syndrome, and Fanconi anemia, and mutations at BRCA1 and BRCA2. These mutations' effects cluster in only a few metabolic pathways, suggesting that they arise from selective pressure rather than genetic drift. One cluster of these diseases affects sphingolipid storage, a secondary effect of which is increased growth of axons and dendrites. At least one of the diseases in this cluster, torsion dystonia, has been found anecdotally to correlate with exceptionally high IQ. Another cluster disrupts DNA repair, an extremely dangerous sort of mutation which is lethal in homozygotes. The authors speculate that these mutations give a cognitive benefit to heterozygotes by reducing inhibitions to neural growth, a benefit that would not outweigh its high costs except in an environment where it was strongly rewarded.

Other scientists gave the paper a mixed reception, ranging from outright dismissal to acknowledgement that the hypothesis might be true and merits further research.

Other evolutionary theories

Other suggested evolutionary accounts include: a long cultural history encouraging scholarship and learning; a contribution of talent in the study of Torah to social success in Jewish communities; the enforcement of a religious norm requiring Jewish fathers to educate their sons, whose high cost caused voluntary conversions, explaining a large part of a reduction in the size of the Jewish population; that historic persecution of European Jews fell disproportionately on people of lower intelligence.

Does a group difference in intelligence exist?

One basic question to be answered in assessing a genetic explanation of unusual intelligence in Ashkenazi Jews is whether today's Ashkenazi Jews really do, as a group, have unusual intelligence. Assessing intelligence, especially of ethnic groups, is notoriously difficult and subject to racial and political biases.

One observational basis for inferring that Ashkenazi Jews have high intelligence is their prevalence in intellectually demanding fields. While Ashkenazi Jews make up only about 3% of the U.S. population and 0.2% of the world population, 27% of United States Nobel prize winners in the 20th century, a quarter of Fields Medal winners, 25% of ACM Turing Award winners, half the world's chess champions, and a quarter of Westinghouse Science Talent Search winners have Ashkenazi Jewish ancestry. However, such statistics do not rule out factors other than intelligence, such as institutional biases and social networks, nor should they be read as a percentage to percentage comparison due to the fractional nature of ancestry (i.e. half Ashkenazi).

Moreover, in addition there's another fact that brings up the question regarding Ashkenazi Jewish intelligence: Their extremely disproportional "share" in the wealthiest people in the United States as well as other countries (mostly Europeans ones). According to Forbes magazine and multiple other sources, despite being a minority, Jews make up more than 20% percent of the 400 Richest Americans, while some claim that the number is even higher.

A more direct approach is to measure intelligence with psychometric tests. Different studies have found different results, but most have found above-average verbal and mathematical intelligence in Ashkenazi Jews, along with below-average spatial intelligence. Some studies have found IQ scores amongst Ashkenazi Jews to be a fifth to one full standard deviation above average in mathematical and verbal tests^{[citation needed]}.

Problems with the genetic explanation

Assuming that today there is a statistical difference in intelligence between Ashkenazi Jews and other ethnic groups, there still remains the question of whether the difference is caused by inheritance or environmental factors. Evolutionary psychologist Steven Pinker suggested that "[t]he most obvious test of a genetic cause of the Ashkenazi advantage would be a cross-adoption study that measured the adult IQ of children with Ashkenazi biological parents and gentile adoptive parents, and vice versa", but noted, "No such study exists, so [Cochran]'s evidence is circumstantial."

The following are specific bases for doubt that genetic inheritance is the cause.

Problems found in studies of Ashkenazi genes

Most, though not all, of the Ashkenazi congenital diseases arose from genetic drift after a population bottleneck, and show no evidence of selective pressure of the kind called for in the Cochran, et al. paper. For example, the mutation responsible for Tay-Sachs disease arose in the 8th or 9th century, when the Ashkenazi Jewish population in Europe was small, just before they spread throughout Europe. The frequency of this mutation among Ashkenazi Jews today accords with genetic drift starting from a population bottleneck, not with selective pressure favoring its spread.

Though long thought to be a genetic isolate, one of recent studies have found that Ashkenazi Jews have higher European admixture than predicted from previous Y-chromosome analyses. This throws doubt on premise #2 of Cochran et al.

Problems with reproductive advantage

In medieval Ashkenazi society, wealth, social status, and occupation were largely inherited. The wealthy had more children than the poor, but it was difficult for people born into a poor social class to advance or enter a new occupation. Leading families held their positions for centuries. Without upward social mobility, genes for greater talent at calculation or languages would likely have had little effect on reproductive success.

It's not clear that mathematical and verbal talent were the prime factors for success in the occupations to which Jews were limited at the time. Social connections, social acumen, willingness to take risks, and access to capital (through both skill and nepotism) likely played at least as great a role. As these traits are also heritable, the force of natural selection may have been more dispersed than it appears at first glance.

The Talmudic tradition

After the destruction of the Second Temple in 70 CE, Jewish culture replaced its emphasis on ritual with an emphasis on study and scholarship. Unlike the surrounding cultures, most Jews, even farmers^{[citation needed]}, were taught to read and write in childhood. Talmudic scholarship became a leading key to social status.

The emphasis on scholarship came before the Jews turned from agriculture to urban occupations. This suggests that premise #3 of Cochran et al. has the causal direction backward: mastery of written language due to the Talmudic tradition may have made the Jews well suited for financial and managerial occupations at the time when these occupations provided new opportunities. Similar cultural traditions continue to the present day, possibly providing a non-genetic explanation for contemporary Ashkenazi Jews' high IQs and prevalence in intellectual fields.

See also

• History of the race and intelligence controversy
• Genetic studies on Jews and Medical genetics of Jewish people
• Race and intelligence

Further reading

• Ernest van den Haag. The Jewish Mystique, 1968

• Richard Lynn. The Chosen People: A Study of Jewish Intelligence and Achievement. Washington Summit Publishers, 2011.

• Cochran, Gregory; Hardy, Jason; and Harpending, Henry (2006): "Natural History of Ashkenazi Intelligence" (PDF). Journal of Biosocial Science 38(5):659–693 SEP 2006.

• Ferguson, B. (2008). How Jews Became Smart.

• Herrnstein, R.J. & Murray, C. (1994). The Bell Curve: Intelligence and Class Structure in American Life. New York: Free Press.

• Lynn, R. and Longley, D. (2006). "On the high intelligence and cognitive achievements of Jews in Britain." Intelligence, 34, 541–547.

• MacDonald, K. (1994). A People That Shall Dwell Alone. Westport, CT: Praeger.

• Murray, Charles (2003). Human Accomplishment: The Pursuit of Excellence in the Arts and Sciences, 800 B.C. to 1950. HarperCollins.

• Storfer, M.D (1990). Intelligence and Giftedness: Contributions of an Early Environment. San Francisco: Jossey-Bass.

External links

• Did Discrimination Enhance Intelligence of Jews?, National Geographic
• "Are Jews Smarter?: What Genetic Science Tell Us", New York Magazine
• The evolution of intelligence: The high intelligence of Ashkenazi Jews may be a result of their persecuted past, economist.com

• Murray, Charles. Jewish Genius, Commentary magazine

• Saletan, William. Jewgenics: Jewish intelligence, Jewish genes, and Jewish values, Slate

• Haslinger, Kiryn. "A Jewish Gene for Intelligence?", Scientific American, 21 September 2005.