A few months ago, I sat down at my desk to open a letter that could tell me whether my father was really my father. In fact, that letter could tell me whether the men going back 10 generations on my paternal side were the biological fathers of their children.
I wasn’t caught up in some bizarre multigenerational paternity suit. A scientific officer at a genetic testing company knew that I was interested in genealogy, and he had offered to run my DNA through a sequencer. A few weeks earlier, I’d swished mouthwash inside my cheeks, sealed the mouthwash in a tube, and mailed the tube to the company.
My doughty Scandinavian ancestors passed the test. My DNA revealed no obvious instances where the man named on a birth certificate differed from the man who was my biological ancestor. But I was lucky. Many efforts to trace male ancestry using DNA terminate at what geneticists delicately call a “non-paternity event.” According to Bennett Greenspan, whose company, Family Tree DNA, sponsors projects that attempt to link different families to common ancestors, “Any project that has more than 20 or 30 people in it is likely to have an oops in it.”
The law of unintended consequences is about to catch up with the genetic-testing industry. Geneticists and physicians would like us all to have our DNA sequenced. That way we’ll know about our genetic flaws, and this knowledge could let us take steps to prevent future health problems. But genetic tests can also identify the individuals from whom we got our DNA. Widespread genetic testing could reveal many uncomfortable details about what went on in our parents’ and grandparents’ bedrooms.