DNA Helix
A DNA double helix is seen in an undated artist's illustration released by the National Human Genome Research Institute to Reuters on May 15, 2012. Reuters/National Human Genome Research Institute/Handout

At least six million Americans who identify themselves as “white” have more "black" DNA than white people in other parts of the United States, according to a recent study published in the American Journal of Human Genetics. Several states, which have been the focal points of racial tensions in the U.S. over the years, are made up of self-described white people whose ancestors are black, the study claims.

Researchers reportedly examined the genetic records of 145,000 people who submitted saliva samples -- where DNA sequence variations are found -- to 23andMe, a California-based private company that provides ancestry-related genetic reports. From the data, researchers determined that people especially from the South have at least 1 percent of African ancestry. The study also found that states with the highest levels of African ancestry, such as South Carolina, Georgia, and Florida, “are not those with the highest proportions of African Americans.”

“European Americans with African ancestry comprise as much as 12 percent of European Americans from Louisiana and South Carolina and about 1 in 10 individuals in other parts of the South,” according to the study.

The study also showed that people with less than 28 percent African ancestry identified themselves as European American, and not as African-American. Only people with more than 50 percent African ancestry identified themselves as African-American, The Washington Post reported, citing the survey. In addition, the study found that African-Americans are more likely to have a European male ancestor (19 percent) than a European female one (5 percent).

"Our study not only reveals the historical underpinnings of regional differences in genetic ancestry, but also sheds light on the complex relationships between genetic ancestry and self-identified race and ethnicity," study author Katarzyna Bryc of 23andMe reportedly said, in a press release.