This discipline also ought to establish who is and is not a descendant of King David, and of the tribe of Levi, both very important sub-groups within the Jewish Community. Conceivably, the entire Jewish nation could be sorted into the original 12 tribes. Only wild cards are the mideival Khazar empire of Eastern Europe, whose king and a great number of subjects converted to Judaism in the 11th Century C.E., as well as the aforementioned wandering bachelors and their shiksas.
Indeed. For a group that has been around as long as this one, admixture is a sure thing. I, for one, know this first hand. Although a Jew of European origins, my Y-chromosome is pure Celtic. Who knew? ;-)