A genetic analysis shows that all of the Ashkenazi Jews alive today â€” of which there are more than 10 million â€” can trace their roots to a group of just 330 people who lived 600 to 800 years ago.
The new study, which now appears in the journal Nature Communications, involved the genetic analysis of 128 healthy Ashkenazi Jews. These complete genomes were in turn compared to each other, along with the DNA of 26 Flemish people from Belgium.
Writing in the LA Times, Karen Kaplan explains more:
“Ashkenaz” in Hebrew refers to Germany, and Ashkenazi Jews are those who originated in Eastern Europe. (Sephardic Jews, by contrast, are from the areas around the Mediterranean Sea, including Portugal, Spain, the Middle East and Northern Africa.) 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).
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.
Sequencing an Ashkenazi reference panel supports population-targeted personal genomics and illuminates Jewish and European origins
The Ashkenazi Jewish (AJ) population is a genetic isolate close to European and Middle Eastern groups, with genetic diversity patterns conducive to disease mapping. Here we report high-depth sequencing of 128 complete genomes of AJ controls. Compared with European samples, our AJ panel has 47% more novel variants per genome and is eightfold more effective at filtering benign variants out of AJ clinical genomes. Our panel improves imputation accuracy for AJ SNP arrays by 28%, and covers at least one haplotype in â‰ˆ67% of any AJ genome with long, identical-by-descent segments. Reconstruction of recent AJ history from such segments confirms a recent bottleneck of merely â‰ˆ350 individuals. Modelling of ancient histories for AJ and European populations using their joint allele frequency spectrum determines AJ to be an even admixture of European and likely Middle Eastern origins. We date the split between the two ancestral populations to â‰ˆ12â€“25â€‰Kyr, suggesting a predominantly Near Eastern source for the repopulation of Europe after the Last Glacial Maximum.
Hat tip to Karen L. Myers.