Kohanim genetics

Last Thursday evening we went to a lecture by Rabbi Kleiman of the Jerusalem Center for Kohanim on the subject of “DNA and tradition.” He presented the results of genetic analysis on the Kohanim and other Jewish groups and then tried to connect these results to Jewish tradition. I found the actual scientific results that he has taken from published, peer reviewed papers in scientific journals very interesting and persuasive. Where I parted company with him was in his use of selected quotations from the Bible and other Jewish sources to imply that the scientific results support these Jewish quotations. Really all he can say is that the findings are consistent with what is written in the Bible or elsewhere in Jewish literature, not that it proves what was written is true.
However, the results themselves are fascinating. The most clear-cut and important result published in the prestigious journal Nature in 1997 by Dr. Karl Skorecki of Haifa University and his associates, is that a large proportion of Kohanim, Jewish men (both Ashkenazi and Sephardi) descended on the male side from the supposed Temple priesthood, share a common genetic marker. This marker is found in the Y-chromosome, the 23rd human chromosome that determines the male sex of an individual. Since this chromsome is much smaller than all others, it is possible to determine markers on it, and suprisingly one marker called “K” was found to be present in 40% of all Kohanim tested, while controls of other Jews (Levis and others) and non-Jews had no perponderance of this marker (other Jews had only 6% of the marker). Levis on the other hand had a greater amount of another marker “L”, but only to the level of 23%. Nevertheless 40% is very significant compared to 6%, and non-Jews had no preponderance of these markers. So this proves that all Kohanim share a common ancestor (Aaron?) and have retained this marker thru many generations. By extrapolation it can be estimated that the originator of this marker was 106 generations back, approximately the time of the destruction of the first Temple in 3000-2500 bce. It should be noted that there is no genetic marker for being a Jew, since over the centuries there have been many converts and intermarriages that dilute out any such “purity.” So there is no evidence for a Jewish “race.” However, the Kohanim result stands because of the self-selection of Kohanim within the Jewish people maintained over the centuries.
Other results of analysis of the mitochondrial DNA that allows matrilineal descent to be documented has been found, but these results are less clear-cut. Such genetic analysis can however be used to test for the relationship of groups and tribes that claim an ancient connection to the Jewish people, such as Spanish conversos, Ethiopian Jews, Bnai Menasseh of India and the Lemba Tribe of S. Africa, compared to the surrounding population. The results in each case are different, some positive and some negative. But, while not conclusive this makes for a fascinating study.
Using the methods of molecular genetics to support this type of argument, an Orthodox Jew cannot at the same time deny their use to support evolution, for example in the independent establishing of evolutionary trees. Rabbi Kleiman concluded that there is no conflict between Judaism and science and that he accepts the concept of evolution, i.e. small biological changes by genetic alterations such as mutations over long periods of time. However, there are many Orthodox Jews who do deny evolution, and this needs Talmudic consideration.
I would like to quote Francis Crick, who said in his book “The astonishing hypothesis: the scientific search for the soul,” that “God is an unnecessary hypothesis.” Note that this does not mean that God does not exist, but that it is not necessary to posit God in order to explain evolution, i.e. random events can explain it. The fact that mutation rates can be calcuated for specific genes over long time periods is support for the randomness of the process. Thus, it is not necessary to introduce (according to the philosophical use of Occam’s razor) an intelligent designer.


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