NEW YORK -- Scientists have found fresh genetic evidence that Jews who consider themselves part of the priestly class known as Cohanim really are part of an unbroken line extending back thousands of years.
The Cohanim are said to be descended from Moses' brother, Aaron. Originally they had primary responsibility for offering sacrifices and serving as arbiters and mentors.
Today, in Orthodox and some other Jewish congregations, Cohanim are still accorded special duties and privileges. They are given the honor of reading first from the Torah during a service and presiding over a traditional ceremony for some first-born boys.
Cohanim aren't allowed to marry widows, divorcees or converts. Because of the Jewish belief that the Temple in Jerusalem will be rebuilt and that Cohanim will serve again as priests there, they try to remain spiritually pure. So they stay away from dead bodies, not attending funerals except for those of immediate family, for example.
Many Cohanim have surnames such as Cohen, Kahn, Kane or similar variations. But not all men with such surnames are Cohanim.
Last year, scientists who studied the Y chromosome in modern-day Cohanim reported evidence that the designation truly has been passed from father to son. The Y chromosome is inherited that way, making it useful for such studies.
More evidence appears in a new study, reported by Israeli and British scientists in Thursday's issue of the journal Nature. They looked for variations in the Y chromosome from 306 Jewish men, including 106 self-identified Cohanim, from Israel, Canada and England.
Most Cohanim had the same version of the Y chromosome or close variants that differ because of random mutations. That shows there has been "reasonable adherence to the policy of father-son inheritance," said researcher David B. Goldstein of Oxford University.
By studying how long it would take for the variants to develop, researchers concluded the inheritance of Cohanim status has gone on longer than 700 years and maybe as long as 3,000 years or so, as tradition maintains.
The sample also contained 81 self-identified Levites, a designation that began with the Levi tribe after the Exodus and is also supposed to pass from father to son.
The study could not confirm that. The Levites showed too much variety in their Y chromosome variants. That could mean that non-Levite Jews took up the designation in the past, or that the original Levites had a lot of variety in their Y chromosomes, Goldstein said.
Rabbi Raphael B. Butler, executive vice president of the Orthodox Union, an umbrella organization of Orthodox congregations, said he doubted the study would affect the designations of Cohan or Levite today. But it's "enlightening" that the results agree with the Jewish tradition, he said.