The poor dental hygiene of ancient people could provide a glimpse into their drug habits. By testing the ancient plaque on the teeth of people who died thousands of years ago, researchers can now tell whether or not they were smoking tobacco, drinking coffee, or taking atropine.  

Since present-day smokers can be identified by the chemical signatures of nicotine that build up in teeth plaque, the researchers wanted to see if the same could be said of ancient human remains, particularly since the substance mineralizes over time and locks in a wide range of substances.

“The ability to identify nicotine and other plant-based drugs in ancient dental plaque could help us answer longstanding questions about the consumption of intoxicants by ancient humans,” explains Shannon Tushingham, co-author of the study published in the Journal of Archaeological Science Reports. “For example, it could help us determine whether all members of society used tobacco, or only adults, or only males or females.”

Currently, the best way for archaeologists to determine the use of plant-based drugs and their spread across the ancient world is to search for associated artifacts, such as pipes, charred tobacco seeds, and even hair and fecal samples. But these items are often rarely preserved and can be difficult to attribute to a specific person.

This means that the use of drugs such as tobacco by ancient people has been difficult to trace in the archaeological record. In steps the use of plaque on teeth – which can be firmly linked to an individual – to search for clues. Amazingly, the researchers were able to not only identify proteins, but also starch grains, plant fibers, and even DNA, still preserved on teeth ranging in age from 300 to 6,000 years ago.

From two pre-contact individuals, they could identify traces of nicotine, the first time that the drug has been shown to survive in detectable levels in ancient plaque. Yet even this simple proof of concept has managed to reveal some fascinating insights into ancient practices, because while one of the individuals was a man buried with a pipe, the other was an older woman.

“While we can't make any broad conclusions with this single case, her age, sex, and use of tobacco is intriguing,” says co-author Jelmer Eerkens. “She was probably past child-bearing age, and likely a grandmother. This supports recent research suggesting that younger adult women in traditional societies avoid plant toxins like nicotine to protect infants from harmful biochemicals, but that older women can consume these intoxicants as needed or desired.”

While this work looked solely at nicotine, the team hope the technique can be used to test for other plant-based drugs on human teeth in other parts of the world.