by Chapter 7 of Gregory Cochran and Henry Harpending’s The 10,000 Year Explosion: How Civilization Accelerated Human Evolution (2009) is called “Medieval Evolution: How the Ashkenazi Jews got their Smarts,” and looks at the evolution of the Ashkenazi minority within Europe over the past 1,500 years.The chapter is based in part on earlier work in Cochran, Hardy and Harpending (2006). The Ashkenazim were a Diaspora Jewish community that was first based in northern France and Germany in the 8th–9th centuries AD, but were descended from a Diaspora community in southern Europe during the Roman empire in which a significant number of the men of the founder population took European wives (Cochran and Harpending 2009: 204–205; Costa et al. 2013).The Ashkenazim were therefore, by origin, a cline
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The chapter is based in part on earlier work in Cochran, Hardy and Harpending (2006).
The Ashkenazim were a Diaspora Jewish community that was first based in northern France and Germany in the 8th–9th centuries AD, but were descended from a Diaspora community in southern Europe during the Roman empire in which a significant number of the men of the founder population took European wives (Cochran and Harpending 2009: 204–205; Costa et al. 2013).
The Ashkenazim were therefore, by origin, a cline (admixture) of Middle East Jews and some European women. This is still evident today in modern Ashkenazim, who have about 40% European DNA (Cochran and Harpending 2009: 204). However, after the early founder admixture, the Ashkenazim became highly endogamous (that is, marrying only within their group) and genetically isolated (Cochran and Harpending 2009: 205, 219).
From the later Middle Ages the Ashkenazim began moving into Eastern Europe and Russia, and modern Ashkenazim are present in America, Israel and Europe.
The Ashkenazim have an average IQ that lies somewhere in the 107–115 range, the highest average IQ of any ethnic group in the world. The average IQ of Europeans, by contrast, is 100.
In the modern world, the Ashkenazim are significantly overrepresented in certain higher professions requiring a high IQ, such as the natural and social sciences (Cochran and Harpending 2009: 188–190). In particular, while the Ashkenazim are less than 0.2% of the world population, they are about 22% of Nobel laureates (though most are men, as you can easily see here).
Cochran and Harpending argue that this high average IQ was driven by genetic changes in the Ashkenazim over about a thousand years while living as a persecuted minority in Europe.
In essence, their thesis is as follows:
(1) because of vicious and terrible Christian persecution, the ban on usury between Christians and their exclusion from Christian societies, the Ashkenazim were driven into certain professions, such as being merchants, bankers and financiers for much of the Middle Ages, and in Eastern Europe also tax-farmers, toll-farmers, and estate managers and other middle-men for Christian rulers. These professions or trades require a high IQ, and especially a high verbal and mathematical IQ;The high average Ashkenazi IQ is therefore largely genetic, and the product of an unusual evolution over the past 1,000 years or so. Further evidence in favour of this is that – in Israel with its First World economic development, education and health care system – the Ashkenazim continue to have an average IQ higher than both Sephardic and Oriental Jewish groups, who have had a different evolutionary history (Cochran and Harpending 2009: 212–213).(2) the most successful Ashkenazim in their trades tended to have more children who survived to adulthood, because they were affluent, and so they had a greater reproductive fitness than other, less successful members of their own community;
(3) because of the very high rates of endogamy (marrying only within the group), the differential success and higher birth rates of the most successful Ashkenazim, over time, led to a kind of elite reproductive advantage with genetic effects on the general population, which gradually raised the average IQ of the Ashkenazim as a group (Cochran and Harpending 2009: 191–220, 222–223).
The by-product of the evolution of high Ashkenazi IQ was probably a number of unusual genetic diseases in the Ashkenazim, such as Tay-Sachs, Gaucher’s disease, familial dysautonomia, and two forms of hereditary breast cancer (BRCA1 and BRCA2). These diseases are about 100 times more common in Ashkenazim than in European populations (Cochran and Harpending 2009: 188), and they are characterised by affecting two specific metabolic pathways, the first of which is probably related to the central nervous system and neuron development, namely, sphingolipid storage disorders (causing Tay-Sachs, Gaucher’s disease, Niemann-Pick disease, mucolipidosis, type IV) (Cochran and Harpending 2009: 214, 220).
As Cochran and Harpending (2009: 190–191) point out, the high average IQ of the Ashkenazim has greatly contributed to modern science, and – in a sense – has changed human history because Western science has been significantly advanced by high IQ Ashkenazi men: we need only think of Albert Einstein, Max Born, John von Neumann, Richard Feynman, Julian Schwinger, Murray Gell-Mann and numerous others who have changed the course of Western science.
Finally, even the Liberal American cognitive scientist Steven Pinker, in an April 2008 lecture, has pointed out that this hypothesis is not unreasonable, and, above all, can be tested, and will be vindicated or falsified soon enough:
There is also a question and answer session here.
BIBLIOGRAPHY
Cochran, Gregory, Hardy, Jason and Henry Harpending. 2006. “Natural History of Ashkenazi Intelligence,” Journal of Biosocial Science 38.5: 659–693.
Cochran, Gregory and Henry Harpending. 2009. The 10,000 Year Explosion: How Civilization Accelerated Human Evolution. Basic Books, New York.
Costa, Marta D. et al. 2013. “A Substantial Prehistoric European Ancestry amongst Ashkenazi Maternal Lineages,” Nature Communications 4.2543
https://www.nature.com/articles/ncomms3543