new thread is being
woven into the complex tapestry of Jewish history, a thread
fashioned from a double twist of DNA.
The DNA data suggest a particular version of Jewish history
and origins that historians have not yet had time to appraise
but that seem to be reconcilable in principle with the
historical record, according to experts in Jewish studies.
The emerging genetic picture is based largely on two
studies, one published two years ago and the other this month,
that together show that the men and women who founded the
Jewish communities had surprisingly different genetic
The earlier study, led by Dr. Michael Hammer of University
of Arizona, showed from an analysis of the male, or Y
chromosome, that Jewish men from seven communities were
related to one another and to present-day Palestinian and
Syrian populations, but not to the men of their host
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
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
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.
Dr. Harry Ostrer, a medical geneticist at New York
University, said the 26 specific genetic diseases found among
Ashkenazim, usually attributed to "founder effects," could be
explained by the idea of a mosaic of small populations. A
founder effect amplifies any mutation present in a small
population that later expands.
"He has really opened up the door for some very interesting
work," Dr. Ostrer said.
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."
"The authors are correct in saying the historical origins
of most Jewish communities are unknown," Dr. Cohen said. "Not
only the little ones like in India, but even the mainstream
Ashkenazic culture from which most American Jews descend."
In a recent book, "The Beginnings of Jewishness," Dr. Cohen
argued that far-flung Jewish communities had adopted the
rabbinic teaching of the matrilineal descent of Jewishness
soon after the Islamic conquests in the seventh, eight and
ninth centuries A.D.
One part of the Goldstein team's analysis, that matrilineal
descent of Jewishness was practiced at or soon after the
founding of each community, could fit in with this conclusion,
Dr. Cohen said, if the communities were founded around this
The data being generated by Dr. Hammer, Dr. Goldstein and
other population geneticists touches on the delicate issue of
whether Jews can be considered a race. Dr. Cohen noted that
the Nazis and their anti-Semitic predecessors had argued that
Jews were a race and therefore irreconcilable with the host
community and that Jews had in response argued they were not,
because they admitted people by conversion.
If the founding mothers of most Jewish communities were
local, that could explain why Jews in each country tend to
resemble their host community physically while the origins of
their Jewish founding fathers may explain the aspects the
communities have in common, Dr. Cohen said.
Despite the definition of Jewishness as being born to a
Jewish mother, and the likelihood of some continuity between
ancient and modern populations, it has not until recently been
clear that genetics had anything much to contribute to
questions of Jewish identity.
Some scholars suspected that Jewish communities had through
intermarriage or conversion become little different from their
host populations. Many say they believe that even if Jews are
a group definable in ethnic, as opposed to cultural or
religious terms, it is either impossible or unwise to define
an ethnic group genetically.
Dr. Schiffman said that as president of the Association for
Jewish Studies he would consider convening a discussion
between the geneticists and the historians on interpreting the
new data. He noted that the study of racial differences had
led to disaster in the past but that the new analysis of
genetic differences was "a form of racial science for the
good, rather than the bad."
"Racial science," Dr. Schiffman said, "has brought so many
terrible things. But it's a norm now in genetics to study the
racial genetics of groups. So I think it's an amazing
Geneticists use the Y chromosome and mitochondrial DNA to
track the movement of populations because each is passed
unchanged from parent to child, escaping the genetic shuffle
that occurs on the rest of genome between generations. Since
the Y chromosome passes down only from father to son, and
mitochondrial DNA is always inherited from the mother alone,
the two elements serve to track the genetic history of men and
But since the Y chromosome and mitochondrial DNA clock up
occasional changes or mutations every thousand years or so, on
much the same time scale as human population splits, different
ethnic groups tend to have characteristic patterns of
The Y chromosome and mitochondrial DNA's in today's Jewish
communities reflect the ancestry of their male and female
founders but say little about the rest of the genome, which is
by now a presumably well mixed set of genes contributed by all
the founders of each community.
Noting that the Y chromosome points to a Middle Eastern
origin of Jewish communities and the mitochondrial DNA to a
possibly local origin, Dr. Goldstein said that the composition
of ordinary chromosomes, which carry most of the genes, was
impossible to assess.
"My guess," Dr. Goldstein said, "is that the rest of the
genome will be a mixture of both."