Ancestry of many living African Americans linked to Maryland cemetery

DNA obtained from the remains of 27 African Americans found in a cemetery near an historical iron forge in Maryland, has been linked to nearly 42,000 living descendants by 23andMe.

The Catoctin furnace near Maryland used the labour of both free and enslaved African Americans in the 18th and early 19th century, when the individuals are believed to have been buried. Analysis of DNA from bones found in the cemetery alongside genomic and geographical data held on over 9 million individuals by direct-to-consumer genetic testing company 23andMe has shown these individuals are most closely related to modern-day Africans from the Wolof and Kango ethnolinguistic groups, from West Africa.

'Recovering African American individuals' direct genetic connections to ancestors heretofore buried in the slave past is a giant leap forward both scientifically and genealogically, opening new possibilities for those passionate about the search for their own family roots,' said Professor Henry Louis Gates Jr. director of the Hutchins Center for African and African American Research at Harvard and a co-author of the paper published in Science.

Most African Americans are unaware of which part of Africa their ancestors came from as slavery erased cultural and linguistic history. It has proved difficult for African Americans to trace their ancestors further back than the 1870 United States Census, the first census published in which black people were listed by name.

A total of 15 family groups were discovered in the cemetery, half of the individuals were under the age of four and no adult males were found. Teenagers were found to have skeletal injuries and high levels of heavy metals believed to be a result of the work undertaken in the iron forge. Some were found to have genetic variants linked to increased risk of sickle cell anaemia and glucose-6-phosphate dehydrogenase deficiency, conditions that are common in people of West African-ancestry today.

The cemetery was excavated due to plans to build a road through it, and as it was unclear who the ancestors of the individuals found there was, consent to extract DNA was sought from a local group the African American Resources Cultural and Heritage (AARCH) Society. Members visited the lab in 2016 and the president at the time consented to research to obtain genomic information on the individuals.

Researchers identified segments of DNA shared by the individuals found in the cemetery and 41,799 individuals who have shared their genomic data with 23andMe. These included individuals who have West African and Irish and British ancestry.

Of those who lived in the US, individuals were found to be most concentrated around Maryland, suggesting descendants largely stayed in the region.

The study has raised ethical questions about the use of genomic data obtained by 23andMe for historical research, consent given to obtain and analyse the genomic data from the human remains, the use of findings for marketing purposes, and subsequent contacting of descendants of slavery identified by 23andMe.