DNA and Tradition: The Genetic Link to the Ancient Hebrews

By Rabbi Yaakov Kleiman

Devora Publishing

Jerusalem, 2004

204 pages

Reviewed by Edward Simon

Rabbi Yaakov Kleiman has written a brief, clear, wide-ranging and accurate description of the use of DNA analysis to trace the origin and dispersion of the Jewish people. And if that sounds almost self-contradictory, it merely indicates the magnitude of Rabbi Kleiman’s accomplishment.

This eminently readable book begins with the almost accidental discovery that Cohanim carry a set of unique genetic markers. From there the author discusses the role of DNA in heredity, how the sequence of markers can be used to trace genealogy, the meaning of family traditions and the historical validity of the Torah itself. He even shows how genetic studies can help answer the vexing questions surrounding the relationship of such diverse groups as the Falasha of Ethiopia, the Lemba of South Africa and the Bnei Menashe of India to the body of the Jewish people.

According to the Torah, our history originated somewhere in the Middle East with Avraham. Some 400 years later, the Children of Israel left Egypt under the leadership of Moshe and Aharon. After the incident with the Golden Calf, the priesthood was vested in Aharon and his children. Is there any scientific way to verify this history?

The answer, surprisingly, is yes!

To analyze the situation, we first have to note that every male inherits the sole Y-chromosome from his father and one of his mother’s two X-chromosomes. While all of the other parental chromosomes are diluted out in succeeding generations, the Y-chromosome comes directly from the founding father of a lineage.

Jews from all over the world show striking similarity in their Y-chromosomes despite such details as skin color or appearance.

Next we note that the Jewish religion is passed through the mother, but that a person’s tribe is determined solely by the father. That means that the only way one can be a priest is if one’s father was a priest. A corollary is that no convert can be a priest. Hence, if these rules were strictly observed, every priest today should contain a copy of the Y-chromosome of Aharon HaCohen!

This hypothesis can be tested using modern genetic techniques that allow specific segments of the DNA of the Y-chromosome to be isolated from individuals and then compared to see how closely related they are. (A similar technique was used in the infamous trial of O. J. Simpson.)

When this procedure was done for several segments of the Y-chromosome, it was possible to identify the CMH or Cohen Modal Haplotype, a set of DNA markers that is found in some 90 percent of Cohanim and in a much lower frequency in non-Cohanim.

Why is this so? Didn’t Aharon get his Y-chromosome from Amram via Levi and ultimately Avraham? If so, all Jews should have the CMH. But they don’t.

Every Jew would have the CMH, except for the fact that there are converts. Thus, the non-priestly Jewish line will have a diluted CMH. Since, as stated earlier, converts cannot become priests, their integration into the Jewish people does not affect the priestly line. This serves to preserve the integrity of the priestly line.

And yet despite the precautions, the CMH of Cohanim from Yemen will differ slightly from the CMH of Cohanim from Romania. This is because during the course of time, random mutations accumulate in the Y-chromosome despite strict patrilineal descent.

The accumulation of random mutations in the Y-chromosome allows us to estimate how long ago Aharon’s Y-chromosome entered the priestly lineage: 3,000 years. This is in excellent agreement to the tradition that the Torah was given on Mount Sinai some 3,300 years ago. The existence of the CMH leads to another striking conclusion: The faithfulness of Jewish women is the highest recorded among any population studied. This is because the frequency of CMH is scientifically significant even among non-priestly Jews, attesting to the integrity of our lineage.

Rabbi Kleiman emphasizes repeatedly that neither the presence nor the absence of the CMH determines if someone is a Cohen, let alone a Jew.

In Jewish religious courts, DNA evidence is recognized but is not equal to witnessing, which is what determines fact. A man may rely on his established family tradition….

Jews from all over the world show striking similarity in their Y-chromosomes despite such details as skin color or appearance. This is consistent with a Middle-Eastern origin and a spread from that region throughout the last 2,000 years. It is possible to calculate from the divergence of the Y-chromosomes how much intermarriage there was over this time. The answer is a striking 0.5 percent per generation. This is in sad contrast to what we observe in America today.

There is much more in this book. By looking at mitochondria, DNA-containing organelles in the cell that are passed exclusively to the next generation by females, it is possible to trace the “founding mothers” as well as the founding fathers. Levites should also share the CMH for the same reason Cohanim do, but many of them do not. Why is this so? What has become of the so-called lost tribes? And finally what is the role of the kingdom of Khazaria, a country celebrated in Jewish legend and in The Kuzari, in the development of European Jewry?

It is possible to calculate from the divergence of the Y-chromosomes how much intermarriage there was over the last 2,000 years. The answer is a striking 0.5% per generation.

Not everything is cut and dried. Rabbi Kleiman does not shy away from these problems and even includes reprints of key papers for readers who relish the nitty-gritty of the primary literature. But he is certainly right when he states that “the Cohanim have passed the test of time and tradition. And tradition has passed the test of science.”

Professor Simon is a professor of biology at Purdue University.


This article was featured in Jewish Action Fall 2005.