“52 percent of Levites of Ashkenazi origin have a particular genetic signature that originated in Central Asia, although it is also found less frequently in the Middle East,” according to a new report. “The ancestor who introduced it into the Ashkenazi Levites could perhaps have been from the Khazars, a Turkic tribe whose king converted to Judaism in the eighth or ninth century.”
I remember Arthur Koestler asserting this in The Thirteenth Tribe. Apparently, the potentate was trying to split the difference between the Christian west and the Moslem east, and made his kingdom jewish by fiat.
See extended entry for the full report.