Were I to submit my cells to DNA tests, results would doubtless show that —barring any surprises—I am a Jew. I have four Jewish grandparents. Genetically speaking, I share a common ancestry with most Jews, no matter where they live, what they look like, or how they practice. Thanks to generations of insularity and historically low rates of intermarriage, Ashkenazi Jews (80 percent of all Jews) are one of the most coherent genetic groups that exist; they are "a gold mine" for people who like to study heredity, says Jon Entine, who in 2007 wrote Abraham's Children, an exploration of Jewishness and DNA. "Jews are more homogeneous than Icelanders or Basques or Costa Ricans," he says.
What a DNA analysis won't show, adds Entine, is who my first Jewish ancestor was. Was it Sarah or Rebecca or Leah, the matriarchs of whom I sing every Saturday morning? Was it a 10th-century convert from Khazar, in modern-day Russia, which might explain my blue eyes? This information is lost to history, which is fine with me. Everybody's a mix. What isn't lost to history is when Jews as a whole became Jews—that is, how far back genetic identity can be traced. And the answer, according to modern DNA analysis, is: to the ancient Middle East.
In the modern world, however, the critical question for Jews is not whether we have Jewish blood. It's how much heredity should continue to matter to Jewish identity. Shlomo Sand, historian and author of The Invention of the Jewish People—much reviewed and rebutted, and recently translated into English—is provoking the international community by arguing that Jews have never been genetically or otherwise "a people." As evidence, he posits that the Khazars, a medieval kingdom of converts to Judaism, are actually the ancestors of most Eastern European Jews. (Entine calls this argument "illiterate.") If Jews aren't related to the people of the Hebrew Bible, Sand's argument continues, then Jews have no exclusive right to modern-day Israel. For the Orthodox, Jewishness is still inherited matrilinearly, according to Jewish law. In a case now before the British Supreme Court, a boy was denied admission to an Orthodox day school because the Orthodox authorities did not recognize the conversion of his mother as authentic. If she was not Jewish, then neither was her son. An appeals court ruled that the Jewish school's admissions criteria were discriminatory, like denying a Christian entry to a Christian school because her parents were born Jewish. The Supreme Court is expected to rule soon.
It is dangerous to define a people through blood. In 1935, an addendum to the Reich Citizenship Law attempted to do so: "An individual of mixed Jewish blood is one who is descended from one or two grandparents who were racially full Jews." A (full) Jew, the Nazis added in paragraph five, has two Jewish parents or three Jewish grandparents.
Ancestry is crucial to Jewish identity, but Jewish identity transcends blood. We share history (itself often bloody), culture, Scripture, and diverse expressions of a single faith. The mixing of DNA with politics is hazardous indeed. As Simon Schama so eloquently argued in his review of Sand's book in the Financial Times, "The legitimacy of Israel both within and without the country depends not on some spurious notion of religious much less racial purity, but on the case made by a community of suffering, not just during the Holocaust but over centuries of expulsions and persecutions." (Sand's larger point, that Israel needs to become more like other Western democracies and less obsessed with ethnic purity, is welcome; the genetic argument simply doesn't get him there.)
During persecutions, insularity is the only option. For those of us who now live, with luck and in freedom, in open societies like America or Britain, homogeneity is not just impossible, it's undesirable; insisting on heredity as the primary conveyance of Jewishness runs counter to the ideals of plurality and democracy. Rabbi Julia Neuberger, president of Liberal Judaism in Britain, wants to radically redefine Jewish identity. She believes Jews should invite all interested parties to join them in faith, culture, history—and the raising of Jewish children. Before Constantine, she reminds me, Jews sought converts. Why not open the tent wide again by making conversion easier?
"Just because the Nazis were obsessed with whether we had one Jewish grandparent or not doesn't mean that we should be," says Neuberger. "It would be an 'up yours' to the Nazis to be more accepting of converts. My view is that we should be incredibly grateful that anybody wants to be Jewish." It is perhaps useful to remember here that Moses' bride, Zipporah, was not a member of the tribe.