We knew it all along: African descent comes in variations
Last Updated on January 28, 2021 by Joseph Gut – thasso
January 29, 2021 – Biomedical research may miss important key information by ignoring genetic ancestry. A recent study of residents of African-American descent of four distinct U.S. cities revealed variations in genetic ancestry and social status that underscore the inadequacy of using skin color as a proxy for race (better yet and more correct: descent) in research.
Dede Teteh of City of Hope Medical Center in Duarte, California, and colleagues present these findings in a publication in the open-access journal PLOS ONE on August 19, 2020. Social science and biomedical research often treat the parts of the US population, namely people of recent African descent, including African Americans, Africans, and Caribbeans, as a homogeneous group, using skin color as a proxy for “race”, even though this entity is largely inadequate and politically incorrect. This approach ignores geographic variations in ancestry and social attainment that could provide more nuanced information.
In a first-of-its-kind study, Teteh and colleagues analyzed and compared skin color, genetic ancestry, and social attainment of 259 residents of recent African descent of i) Norman, Oklahoma, ii) Cincinnati, Ohio, iii) Harlem, New York, and iv) of Washington, DC. Each of these cities has a unique history that has shaped its population structure today.
Statistical analysis revealed between-city differences in ancestry, skin pigmentation, and social attainment. It also showed that men were more likely to be married if they had darker skin color, and women if they had lighter skin color. People with darker skin color and a greater degree of West African ancestry were more likely to have attained graduate degrees and professional jobs than people with lighter skin.
These findings highlight and deepen understanding of the complexity and heterogeneity of race, ancestry, and social attainment in the U.S., especially variations between geographic regions. While the sample size is small, this study supports the importance of considering local social context and genetic ancestry when conducting social science or biomedical research.
The authors mention that this study expands the knowledge of the complexity of ancestry, and social attainment across four cities in the United States. Their findings support the heterogeneity of the African American population in the U.S. due to regional differences and local history. Thus, the African American population should not be viewed as a singular entity, but as an assembly of very individual groups of people, all with their own local social histories and genetic backgrounds.
These findings are not so surprising, however. We have to expect that Africa presents a huge human genetic diversity because of its complex population history and the dramatic variation in climate, diet, and exposure to infectious disease, which have resulted over time and still result in high levels of genetic and phenotypic variation in African populations or populations who arrived in the so called “New World”, mostly be rather questionable means, unfortunately. Confounding factors, such as the social environment of living and/or education and economic basic may then bring out heterogeneous behaviours and preferences such as those described.
See here a sequence on the topic: