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Ancient DNA Reveals Legacy of African Americans from Catoctin Furnace, Maryland

map of Catoctin Furnace enslaved people and their descendants in the US
Map showing the proportion of 23andMe research participants who share DNA with Catoctin individuals. | Harney et al., Science: 381, 6657

Between the 16th and 19th centuries, as many as 10 million enslaved Africans were forcibly brought to the Americas from Africa by colonizer nations during the transatlantic slave trade — hundreds of thousands of which were brought directly to U.S. shores.

But due to centuries of intentional erasure and inhuman treatment of enslaved families and their descendants, most records from the time omit details about the identities of these individuals. As a result, much about the lives of early African American populations in the United States remains unknown and hidden from history.

Now, in a new study in Science, researchers show how a novel genomic approach combining ancient DNA (aDNA) with data from the 23andMe genetic database can be used to provide insights into the lives and legacy of the free and enslaved individuals who lived, worked and died at the Catoctin Iron Furnace in Maryland between 1774 and 1850.

Not only do the study's findings shed light on their identities, but they also bridge the gap between nearly 42,000 living African Americans and their enslaved ancestors and other relatives — familial connections that would otherwise be lost to time.

"What makes the work … so pioneering is that the research was initiated by an engaged local community of African Americans and the results were structured to meet their needs, priorities and sensibilities of the larger African American community," writes Fatima Jackson, a professor at Howard University, in a Science Perspective published in conjunction with the study. "This is the way that this type of research should be performed, and it provides a blueprint for future studies."

The Catoctin Iron Furnace

In 1776, the Catoctin Iron Furnace, located in Frederick County, Maryland, began smelting pig iron, tools, household items and even munitions for the newly formed Continental Army in their fight against the British during the Revolutionary War.

For many years, operations at Catoctin Furnace relied on the labor of enslaved Africans and African Americans. At least 271 enslaved and an unknown number of free African Americans worked at Catoctin and its surrounding village, performing a host of highly skilled labor roles.

However, in the late 1840s, the furnace's labor force switched primarily to wage labor performed by a predominantly white work force of European immigrants.

Gradually, the contributions of African Americans at Catoctin were largely forgotten.

That was until the rediscovery and excavation in 1979 and 1980 of an African American cemetery located at the furnace — a finding that cast a spotlight on the critical role that enslaved and free African Americans played in the furnace's history and in the growth of industrial wealth and power early in the nation's history.

Interred in the Catoctin Furnace African American Cemetery were more than 100 free and enslaved individuals who labored at the furnace between 1774 and 1850. While recent osteological and genomic analyses of the remains of these individuals have shed light on the life histories and ancestry of these individuals, many questions remained.

"One of the questions that was most important to stakeholders at Catoctin Furnace Historical Society was 'what happened to the African Americans who were enslaved at Catoctin Furnace and the descendants after the furnace stopped relying on enslaved labor?'" said Éadaoin Harney, the study's lead author and a researcher at 23andMe.

Bridging the Gap Between Colonial African Americans and Modern Descendants

To address this question, Harney and a team of researchers from the Smithsonian's National Museum of Natural History, Harvard University, the Catoctin Furnace Historical Society and 23andMe analyzed aDNA from 27 colonial African Americans buried at Catoctin Furnace and compared the genome-wide aDNA to data from more than 9.2 million participants in the 23andMe genetic database.

The novel approach allowed the authors to draw identical-by-descent (IBD) connections between present-day and historical people. IBD is a term used in genetic genealogy to describe a matching genetic segment shared by two or more people that has been inherited from a common ancestor through a parent.

In addition to revealing five biological family groups among the Catoctin individuals, the IBD-based analysis identified 41,799 genetic relatives living throughout the U.S. today, including as many as 2,975 possible direct descendants. What's more, according to the findings, one of the highest concentrations of closely related possible descendants of the Catoctin workers remains in Maryland, suggesting that some stayed in the region following the furnace's transition away from enslaved labor.

"As a part of this study, we developed and fully described an approach for identifying IBD genetic connections between historical and living individuals in the hopes that it could be used in future studies, including those led by other researchers," said Harney. "We hope that this study inspires others to use our approach to learn more about historical individuals, particularly those whose stories have been excluded from the historical record."

[Credit for associated image: diskychick on Flickr