Ashkenazi Jews – Who are they and where did they come from

The name Ashkenaz was applied in the Middle Ages to Jews living along the Rhine River in northern France and western Germany. The center of Ashkenazi Jews later spread to Poland-Lithuania and now there are Ashkenazi settlements all over the world. The term “Ashkenaz” became identified primarily with German customs and descendants of German Jews.

Ashkenazim focused on biblical and Talmudic studies. Centers of rabbinic scholarship appeared in the tenth century in Mainz and Worms in the Rhineland and in Troyes and Sens in France. Ashkenazi scholarship centered around oral discussion. The first major Ashkenazi literary figure was Rashi (Solomon ben Isaac of Troyes, 1040-1105), whose commentaries on the Bible and Talmud are today considered fundamental to Jewish study. The tosafists, Ashkenazi Talmudic scholars in northern France and Germany, introduced new methods and insights into Talmudic study that are also still in use. While Ashkenazi Jews experienced anti-Semitism, they were  willing to die as martyrs rather than convert.

Ashkenazi Jews have the reputation of a demographic group with higher than average IQ. One observational basis for inferring that is their prevalence in intellectually demanding fields. While only about 3% of the U.S. population is of full Ashkenazi Jewish descent, 27% of United States Nobel prize winners in the 20th century, 25% of Fields Medal winners, 25% of ACM Turing Award winners, 6 out of the 19 world chess champions, and a quarter of Westinghouse Science Talent Search winners have either full or partial Ashkenazi Jewish ancestry.

According to an article published in the Los Angeles Times on September 9th 2014, all of the Ashkenazi Jews alive today can trace their roots to a group of about 330 people who lived 600 to 800 years ago. The LA times based its article on a publication of a new study in the journal Nature Communications.

According to the publication, an international team of scientists sequenced the complete genomes of 128 healthy Ashkenazi Jews and compared each of those sequences with the others, as well as with with the DNA of 26 Flemish people from Belgium. Their analysis allowed them to trace the genetic roots of this population to a founding group in the Middle Ages.

About 80% of modern Jews have Ashkenazi ancestry, according to the Hebrew University of Jerusalem. Despite their close ties with Europe, no more than half of their DNA comes from ancient Europeans, the researchers found. Only 46% to 50% of the DNA in the 128 samples originated with the group of people who were also the ancestors of the Flemish people in the study. Those ancient people split off from the ancestors of today’s Middle Easterners more than 20,000 years ago, with a founding group of about 3,500 to 3,900 people, according to the study. The rest of the Ashkenazi genome comes from the Middle East, the researchers reported. This founding group “fused” with the European founding group to create a population of 250 to 420 individuals. These people lived 25 to 32 generations ago, and their descendants grew at a rate of 16% to 53% per generation, the researchers calculated. Today there are more than 10 million Ashkenazi Jews around the world, including 2.8 million in Israel, according to the Hebrew University of Jerusalem.

The authors of the new study come from nearly two dozen research groups in New York City, Belgium and Israel. Many of the co-authors are not Jewish, but they are interested in studying this group because it is genetically isolated (since Jews have historically married within their faith, their gene pool is closed). That makes it easier to identify genes linked to specific diseases, like Parkinson’s and cancer, links that could well apply to non-Jews as well.

The study was funded by the National Institutes of Health and the National Science Foundation, along with several private foundations.