Ancient DNA reveals genetic lineage and legacy of African Americans from Catoctin Furnace, Maryland

Combining ancient DNA (aDNA) with data from the 23andMe genetic database, researchers have uncovered the lineage and legacy – including more than 40,000 living relatives – of free and enslaved African Am

ericans who labored at the Catoctin Iron Furnace in Maryland, between 1774 and 1850. “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 in a related Perspective. “This is the way that this type of research should be performed, and it provides a blueprint for future studies.” 

The vast majority of Black and/or African American individuals living in the United States descended from the hundreds of thousands of enslaved Africans forcibly transported to the US between 1501 and 1867. However, due to the centuries of inhumane treatment of enslaved families and their descendants, historical records often omit details about the lives of these individuals. As a result, few contemporary African Americans have been able to trace family lineages back to their earliest enslaved ancestors in the United States. Ancient DNA technologies have the potential to provide insight into the identity of enslaved individuals and to restore lost familial histories. 

In this study, Éadaoin Harney and colleagues analyzed aDNA from 27 colonial African Americans interred at the Catoctin Furnace between 1774 and 1850. By comparing the genome-wide aDNA to data from more than 9.2 million participants in the 23andMe genetic database, the authors were able to draw identical-by-descent (IBD) connections between present-day and historical people. In addition to revealing five biological family groups amongst the Catoctin individuals, Harney et al.’s IBD-based approach identified 41,799 modern genetic relatives living throughout the US. One of the highest concentrations of close Catoctin relatives remains in Maryland. What’s more, the findings show that the Catoctin individuals are most closely related to small number of African groups, particularly the Wolof of West Africa and the Kongo of Central Africa.