Tartar, or calculus, coats the tongue-side surface of teeth from a skull that was buried for decades.
Line S. Larsen
Want to know whether an ancient Sogdian smoked cannabis or a Viking got high on henbane? A new method, which analyzes drug residue in the tartar of teeth, may soon be able to tell. The method, which found drug traces on 19th century skeletons—and more substances than standard blood tests in 10 recently deceased individuals—could trace humanity’s drug habits back hundreds of thousands of years. It’s a “new frontier,” says archaeologist Shannon Tushingham of Washington State University, Pullman, who investigates ancient tobacco use in North America, but was not involved in the new work.
To study the history of medicines and drugs, most scientists scour smoking pipes and drinking vessels for lingering psychoactive molecules. But analysis of drug-coated artifacts often misses substances like hallucinogenic mushrooms that didn’t need containers. And the artifacts don’t reveal who got buzzed.
Archaeologist Bjørn Peare Bartholdy, a doctoral student at Leiden University, suspected farmers in a doctorless 19th century Dutch village may have been self-medicating to manage pain and disease. So he and and supervisor Amanda Henry turned to a new technique: examining the skeletons’ dental calculus, the hardened plaque known as tartar that your dentist scrapes off each year. Tartar traps bits of food, drink, and other substances while a person is living, and it can survive more than 1 million years on fossils. Henry and others have been investigating the crusty stuff for decades, mostly to understand the diets of past peoples.
But there was no standard test to tease out the trapped remains of opiates, cannabis, and other drugs they suspected the farmers had been using. The archaeologists reached out to researchers at Aarhus University in Denmark, including forensic dentist Dorthe Bindslev, to see whether they could retool standard methods used to detect drugs in the blood or hair of living or recently deceased people.
Bindslev and colleagues used hydroxyapatite—the main mineral in tartar—and mixed in known amounts of legal drugs like caffeine, nicotine, and cannabidiol, as well as controlled substances like oxycodone, cocaine, and heroin. They measured 67 drugs and drug metabolites by passing the mixtures through a high-performance mass spectrometer, which detected different molecules based on their charge and weight.
Then they tested their new method on 10 cadavers of suspected drug users undergoing autopsies in the Aarhus Department of Forensic Medicine and compared the results with those of blood-based drug tests. The novel protocol identified 44 drugs and metabolites—slightly more than standard blood work—including heroin, a heroin metabolite, and cocaine, they report in Forensic Science International. “It’s a really nice validation study” that would have been impossible in skeletons long missing their blood, says archaeologist Jelmer Eerkens of the University of California, Davis.
Because tartar seems to keep a long-term record of drug intake, it could be used in place of hair samples when criminal investigators need to test for substance use after drugs leave the bloodstream. And it could help rewrite the history of drug use, Tushingham says.
But the method, using some samples as small as sand grains, requires a highly sensitive mass spectrometer not found in typical chemistry or archaeology laboratories. And “you only have one shot” as the measurement destroys the sample, says study co-author Jørgen Hasselstrøm, a forensic toxicologist. It’s also unclear how long tartar retains the telltale molecules. Some compounds may degrade over time, even within calculus. The procedure also would miss plants once used as intoxicants, stimulants, and medicines, but forgotten by modern people, Tushingham says. Still, she commends the research: “This sort of baseline information can really push us forward into new and interesting directions.”
The Aarhus team has already found nicotine and other drugs in the tartar of the Dutch skeletons, in results they hope to publish in the coming year. And Bindslev is eager to try the method on ancient teeth she’s analyzed for other reasons, including remains from Viking sites and monasteries where monks administered early pharmaceuticals. When it comes to studies of ancient drug use, tartar “will have a future,” she says.