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Study Says All Ashkenazi Jews Are 30th Cousins

Researchers identify 350-person founding population of Ashkenazi Jewry

Stephanie Butnick
September 10, 2014
DNA. (Shutterstock)
DNA. (Shutterstock)

According to a new study, all Ashkenazi Jews are basically cousins. More specifically, Ashkenazi Jews are at least 30th cousins. LiveScience reports on the international team’s new study, which found that “the central and eastern European Jewish population, known as Ashkenazi Jews, from whom most American Jews are descended, started from a founding population of about 350 people between 600 and 800 years ago.”

According to Columbia University researcher Itsik Pe’er, who was involved with the study, their research also showed that the group of 350 was made up of Jews of Middle Eastern and European—thereby disproving the much-debated theory that Jews descended from Khazars, a Turkic people who lived in the Caucasus region between the 7th and 10th centuries.

Here’s how the study was performed, according to LiveScience:

The team analyzed the genomes of 128 Ashkenazi Jews, comparing them with a reference group of 26 Flemish people from Belgium. From that the researchers were able to work out which genetic markers in the genome are unique to Ashkenazi. The number of similarities within the genomes allowed the scientists to compute a rough estimate of the founding population and put upper and lower limits on the amount of time that had passed since that group originated. In this case it is 30 to 32 generations, or at most 800 years. “[Among Ashkenazi Jews] everyone is a 30th cousin,” Pe’er said. “They have a stretch of the genome that is identical.”

The discovery holds perhaps the most significance for doctors and Jewish patients. Just last week a new study revealed that all Ashkenazic women, even those without any family history of cancer, may carry the BRCA1 and BRCA2 genetic mutations linked to breast and ovarian cancer. The more genetic information available regarding Ashkenazi Jews, the fewer genome sequences doctors need to test and analyze when looking for potential problems or mutations.

This is pretty big stuff. Now go call your cousin.

Stephanie Butnick is chief strategy officer of Tablet Magazine, co-founder of Tablet Studios, and a host of the Unorthodox podcast.