Karen Kaplan reports in the L.A. Times:

DNA ties Ashkenazi Jews to group of just 330 people from Middle Ages

Albert Einstein and all other Ashkenazi Jews can trace their roots to a group of about 330 people who lived during the Middle Ages, a new study finds.

By KAREN KAPLAN

So says a new study in the journal Nature Communications. 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. …

… 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.