The great thing about tobacco pipes, according to Julie Schablitsky, is that they are hard to not find. They were ubiquitous in the 17th, 18th, and 19th centuries—to the point, she says, that “wherever you have people during this historic period, you’ll find these clay tobacco pipes in the ground.” And wherever these people left broken tobacco pipes, they were also unwittingly leaving their DNA.
Traditionally, the archaeological study of DNA has focused on human remains such as bone and teeth. But geneticists are now able to extract DNA hidden inside ordinary objects, including tobacco pipes, which can contain centuries-old saliva. Schablitsky, an archaeologist with the Maryland State Highway Administration, and her collaborators recently analyzed the DNA from one such 19th-century pipe—uncovered in the slave quarters of a Maryland plantation called Belvoir.
The DNA showed that a woman had used the pipe, and her genetic ancestry most closely matched people living today in Sierra Leone. She was most likely enslaved on the plantation.
Schablitsky got the idea to analyze DNA on the pipe from talking to descendants of people enslaved at Belvoir. When her team first found the slave quarters in 2014, they got in touch with a historian who specializes in local African American history and spread the word. The news eventually reached Shelley Evans, a retired Baltimore City schoolteacher. She had found records of her ancestor Thomas Burley, a freeman, buying his wife and daughter out of slavery at Belvoir. “My third great-grandmother, she lived here,” says Evans. “She was born there. Her mom and dad had to have been there as well.” The pipe could have belonged to one of her ancestors.
So while excavating the slaves’ quarters, Schablitsky and her team collected pipe fragments, using sterilized forceps to prevent contamination. They particularly focused on the pipes, because clay is porous, which means the DNA in saliva can easily penetrate inside. By contrast, DNA only sits on the surface of metal artifacts such as jaw harps or forks, and it’s unlikely to be present after decades in the ground.
Schablitsky sent four pipe samples off to an ancient-DNA lab at the University of Illinois at Urbana-Champaign. One of the four yielded enough DNA for further analysis. Unfortunately, the DNA was still too degraded to link to individuals alive today. But the Illinois lab got in touch with Hannes Schroeder at the University of Copenhagen, who specializes in working with ancient and degraded DNA.
Schroeder’s lab uses algorithms to compare genetic material from old samples with that of modern reference populations around the world. He had previously used DNA to trace the origins of enslaved people buried on the Caribbean island of St. Martin. A 2015 paper connected these people to Bantu-speaking groups in Cameroon and others in present-day Nigeria and Ghana.
Schroeder applied the same techniques to DNA taken from the pipe in Belvoir. Of the African reference populations, the woman in Belvoir was most similar to the Mende people in Sierra Leone.
Recent research on ancient DNA has invested artifacts with new significance. The DNA in the clay pipe, for example, contains within it a record of the transatlantic slave trade. “You start with one small insignificant piece of tobacco pipe, and you end up talking about one of the most significant events in American history,” says Schroeder.
Given the ubiquity of tobacco pipes, Schablitsky hopes that fellow archaeologists will start using them as a source of old DNA to fill gaps in history. Few records exist, for example, of exactly where in Africa enslaved people came from. You might imagine an alternative record written in the DNA inside clay pipes that dot the landscape. Theresa Singleton, a professor at Syracuse University who studies the archaeology of slavery, said the discovery in Belvoir holds “great promise” for future research—but the cost of DNA analysis may put it out of reach for some archaeologists.
Another limitation is that geneticists have historically sampled relatively few Africans. “The reference database for Africans and also for the diaspora is still very weak,” says Fatimah Jackson, a biologist at Howard University. (Jackson is collaborating with Schroeder on another project, but was not involved in this one.) For example, the woman smoking the pipe in Belvoir most closely matched Mende people in the existing reference database—but she might be more closely related to another group whose DNA is not even in the database. The only way to know is to go out and collect more samples. This problem is compounded by the fact that people in Africa are more genetically diverse than people on other continents. Geneticists such as Jackson are currently working to diversify reference data sets, but it is a problem that still besets both genetics research and consumer DNA tests such as those offered by 23andMe and AncestryDNA.
In 2018, four years into the Belvoir excavation, archaeologists discovered they might not be limited to DNA from the tobacco pipe after all. Just a short walk from the slave quarters is a burial ground with as many as dozens of people. The archaeological team asked the descendants, including Evans, whether they wanted to test the DNA in the bones buried there. “I hope that comes to pass,” says Evans. Her ancestors might be buried there. The woman who smoked the pipe might be buried there.