3.5 million Ashkenazi Jews 'traced to four female ancestors'
Saturday, 14 January 2006
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A total of 3.5 million Ashkenazi Jews are descended from just four "founding mothers" who lived in Europe at least 1,000 years ago, according to a study by Israeli geneticists.
The four women were part of a small group which founded the Ashkenazi community, established in Europe after migration from the Middle East, and was ultimately descended from Jews who migrated to Italy in the first and second centuries AD.
The discovery that the women are the ancestors of some 40 per cent of all eight million Ashkenazi, or European Jews, has been made possible by analysing the michrondrial DNA [mtDNA] component of the human genome. MtDNA is only transmitted through the female line.
The researchers found that the mtDNA common to the Ashkenazi group of women is virtually unknown among non-Jews but is also found in a minority of non-European, or Sephardic Jews, which the study team says is "evidence of shared maternal ancestry of Ashkenazi and non-Ashkenazi Jews".
The study showed that it was common to the group during what the team say was "a major overall expansion in Europe during the last millennium". The Ashkenazi population has frequently been studied by human geneticists because some 20 recessive hereditary disorders are found within the group.
The research is part of the human genome project, in which mapping of human DNA has significantly increased not only the possibility of predicting genetic diseases, but also of identifying the shared ancestries of individuals.
The researchers say the women had apparently lived somewhere in Europe, but not necessarily in the same place or even the same century.
The research, published in the American Journal of Human Genetics, was conducted as part of a doctoral thesis by Dr Doron Behar under the supervision of Professor Karl Skorecki of the Rappaport Faculty of Medicine and Research Institute at the Haifa-based Technion-Israel Institute of Technology. A team of other researchers from other universities around the world contributed to the study.
Professor Skorecki is famous for his 1997 discovery of genetic evidence that most latter-day Kohanim, Jewish priests entitled to give blessings and whose office is handed down from generation to generation, are descendants of a single male. Those findings were consistent with the religious view that the Kohanim were descended from Aaron, the biblical high priest and older brother of Moses.
The professor said yesterday that the DNA type provided no evidence of whether the four women were themselves especially fertile. But he said it was clear the group as a whole had "enjoyed reproductive success despite their living ... in a continent characterised by natural and human disaster". He said the population growth had happened despite plague, wars and other events.
The research team says the study has "significant implications beyond their inherent interest and relevance to human history; they are vital to understanding the mechanisms of genetic health and disease in human populations".
Professor Skorecki was modest about the study's findings. He said that as a "physician who is also interested in history" he was surprised that the study had aroused as much interest as it had.
Suggesting he was not sure genetics deserved such an especially high profile as a tool for studying population development, he added: "There are many other ways of learning history, like archaeology, the study of archives, linguistics and so on. But somehow genetics seems to capture the public imagination."
