Adam Kirsch writes about tractate Kiddushin, the current portion of the Talmud studied in the daily practice of “Daf Yomi” — a folio page of Talmud a day:
…21st-century geneticists discovered what they called the Cohen Modal Haplotype, a set of genes carried on the Y chromosome, which are carried by a majority of Jewish families that self-identify as kohanim. This suggests that the priestly identity was, in many cases, accurately passed down for a hundred generations.
Strong warnings are issued against high-born Jews marrying low-born Jews: According to Rabba bar bar Chana, “Anyone who marries a woman who is not suited for him [due to her lineage], the verse ascribes blame to him as though he plowed the entire world and sowed it with salt.” Such warnings are only necessary, however, because the temptation to marry “below” one’s station was often irresistible. The reason, of course, was money: It would have taken a rare commitment to lineage to reject a potential rich suitor just because he was rumored to have a mamzer or a slave somewhere in his family tree.
Rabbi Yehoshua ben Levi hints at this dynamic when he says, “Money purifies mamzerim.” The tone of this statement is hard to parse: Is Yehoshua being cynical or sarcastic about social-climbing mamzerim, or is he acknowledging an inevitable fact of life, or is he possibly even praising the power of money to overcome distinctions of birth? At any rate, it’s clear that the rabbis do not believe in scrutinizing people’s family background too closely. “A family that has become assimilated remains assimilated,” says Rabbi Yitzchak: That is, if a family of flawed lineage manages to marry into a family with pure lineage, their descendants are considered pure. This looks like a contradiction of the stated law on the subject, which says that the children of flawed unions inherit the flaw of their parents.
But for the sake of social peace, the rabbis recognize that it’s better to draw a curtain over such questions. Indeed, the amora Ulla asked rhetorically, “Is that to say that we know where we come from? Perhaps we are from those about whom it is written: ‘They have ravished the women in Zion, the maidens in the city of Judah.’” In other words, even a pious and learned Jew might be descended from a woman raped by gentile invaders. In this way, the Talmud marks a transition from an aristocracy based on birth and lineage to one based on learning and piety.
