Over the last decade and a half, geneticists have been working to piece together the genealogical history of all the Jewish communities around the world. They have managed to find links pointing to a common ancestry and common religion. However, one origin of the Jewish population, the Ashkenazim of Eastern and Central Europe, has eluded geneticists until now.

In a study published in the journal Nature Communications on Tuesday, researchers were able to trace the DNA of the Ashkenazim to prehistoric European women, strongly suggesting that the Jewish community of the early Roman Empire may be the Ashkenazi ancestors. This finding suggests that the women who founded the Ashkenazi Jewish community were not from the Near East and single men who married and converted local women started that many Jewish communities outside of Israel.

The study adds to a new body of research looking into the mitochondrial DNA to determine lineages. Previous DNA studies had showed that men whose Y chromosomes had DNA patterns typical of the Near East were the ones who founded Jewish communities around the world.

Martin B. Richards of the University of Huddersfield in England took that research a step further by analyzing the genetics of the mothers. His research actually decoded the entire mitochondrial genomes of people from the Near East and Europe. Mitochondrial DNA is a genetic element inherited just through the female line and is separate from the main human genome.

What Richards saw was that unlike the Y chromosome, the mitochondrial DNA showed no similar pattern across the Jewish population but instead resembled the DNA of the surrounding population. This suggested that single men, perhaps as traders, had migrated to different areas and taken local wives, who then converted to Judaism.

That answered the question for some small Jewish communities, but not yet the Ashkenazim. Mitochondrial DNA can change quickly, and the Ashkenazi DNA had been too many steps removed make determining its origin easy. Because Richards had mapped the entire mitochondrial genome, he was able to follow the lineages farther than any previous researcher.

He found that the main ancestors of the Ashkenazim traced to Europe some 10-20,000 years ago and the same is true of most of the small lineages as well. Then the four major lineages came from Rome around 2,000 years ago.

“Thus the great majority of Ashkenazi maternal lineages were not brought from the Levant, as commonly supposed, nor recruited in the Caucasus, as sometimes suggested, but assimilated within Europe,” reported the study.