The Ashkenazi Jews—the Jews of Europe—began as a distinct community about 1,200 years ago along the Rhine. The word “Ashkenaz” was the Hebrew name for Germany, so the Ashkenazim are literally “German Jews,” although they later came to inhabit other areas, particularly Poland.
Today the Ashkenazi Jews, some 11 million strong, live throughout the world, with the largest concentrations in Israel and the United States. There are many other Jewish communities— such as the Sephardic Jews who once lived in Spain, the Mizrahi Jews of the Middle East and North Africa, and the Bene Israel of India—but the vast majority of the world’s Jews are Ashkenazi.
They have had a surprisingly large influence on the world over the past couple of centuries, and they have played an outsized role in science, literature, and entertainment. Might they be smarter than other groups of people?
Apparently so. Ashkenazi Jews have the highest IQ of any ethnic group known. They average around 112–115, well above the European norm of 100. This fact has social significance, because IQ (as measured by IQ tests and their equivalents, like the Graduate Record Exam [GRE] or the Scholastic Aptitude Test [SAT]) is the best available predictor of success in academic subjects and many jobs.1 Jews are just as successful in such jobs as their tested IQ would predict, and they are hugely overrepresented in those jobs and accomplishments with the highest cognitive demands.
We’re not the first to notice this. Popular opinion has held that European Jews are smart for a long time. At the turn of the century in London, for example, Jews took a disproportionate share of prizes and awards in the school system. This was not the case in classical times: Surviving writings from the ancient Greeks and Romans offer no hint that the Jews were considered unusually smart.
So why are the Ashkenazim especially intelligent?
To solve this puzzle, it may be useful to look at what we know about the DNA of the Ashkenazi Jews, because it turns out that they have another interesting characteristic. Namely, they have an unusual set of serious genetic diseases, such as Tay-Sachs disease, Gaucher’s disease, familial dysautonomia, and two different forms of hereditary breast cancer (BRCA1 and BRCA2), and these diseases are up to 100 times more common in Ashkenazi Jews than in other European populations. For a long time, those disorders have posed another puzzle—why are they so common in this particular group?
We believe that these two puzzles have a single explanation. We propose that the Ashkenazi Jews have a genetic advantage in intelligence that arose from natural selection for success in white-collar occupations during their sojourn in northern Europe.
Strong selection for intelligence also produced some unpleasant side effects, in the form of alleles that boost IQ in carriers while causing harm to homozygotes.
This kind of explanation is controversial, of course. It is true that many dismiss the idea that intelligence is measurable, is influenced by genes, or can vary from group to group. These criticisms and dismissals, interestingly, hardly ever come from scientists working in the area of cognitive testing and its outcomes: There is little or no controversy within the field. IQ tests work—they predict academic achievement and other life outcomes, and IQ scores are highly heritable. If genes influence intelligence, then, over time, a situation in which intelligence boosts fertility must result in higher intelligence. That simple logic is the very essence of the theory of evolution by natural selection: Genes that cause increased reproduction gradually become more and more common in a population.
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