Can DNA Prove Jewish Identity?

Dear JITC-

Can DNA prove Jewish Identity?


Dear Corey-

Thanks for your question. There are a couple of things to consider when examining such a question. The first thing to understand is that the Torah’s methodologies do not necessarily line-up with our modern assumptions. I’ll explain.

When I was a kid, I heard someone opine that “obviously” the Torah was written by humans because it lists the bat among the unclean species of birds and an all-knowing God would know that bats aren’t birds.

The problem with this person’s conclusion was that it was based on the assumption that all systems divide wildlife the way he does: mammals, birds, fish, reptiles, etc. In fact, the Torah does not use this classification system. Rather, the Torah uses “beasts, flying things, sea creatures, creeping things, etc.” So a cow is a beast, a bat is a flying thing, a whale is a sea creature and a mouse is a creeping thing, irrespective of the fact that we would classify them all as mammals. Our current assumptions about what’s “obvious” is not the only way of looking at the world.

The next thing to consider is that not everything can be proved using science. Some things require eyewitness testimony or an unbroken tradition. Let’s consider the case of tzaraas, a type of spiritual skin affliction in people or mold in a house. If something is afflicted with tzaraas, there are rules about to what it transmits impurity but these rules only take effect once a kohein declares the blemish to in fact be tzaraas. This is different from medical science in which a house with mumps or measles can spread infection regardless of whether a doctor has pronounced a quarantine. So spiritual matters can differ from purely temporal experiences.

Similarly, someone may have convicted a crime, and we may know it for a fact, but it may not be actionable in halacha without proper testimony. The idea of “proof” in the absence of a tradition or eyewitness testimony may or may not be relevant in a variety of cases, including such questions as: “Can we eat this locust?” “Should we use this blue dye in our tzitzis?” “Does this food contain non-kosher ingredients?” “Did this milk come from a cow?” “Is this person a kohein?” “Is this person Jewish?” and “Can this woman remarry?” Sometimes, proving something with science is an acceptable standard and other times it isn’t. (Opinions as to where the line falls may vary.)

The DNA question actually dates back to the 1950s, when blood tests were first being used to determine paternity. Rav Bentzion Chai Uzziel, the Sephardic Chief Rabbi of Israel, ruled that blood tests are not acceptable for this purpose while Rav Shlomo Zalman Auerbach permitted them. (The question is rooted in a Talmudic discussion in Niddah 30a; Rav Uzziel had a very straightforward interpretation, while Rav Auerbach was more liberal in his approach.)

Rav Ovadiah Yosef later addressed a case in which a young woman had a baby outside of marriage. A certain man claimed to be the father, which the woman denied. The man wanted a DNA test to prove his claim but the woman refused. The beis din hearing the case initially told the woman that her refusal to allow the test would be taken as an admission that the man’s claim was correct. (Otherwise, why should she refuse the test?) Rav Ovadiah interceded, saying that paternity is not considered provable under halachic principles so we cannot coerce someone with DNA, which would be considered inconclusive.

The Talmud in Baba Basra 58a records a story in which a paternity case was resolved based on the actions of one of the man’s putative sons rather than on scientific evidence. The Rashash says that this was done in this way so as not to determine conclusively that the mother’s other sons were actually illegitimate. He cites the commentaries to mishna Eduyos 8:7 that mamzeirus (illegitimacy) should not be publicized.

This is similar to our example of tzaraas not being infectious until diagnosed; perhaps the other sons are illegitimate but the halachic problem does not arise until someone is actually known to be a mamzer and we have no obligation to go looking for trouble. In fact, it’s probably preferable if we don’t! Arguably, this is part of the reason why blood tests were not embraced to prove paternity: because if halacha accepted them as conclusive, they would also prove illegitimacy, which we’re not supposed to do.

Rav Kook made an interesting observation regarding halacha and science. The halacha is that if a doctor says that a certain sick person may not fast on Yom Kippur and the patient says that he wants to fast, we listen to the doctor. Conversely, if the doctor says that the sick person may fast but the patient is convinced that doing so will be dangerous, we listen to the patient. We see from this that scientific information is useful in halacha but it’s not the last word. The doctor’s opinion does not automatically trump the patient’s. Rather, it’s taken into consideration among other factors.

In any event, genetic testing would be of limited use in actually determining one’s Jewishness. A person might have Jewish ancestry but not be halachically Jewish. A full-fledged convert might have no Jewish genetic material at all. And what about sperm and ova from Jewish donors that might be brought to term in a non-Jewish woman’s womb?

So, for a variety of reasons, DNA testing is not considered a halachic “slam dunk.” Rather, it is just one more thing to be taken into account when rendering a decision. It carries more weight for things that might require a lower standard of proof, such as identifying a deceased’s remains to allow his widow to remarry and Israel’s Law of Return, than it does for, say, allowing someone to marry in or to serve as a kohein. But DNA is not a legal trump card because if we used it to include those who have a tradition of being on the outside, it could also be used to exclude those who have a tradition of being on the inside. While DNA might be useful in reaching a conclusion, such a test is therefore not accepted as a sole determinant in halacha.


Rabbi Jack Abramowitz
JITC Educational Correspondent

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