A Lineage Claimed for Three Thousand Years, and What Genetics Found

Priestly status is transmitted from father to son by an unbroken claim of descent from Aaron that Jewish communities have maintained by tradition and by family record for millennia without any central registry, since the priesthood needed no such registry as long as the Temple stood and its personnel were locally known; the claim survived the loss of the Temple as an inherited status even after it lost its original function.

In the 1990s a genetic study of Y-chromosome markers among self-identified kohanim from geographically separated Jewish communities, including Ashkenazi and Sephardi populations that had been apart for many centuries, found a shared genetic signature, later called the Cohen Modal Haplotype, at notably higher frequency among kohanim than among other Jews, a finding read by many as independent evidence for a real shared paternal line, though later research has qualified how precisely it can date or confirm any individual family's claim.

The office remains visible in ordinary religious life: a kohen is called first to the Torah reading in traditional synagogues, and the priestly blessing, Birkat Kohanim, is still recited by kohanim over the congregation on major festivals, drawing especially large gatherings of kohanim performing it together at the Western Wall in Jerusalem during Passover and Sukkot.