Ancient Tooth Plaque Shows Our Ancestors Used to Feast on Weeds

Purple nutsedge is a pest today, but thousands of years ago it was probably valued for its cavity-preventing properties

The skeleton of a young man, whose tooth plaque was used in the study. Photo: Donatella Usai/Centro Studi Sudanesi and Sub-Sahariani (CSSeS)

Purple nutsedge looks like ordinary grass, but farmers know better. The plant grows in more than 90 countries and infests the beds of around 50 crops, earning it the nickname "the world's worst weed." It's resistant to many pesticides and its extensive tuber system makes it difficult to eradicate once its taken root. As such, it's also one of the costliest weeds in the world. 

Purple nutsedge, however, wasn't always so despised. In fact, it used to be a staple. A new study reveals that purple nutsedge was a regular part of the diet of humans living 2,000 years ago in Sudan. To arrive at this finding, researchers turned to tooth plaque, a technique previously used to study Neanderthal diets. The Toronto Star elaborates on the method:  

They used several different techniques to examine what was trapped in the teeth of 20 Al Khiday skeletons, including a novel approach that involves analyzing chemical compounds released after heating the specimens to very high temperatures. What they discovered was strong evidence that these ancient peoples ingested Cyperus rotundus, known commonly as purple nutsedge.

People were still eating the weed, the researchers point out, well after the adoption of agriculture. This might have been due to the fact that purple nutsedge has some medicinal value as an anti-cavity agent. Fewer than one percent of the skeletons' teeth at the site in Sudan contained cavities, National Geographic writes.

This is out of the ordinary for ancient farming communities, whose carbohydrate-rich diets tended to cause a plague of cavities. Prior to the advent of agriculture, people's teeth remained in much better shape because their diet was more meat-heavy. The ancient people living in Sudan, it seems, might have stumbled upon a work-around that allowed them to enjoy their cereals without the burden of cavities. 

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