A reevaluation of the anthropological genetics literature on Jewish populations reveals them not simply to be a body of genetically related people descending from a small group of common ancestors, but rather a “mosaic” of peoples of diverse origins. Greek and other pre-medieval historiographic sources suggest the patterning evident in recent genetic studies could be explained by a major contribution from Greco-Roman and Anatolian-Byzantine converts who affiliated themselves with some iteration of Judaism beginning in the first and second centuries ce and continuing into the Middle Ages. These populations, along with Babylonian and Alexandrian Jewish communities, indigenous North Africans, and Slavic-speaking converts to Judaism, support a mosaic geography of Jewish ancestry in Europe and Western Asia, rather than one arising from a limited set of lineages originating solely in Palestine.