If the brightness of European Jews is primarily due to their culture, then we should all seek to be adopted by a Jewish mother. If, on the other hand, it is necessary to be actually born from Jewish parents, then any cultural tips we may get from them may be a bonus, but it is their genes that are crucial.
Some researchers have just had a look at this, and seem to have found a genetic explanation for part of the reason why European Jews are particularly bright.
Dunkel, C. S., Woodley of Menie, M. A., Pallesen, J., & Kirkegaard, E. O. W. (2019, January 24). Polygenic Scores Mediate the Jewish Phenotypic Advantage in Educational Attainment and Cognitive Ability Compared With Catholics and Lutherans. Evolutionary Behavioral Sciences. Advance online publication. http://dx.doi.org/10.1037/ebs0000158
A newly released multivariate polygenic score for educational attainment, cognitive ability, and self-rated mathematical ability in the Wisconsin Longitudinal Study was examined as a mediator of the group difference between Jews (n 53) and 2 Christian denominations, Catholics (n 2,603) and Lutherans (n 2,027), with respect to educational attainment, IQ, and performance on a similarities measure. It was found that the Jewish performance advantage over both Catholics and Lutherans with respect to all 3 measures was partially and significantly mediated by group differences in the polygenic score. This result is consistent with the prediction that the high average cognitive ability of Jews may have been shaped, in part, by polygenic selection acting on this population over the course of several millennia.
Public Significance Statement
Ashkenazi Jews exhibit high levels of general intelligence. The hypothesis that differences in general intelligence between Jews and Catholics and Lutherans is partially mediated by polygenic scores for educational attainment was tested. The results support the hypothesized partial mediation.
Data were sourced from the Wisconsin Longitudinal Study (WLS). The WLS is a longitudinal study of randomly sampled Wisconsin high school students beginning in 1957; the last wave of data collection was in 2011. The 1957 sample included 10,317 Wisconsin high school seniors. The sample is overwhelmingly of European descent.
9000 of the study participants were genotyped as part of the recent GWAS for intelligence (Lee 2018) and in this study the educational attainment polygenic score was used. It is the stronger predictor. The students were tested on the Henmon-Nelson Test of Mental Ability, a 30-min test consisting of 90 items of increasing difficulty in spatial, verbal, and mathematical ability. The reliability of the test .95; and it correlates .80 to .85 with Wechsler full scale IQ. When subjects were in their 50s they were given 8 items of the Wechsler Similarities test by phone. Intelligence was well tested.
The Jews in this sample are much brighter than the Christians. They had much, much higher educational levels, perhaps a gene-culture synergistic effect, or simply that educational levels measure ability and motivation. Perhaps the 8 point IQ advantage is enough to explain it.
To illustrate the differences between the Jewish and two Christian groups, we combined the two Christian groups and computed Cohen’s d for PGS and IQ. For PGS Cohen’s d 1.33, which is a very large effect size. For IQ, Cohen’s d .57, which is a medium effect size. These group differences are portrayed in Figure 1.
The correlations between the polygenic scores and the intellectual measures are .2 to .3 which is low. Aware that the Jewish sample is small, the authors drew 1000 same sized samples at random from the Christian population to get an estimate of the likelihood of absolutely chance differences between the Jewish and Christian students, and this turns out to be very low, so it is very likely to be a real difference.
The sample of Jewish students is small. However, researchers looking at small samples of ancient genomes argue that DNA is informative even in small samples, because it is a cumulative record of genetic pairings, and is highly informative thereby, but there is still a chance of quirky findings. The authors a well aware of this, and regard their findings as tentative. They certainly do not argue that Jewish cultural transmission is irrelevant, and say that it might support and amplify the genetic factors found by the polygenic scores.
Rare variants associated with lipid storage disorders may indeed confer a heterozygote advantage, which may have augmented the Jewish Group GCA above that which would be predicted by differences in the level of PGS alone, perhaps accounting for the relatively higher frequencies of these disorders in this population. Direct tests of this model still need to be carried out, however.
Dunkel and colleagues have established a tentative link between polygenic scores and Jewish intellectual advantage. This is an important step forwards, and worth testing on larger samples and with better polygenic score data.