Most men can only name their male ancestors going back a few generations.
Members of the Jewish priesthood (Cohanim) are an unusual group in that the men
of this ancient priestly class can claim descent from a single male ancestor.
According to biblical accounts, the Jewish priesthood began about 3,000 years
ago when Moses anointed his older brother Aaron the first high priest. Ever
since, the priestly status has been handed down from father to son through the
If this hereditary tradition has been closely followed, the Y chromosomes of
the Cohanim today should bear some resemblance to one another because of their
unbroken link back to a common ancestor, Aaron.
Genetic studies among Cohanim from all over the world reveal the truth behind
this oral tradition. About 50 percent of Cohanim in both Sephardic and
Ashkenazic populations have an unusual set of genetic markers on their Y
chromosome. What is equally striking is that this genetic signature of the
Cohanim is rarely found outside of Jewish populations.
Gene-scan outputs of microsatellite DNA analysis of genetic samples taken from a Lemba (top) and a member of the Cohanim.
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The Y chromosome also keeps track of time. Small mutations occur in the DNA
being passed on, and these changes build up with each generation. Like the tick
of a clock, the number of these mutations is a measure of time passed. By
looking at the differences between Y chromosomes in the Cohanim, researchers
can estimate roughly how many generations ago members of the priesthood had a
common ancestor. Remarkably, the evidence suggests the Cohanim chromosomes
coalesce at a date that corresponds with when the priesthood is
thought to have begun.
What researchers may have found is a marker indicating paternal connection to
the people from whom the ancient Hebrews emerged—potentially a powerful tool
that enables us to look into the history of many Judaic populations.