I had an extraordinary experience, recently, when I went to hear a talk by Christopher Buckley, the son of William Buckley, the author of several humorous books.
Mr. Buckley was speaking at the Jewish Community Center and began his talk with the startling announcement that he is Jewish. He just learned this because his niece (they have the same maternal grandmother) had submitted a National Geographic DNA swab and found that her mitochondrial DNA had three alleles that were Ashkenazi Jew. The grandmother considered herself a High Church Episcopalian. She would have been very offended.
This was striking to me because my former wife and the mother of my children also found her DNA was four alleles Ashkenazi Jew.
What is surprising in the case of my former wife is that her Irish Roman Catholic family had kicked her out of the house when they found she was having sex with me, a Jew. The whole story is well told in Philip Roth's first book Goodbye Columbus. Roth occupied the same apartment as I, just as I was leaving the University of Chicago. He got the story from our mutual roommates.
When my wife and I were married in Israel by the Orthodox rabbis who wouldn't speak Hebrew, it was a long and arduous ordeal.... over six months to get permission to get married. The rabbis always assumed my wife-to-be was Jewish and never believed that I was despite countless efforts by my father, a reform Rabbi to convince them by mail.
That is the wonderful irony of National Geographic DNA.