In a rare political riposte, Senator Elizabeth Warren on Monday released an analysis of her DNA indicating that she has a Native American ancestor, likely between six and 10 generations back in her family history.
President Trump has mocked Ms. Warren’s claims of Native American ancestry, often calling her Pocahontas. The new analysis appeared to be scientifically rigorous, researchers said, but it cannot give someone a cultural identity as Native American.
The research on Ms. Warren’s DNA was led by Carlos Bustamante, a Stanford University geneticist who has written a number of studies on the genetic ancestry of people in the Americas. The results were first reported by the Boston Globe.
The study did not appear in a peer-reviewed journal and had not gotten rigorous scrutiny from other scientists. But Deborah Bolnick, a geneticist at the University of Connecticut who studies Native Americans and was not involved in the analysis, said the Stanford team used well-established methods.
“It’s well done,” she said. “It’s consistent with what you might expect if someone had a single ancestor a few generations back.”
Dr. Bolnick cautioned that membership in a Native American tribe is not something inscribed in DNA.
“What determines tribal belonging is very much based on a person’s social connections and lived experiences,” she said. “These are things not defined by the DNA in our bodies.”
In a video that Ms. Warren released along with the analysis, she described how her mother had discussed their Native American ancestry. Family lore held that there were Cherokee and Delaware indigenous ancestors.
The Cherokee Nation condemned Ms. Warren’s analysis in a statement Monday.
“Using a DNA test to lay claim to any connection to the Cherokee Nation or any tribal nation, even vaguely, is inappropriate and wrong,” said Chuck Hoskin Jr., the tribe’s secretary of state. “Senator Warren is undermining tribal interests with her continued claims of tribal heritage.”
In an interview, Dr. Bustamante said that he didn’t know much about the political controversy before being asked to examine Ms. Warren’s DNA. “I got a phone call out of the blue,” he said.
Dr. Bustamante is an adviser to Ancestry.com and has served as an adviser to 23andMe, both consumer testing companies. He said he has not donated money to Ms. Warren.
He and his colleagues have developed statistical tools used to look at the DNA of individuals to determine their ancestry.
In 2012, for example, they examined the genome of Otzi the Iceman, a 5,300-year-old hunter who died and was buried under ice in the Alps. (They discovered, to their surprise, that he had strong genetic links to the island of Sardinia.)
Ms. Warren had her DNA sequenced at a laboratory with a method known as genotyping, in which researchers examined a small fraction of her DNA.
The human genome contains over 3 billion base pairs, the genetic letters that spell out genes. Dr. Bustamante was able to study 764,958 bases of Ms. Warren’s DNA.
Dr. Bustamante and his colleagues compared Ms. Warren’s DNA to that of 148 individuals from the Americas, Europe, Africa and Asia.
His team found many segments of DNA typical of Europeans and was able to assign 95 percent of Ms. Warren’s DNA to European ancestors.
Only five short pieces of DNA stood out as exceptions. Those five contained variants typically found in Native Americans. The biggest of these pieces is 4.7 million bases long.
The short length of these segments means that Ms. Warren’s Native American forebear was not a recent ancestor. Instead, the size suggests the ancestor lived six to ten generations ago.
Dr. Bustamante cautioned that genes can’t give a perfect picture of ancestry that far back. As more generations pass, it’s more likely that an ancestor’s DNA will disappear entirely from a lineage.
“We can see nearly definitive evidence of at least one Native American ancestor,” Dr. Bustamante said. “But there could have been more.”
In this respect, Ms. Warren is not exceptional.
In 2014, researchers at 23andMe looked at the DNA of people who said they were of European ancestry. The researchers estimated that in as many as five million European-Americans, at least 1 percent of the genome is Native American.
Since Dr. Bustamante used a different method to assess Ms. Warren’s DNA, however, it is not possible to compare her ancestry directly to that of 23andMe customers.
Dr. Bustamante could not say from Ms. Warren’s DNA which tribe her ancestor belonged to. He was able only to compare Ms. Warren’s DNA to that of indigenous people in Peru and Mexico, as well as First Nations people in Canada.
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He did not study any Native Americans in the United States, with whom Ms. Warren would presumably be most closely related.
Native American tribes have felt exploited and deceived about how their DNA has been studied in the past. The long-running distrust means that relatively little is known of their DNA.
Krystal Tsosie, an indigenous geneticist and bioethicist at Vanderbilt University, said another concern among Native Americans is that people might use results from consumer genetic tests to claim that they belong to particular tribes, regardless of a tribe’s own rules for membership.
“There are all these questions about how this can potentially harm our sovereign status,” she said.
Without data on Native Americans in the United States, Dr. Bustamante and his colleagues were careful to limit their conclusions. Ms. Warren has an ancestor who descends from the first people who traveled from Asia into the Americas, and from whom Native Americans descended, he said.
Ms. Tsosie said she hopes Ms. Warren’s report would put a spotlight on the complicated issues surrounding Native American identity today. Still, she worried that some people might argue that being Native American is nothing more than a result from a DNA test.
“I’m really grateful that Elizabeth Warren decided to consult a leader in the field,” Ms. Tsosie said. “But I’m concerned that these issues will be weaponized.”
