Unprecedented Study Of Ancient DNA Sheds Light On History Of Enslaved And Free African Americans

The study, published in Science, links living individuals to African Americans who worked in a forge more than 200 years ago 

Iñigo Olalde, Ikerbasque research fellow at the University of the Basque Country (UPV/EHU), has participated in the first study to combine ancient DNA technology with an ancestry testing database and to use a new method to determine genetic relationships. The study offers a new way of complementing genealogical, historical, bioarchaeological and biochemical work and is designed to reconstruct the life histories of marginalised people.

Few African Americans have been able to trace their family lineages back to ancestors who died before the 1870 United States census, because there is no earlier census in which black people were listed by name. Genetic analysis of ancient remains has the potential to help recover information about individuals whose histories were omitted from written records. The journal Science has published a study led by Harvard University which, by analysing the ancient DNA of 27 individuals of African-American origin buried in the Catoctin Furnace cemetery (Maryland, USA), has enabled more than 40,000 living relatives to be linked to the enslaved and free individuals who worked there shortly after the founding of the United States.

The study, promoted to restore knowledge about their ancestors to African-American communities, offers a new way of complementing genealogical, historical, bioarchaeological and biochemical efforts in order to reconstruct the life histories of people omitted from the records and to identify their present-day relatives. In that respect, the work reveals how these 27 individuals are related, what genetic conditions they may have had, where in Africa and Europe they or their ancestors had probably come from, and where in the USA they have direct descendants and other living distant genetic relatives.

The Ikerbasque research fellow of the UPV/EHU Iñigo Olalde has participated in the study that amounts to a breakthrough. The reason is that sections of the entire genomes of the remains of these individuals were sequenced or revealed, they were then compared with a database of DNA information from more than 9 million living individuals –who gave their consent to participate in the research– and a new method was used to determine the degree of genetic kinship between all of them. So it is the first piece of work to link ancient DNA technology, which allows whole genome data to be efficiently sequenced from human remains, to a personal ancestry testing database, and a new algorithm to be used.

DNA analysis to build up hidden histories

Specifically, the Ikerbasque and Ramón y Cajal research fellow in the UPV/EHU’s BIOMICs group Iñigo Olalde, whose research focuses on the recovery and analysis of ancient human genomes to study the history of populations in the past, was involved alongside his colleagues at Harvard University in the genetic kinship analysis of the individuals found at the Catoctin Furnace; as a result, five genetic families, consisting of biological mothers, children and siblings, were identified.

As the authors point out, the results demonstrate the power of joint analysis of DNA from ancient remains and the extremely large databases generated through ancestry testing, and also serve as a model for obtaining direct genome-wide genetic ancestry information on enslaved people in the USA.

The study demonstrates that, when research is conducted responsibly with the involvement of stakeholders, long-buried DNA can be used to uncover hidden and forgotten histories. The study opens a door to the analysis of identical DNA segments by ancestry and the comparison of historical or ancient DNA with personal genome databases to deepen our understanding of human history.

The authors suspect that many of the connections between living relatives and these 27 individuals at the Catoctin Furnace can be traced back to common ancestors who lived in Africa or Europe during or before the transatlantic slave trade. Genetic findings reinforce knowledge about the location in Africa where different groups of enslaved individuals in early America had originally come from.

Many of the individuals found at Catoctin were of European descent, mainly on the paternal side, which is consistent with known stories of sexual exploitation of enslaved people by their enslavers. The authors say they are privileged to be able to contribute to a greater understanding of the impact of slavery on enslaved people, their descendants, and their unacknowledged contributions to American history.