Author: Tina Hesman Saey / Source: Science News
Michael Douglas, a new resident of southern Maryland, credits genetic testing for helping him find his heritage — and a family he knew very little about.
Douglas, 43, is adopted. He knew his birth mother’s name and had seen a birth certificate stating his birth name: Thomas Michael McCarthy. Over the years, Douglas had tried off and on to find his birth family, mostly by looking for his mother’s name, Deborah Ann McCarthy, in phone books and calling the numbers. “I think I must have broken up a lot of marriages,” he laughs.
His search gained urgency in the last five years as he battled a life-threatening illness. “We planned my funeral three times,” he says. Douglas has a genetic disease called Ehlers-Danlos syndrome, caused by a variant in a gene that helps build the body’s connective tissue. His stretchy skin and hyperflexible joints are characteristic of the disease.
This feature is part of a series on consumer genetic testing. See the whole series.
“As a kid, I was always dislocating something,” he says. His blood vessels don’t constrict properly to maintain his blood pressure, so Douglas sometimes faints when he stands up. For five years, he has had a constant migraine. Headaches are typical of about a third of people with Ehlers-Danlos. On top of that, he has B cell lymphoma. “I feel like I have the flu every day,” he says.
It was time, he decided, to track down his birth family and learn more about his medical history.In June 2017, Douglas flew to Ireland on what he calls his “death trip.” He wanted to see the land of his McCarthy ancestors. He chose Fethard, because the walled medieval town has a pub called McCarthy’s. (Douglas learned later that he and the pub owner are related.) His health improved during the visit, which he attributes to Ireland’s cool weather. When he returned to Phoenix, where he and his adopted family lived, he had new resolve to find his birth family.
“That’s it,” he decided. “I need my DNA run to find out who I am.” He sent his DNA to three testing companies: Family Tree DNA, AncestryDNA and MyHeritage. With his results plus sleuthing of genealogical records by some helpful strangers, Douglas found his biological family last November and dove headfirst into a new life.
In February, he moved from Phoenix to Maryland to help care for his biological mother as she recovers from a stroke. The new family dynamic hasn’t been easy, but Douglas has bonded with one of his two biological brothers. “And I have a relationship with my ancestors that I did not know before.” He is pleased to find that he resembles his great-grandfather Thomas Rodda, a bicycle maker. Douglas himself is a Star Wars costume maker.
Adoptees like Douglas and birth parents looking for children they gave up often use commercial DNA tests in hopes of reconnecting, says Drew Smith, a genealogical librarian at the University of South Florida in Tampa. Many states make it difficult for adoptees to get birth certificates or other documents that could help them track down birth families. DNA tests are “an end run around the documentation problem,” Smith says.
But the pool of people looking for their genetic roots is much larger. AncestryDNA, the ancestry testing service with the biggest customer base, has persuaded about 10 million people to take its DNA test. 23andMe, Living DNA, Family Tree DNA, MyHeritage, National Geographic’s Geno 2.0 and others also offer customers a chance to use genetics to connect with living relatives and with families’ pasts. A few companies even give hints about ties that go back to Neandertals (SN: 11/11/17, p. 10). But such testing services may not be able to tell you as much about who you are and where your family came from as they claim.
False precision
I got my DNA tested for this multipart reporting project. My assignment was to investigate the science behind DNA testing (SN: 6/9/18, p. 20), but it was also a welcome excuse to learn more about my family’s history.
I already knew a lot about three branches of my family tree. Based on birth and death records, plus census and other documents, most of my family stems from England and Germany. But I dreamed of connecting to relatives on the Hungarian branch, which I knew less about. So I sent saliva or cheek swabs to a handful of testing companies.
My ethnicity estimates were all over the European map. Generally, estimates are most accurate on the broad continental scale. All of the companies agree that my heritage is overwhelmingly European. But that’s where the consensus ends. Even the companies that limit their estimates to broad swaths of the continent told different stories. National Geographic’s Geno 2.0 says that I am 45 percent Southwestern European. Veritas Genetics puts my Southwestern European heritage at only 4 percent and tells me I’m mostly (91.1 percent) north-central European.
The companies that try to dig down to the country level see their confidence in the results go down, but that doesn’t stop them from making very specific estimates. In most reports, the main results given are at the lower end of the confidence scale. 23andMe, for instance, says it has 50 percent statistical confidence in the ethnicity results.
Along with the wide variations between companies, the estimates often didn’t match what I know about my family tree. 23andMe says I’m 16.6 percent Scandinavian. When I sent raw data from 23andMe to MyHeritage to do its own analysis, that company reported no Scandinavian ancestry in my background; it said I’m 16.9 percent Italian. As far as I know, I have no ancestors from Italy or Scandinavia.
Only 23andMe called out my German heritage, though the company lumped it in with French for a total of 18.8 percent. Hungarian is not specifically identified in any company’s estimates. I can only guess that 23andMe’s 3.9 percent Eastern European and 0.3 percent Balkan findings cover that part of my ancestry. Both 23andMe and AncestryDNA say that I have Ashkenazi Jewish heritage. News to me.
Multiple companies agree that a sizable chunk of my heritage is from the British Isles. But even in that, estimates run from 23andMe’s 26.6 percent British and Irish, to Living DNA’s calculation that 60.3 percent of my DNA comes from Great Britain and Ireland, to MyHeritage’s even higher 78.7 percent.
When I shared these inconsistencies with Deborah Bolnick, an anthropological geneticist at the University of Texas at Austin, I could practically hear her shaking her head over the phone.
“They present these very specific, precise numbers down to the decimal point. But it’s a false precision,” Bolnick says. “The tests that are available may not be as nuanced, sensitive and fine scaled as…
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