[Paleopsych] Reuters: Study Finds Why Jewish Mothers Are so Important

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Study Finds Why Jewish Mothers Are so Important
http://www.nytimes.com/reuters/news/news-science-jews.html

    By REUTERS
    Filed at 12:21 p.m. ET

    WASHINGTON (Reuters) - Four Jewish mothers who lived 1,000 years
    ago in Europe are the ancestors of 40 percent of all Ashkenazi Jews
    alive today, an international team of researchers reported on
    Friday.

    The genetic study of DNA paints a vivid picture of human evolution
    and survival, and correlates with the well-established written and
    oral histories of Jewish migrations, said Dr. Doron Behar of the
    Technion-Israel Institute of Technology, who worked on the study.

    The study, published in the American Journal of Human Genetics,
    suggests that some 3.5 million Jews alive today all descended from
    four women.

    For their study, Behar and geneticist Karl Skorecki, with
    collaborators in Finland, France, Estonia, Finland, Portugal,
    Russia and the United States sampled DNA from 11,452 people from 67
    populations.

    ``All subjects reported the birthplace of their mothers,
    grandmothers, and, in most cases, great-grandmothers,'' they wrote
    in their report.

    They looked at mitochondrial DNA, which is found in cells, outside
    the nucleus and away from the DNA that carries most genetic
    instructions. Mitochondrial DNA is passed down virtually unchanged
    from mother to daughter, but it does occasionally mutate, at a
    known rate.

    Researchers can use this molecular clock to track genetic changes
    through time, and used it, for instance, to compute when the
    ``ancestral Eve'' of all living humans lived -- in Africa, about
    180,000 years ago.

    Now they have found four ancestral Jewish mothers.

    ``I think there was some kind of genetic pool that was in the Near
    East,'' Behar said in a telephone interview.

    ``Among this genetic pool there were four maternal lineages, four
    real women, that carried the exact specific mitochondrial DNA
    markers that we can find in mitochondrial DNA today.''

    SETTLING EUROPE

    They, or their direct descendants, moved into Europe.

    ``Then at a certain period, most probably in the 13th century,
    simply by demographic matters, they started to expand
    dramatically,'' Behar said.

    ``Maybe it was because of Jewish tradition, the structure of the
    family that might have been characterized by a high number of
    children.''

    But these four families gave rise to much of the population of
    European Jews -- which exploded from 30,000 people in the 13th
    century to ``something like 9 million just prior to World War II,''
    Behar said.

    The Nazis and their allies killed 6 million Jews during the war,
    but there are now an estimated 8 million Ashkenazi Jews, defined by
    their common northern and central European ancestry, cultural
    traditions and Yiddish language.

    Behar said as they sampled people from Ashkenazi communities around
    the world, the same mitochondrial genetic markers kept popping up.
    They did not find the markers in most of the non-Jewish people they
    sampled, and only a very few were shared with Jews of other origin.

    This particular study does not provide a direct explanation for
    some of the inherited diseases that disproportionately affect Jews
    of European descent, such as breast and colon cancer, because most
    diseases are caused by mutations in nuclear DNA, not the DNA
    studied by Behar's group.

    These genes are believed to date from a ``bottleneck'' phenomenon,
    when populations were squeezed down from large to small and then
    expanded again. Behar and Skorecki's team have found what is known
    as a ``founder effect'' -- when one or a small number of people
    have a huge number of descendants.

    What the study also shows, Behar said, is that Jewish mothers are
    highly valued for a good reason. ``This I could tell you even
    without the paper,'' he said.