Millions of Africans were taken from their homelands and forcibly spread throughout the Americas from the 15th to the 19th century. Today, the descendants of these original Africans continue to live throughout the Americas, but centuries of separation from Africa have vastly changed their genomes. In a new study, researchers have begun to unravel the genome of Africans living in the Americas to better understand what caused their DNA changes, and how these changes affect this population's health.

In the study, now published in the online journal Nature Communications, researchers sequenced the genome of 642 individuals of African ancestry living in North, Central and South America, as well as the Caribbean. The results were then compared with the DNA of Yoruba-speaking individuals from Ibadan, Nigeria in West Africa, an area from where many of the first Africans in the Americas originally hailed. This sequencing will hopefully reveal how the DNA of Africans in Africa differs from Africans living in the Americas, Science Mag reported.

The genome sequencing will provide important insight into the individualized health risks of those of African ancestry living in the Americas. This specific demographic suffers a disproportionate burden of disability and disease, and faces higher risk of death from common chronic illnesses like asthma, diabetes and other ailments when compared to other demographics, Science Mag reported. However, the reason for this remains largely unknown.

"This will contribute to the public database and give clinicians more information to better predict and track human disease," said lead study author Dr. Kathleen Barnes, Science Mag reported. "It will allow us to tailor clinical to specific individuals based on their ethnic and racial backgrounds."

It’s also not clear what led to the genetic changes that caused this group to be at higher risk for certain diseases, although the team suggested it may be partly due to the large amount of genetic material from European and Native American populations that also exists in the DNA of black individuals living in the Americas.

In addition to new insights regarding the health risks of this population, the sequencing will help those of African ancestry living in the Americas better understand their personal identity and how they came to be the distinct group they are today. Although it will likely take many years to completely sequence the DNA of this large population, already the endeavor has produced fruit. For example, the researchers found that African ancestry varies widely depending on where in the Americas DNA samples were taken. For example, African ancestry only made up about 27 percent of the genome of the average Puerto Rican, while it made up about 89 percent of the genome of Jamaicans.

In addition, the study showed that Africans in areas such as the Dominican Republic and Colombia had significant Native American ancestry as well, as opposed to populations elsewhere in the Americas.

Source: Mathias RA, Taub MA, Barnes K, et al. A continuum of admixture in the Western Hemisphere revealed by the African Dispora genome. Nature Communications . 2016

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