Common genetic threads link thousands of years of Jewish ancestry

The genetic, cultural and religious traditions of contemporary Jewish people originated in the Middle East over three thousand years ago. Since that time, Jewish communities have migrated from the Middle East into Europe, North Africa and across the world. The migration of Jews to new locales is known as the Diaspora. This study shows that although Jewish people experienced genetic mixing with surrounding populations, they retained a genetic coherence along with a religious one.

"Previous genetic studies of blood group and serum markers suggested that Jewish groups had Middle Eastern origin with greater genetic similarity between paired Jewish populations," says senior study author, Dr. Harry Ostrer, professor of pediatrics, pathology and medicine and director of the Human Genetics Program at NYU Langone Medical Center. "More recent studies of Y chromosomal and mitochondrial DNA have pointed to founder effects of both Middle Eastern and local origin, yet, the issue of how to characterize Jewish people as mere coreligionists or as genetic isolates that may be closely or loosely related remained unresolved."

"We have shown that Jewishness can be identified through genetic analysis, so the notion of a Jewish people is plausible. Yet the genomes of the Jewish Diaspora groups have distinctive features that are representative of each group's genetic history," says Dr. Ostrer. "Our study demonstrated that the studied Jewish populations represent a series of geographical isolates or clusters with genetic threads that weave them together," added Dr. Gil Atzmonl assistant professor of medicine and genetics at Albert Einstein College of Medicine of Yeshiva University, the study's lead author. "These threads were observed as identical strands of DNA that were shared within and between Jewish groups. Thus, over the past 3000 years, both the flow of genes and the flow of religious and cultural ideas have contributed to Jewishness."

To better understand the relatedness of current Jewish groups, Dr. Ostrer and colleagues performed a genome wide analysis of Iranian, Iraqi, Syrian, Italian, Turkish, Greek and Ashkenazi Jews and compared these results with non-Jewish groups. The researchers identified distinct Jewish population clusters that each exhibited a shared Middle Eastern ancestry, proximity to contemporary Middle Eastern populations and variable degrees of European and North African genetic intermingling.

The history of Jewish people could be found in their genomes. The two major groups, Middle Eastern Jews and European Jews, were timed to have diverged from each other approximately 2500 years ago. Southern European populations show the greatest proximity to Ashkenazi, Sephardic and Italian Jews, reflecting the large-scale southern European conversion and admixture known to have occurred over 2,000 years ago during the formation of the European Jewry. An apparent North African ancestry component was also observed as was present in the Sephardic groups potentially reflecting gene flow from Moorish to Jewish populations in Spain from 711 to 1492. The structure of the genomes of Ashkenazi Jewish populations indicates a severe bottleneck followed by expansion during the 19th century when the Jewish population in western and eastern Europe increased about twice as fast as the non-Jewish population. This has been referred to as "the demographic miracle." Within every Jewish group, there was a high degree of relatedness between any two of its members. For Ashkenazi Jews, the relatedness was similar to what one might observe for fifth cousins.

Dr. Ostrer noted, "The study supports the idea of a Jewish people linked by a shared genetic history. Yet the admixture with European people explains why so many European and Syrian Jews have blue eyes and blonde hair. "

The researchers include Gil Atzmon, Albert Einstein College of Medicine, Bronx, NY, Albert Einstein College of Medicine, Bronx, NY; Li Hao, New York University School of Medicine, New York, NY; Itsik Pe'er, Columbia University, New York, NY; Christopher Velez, New York University School of Medicine, New York, NY; Alexander Pearlman, New York University School of Medicine, New York, NY; Pier Francesco Palamara, Columbia University, New York, NY; Bernice Morrow, Albert Einstein College of Medicine, Bronx, NY; Eitan Friedman, Tel-Aviv University, Tel-Aviv, Israel; Carole Oddoux, New York University School of Medicine, New York, NY; Edward Burns, Albert Einstein College of Medicine, Bronx, NY; and Harry Ostrer, New York University School of Medicine, New York, NY.