Literary critic Adam Kirsch is reading a page of Talmud a day, along with Jews around the world.In theory, all Jews belong to one of three lineages—priests, Levites, and Israelites. Sometimes this inheritance is advertised in last names: If your name is Cohen, you are ostensibly descended from the priests, kohanim, whose ultimate ancestor is Moses’ brother Aaron. If your name is Levi, you presumably come from the tribe of Levites, who were designated in the Torah as the priests’ assistants. But the names are not always reliable—not all kohanim are named Cohen—and thanks to the many vicissitudes of Jewish history, any definitive proof of ancestry is impossible to come by. That is why it was so striking when 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.Today, what lineage a Jew belongs to matters only in occasional ritual contexts. But in Temple times, the boundaries between the priestly caste and the general population of Israelites were sharply patrolled. Indeed, the rules and privileges pertaining to priestly families—the elite of Second Temple Judea—constitute a major concern of the Talmud, especially when it comes to who is entitled to terumah, the portion of the sacrificial offerings reserved for priests. In this week’s Daf Yomi reading, Tractate Kiddushin explaines the detailed rules for how lineage is defined and passed down, especially in the case of marriages between different castes.The first mishna in chapter 4 explains that, while today we talk mainly about three categories of Jewish birth, there were originally 10 lineages, traced back to the Jews who “ascended from Babylonia.” These Jews, who returned to the land of Israel from the Babylonian exile, included not just priests, Levites, and Israelites, but several problematic subcategories, including converts, emancipated slaves, mamzerim or children of forbidden relationships, and shetuki or children of unknown paternity. Priests, Levites, and Israelites, we learn “are permitted to marry one another,” since they are considered to have unflawed lineage. Members of inferior groups, like converts and foundlings, are similarly allowed to marry one another.But when members of different groups intermarry, how is the status of the child determined? The general rule is laid down in Kiddushin 66b, where the mishna explains that in legitimate unions—that is, marriages where the partners are legally permitted to one another—the status of the child follows that of the father. If a man who is a Levite marries a woman who is an Israelite, then, their child is a Levite. To this extent, Jewish inheritance is patrilineal.Things are different, however, when it comes to prohibited marriages. There are, in fact, two types of prohibited unions, which can be thought of as “discouraged but permitted” and “legally void.” The first type is one where the partners can be legally betrothed, even though their marriage constitutes “a transgression.” Such marriages—the Talmud gives the example of a marriage between a priest and a divorced woman—are not supposed to take place, but if the man betroths the woman, it is still considered effective. In these cases, children follow the lineage of the “flawed” parent: In the case of a priest and a divorcee, the sons would not be priests, since they would inherit their mother’s taint.More serious are unions of the second type, where betrothal cannot take place at all. This in turn is divided into two subcategories: relationships where the woman cannot marry one particular man, and those where the woman cannot marry any Jewish man. The former covers the many relationships discussed in Leviticus 18, and analyzed in various places in Seder Nashim: For instance, a man cannot marry both a woman and her daughter, nor his father’s wife, nor his aunt. (The same chapter of Leviticus includes the prohibition of homosexuality: “Thou shalt not lie with mankind as with womankind, it is abomination.”) In these cases, a man and woman who are forbidden to marry cannot be betrothed, and if they have sex, their child is a mamzer, an outcast who is in turn forbidden to marry any legitimately born Jew.Then there is the second type of forbidden betrothal, in which a woman is prohibited from marrying, not this or that particular man—e.g., her uncle or her brother-in-law—but any Jewish man. This category includes all gentile women, including Canaanite slaves. If a Jewish man has sex with a gentile woman, their child is considered not even a mamzer, but an out-and-out gentile. With forbidden relationships, then, inheritance is matrilineal, following the status of the mother and not the father. By the same token, the Gemara in Kiddushin 68b, explains, if a Jewish woman has sex with a gentile man, their child is Jewish: “He is not a mamzer. Rather, he is merely called disqualified,” that is, disqualified to marry into the priesthood. Here is the origin of the matrilineal rule that still governs in Judaism today, by which Jewishness is passed down from mother to child.You might think that the land of Israel would be the place to find the best and purest Jewish lineages. But already in Talmudic times, the rabbis recognized that Jewish lineages had become irretrievably confused, thanks to the many vicissitudes of Jewish history. For instance, at the time of the Babylonian exile, in 586 BCE, the elite of Judean society was deported to Babylonia. When the exiles began to return, about 70 years later, the rabbis say that the best-born families actually remained behind in Babylon. Ezra, one of the leaders of the return to Jerusalem, “did not ascend from Babylonia until he made it like fine flour”: That is, he sifted the Jewish community according to purity of lineage, and paradoxically, he chose the impure to come with him to rebuild the Temple. The rabbis go on to demonstrate this with a number of biblical citations, which are used to show that several of the named individuals who returned to Jerusalem had mamzerim among their ancestors.Why should the impure have been chosen for the holy task of rebuilding Jerusalem? The Talmud doesn’t explain, but it does suggest that keeping lineages pure has always been a tricky task. 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.***To read Tablet’s complete archive of Daf Yomi Talmud study, click here.