Dirty, old teeth reveal fishy diet
Yuck factor aside, ancient tartar-encrusted teeth may be a biological goldmine for scientists, thanks to a new technique for extracting food particles from the teeth of prehistoric humans.
The method has already solved the mystery of what early coastal Brazilians ate.
In the future, similar studies may reveal clues about other ancient diets, particularly in areas with few ancient plants preserved.
"There is great potential of dental calculus [old tooth tartar] analysis in past populations that inhabited tropical regions," says Assistant Professor Sabine Eggers, co-author of a new study about the method.
Eggers is a researcher in the Biological Anthropology Laboratory at the University of São Paulo, Brazil.
After being awarded a Fulbright Commission grant, Eggers and colleagues created the new tartar extraction method, which involves a 'dental wash' containing 4% hydrochloric acid as the main active ingredient.
Their findings have been accepted for publication in the Journal of Archaeological Science.
Eggers explaines that ancient tartar could reveal what an individual ate in the days or weeks before death.
Evidence suggests some prehistoric populations cleaned their teeth, using fibrous foods and shell fragments as natural abrasives. But many groups simply let nature take its course.
Teeth from burial sites
To test the dental wash, the scientists gathered several teeth from Brazilian burials dating from 2800 to 1805 years ago. All were excavated at a southeastern coastal site called Sambaqui Jabuticabeira II.
The site has yielded several large piles of mollusc shells mixed with other debris, which are associated with human activity.
The researchers swirled recovered teeth in the solution to loosen the tartar. To isolate the particles in the tartar, the scientists strained and spun the solution in a centrifuge.
They found three types of microfossils. Most common were starch grains from tubers. The researchers also found diatoms, microscopic algae used as a food source by marine organisms, and phytoliths, tiny mineral particles produced by plants.
The first two microfossils suggest the individual's last meals probably consisted of shellfish accompanied by some sort of tuber.
"At the moment, we do not know where the phytoliths came from," Eggers says. "They might have been part of a plant eaten or a plant element, such as palm leaves, chewed for the production of ropes, baskets, hammocks or some kind of clothing."
The flip-side of testing
Although the dental wash was successful, it made some of the ancient teeth brittle and others turned bright white.
Since scientists hope to leave specimens in a condition as close to the original as possible, the researchers suggest the dental wash recipe requires further tinkering. They also say particles might be removed using sound waves.
Dr Sheila Souza, a scientist at Brazil's National School of Public Health and colleagues have also been recovering particulate matter from ancient teeth.
"It is really new to try the washing technique proposed by the researchers," Souza says.
She adds that the new dental wash technique is interesting but problematic for the reasons the inventors cite themselves.
Souza agree that it is important to analyse ancient teeth, however, particularly in Brazil, where early plant evidence has been sparse in some areas.
"We are really opening a big, new field to improve prehistoric reconstructions about the Sambaqui diet and lifestyle with calculus and microfossils," she says.