Study of Jewish lineages reveals genetic 'heirloom'

Jewish men who report such family lineage still share a remarkable set of similarities in the genetic makeup of their Y chromosomes, but further study by UA population geneticist Michael Hammer and a group of Israeli colleagues has now traced several lineages of the priestly caste to several unrelated men in the Near East more than 3,000 years ago.

"I think it's still sort of amazing that there is a genetic marker," said Rabbi Sam Cohon of Temple Emanu-El in Tucson.

"The question of whether it was one progenitor or was it four or five, it doesn't damage my faith in any way," Cohon said.

"The original idea was to test the idea of a single male lineage," said Hammer, director of the UA's Human Origins Genotyping Lab.

Hammer said the new research, while revising the initial conclusion, actually offers more evidence than before for the direct line of descent from a core of early priests who lived in the Near East in the time between the Exodus from Egypt and the dispersion of the Jews.

Hammer describes the Cohanim tradition as "a family heirloom passed from father to son."

To trace that heritage, Hammer and his colleagues used other information passed from father to son — unique mutations in the Y chromosome, the only part of male DNA that is not recombined with the mother's genes in each succeeding generation. Mutations in that chromosome create "markers" that geneticists read to prove direct descent.

For the most recent study, results of which were published in July in Human Genetics, researchers greatly expanded the number of genetic markers used to create what they call the extended Cohen Modal Haplotype, or CMH.

The study involved 215 Cohanim and 1,575 Jewish men from diverse communities and 2,099 non-Jewish men from the Near East, Europe, Asia and India.

The set of markers identifying the predominant strain of Cohanim was "remarkably absent in non-Jews," according to the study.

The study concluded that "the extended CMH represents a unique founding lineage of the ancient Hebrews that has been paternally inherited along with the Jewish priesthood."

Not all members of the Cohanim are named Cohen or Kahane and the like, said Rabbi Cohon, and not all Cohanim become rabbis. In his case, Cohon said his father and grandfather were rabbis, but his brothers are not and his 13-year-old son wants to be a lawyer.

But knowledge of being descended in the priestly caste is passed on from father to son, he said. "You just kind of know. Your dad knows it and he tells his sons. In my case, it is part of my Hebrew name."

Hammer, who is Jewish but not a Cohanim, said the study is a niche he has explored in population genetics that is part of a broader study of Jewish origins.

He said the research was "probably stimulated by my being Jewish," but also undertaken because Jews present a unique opportunity for such study.

"They are a very small minority with a very unusual history of moving from place to place and, in the case of European Jews, establishing a whole cultural tradition, eating bagels, speaking Yiddish."

It raises questions, he said. "Is it a genetic people or a culture just passed around?"

The answers he has learned so far indicate that the Jews retain their genetic makeup along with their culture and religion.

"In fact, there is a very strong genetic component that goes way back to the Near East," he said.

DID YOU KNOW

Michael Hammer is director of the UA's Human Origins Genotyping Lab, which analyzes DNA samples mailed in by the members of the public who join National Geographic's Genographic Project. The Genographic Project is a five-year scientific study that seeks to uncover the migration history of the human species.

"I think it's still sort of amazing that there is a genetic marker. The question of whether it was one progenitor or was it four or five, it doesn't damage my faith in any way."

Sam Cohon

rabbi of Temple Emanu-El in Tucson