The Legacy of the Priestly Gene

When Hashem ordained Aaron as the High Priest, it was decreed that his sons and their descendants forever would serve as priests, engaging in holy service in the Temple, performing priestly blessings, accepting offerings, and more. The priesthood is inherited from father to son and not through daughters. Thus, the son of a priest’s daughter, whose husband is not a priest, does not inherit the priesthood (see Leviticus chapters 8 and 21, among others).

While the underlying reasons are spiritual and rooted in Torah commandments, modern genetic research offers a fascinating perspective. A comprehensive international genetic study involving contemporary Kohanim, led by Professor Karl Skorecki of the Technion’s Faculty of Medicine, included renowned scientists from the United States and England, such as Dr. David Goldstein from Oxford University and Dr. Gerald Bradman from University College London.

Published in outlets such as Discover (April 1997) and Science News (October 1998), the study found a shared gene in the DNA of Kohanim from diverse backgrounds—English, Tunisian, Canadian, Russian, Yemeni, Ashkenazi, and Sephardi. The prevalence of this gene is unmatched in any other population group.

Remarkably, 70–80% of Kohanim share this gene. Among non-priestly Jews and non-Jews, it is found in only about 5% of cases. This strongly suggests that all Kohanim descend from a common ancestor predating the Sephardi–Ashkenazi split more than a thousand years ago. Intriguingly, this gene is passed exclusively from father to son via the Y chromosome.

Thus, only grandsons through the son carry the distinctive gene linking them to the priestly lineage. Additionally, analysis of this gene allows researchers to estimate the number of generations that have passed since the original family forebear, as discussed by Dr. Avraham Amar, head of the Tissue Typing and Coordination Unit at Hadassah Ein Kerem, in the journal Discovery 3 (page 14).

Researchers concluded that approximately 106 generations have passed since the first Kohen ancestor. To calculate this in years, the number of generations must be multiplied by the length of a generation. While generations typically average around 30 years—though Kohanim may be born at varying ages of their fathers—this yields approximately 3,180 years. This aligns closely with the time of Aaron the Priest during the Exodus, about 3,300 years ago. Even accounting for variation in generational length, this reflects a remarkable alignment with Torah tradition.

Dr. Avraham Amar, in his review of this innovative research in Discovery 3, concludes: “Those who refuse to believe in the tradition of the Jewish people must bow to the scientific evidence supporting the truth and reliability of Torah tradition, meticulously handed down through generations.”