Plaque gives us clues about ancient diets

Dental plaque is not a welcome presence in modern mouths today, but, for scientists digging into the past, analysing plaque, or dental calculus, from the teeth of ancient remains can offer clues about what individuals ate and inhaled.

A new study of dental calculus from the remains of 14 individuals at Al Khiday, a prehistoric site on the White Nile in central Sudan, suggests that a plant called purple nut sedge (Cyperus rotundus) – today considered a weed – was chewed there during both pre-agricultural and agricultural periods.

“By extracting material from samples of ancient dental calculus, we have found that, rather than being a nuisance in the past, the purple nut sedge’s value as a food, and possibly its abundant medicinal qualities, were known,” says researcher Karen Hardy from the Universitat Autònoma de Barcelona.

“We also discovered that these people ate several other plants, and we found traces of smoke, evidence for cooking and for chewing plant fibres to prepare raw materials. These small biographical details add to the growing evidence that prehistoric people had a detailed understanding of plants long before the development of agriculture.”

Studying chemicals and microfossils in dental calculus will help to "counterbalance the dominant focus on meat and protein that has been a feature of pre-agricultural dietary interpretation up until now," write the study authors in Plos One: "The new access to plants ingested, which is provided by dental-calculus analysis, will increase, if not revolutionise, the perception of ecological knowledge and use of plants among earlier prehistoric and pre-agrarian populations."