Aug. 20 (UPI) -- The genetic ancestry of Black Americans is exceptionally diverse, according to a new survey of residents in four U.S. cities.
The results, published this week in the journal PLOS One, call into question the use of skin color as a proxy for race in social science and biomedical research.
Historically, social scientists and biomedical researchers have treated Black people in the United States, including African American, African and Caribbean people, as a homogeneous group. According to the authors of the latest study, the practice is certain to erase important scientific nuances.
"This practice is not new and is reflective of age-old ideas and theories about human races," senior study author Rick Kittles, director of the Division of Health Equities at City of Hope Medical Center, a comprehensive cancer center near Los Angeles, told UPI in an email, adding that racial thinking presupposes that Black Americans are a homogeneous group.
"While current science does not support this, the racial thinking is still evident in study designs and conclusions drawn," he said.
In an effort to demonstrate the unique ancestral diversity that racial reductionism ignores, a team of physicians and scientists, led by Dede Teteh, postdoctoral researcher at City of Hope, analyzed the skin color, genetic ancestry and social attainment of 259 Black residents of Norman, Oklahoma; Cincinnati, Ohio; Harlem, New York; and Washington, DC.
"We focused on those factors because they all mediate how African Americans are seen and treated in the U.S.," Kittles said. "Skin color and genetic ancestry are how many people historically in the U.S. define race."
Their efforts revealed significant differences in ancestry, skin pigmentation and social attainment between the residents of the four cities.
Among the correlations revealed by the analysis, researchers found men with darker skin pigmentation were more likely to be married, while women were more likely to be wed if they had lighter skin color. Researchers also found residents with darker skin color and stronger West African ancestral roots were more likely to have earned graduate degrees and secured professional jobs than those with lighter pigmentation.
"There are still communities in the U.S. where skin color and genetic ancestry are strongly correlated with socio-economic variables and social attainment," Kittles said.
Researchers hope their work will motivate social scientists and biomedical researchers to account for the ancestral diversity of Black Americans as they design and execute studies.
"This research will help justify the need to take into account local history and experiences when one is studying African Americans," Kittles said. "African Americans are a macro-ethnic group with diverse genetic ancestries and local histories geographically here in the U.S."
In followup studies, researchers hope to expand their survey efforts to include larger populations of African Americans across the U.S.
"We'll also take into account variables such as racial identity and how that influences how African Americans see themselves and how they are seen by others in the health care system," Kittles said.