Millions of Americans are using DNA test kits sold online to research their ancestry, either out of simple curiosity or to find answers about their identity.
But some academics warn the craze could reinforce racial stereotypes and divisions.
For around $100 and a few drops of saliva, a number of companies offer to decipher the genome of their clients and, by comparing their DNA to other profiles, tell them whether their ancestors came mostly from West Africa, southern Europe or from the indigenous peoples of the Americas, for example.
In a country whose population, for the most part, arrived in various waves of migration -- and where genealogy has caught the public imagination -- the DNA tests have proven wildly successful.
The main companies offering the service, Ancestry and 23andMe, say they have tested between 15 million people between them.
"I know my family tree, but there could have been something from another country that I did not know," said Beverley Shea, a 67-year-old pensioner who did the test because she was "just curious."
"My test was boring," she joked. "I am exactly what I thought I was: Irish, English, Scottish, Welsh..."'A form of racism'
Promoters say the new technology shows people their diverse backgrounds and will only increase racial tolerance.
"There is spectacular human diversity in the world and we celebrate and embrace it," says the 23andMe website.
By way of proof, the site showcases an African-American descended from a slave and a white person descended from a slave-owning family who found out through the company's tests that they have a common ancestor. They now meet at that ancestor's grave in the spirit of "reconciliation."
However, researchers from the University of California have shown that when white supremacists are confronted with evidence of a black ancestor, they scramble to explain away the results.
Two sociologists, Joan Donovan and Aaron Panofsky, became interested in discussions on a far-right website called Stormfront, where users said they had received "bad news" from their DNA tests.
Their research "points out that based on white nationalists' responses to genetic information upon learning their test results, there is no reason to believe that they would give up their racial ideology, and, more importantly, that genetic information cannot be relied on to change the views of white nationalists."
Timothy Caulfield, a specialist in health care law at the University of Alberta in Canada, warns that the DNA tests might even be reinforcing racial interpretations of society.
"These services are marketing the idea that biological differences matter, that at some fundamental level, your biology defines who you are," he told AFP.
In one advert for Ancestry's DNA testing service, a man tells how he used to wear Bavarian lederhosen because he thought he was descended from German immigrants, but switched to a kilt because he found he had Scottish ancestors.
"They are basically marketing a form of racism, a form that your genes are meaningful, you should think of what group you belong to based on your genes," said Caulfield.
He acknowledged that most people just did it "for fun," and that "it does not really alter the way the see the world."
But he said "it's emerging at a terrible time... where there is more tribalism, a time when people are looking for reasons to find others groups to be different."
Anthropologist John Edward Terrell also warned in the magazine Sapiens that these services are reviving the concept of "race" in a modern guise.
"Human races are inventions of the human mind. Substituting words like 'ancestry' or 'heritage' for the disreputable old term 'race' may sound like progress, but it isn't," he said.More than biology
Native Americans showed this week they are already aware of the problem, when they rejected claims by Democratic Senator Elizabeth Warren that DNA tests showed her Native heritage.
The Cherokee Nation's Secretary of State, Chuck Hoskin Jr., said Warren's use of a DNA test to claim a connection to any tribal nation was "inappropriate and wrong."
"It makes a mockery out of DNA tests and its legitimate uses while also dishonoring legitimate tribal governments and their citizens," he said.
That sentiment was echoed by Brandon Scott, editor of the Cherokee Phoenix, the nation's oldest native newspaper founded in 1828.
He said Warren's actions -- carried out in response to taunts by President Donald Trump, who dubbed her "Pocahontas" for claiming Native American ancestry -- "add some legitimacy to the myth that Native American heritage is tied to DNA."
"Heritage is not just who you are biologically," he said. "Our identity isn't present in a faux-buckskin outfit or a made-in-China headdress. It is in our communities, it is in the words of our elders and the faces of our children."