Math Support for the Old Testament

This story has been paraphrased from a wonderful book “Blood Matters” by Masha Gessen.

In Judaism, Cohanim are a priestly caste endowed with a set of particular privileges in synagogue and burdened with a set of restrictions in ordinary life. The Cohen lineage is paternal (Cohen is the singular and the Cohanim the plural form in Hebrew). All Cohanim are believed to be the sons of Aaron, brother of Moses. Moses was supposed to receive the priesthood along with the leadership of the Jewish people, but when he argued with God that he should not be the leader, it was given to his brother Aaron. Aaron received the priesthood along with his children and any descendants that would be subsequently born. See the illustration below of Moses ordaining Aaron. Keeping in mind that the Old Testament's chronology for the exodus occurring approximately 1500 BC, this all would date back around 2010 + 1500 = 3610 years.

Only recently, the belief that the Cohanim are all descendants of a single predecessor has been confirmed with the help of genetic testing and… math. Here is the story of how it happened.

Fifteen years ago, an Israeli doctor, Karl Skorecki, who is an Ashkenazi Jew of Cohen lineage, noticed a very differently looking Cohen of North African origin, a Sephardic Jew, in the synagogue and wondered whether all Cohanim’s DNA carries traces of their common predecessor. As Cohen lineage goes from father to a son, and males receive the X chromosome from their mother and Y chromosome from their father. Y chromosome’s DNA would be the one to have the presumed “stamp” of Aaron.

Skoreski contacted an Arizona geneticist by the name of Michael Hammer, who had distinguished himself in Y-chromosome research. It was a perfect research hypothesis: simple and verifiable, and Hammer loved it. Together, Skoreski and Hammer analyzed the DNA of a large set of Jewish men who have been told by their fathers (and usually by their last name) that they are Cohanim. Since then this research has been repeated a number of times and extended following the significant progress in our ability to decode DNA.

And indeed, all these studies proved that about 46% of the men claiming to be Cohanim are descendants of a single male – presumably Aaron. They also were able to determine when this common ancestor lived. To do this, they looked at the level of relatedness – or, rather, the degree of difference – among the Y-chromosome DNA of his various descendants. The difference is measured in mutations, because the rate that mutations accumulate on the Y chromosome is relatively constant. Using an estimate of the average time it takes a mutation to occur, the researchers calculated that the common ancestor had indeed lived somewhere around 3,000 +/- 1,000 years ago. In other words, the man, presumably Aaron, the first Cohen, may have lived during the exodus from Egypt. More than this, statistical analysis revealed that this common ancestor likely have lived in the Near East, as Cohanim DNA patterns contain similarity to those of Beduins, Yemenis and Jordanians. Just like that - science meets the Old Testament.

To read more about this, see Wikipedia and the latest article by M.Hammer and his colleagues.


  1. This is so amazing! I love the study of DNA, and am interested in finding our more about our Native American Lineage. We also believe that my husbands maternal grandmother was Jewish, since they escaped from the Austro-Hungarian region in the early 20th century. Her mother knows that they had a differing last name, however does not know the original name. She was 8 years old at the time, and their name became Mehic. If anyone has any suggestions as to how we may find out either or both lineages, please share it with me. This is truly amazing and interesting.


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