fb-pixel Skip to main content
Ideas | Linda Rodriguez McRobbie

Genetic testing is about to redraw a lot of family trees

Verónica Grech for the Boston Globe

Would you still be you if your grandfather isn’t actually your grandfather? Or your father isn’t your father?

Urban legend — even among scientists — puts the rates of misattributed paternity as high as 10 percent, although unbiased research puts the “cuckoldry” figure at closer to 1 percent. That’s still a lot of people.

Misattributed paternity is just one of the family bombshells genetic testing has the potential to detonate. From unknown siblings and cut-off family members rediscovered, to infidelity and undisclosed sperm donation, there’s a whole forest of family trees waiting to be cut down.

Most easy ancestral DNA kits rely on analysis of the 22 pairs of autosomal chromosomes, genetic material inherited from both parents; most also offer to connect users to a database containing the genetic information of other people, in the hopes of finding a genetic relative. In some cases, adoptees locate their birth families. In other, the genetic trail goes cold, leaving the user with more questions than answers. That was the result, detailed in a 2013 Matter story, for Cheryl Whittle, a 66-year-old Virginia woman who determined through a 23andMe kit that the man she’d thought was her father wasn’t.

Then there’s the case of “George Doe,” a stem cell biologist who shared his story on Vox. Doe bought his parents and himself 23andMe testing kits. After taking the test and ticking the opt-in box that asks whether you want to see other close relatives, Doe found a half-brother he never knew existed, his father’s son from before his parents married. The information was an earthquake to his family, and his parents divorced. “I’m really devastated at the outcome,” Doe told Vox. “I love my family. This is nothing I ever would have wished.”


Stories like these will proliferate as genetic testing becomes more popular and more affordable; already, most ancestry spit or swab kits cost less than $99. Even as the industry grows from $111 million in 2017 to an estimated $340 million in 2022, standards of practice remain murky, with little agreement across the board on exactly how to conduct this new market. For now, a number of bioethicists are warning that consumers are not sufficiently educated about the potential risks of obtaining and then sharing their genetic information.


In 2017, a team of Belgian bioethicists and geneticists examined the privacy policies of 43 direct-to-consumer genetics testing companies to determine the possibility of using the easy kits for paternity tests. What they found was a lot of murkiness, according to the study, which was published in the European Journal of Human Genetics. Companies were vague about whether minors could participate in testing. Also, a majority of the terms-of-service agreements neglected to highlight the “vulnerability of minors and family members in receiving unexpected information.” Of course, it’s not just minors who are vulnerable.

Users of 23andMe’s DNA Relative service do receive a warning that they may “discover unexpected information.” It adds that, “though uncommon, unexpected relationships may be identified that could affect you and your family.” A 23andMe spokesperson acknowledged that stories like Doe’s do occur, though rarely, and explained, via e-mail, “We do note on our website that by participating in this feature you may learn information that can be life-altering — information you can’t unlearn. This is why we make the feature optional and ensure customers know the type of information they may learn ahead of time, before participating.” Other companies, as the Belgian study observed, are not as forthcoming with the potential drawbacks, and the warnings are more difficult to find.


Another big issue with easy DNA testing is privacy. Though sites like 23andMe allow people to choose whether they enroll in information-sharing databases, that doesn’t eliminate the possibility of finding out information, genetic or otherwise, about someone who didn’t consent to a genetic test. A sperm donor, for example, may not have submitted his genetic material to a database directly, but it is possible to locate him through a relative who has. Beyond genealogy, genetic testing carries with it a range of other strange problems. Some companies already offer “infidelity DNA testing,” offered to people who has reason to believe that their partner is cheating. They’ll test samples — including “blood, hair, or used condoms,” according to one such company — to determine whether they match a sample of your own genetic material. Notably, one company offers the service both in the United States and Britain. In the Britain, however, users cannot send in genetic material that doesn’t belong to them without written consent from its actual owner. The United States, such a privacy safeguard doesn’t exist.

The science of genetics is moving very quickly; already we’ve seen the cost of sequencing an entire human genome plummet from $3 billion to just about $1,000 in the space of two decades. Humanity is on the verge of learning a lot of life-altering information that it can’t unlearn — and only part of that has to do with our genes.