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

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. Albert Einstein was an Ashkenazi Jew, as were Gertrude Stein and Carl Sagan. Steven Spielberg and Scarlett Johansson are also Ashkenazi Jews, along with three current members of the U.S. Supreme Court (Ruth Bader Ginsburg, Stephen Breyer and Elena Kagan). 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. 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.