Enslaved African Americans in Maryland Linked to 42,000 Living Relatives

A construction team working on a highway expansion in Maryland in 1979 discovered human remains on the grounds of an 18th-century ironworks. Eventually, archaeologists uncovered 35 graves in a cemetery where enslaved people had been buried.

In the first effort of its kind, researchers now have linked DNA from 27 African Americans buried in the cemetery to nearly 42,000 living relatives. Almost 3,000 of them are so closely related that some people might be direct descendants.

Henry Louis Gates Jr., a historian at Harvard University and an author of the study, published Thursday in the journal Science, said that the project marked the first time that historical DNA had been used to connect enslaved African Americans to living people.

The cemetery was located at a former ironworks called the Catoctin Furnace, which started operating in 1776. For its first five decades, enslaved African Americans carried out most of the work including chopping wood for charcoal and crafting items such as kitchen pans and shell casings used in the Revolutionary War.

Upon their discovery, some of the remains were taken to the Smithsonian Institution for curation. In 2015, the historical society and the African American Resources Cultural and Heritage Society in Frederick, Maryland, organized a closer look.

At Harvard, researchers extracted DNA from samples of the cemetery bones. Genetic similarities among 15 of the buried people revealed that they belonged to five families.

Following Smithsonian guidelines, the researchers made the genetic sequences public in June 2022. They then developed a method to reliably compare historical DNA to the genes of living people.

Éadaoin Harney, a former graduate student at Harvard, continued the genetic research after she joined the DNA-testing company 23andMe, focusing on the DNA of 9.3 million customers who had volunteered to participate in research efforts.

Harney and her colleagues looked for long stretches of DNA that contained identical variants found in the DNA of the Catoctin Furnace individuals.

The researchers found 41,799 people in the 23andMe database with at least one stretch of matching DNA. But a vast majority of those people were only distant cousins who shared common ancestors with the enslaved people.

Almost 3,000 people had especially long stretches of matching DNA, which could mean they are direct descendants or can trace their ancestry to cousins of the Catoctin Furnace workers.

This article originally appeared in <a href="https://www.nytimes.com/2023/08/03/science/catoctin-african-americans-dna.html">The New York Times</a>.