The Chief Rabbinate’s interest in genetic testing as a tool to establish Jewishness should set off a historical warning light for everyone, but particularly for Jews.

Over the past year the rabbinical courts began proposing that individuals in the process of “clarifying their Jewish states” undergo genetic testing: specifically of mitochondrial DNA, which is inherited from the mother. Dozens of Israelis have undergone the test in the past year, and it has helped about two-thirds of those whose Judaism had been in doubt.

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>> Israel's rabbis think genetic testing can 'prove' Jewishness. They're wrong | Opinion

Every year, more than 4,000 Israelis are required to prove whether they are Jewish. In most cases they are the children of immigrants from the former Soviet Union who want to register for marriage. Until recently, the process involved presenting documents, such as birth and death certificates. Now, as if Judaism is a matter of race, not religion, rabbinical courts are inviting people whose documents did not satisfy them to undergo a DNA test.

This is a test that can make things easier for people the rabbinical courts did not recognize as Jews. But we must not be misled into thinking it is a sign of improved service by the rabbinate. It is inconceivable that an Israeli who wants to marry should have to take a DNA test to prove that they are Jewish. Although the test is voluntary at present, and is used only to prove a person’s Jewishness, it could open the door to negating the Jewish status of a person who was previously recognized as Jewish.

A few months ago Yisrael Beiteinu Chairman Avigdor Lieberman slammed the Interior Ministry, and rightly so, for asking immigrants from the former Soviet Union to take a DNA test. Lieberman accused the ministry of discrimination and said the voluntary nature of the test was meaningless if refusing to undergo it results in not being recognized as Jewish and therefore being disqualified from marrying in Israel. The way to cut the red tape is not to make verification methods more sophisticated, but rather to do away with them, among other ways by introducing civil marriage.

In Israel, which grants citizenship according to bloodlines only; where a person’s Jewishness has legal significance that affects the right to immigrate and to obtain citizenship, as well as affecting personal status and even the right to buy property, the thought of making DNA testing part of the process of determining Jewishness according to religious law is spine-chilling. While there is no overlap between determining Jewishness according to Jewish religious law and determining Jewishness for the purposes of the Law of Return, the complex relationship between state and religion in Israel demands extreme caution.

No door should be opened for Israel to become a country where entry and citizenship will someday depend on a genetic test. This is a slippery slope, at the bottom of which Israel is liable to define itself not only as the nation-state of the Jewish people, but as the state of the Jewish race.

The above article is Haaretz’s lead editorial, as published in the Hebrew and English newspapers in Israel.