In the spring of 2012, 34-year-old Jackie and her older sibling Alex (names changed) spit a few millilitres of saliva into plastic tubes and shipped them off to 23andMe, a personal genomics company, for consumer-grade scans of their DNA. Their family has a long history of cancer, alcoholism and bipolar disorder, and Jackie, who happens to work for a biomedical research lab, wanted to learn all she could about her health risks and propensities.
Alex wasn’t quite so into it. Jackie is curious by nature, the kind of person who’s always asking questions. Her brother’s just the opposite: a military man with little time for facts that don’t bear directly on his mission goals.
When they both got e-mails saying that their genome data could be viewed online, Alex didn’t open his.
The two agreed to look over their reports together, though. Meeting at their mother’s place, they logged into 23andMe.com and checked the hints about their health and heritage that had been extracted from their genomes. None of what they found was so surprising, at least until they reached a screen that promised access to “close relatives” who might be in the system. Opting in, the siblings learnt a fact about themselves that would have been disturbing, were it not so obviously in error: Jackie had an uncle, the software told them – an Uncle Alex.
When Jackie wrote about the glitch on the 23andMe message board, she got a quick reply: that’s not an error, another user wrote; it means that you and Alex are more distantly related than you think. The scientists in Jackie’s lab agreed: Full siblings have about one-half their DNA in common, as do parents and their children. But the genome scan must have shown that she and Alex share one-fourth of their DNA instead. That proportion could imply that two samples came from a niece and her uncle, or from a girl and her grandfather. But it could also mean that Jackie and Alex were half-siblings – that they shared one parent, but not the other.
Alex, who is eight years older than his sister, refused to believe the news. When Jackie called him to explain what the “uncle” thing was all about, he snapped at her. “Mom did not cheat on Dad,” he said. “It’s a data-entry mistake. You’re crazy!”
But for Jackie, something had begun to click. She and her brother had never looked that much alike, and their personalities were opposite. Their parents had been separated for 20 years, and Jackie was never close with the man she’d always called her dad.
Jackie had sent in her DNA to learn something new about herself, but ended up more confused than ever. That night, she went to her mother’s house and heard about a one-night stand with a much older man, her biological father, now dead for many years. When she got home that night she went to the bathroom. ”I didn’t recognise myself,” she says. “I looked in the mirror and thought, who is this person?”
Last December, 23andMe announced that it would be cutting prices for its genome scans. The seven-year-old company reduced the cost from $299 (R2 900) to $99, in the hopes of building a database of 1 million users by the end of the year. (They’re one-quarter of the way there.) If that happens, how many of those clients will find themselves in the same dismaying situation as Jackie and her brother?
The study of false fatherhood, or non-paternity, has turned up a wide variety of answers. University of Oklahoma anthropologist Kermyt Anderson says that measured rates of non-paternity vary quite dramatically depending on the group of people being tested. Among those men who are quite confident of their status as biological fathers – the ones who volunteer their families for genetic studies of inheritance, for example – Anderson found a rate of non-paternity of roughly 1.7 percent. At minimum, he says, 1 in 60 dads raises children that don’t belong to him.
Anderson also went through data from companies that make their money testing for paternity. The men who send off DNA for these commercial tests presumably have cause to be suspicious. These men should have the highest incidence of non-paternity, Anderson says. When he checked the research on this population, he found a median rate of close to 30 percent.
The true number across the US population probably falls between these two extremes.
But while it’s often said that 10 percent of fathers are raising someone else’s child, this interpolation isn’t quite supported by the facts. The best summations of the data figure an overall prevalence of non-paternity at more like two or three percent. One analysis from 2008 looked at several dozen studies going back to the 1890s and found an average rate of 3.1 percent, but also hinted that the numbers might be declining over time (possibly in concert with increasing contraceptive use).
Which is all to say that the expanded 23andMe database may include as many as 30 000 customers like Jackie (3 percent of 1 million) who have gone their whole lives without knowing that their father doesn’t share their genes. Even now, among the 250 000 people who have already been genotyped by the company, one might expect that 6 000 or 7 000 were unwittingly involved in cases of non-paternity. Some of these people have sent off their saliva and got back a secret that changed their families for ever, for better or for worse.
The rise of personal genomics has not created this phenomenon, of course. Non-paternity results can arise even in the course of routine medical testing. What happens if a doctor sees that a baby’s blood type could not have come from its father? In the past few decades, the medical establishment has decided that these findings should be concealed, to protect the mother’s privacy and avoid unnecessary harm.
But when people sign up for a service such as 23andMe, they may have no idea that a family secret is about to be exposed.
23andMe does take some steps to warn its users of the risks. The top question on the company FAQ is “What unexpected things might I learn?” and the answer mentions that “genetic information can also reveal that someone you thought you were related to is not your biological kin.” The terms of service specify that “once you obtain your genetic information, the knowledge is irrevocable”, and that “you may learn information about yourself that you do not anticipate”.
Yet it’s also true that the chances of discovering a case of non-paternity through 23andMe, and the relative significance of that discovery, far outweigh almost every other finding that the service can provide. Much of what the scan can tell you is perfectly trivial. Do you have the genes for blue eyes or red hair? Do you have the genes for tasting bitterness in Brussels sprouts? (Maybe, but who cares?)
Other data points from your personal genomic scan will be more suggestive than deterministic. The test might tell you that you’re at a somewhat heightened risk for diabetes or arthritis, but it can be hard to know which bullet points are based on solid science, and which are based on single studies with unconvincing correlations.
I asked the company’s senior research director Joanna Mountain which genome data would have the most real-world significance for customers, and she named four: major risk factors for Parkinson’s disease, Alzheimer’s, a form of heart disease called TTR-related cardiac amyloidosis, and breast and ovarian cancer.
Given the stakes, 23andMe tries to protect its users. To check your status as a carrier for the genes in question, you must confirm that you’re prepared to know the truth and understand the consequences. Even so, the actual risk of carrying these genes is very low. Just 0.013 percent of the population carries the relevant mutations predisposing them to breast and ovarian cancer, for example. (Among Ashkenazi Jews, it’s 2 or 3 percent.) One or 2 percent of people will turn out to have the major risk factor for Alzheimer’s, and the gene for cardiac amyloidosis matters most to African-Americans, among whom the rate is still just a few percent.
So the chances that you’re carrying these genes – the risk that you’re at a heightened risk for one of these diseases – tops out at 2 or 3 percent, even in the ethnic groups that are most heavily afflicted. That’s directly comparable to the risk of non-paternity, except when it comes to non-paternity, we’re not talking about people who are merely “carriers” of a twisted gene. If your father’s not your father, that’s the end of the story. It’s not a risk factor; it’s a fact.
Science is getting personal. Medicine is getting personal. Information is getting personal. That means each of us will have to figure out a personal approach to the swelling stream of data. At some point, all of us may have to decide: Do I want to know the truth or not? Am I a Jackie or an Alex?
As time went by, Jackie found some satisfaction in her newfound knowledge. Her lack of closeness with her father wasn’t from some failing on his part or on hers, she thought; it wasn’t cause for guilt or shame or disappointment. It was only nature. Their relationship had been doomed by mismatched nucleic acids. “I didn’t connect with my dad, and now it makes sense,” she says. “It’s fine. It is what it is.”
Jackie doesn’t plan to tell her father what she knows. There’s no point in hurting him, she says.
Some people seem to have this inborn curiosity, a need to dig into their pasts. Now those people have a better tool for excavation – and when 1 million customers start to pick away, they’re sure to tap a heavy vein of secrets. – Washington Post