Curious about their roots, consumers are spending tens of millions of dollars each year getting their DNA tested and then proclaiming they are one-quarter Irish, 22 percent Scandinavian or 14 percent Native American.
These pie charts of ethnicity make for great water-cooler conversation. But what about the science? Experts say it is still in its infancy, can reinforce stereotypes and sometimes is flat-out wrong.
Scott Woodward, a former employee of Ancestry.com who helped build the company's database of ethnic markers, said DNA services are prompting millions to ask questions about their family history. He sees that as beneficial. But he's troubled that so many consumers see ethnic analysis as a hard science, when there are well-known limitations.
"It is a very, very hard problem," said Woodward, a Utah academic who previously was Ancestry's director of genomic discovery. "People like to draw hard lines with ethnicity, and they should be fluffy clouds."
Ancestry — the industry leader, with more than 5 million people tested — marketed its DNA-testing kits by claiming it offers five times more detail about family history than competitors. Some independent evaluators have praised the company for how it presents ethnicity data and places it in a historical context.
But Ancestry officials acknowledge there are large data gaps that prevent making connections between people's DNA and certain ethnic groups worldwide.
Ancestry is strong in analyzing the bulk of the U.S. population — people of European descent and African-Americans whose ancestors came across the Atlantic on slave ships, particularly from West Africa.
But the company's analysis is less strong in teasing out the ethnic background of people whose ancestors came from China or India — countries that now comprise 37 percent of the world's population.
"We want to make it better," said Catherine Ball, chief scientific officer for Ancestry. "We are proud of the work we have done so far, yet dissatisfied. We always want to make it better."
A three-month investigation by McClatchy revealed Ancestry's growth in DNA testing has come with a pattern of broken promises to customers and privacy concerns. But for consumers comfortable with paying a company to analyze their DNA and store it for perpetuity, the bigger question is: Are these test results accurate?
Companies such as Ancestry, 23andMe and Helix make ethnicity estimates by comparing people's DNA to "reference populations" — people who have agreed to have their DNA tested and their family histories shared. Ancestry say it has developed a reference panel made up of 3,000 DNA samples worldwide.
After a customer submits his or her DNA for analysis, Ancestry examines 700,000 markers in that sample and compares it to its reference panel. "Then we come up with statistically plausible distribution of where your ancestors come from," Ball said during a recent interview at Ancestry's science offices in San Francisco.
Ancestry built its ethnicity reference panel from a DNA database compiled by the Sorenson Molecular Genealogy Foundation, which, from 2000 to 2012, collected DNA samples from roughly 100,000 people worldwide. The goal of the foundation, launched by the late Utah billionaire James L. Sorenson, was to demonstrate how people of the world are related to each other.
Utah-based Ancestry.com acquired the database in 2012, six years after Sorenson died. The company now uses the data to explore ethnic differences between customers, a purpose far different than Sorenson's lofty goal.
The Sorenson data has "served as the backbone of our proprietary databases," said Ball. "That has enabled us have a very strong ethnicity estimates for places such as western Africa, places like Scandinavia."
But the foundation's international sampling was far from comprehensive. China and other countries have restrictions on taking DNA out of the country, which limited the number of samples taken from that part of the world. Moreover, the Sorenson foundation had a particular focus on regions where the bulk of the U.S. population originated, said Woodward, who served as the foundation's executive director for 12 years.
As a result, Ancestry's reference panel — detailed in a 2013 "white paper" released by the company — has relatively few DNA samples from China, India and other part of Asia.
For some African-Americans, Ancestry's analysis is superior to that of other companies. Megan Rose Dickey, a writer for TechCrunch, was impressed last year that Ancestry could give her percentage estimates of how much of her DNA came from what is now Nigeria, Ghana and Senegal, instead of lumping it all in as from "West Africa."
Yet others have been less satisfied. When Chinese-Americans take Ancestry DNA tests, they generally learn they have a high percentage of "Asia East" DNA, a category that includes all of China — which has more than 50 ethnic minorities and one fifth of the world's population — and several neighboring countries.
"From a customer’s viewpoint, the DNA kits are not cheap at $100," wrote Maria Adcock, a Chinese-American blogger, in a product review last year. "Customers want value, and at least for Asian Americans this value may prove limited."
For years, anthropologists and other critics of commercial DNA testing have warned consumers to approach these tests with a high degree of skepticism.
"They might be accurate, but it might be just as accurate to look at yourself in the mirror," said Jonathan Marks, an anthropology professor at University of North Carolina-Charlotte.
Marks agreed there is benefit in people exploring their ancestor's origins. But DNA tests, he said, too often become an end point in this exploration, instead a place to start.
"People need to realize that genomics companies are a mix of science and corporate hucksterism," Marks said. "You need to think about the difference between the product they are selling, and the product you are buying."
Defenders of DNA testing say it has sparked healthy conversations about heritage, and has furthered family discoveries. Because of DNA testing, orphans have tracked down biological parents. A Vietnam war veteran learned of a son born in Vietnam and later met him for the first time. A daughter learned that her parent's fertility doctor was her father, having deceptively used his own sperm to impregnate her mother, according to a lawsuit filed in Idaho.
But DNA testing, and the way it is interpreted, also may be reinforcing racial stereotypes, according to a 2014 report published in Social Psychology Quarterly. "An unintended consequence of the genomic revolution may be to reinvigorate age-old beliefs in essential racial differences," the report's authors said.
Woodward says he worries about false perceptions as DNA testing booms.
"The whole idea of what is a race biologically is still pretty problematic," he said. "We can take all of the humans on the earth, and we are essentially one big species. The amount of variation, the amount of uniqueness from one population to another population is pretty small compared to the overall."
Ancestry itself has been accused, at times, of reinforcing racial stereotypes.
During this year's Winter Olympics, Ancestry ran TV ads urging people to discover "their greatness." The voice-over equated Scandinavian heritage with "precision," Central Asian heritage with "grace" and British heritage with "drive."
Reaction was strong. Online commenters criticized Ancestry for "textbook racism." A watchdog group, the Center for Genetics and Society, labeled the ad spot as a "socially divisive, genetically essentialist marketing ploy."
For their part, Ancestry officials say they are constantly reevaluating how they market their services and present DNA results to customers. Ball said the company wants to diversify the samples its uses in the ethnicity reference panel, but collecting such samples internationally can be problematic.
"There are a lot of complicated sociopolitical dynamics and cultural dynamics, and you have to be respectful of that too," she said.
Ball added that, if Ancestry has statistical biases, it reflects genomic research, which receives much of its funding from U.S. and European sources. "That doesn't mean we are happy," she said. "We are always pushing."
Others are pushing as well.
In 2016, investors launched a Chinese company called WeGene, promising a more granular analysis of ethnicity for people of Chinese and Asian backgrounds. Customers who have had their DNA analyzed by Ancestry or 23andMe can load their raw data onto the WeGene site, and get a more breakdown of their ancestry, whether it be Han Chinese, Hmong, Tibetan, Dai or other ethnic groups.
But the accuracy of WeGene's analysis is difficult to verify. As the anthropologist Troy Duster wrote in 2009, "There is a complete absence of regulation or quality control with genetic ancestry testing."
Coming tomorrow: Why is AncestryDNA's main research partner so secretive?