European Jews Are Closer Than You Think

All European Jews are more closely related than you think. Chances are, if you run into a fellow member of the Jewish community, you're at least 30^th cousins.

A new study suggests that the central and eastern Jewish population, known as Ashkenazi Jews, started from a founding population of about 350 people between 600 and 800 years ago.

The findings, published in the journal Nature Communications, contradicts the previous notion that today's European Jews descended from people from the Levant and local Europeans. Another theory, called the "Khazar theory," asserted that Ashkenazi Jews descended from Khazars, from the Russian steppes - although, this is unlikely based on genetic evidence, according to study researcher Itsik Pe'er, an associate professor of computer science and systems biology at Columbia University.

Pe'er and his colleagues analyzed the genomes of 128 Ashkenazi Jews, comparing them with a reference group of 26 Flemish people from Belgium. From there, the researchers were able to distinguish which genetic markers in the genome belonged solely to Ashkenazi. Based on the number of similarities in their DNA, scientists estimated how much time had passed since that group originated - in this case, it's 30 to 32 generations, or at most 800 years.

"[Among Ashkenazi Jews] everyone is a 30th cousin," Pe'er told Live Science. "They have a stretch of the genome that is identical."

While this is all very fascinating, this revelation actually has some important implications. It sheds some light on the Jewish migration in Europe, for in the middle ages this group of people were banished from various kingdoms and forced to move around a lot.

Beyond this migratory history the results can also be useful in the clinical field. Ashkenazi Jews are prone to certain diseases like Tay-Sachs, cystic fibrosis and breast cancer. By identifying the genomes unique to Ashkenazi, the researchers make it so doctors can more easily pinpoint which genes are causing the problem, and which are simply normal variations in the DNA.

Not to mention, it also paves the way for future studies.

Conducting a genetic study on a population knowing all the variants in that population allows you to study them cost effectively," Pe'er told Live Science. "You don't have to look at everything."