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But not everyone believes the tests are actually as vague as Balding and Thomas do.
"What most companies offer today is a measure of ancestry that maps to a geographic region. The basic data consists of genetic variants (alleles) that are at different frequencies in different geographic regions," Dr. Michael Zwick, an associate professor at Emory University's Departments of Human Genetics and Pediatrics and assistant dean of research at Emory's School of Medicine, told the AJC.
Zwick said that while there is always uncertainty, estimates get better over time.
"These sorts of measures are well-supported in my view, although you have to recognize that our genomes undergo recombination – mixing – every generation," he said. "So, really what these estimates are showing is the probable origins of parts of your genome related to a geographic region."
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Bennett Greenspan, the president of the DNA testing service Family Tree DNA, told the AJC that his company's tests "are highly repeatable and for close relative relationship testing, they are very accurate."
"DNA [testing] works very well. It's very repeatable, and if you know what you are doing it will provide as much evidence as the CODIS system, which the courts use for cases all the way to murder," Greenspan added. "It does give a general picture of one's history."
A representative of 23andMe said the company's reports are "highly accurate," adding that 23andMe is "the only consumer genetic testing that has received FDA authorization for the health reports it offers customers."
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A media representative from Ancestry.com, one of the leading online services for tracing ancestry, said that the company compares an individual's DNA with that of people from over 350 regions in the world. The service combines data from the largest DNA network of almost 10 million people with more than 10 billion historical records and 90 million family trees to create its reports.
"Ancestry is equipped with the resources to facilitate and empower positive connections between consumers. In today's climate of divisiveness and nationalism, consumers are missing a sense of connectedness and belonging," the representative added.
Most of these genetic services provide a percentage breakdown showing where your ancestors were most likely from. But from the viewpoint of a historian, while this information is indeed interesting and could prove fulfilling for many people, cultural belonging is a bit more complicated.
"There are lots of different ways of understanding heritage. I think as historians, we're interested in why people believe what they do, which is quite different than saying that people are something," Dr. Jeffrey Lesser, chair of Emory University's Department of History and director of the Halle Institute for Global Research and Learning, told the AJC.
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Lesser said that the stories parents and grandparents tell their children and grandchildren are more important to forming individual cultural identities than what genetics a person may or may not have.
He's read reports of people trying three different consumer DNA services and getting three separate results. But he’s also has had many friends who have used such services and found it fulfilling.
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"For me, I'm very interested in why it is that all of a sudden people have become very interested in DNA testing. That's an interesting cultural phenomenon," Lesser said. He often wonders if the results ever make an individual change something about their lives or how they identify culturally.
When it comes to how DNA testing has been used by historians and scientists to study migration and groups of people around the world, Lesser said that the reality gets somewhat complicated.
"There are particular groups of people in Europe and particular groups of people in Africa who have closer DNA matches than two groups in Europe or two groups in Africa," he said. "In that regard, some of the work by scientists, who have looked at different kinds of gene pools, have shown us these interesting results. But that's something quite different than Ancestry.com or something like that."
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While DNA tests may reveal a general picture of a person's ancestry, cultural heritage and identity can't so easily be reduced to genetics, according to Lesser.
"The reality of the human condition is that at the genetic level, we are from many, many different places," Lesser said.