The Grapevine

Genetic Analysis Of African Americans From African Diaspora And Great Migration Reveals Unique Ancestry, Origins

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The genome of African Americans changes depending on what part of the country they live. Pixabay, Public Domain

Where are you really from? It’s a question that most African Americans cannot answer beyond their home state. The African diaspora forcibly transplanted millions of Africans from their homeland to a new continent across the sea. Several hundred years later, the Great Migration saw 6 million African Americans leave their new home in the American South for other areas of the country in search of work and racial equality.

These moves greatly changed the genome of the modern-day black American, but now a recent study has helped to outline the diverse genome of this demographic with the hopes of not only shedding light on where Black Americans come from, but also using it to help keep them healthy.

Race matters, but not exactly as you may think. Although most racial stereotypes have absolutely no scientific basis, in the health field, researchers understand just how important a role an individual's racial background plays in their overall health. According to a 2005 study, understanding the unique gene patterns across patient populations can help identify groups more at risk for developing certain diseases and may even one day lead to tailored preventative medicine therapies. One new company called BaseHealth actually claims to give doctors access to their patients' genetic information in order to help them build personalized medicine plans, Fastcoexist reported.

For example, minorities are more likely than non-Hispanic whites to develop chronic diseases, and Black Americans specifically are twice as likely as non-Hispanic whites to develop diabetes. Unfortunately, African Americans, like many racial minorities in the U.S., have long been underrepresented in genetic research.

“Many minority populations are understudied in medical genetics, and we're trying to change that. One way to help is to develop better models for genetic diversity in these populations,” lead researcher Dr. Simon Gravel told Medical Daily.

For the study, which is now published in the online journal PLOS Genetics, Gravel and his team from McGill University used genetic data from 3,726 black Americans from across the U.S. to help estimate their patterns of ancestry. The researchers hoped to reveal genomic changes that occurred among black Americans from before the Civil War up until the Great Migration (1910-1970) to better understand the unique genetic diversity of this group.

The analysis helped to lay out the great changes that occurred in the genome of this demographic which eventually lead to who they are today. For example, the report found that on average before the advent of transatlantic travel, the average black American was 82.1 percent African, 16.7 percent European, and 1.2 percent Native American. Today, however, black Americans living in the North or West are more likely to have a higher percentage of European ancestry, a fact that has caused distinct regional differences in black American ancestry. For example, the study found that 21 percent of the genome of the average black American living in the Southwest had European ancestry, but in the American South only 14 percent of the genome could be traced back to Europe.

What’s most interesting is that the majority of this mixture in the black American genome occurred in the past, tapering out in post-Civil War times. For example, the study suggests that the small Native American contributions to the black American genome occurred in the very first years of African slavery in America, as early as 1486. European mixture was also early, tapering out once slavery ended, suggesting that the end of slavery also led to the end of sexual coercion and the acceptance of interracial sexual relations.  

The study is not without certain limitations. For example, only two of the volunteers were born after 1970 so it's likely the onset of civil rights in America may have changed the amount of interracial mixing, as a result the genome of younger generations of black Americans may once again look different than that of their ancestors. According to The Guardian, mixed-race individuals are the fastest growing demographic.

The results are interesting, but what do they mean for black American health? According to the researchers, a whole lot. Gravel believes these findings will provide a better understanding of genetic diversity in African-Americans.

“This will be particularly useful for population genetic research, and it may also help improve the statistical analysis of nationwide cohorts including African-Americans,” Gravel concluded.

And, although there is no concrete evidence that having additional European DNA may increase or decrease an individual's risk for certain diseases, research has shown that identifying as more than one race may increase risk for more mental health conditions. For example one study from the University of North Carolina found that traits such as a lack of self-esteem, social isolation, and the struggle with identity formation are far more common among individuals who identify as being mixed race. These traits may lead individuals to engage in more risky behavior such as early sexual activity and substance abuse.

The results have the potential to widely impact black American healthcare and to inform individuals’ understanding of how they came to be who they are today.

“Many minority populations are understudied in medical genetics, and we're trying to change that,” concluded Gravel.

Source: Gravel S, Baharian S, Barakatt M, et al. The Great Migration and African-American Genomic Diversity. PLOS Genetics . 2016

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