NEW YORK (JTA) — A new study concludes that all Ashkenazi Jews can trace their ancestry to a “bottleneck” of just 350 individuals, dating back to between 600 and 800 years ago.

The study, published in the Nature Communications journal Tuesday, was authored by Shai Carmi, a computer science professor at Columbia University, and more than 20 medical researchers from Yale, Columbia, Yeshiva University’s Albert Einstein College of Medicine, Memorial Sloan-Kettering Cancer Center, Hebrew University of Jerusalem and other institutions.

Researchers analyzed genomes of 128 Ashkenazi Jews and compared them to those of non-Jewish Europeans in order to determine which genetic markers are unique to Ashkenazi Jews. They found that the Ashkenazi Jews’ genetic similarities were so acute that one of the study’s researchers, Columbia professor Itsik Pe’er, told the Live Science  website that among Ashkenazi Jews, “everyone is a 30th cousin.”

The findings will enable researchers to catalogue nearly all of the genetic variations from the founding population, the study’s authors said. Such thorough genetic cataloging could help clinicians interpret individual genetic mutations, improve disease mapping and provide insight into the histories of Middle Eastern and European populations, the study said.