Magazine article Science News

The Priests' Chromosome? DNA Analysis Supports the Biblical Story of the Jewish Priesthood

Magazine article Science News

The Priests' Chromosome? DNA Analysis Supports the Biblical Story of the Jewish Priesthood

Article excerpt

DNA analysis supports the biblical story of the Jewish priesthood

A bit more than 3 years ago, while sitting in a synagogue in Toronto, Karl Skorecki looked at some of his fellow worshippers with curiosity.

Like several others in attendance that day, Skorecki, then a kidney disease researcher at the University of Toronto, considered himself a cohen, which is Hebrew for priest. According to biblical accounts, after the Jewish exodus from Egypt, Moses' brother Aaron was selected as the first cohen. The designation was also given to his sons, providing the basis for a firmly entrenched Jewish tradition in which a male cohen bestows the status upon his children. A daughter of a cohen can become a priest, but she cannot pass on the honor.

Like all cohanim (plural of cohen), Skorecki has no proof that he belongs to the priesthood other than the word of his father and his father before him. As he sat in the synagogue years ago, Skorecki wondered whether he had anything besides this oral legacy in common with the other cohanim he knew.

The answer, he realized, could reside in his DNA. The Y chromosome passes solely from father to son, exactly like the cohen status. If all modern cohanim were indeed descendants of Aaron, or a relative of him, their Y chromosomes should have an ancient common origin, explains Skorecki, who is now at the Technion-Israel Institute of Technology in Haifa.

Two recent studies by Skorecki and several of his colleagues find that the cohanim indeed have some Y chromosome features distinct from other Jews. This shared genetic material, moreover, may stem from an ancestor who lived several thousand years ago, roughly the time estimated for the beginning of the Jewish priesthood.

Calling the results "powerful," Laurie Zoloth-Dorfman, director of the Jewish studies program at San Francisco State University, compares their impact to her experience when she visited Jerusalem for the first time and laid her hands on the Western Wall of the Second Temple that she had read about in the Old Testament.

"It's to me an extraordinarily moving and intense experience of history and sacred history coming together," she says. "I think the [Y chromosome research] does the same thing genetically. It's a tangible, embodied moment of connection to our past."

For several centuries, starting about 3,000 years ago when the First Temple of Jerusalem was built, the cohanim played a leading role in the Jewish community. Today, rabbis have taken over as the teachers and authorities of Jewish religion and law. They acquire their place through religious training rather than through heredity.

The cohanim still often play a special role in worship services, such as being the first to read from the Torah. They also may recite blessings at Jewish festivals.

While anyone can claim to be a cohen and would likely draw no challenge, the priesthood's few remaining privileges are countered by obligations. Cohanim cannot get married to widows, divorcees, or anyone from outside the Jewish faith, even converts. Moreover, they can't attend most funerals, because contact with the dead would contaminate their religious purity.

"There are real restrictions to those cohanim who follow the traditions. Surprisingly, many do, even individuals who might not be observant in other respects," says Skorecki.

To explore the origins of the cohanim, Skorecki turned to an area of research called genetic archaeology, or genetic anthropology. Until recently, this discipline has focused on mothers, not fathers. That's because when sperm fertilize eggs, snippets of genetic material known as mitochondrial DNA are passed on only from the mother to the embryo. For reasons still unexplained, a sperm's mitochondrial DNA is lost (SN: 1/25/97, p. 58).

Making use of this oddity, scientists have studied variations in mitochondrial DNA to reconstruct the evolution and movement of people. …

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