Jews have an aristocracy. An aristocracy, however, without castles, but with titles, privileges, duties and restrictions. Unlike most aristocracies, the Jewish aristocracy does not use formal salutations such as “Your Grace” or “My Lord.” For Jews, these aristocrats are the kohanim, the priests who once served in the Temple of Jerusalem. A kohen (singular form of kohanim) is just like any baron, marquis or duke—but not quite. And then there are their assistants, the Levites.

According to the Torah, Jacob had twelve sons. Each son was the founder of one of the twelve tribes of Israel. Each tribe had a separate territory, with the exception of the tribe of Levi.

Are these tribal affiliations just a matter of folklore and tradition?During the Exodus, when the Israelites made the Golden Calf, only the Levites refused to worship it. As a result, they were appointed servants to G‑d. Of the members of this tribe, those who were descended from Aaron, brother of Moses, became the kohanim. Aaron was the first kohen, and also the first high priest.

Ever since then, many Jews have identified themselves as either Levites (levi’im) or kohanim. Throughout the centuries down to modern times, these Jews identified themselves as descendants simply because their fathers were kohanim or levi’im. But are these tribal affiliations just a matter of folklore and tradition? Can such claims actually be proven?

Today they can, and the key is DNA testing. The principle is that if all kohanim are in fact descended from Aaron, they should all share the same genetic traits. In the various studies that have been done with Jewish males in numerous parts of the world, both Ashkenazim and Sephardim, over 98 percent of those who claimed to be kohanim were found to have the Y-chromosome Alu Polymorphism (YAP) marker. The principle is that the male Y-chromosome does not change from generation to generation.

Prof. Karl Skorecki, director of Nephrology and Molecular Medicine in the Faculty of Medicine at Technion in Haifa, has been quoted in the Jerusalem Post as saying, “The simplest, most straightforward explanation is that these men have the Y-chromosome of Aaron.” He stated that “the study suggests that a 3,000-year-old tradition is correct and has a biological counterpart.”

Dr. Henry Ostrer, chair of the Human Genetics Program at New York University, confirmed this conclusion.

“The study suggests that a 3,000-year-old tradition has a biological counterpart.”The result is that anyone can be tested as to whether he carries the genetic markers of someone who is a kohen. This breakthrough came about in 1997 as a result of a cooperative research venture at Rambam Hospital in Haifa, the University College of London and the University of Arizona.

In fact, there is now an International Kohanim Society with thousands of kohanim in many parts of the world registered in a computerized database. It is being expanded to include Levites.

In 2007, the first Kohen-Levi family reunion in 2,000 years was held in Jerusalem. The gathering was organized by the Center for Kohanim in Jerusalem and its director, Rabbi Yaakov Kleiman, who is also the author of DNA & Tradition: The Genetic Link to the Ancient Hebrews.

Of particular interest was the discovery that both Ashkenazi and Sephardi kohanim shared a common set of genetic markers. This clearly indicated that the genetic line predated the separate development of the two communities, which began around 1000 CE, and indicates that the two communities are part of the same people. The conclusion is that the tradition of identifying oneself as a kohen does in fact conform with genetic realities, and directly links all kohanim to a common ancestor. The accuracy of these findings is largely due to the historically very low rate of intermarriage between Diaspora Jews and gentiles. It is also due to the fact that converts could never become kohanim, and the status of being a kohen passed only from father to son. Therefore, the set of Y-chromosomal markers known as the Cohen Modal Haplotype remained fairly consistent and points to descent from a common ancestor.

(However, it should be noted that the Cohen Modal Haplotype has been found in certain groups of non-Jews, particularly in southern Africa and among the Kurds.1)

What does it mean to be a kohen?

All privileges come with a price, and the restrictions on kohanim are manyThe kohanim have the privilege of being called for the first aliyah to say the blessing over the Torah during religious services. There is also the privilege of saying the priestly blessing. In Israel, and in Sephardic synagogues in the Diaspora, this blessing is recited on a daily (or weekly) basis. In Ashkenazi communities in the Diaspora, it is recited on major Jewish holidays.

However, all privileges come with a price, and the restrictions on kohanim are many. Many of these restrictions were designed to maintain what is referred to as ritual purity, since the kohanim formed a holy order in the Temple of Jerusalem. Following the destruction of the Second Temple in the year 70 CE, many of the laws and practices are still maintained in traditional Judaism, except those which could only be followed in the actual presence of the Temple.

Kohanim are forbidden to be in contact with dead bodies, take active part in a funeral, or even be under the same roof as a corpse, except in the case of the death of a close relative. This includes entering any place in which a dead body is present, such as a cemetery. A male kohen is prohibited from marrying a woman who is a divorcee or a convert. Failure to abide by the marriage prohibitions does not invalidate the marriage, but the kohen loses his status as long as he is married, and his offspring from that relationship do not have the status of a kohen.

Although the Temple no longer exists, and the kohanim no longer carry out the ancient rituals that were an integral part of Temple practice, Jews are awaiting the messiah, upon whose arrival the Temple will be rebuilt.

The wife or unmarried daughter of a kohen has the status to a certain extent of a kohen, even though she does not have all the duties, rights, responsibilities and restrictions of a kohen.

Jewish men and women are Jewish because their mothers are Jewish. Their tribal affiliation, however, such as being a kohen or a Levi, comes from their fathers. When a woman marries, she takes on the tribal affiliation of her husband (Kohen, Levi or Israel) regardless of the status of her father. The affiliation that the woman received from her father goes into abeyance.

Any children of the marriage will take their tribal affiliation from their father, not their mother, just as their mother takes her status from her husband after marriage. If the couple adopt children, they will not automatically take on the Judaism of the mother, nor the tribal affiliation of the father.

In order to have a functioning Temple, an educated and trained priesthood is necessary. For some, this is the motivation in identifying those who are truly kohanim. There are many programs designed to educate them on their responsibilities and their role in the traditional Jewish religious aristocracy.