Descended from Converts? https://mosaicmagazine.com/picks/uncategorized/2013/10/descended-from-converts/

October 10, 2013 | Kate Yandell
About the author:

A new genetic study of Ashkenazi Jews traces their maternal lineage to Europe rather than the Near East—suggesting, if true, that Jewish men married local women.

Read more on Scientist: http://www.the-scientist.com/?articles.view/articleNo/37821/title/Genetic-Roots-of-the-Ashkenazi-Jews/