Each woman left a genetic signature that shows up in their descendants today, he and colleagues say in a report published online by the American Journal of Human Genetics. Together, their four signatures appear in about 40% of Ashkenazi Jews, while being virtually absent in non-Jews and found only rarely in Jews of non-Ashkenazi origin, the researchers said.
They said the total Ashkenazi population is estimated at around 8 million people. The estimated world Jewish population is about 13 million.
Ashkenazi Jews are a group with mainly central and eastern European ancestry.
The common ancestors go back somewhere on the order of 2,000 years. The results are based on 11,000 DNA samples from 67 different populations.