The racial and ethnic groups people identify with may not accurately represent their genetic backgrounds or ancestries, a new study of people in the United States suggests.
This discrepancy between people’s self-reported identities and their genetics is important for scientists to acknowledge as they strive to develop medical treatments tailored to different patients, the researchers behind the study say.
“This paper is very important because it clarifies at the highest resolution the relationship between genomic diversity and racial/ethnic categories in the US,” said study co-author Eduardo Tarazona-Santos, a professor of human population genetics at the Federal University of Minas Gerais in Brazil.
The findings are “critical to develop appropriate precision medicine solutions for all,” he told Live Science in an email. Precision medicine tailors treatments to individual patients, taking their genes, environment and lifestyle factors into account.
Medicine for all
In their study, published Thursday (June 5) in The American Journal of Human Genetics, Tarazona-Santos and his colleagues analyzed the DNA of more than 230,000 people who contributed to the All of Us research database. This trove of data has been compiled through a National Institutes of Health program aimed at advancing precision medicine by recruiting people from diverse and underrepresented populations.
Historically, many large-scale genetics studies have predominantly included people of European ancestry, making efforts like the All of Us project crucial for reducing medical inequity. However, the program has faced significant funding cuts in recent months, which has significantly slowed recruitment and progress.
Related: What’s the difference between race and ethnicity?
Using a method called principal component analysis, the team identified genetic similarities and differences among the people included in the database. They also used genetic catalogs that contain DNA samples from all over the world, such as the 1000 Genomes Project, as a way to assess how people’s genetic ancestry compared with the racial (white, Black or African American, Asian American) and ethnicity (Hispanic/Latino or not) categories used in the All of Us questionnaire.
People who identified as being from the same racial and ethnic groups had a number of genetic differences, the team found. In fact, “most genetic variance is within race and ethnicity groups rather than between groups,” the study authors wrote in the report.
Rather than sorting people into “distinct clusters” divided by racial and ethnic lines, the analyses found that people within different races and ethnicities show “gradients” of genetic variation. “We found gradients of genetic variation that cut across those categories,” the authors wrote.
The new study’s findings counter a controversial paper published in Nature in 2024 that had also analyzed genomic data provided by All of Us participants. At the time, the paper was criticized by some experts, who argued that the technique used to analyze the race and ethnicity data could be misconstrued to support the incorrect idea that humans can be neatly categorized into distinct races. The new study, which used a different data-crunching technique, found the opposite.
Variation among U.S. states
The research also found that, even within the same ethnic and racial group, people show genetic variation across different U.S. states. This could reflect the “historical impacts of U.S. colonization, the transatlantic slave trade, and recent migrations,” the authors wrote.
A key example of this was seen in participants who identified as Hispanic or Latino and lived in states like California, Texas and Arizona, who were found to have a high proportion of Native American ancestry compared with Hispanic and Latino people in other parts of the U.S. This makes sense considering many of these states were historically part of Mexico, which has a large population of people with mixed Indigenous and European ancestries, the researchers argued.
By contrast, of people who identified as Hispanic or Latino, those in New York were found to have the highest proportion of African ancestry, which is “consistent with recent migration from the Caribbean to New York.”
The authors said their findings show that the genetic backgrounds of people in the U.S. are highly complex and that “social constructs of race and ethnicity do not accurately reflect underlying genetic ancestry.” In light of this, the researchers have said they “do not recommend using race and ethnicity as proxies for ancestry in genetic studies.”
Tesfaye Mersha, a professor of pediatrics and a human genetics researcher at Cincinnati Children’s Hospital Medical Center and the University of Cincinnati, said that he agrees that these self-reported categories should not be used in genetic studies. Instead, the categories should be confined to social studies “where we know they will have a big impact,” he told Live Science in an email.
That said, Mersha also warned against overinterpreting the study’s takeaways about regional and state-level genetic variation.
“Some states had very low participant numbers, which may skew regional estimates and limit generalizability,” he noted. “Moreover, high population mobility across states blurs geographic boundaries, especially in the absence of multigenerational ancestry data,” he said. In short, because people move around a lot, it’s difficult to draw conclusions without having a clear sense of how long their families have been based in a given state.
