Levite: A member of an ancient caste of hereditary Jewish priests. Membership in the Levites is determined by paternal descent. The Levites have traditionally been considered the descendants of Levi, a son of Jacob. However, research has disclosed an unusual genetic signature called R1a1 on the Y chromosome in more than half of Levite males of Ashkenazi Jewish origin. (The Ashkenazi Jews, from whom most American Jews descend, are one of the two main branches of Jews.) The R1a1 signature on the Y chromosome in the Levites appears to have originated in Central Asia and is thought to have come from the Khazars, a Turkic tribe whose king converted to Judaism in the eighth or ninth century. Modern-day descendants of these converts make up a large proportion of the Ashkenazi Levites today.