You Are Not Your DNA

(Bloomberg Opinion) -- People are reading too much meaning into DNA – Elizabeth Warren’s and their own. It continues to carry a mystique as a key to who we are, where we belong, and when and how we’ll die. Just days before Warren announced her DNA ancestry results, headlines were warning of a new threat to the genetic privacy of us all. But the experts offered no compelling examples of what DNA snoops might find out about us and how that information would cause us harm.

The privacy warnings came from a paper in Science, which proclaimed that detectives, or hackers for that matter, could find the identity of “almost anyone” from a sample of DNA. Of course, if you committed rape or murder and left your DNA at the scene, this DNA matching capability could reveal that you are the perpetrator. But what can it reveal about the rest of us?  

The reason it’s now possible to connect names with otherwise anonymous DNA is that so many people have entered their DNA into databases to trace their genealogy, and many have posted it publicly in the hope of connecting with relatives. Detectives investigating a notorious cold case, that of the Golden State Killer, recognized that they could make use of this data. They had the killer’s DNA, but no match to any suspects.

So they created a fake customer for an online genealogy service and found partial matches to people likely to be the killer’s relatives, after which they found the source of the DNA sample through his family tree. The Science paper demonstrates that this case wasn’t a lucky fluke. The same strategy would work to track down about 60 percent of people of European ancestry. And as more people sign up for genealogy services, that will grow to encompass almost everyone.

A similar ominous tone followed another paper released the same week in the journal Cell. There, scientists demonstrated that it’s possible to link DNA samples collected through law enforcement to samples that contain other sorts of genetic information, and use it to match not just individuals who have volunteered their DNA but also family members who have not.

One serious concern is that, in principle, someone could use the same techniques to unmask the identities of people who donated DNA for scientific studies. But it would be against the law for anyone to use any of their genetic information against them.

Back in the 1990s, scientists and medical ethicists worried that the health insurance system would refuse coverage over genetic risk factors, and that might lead to employers firing people over their DNA. And so the U.S. and many other countries adopted laws to prohibit genetic discrimination.

How has that worked out? I asked Bartha Maria Knoppers, a law professor and director of the Centre of Genomics and Policy at McGill University in Canada.  She said there hasn’t been any problem with genetic discrimination. That might be because companies are respecting the law, but also, DNA turned out to be much less predictive than people thought it would be.

A small minority of people carry a real genetic time bomb, such as Huntington’s disease or mutations associated with a high risk of certain cancers. For most of us, our health is tied to multiple genes and environmental factors, such as exposure to pollution, stress and diet – and to some extent random chance.

Knoppers said that fears set off by these new reports might inhibit the free sharing of data that’s becoming important for international collaboration in science. Subjects should be informed that if they give DNA for a study, it’s hypothetically possible for them to be identified.  But it is a hypothetical problem.

The news stories also hinted at a risk that use of genealogy might lead police to arrest innocent people. When I was researching a previous column about the implications the Golden State Killer case, experts said that technique will help detectives catch the right person, as long as there’s a complete sample of DNA at the crime scene, and they can match it to DNA directly from any suspect tracked through relatives. DNA has helped to free the innocent, and call attention to the problem of wrongful convictions.

DNA has also contributed to wrongful convictions, in cases where detectives try to use minute fragments left from someone merely touching an object, or mixtures of DNA from different people. But that’s a separate issue.

Beyond forensics, DNA has revolutionized the understanding of evolution and where we as a species came from. But there are limits to what it can reveal about any given individual. Since Elizabeth Warren published her genetic profile, everyone is reading something different into the test results. Supporters say she has now proven that she is indeed part Native American, while her foes say the test proves the opposite, that she has too little Native American ancestry to qualify.

What do the geneticists say? News stories have quoted several boasting about how accurate their tests are in finding minuscule contributions to people’s DNA. But they can’t answer whether Warren’s result means she can identify as Native American. That's a line drawn by cultures, not by science.

One of the most interesting things DNA ever revealed was that all humans share a recent common origin in Africa, and that there’s been a long history of mixing. Studies show that many Americans have a combination of European, African and Native American ancestors, and that the degree of mixing varies by region. There is no scientific way to decide who qualifies to be in which race, because scientists now recognize that there are no lines separating races – only a continuum of skin colors and other traits that vary around the globe. A scientist once told me that race is just family resemblances writ large.

And so the bad news is that a DNA test can’t really tell you who you are or divine your future health. But the good news is that any hackers who stole your DNA wouldn't learn much either.

To contact the editor responsible for this story: Philip Gray at philipgray@bloomberg.net

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.

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