In DNA, New Clues to Jewish Roots
The finding suggested that Jewish men who founded the communities traced their lineage back to the ancestral Mideastern population of 4,000 years ago from which Arabs, Jews and other people are descended. It pointed to the genetic unity of widespread Jewish populations and took issue with ideas that most Jewish communities were relatively recent converts like the Khazars, a medieval Turkish tribe that embraced Judaism.

A new study now shows that the women in nine Jewish communities from Georgia, the former Soviet republic, to Morocco have vastly different genetic histories from the men. In each community, the women carry very few genetic signatures on their mitochondrial DNA, a genetic element inherited only through the female line. This indicates that the community had just a small number of founding mothers and that after the founding event there was little, if any, interchange with the host population. The women's identities, however, are a mystery, because, unlike the case with the men, their genetic signatures are not related to one another or to those of present-day Middle Eastern populations.

The new study, by Dr. David Goldstein, Dr. Mark Thomas and Dr. Neil Bradman of University College in London and other colleagues, appears in The American Journal of Human Genetics this month. Dr. Goldstein said it was up to historians to interpret the genetic evidence. His own speculation, he said, is that most Jewish communities were formed by unions between Jewish men and local women, though he notes that the women's origins cannot be genetically determined.

"The men came from the Near East, perhaps as traders," he said. "They established local populations, probably with local women. But once the community was founded, the barriers had to go up, because otherwise mitochondrial diversity would be increased."

In ancient Israel, the Jewish priesthood was handed from father to son. But at some time from 200 B.C. to A.D. 500, Jewish status came to be defined by maternal descent. Even though the founding mothers of most Jewish communities were not born Jewish, their descendants were.

"It's precisely that custom that allows us to see these founding events," Dr. Goldstein said

Like the other Jewish communities in the study, the Ashkenazic community of Northern and Central Europe, from which most American Jews are descended, shows less diversity than expected in its mitochondrial DNA, perhaps reflecting the maternal definition of Jewishness. But unlike the other Jewish populations, it does not show signs of having had very few female founders. It is possible, Dr. Goldstein said, that the Ashkenazic community is a mosaic of separate populations formed the same way as the others.

The idea that most or all Jewish communities were founded by Jewish men and local women is somewhat at variance with the usual founding traditions. Most Jewish communities hold that they were formed by families who fled persecution or were invited to settle by local kings.

For instance, Iraqi Jews are said to be descended from those exiled to Babylon after the destruction of the First Temple in 586 B.C. Members of the Bene Israel community of Bombay say they are the children of Jews who fled the persecutions of Antiochus Epiphanus, who repressed the Maccabean revolt, around 150 B.C.

Most of those founding narratives do not have strong historical support. Dr. Lawrence H. Schiffman, professor of Hebrew and Judaic studies at New York University, said the new genetic data could well explain how certain far-flung Jewish communities were formed. But he doubted that it would account for the origin of larger Jewish communities that seemed more likely to have been formed by families who were fleeing persecution or making invited settlements.

Dr. Shaye Cohen, professor of Jewish literature and philosophy at Harvard, said the implication of the findings and the idea of Jewish communities' having been founded by traders, was "by no means implausible."
http://www.nytimes.com/2002/05/14/science/social/14GENE.html?pagewanted=all&position=top