The origin of the Ashkenazi Jews, who come most recently from Europe, has largely been shrouded in mystery. But a new study suggests that at least their maternal lineage may derive largely from Europe.
Little is known about the history of Ashkenazi Jews before they were expelled from the Mediterranean and settled in what is now Poland around the 12th century. On average, all Ashkenazi Jews are genetically as closely related to each other as fourth or fifth cousins, said Dr. Harry Ostrer, a pathology, pediatrics and genetics professor at the Albert Einstein College of Medicine in New York and the author of "Legacy: A Genetic History of the Jewish People" (Oxford University Press, 2012).
But depending on whether the lineage gets traced through maternal or paternal DNA or through the rest of the genome, researchers got very different answers for whether Ashkenazi originally came from Europe or the Near East.
Past research found that 50 percent to 80 percent of DNA from the Ashkenazi Y chromosome, which is used to trace the male lineage, originated in the Near East, Richards said. That supported a story wherein Jews came from Israel and largely eschewed intermarriage when they settled in
The genetics suggest many of the founding Ashkenazi women were actually
converts from local European populations.
"The simplest explanation was that it was mainly women who converted and they married with men who'd come from the Near East," Richards told LiveScience.According to Jewish law, the religion is passed down through the mother, so if a
Jewish man marries a non-Jewish woman, their children would n
ot be considered Jews. ---
Sources:
https://www.livescience.com/40247-ashkenazi-jews-have-european-genes.htmlhttps://www.bbc.com/news/magazine-26067980 
