Ashkenazi Jewish genetics: a match made in the Mediterranean
How and when did the Ashkenazim come to be?
Sometime after the year 1000 AD, a group of Jews began migrating eastward across Europe, into the principalities of Germany and the kingdom of Poland, attracted by the combination of religious tolerance and economic opportunity. These territories were beyond the frontiers of the Roman Empire; they were lands that Jews had traditionally not occupied. By the time these pioneers arrived in the small towns of Germany and the hamlets of Poland, Jewish communities had already been established in Persia and Egypt for 1,500 years.
For the next 800 years, these Jews waxed in numbers due to their essential economic position in the developing lands of Eastern Europe, but unlike the Hebrews of antiquity, they became culturally invisible to their gentile neighbors, quietly navigating a closed social universe organized around adherence to their own laws and focused on their own texts. Their ultimate origins were a mystery to the gentiles around them, and indeed became forgotten even to themselves. Were they the descendants of the ancient Hebrews, converts to the religion, or a mix of both? These possibilities were hidden from the Jews of Eastern Europe as their memory of their past faded and their written culture focused purely on matters of religion.