Luckily, prehistoric people didn't brush their teeth. Otis Historical Archives Nat'l Museum of Health & Medicine / Wikimedia Commons New archaeological research may have revealed that the original "paleo diet" contained wheat and barley and was not restricted to only meat and vegetables as the diet typically is today.

Scientists from Cambridge, Cardiff, UCL, and York studied the remains of nine people who lived about 9,000 years ago in the late Mesolithic (6600 B.C. to 6450 B.C.) and the Mesolithic-Neolithic phases (6200 B.C. to 5900 B.C.) and found plant matter fossilized in their teeth.

Thanks to poor dental hygiene, microfossils were trapped in ancient plaque on their teeth. The researchers say these plaques contain plants — cereals, in fact — that weren't thought to be part of people's diets for another four centuries.

"There has been a long-standing view that for the most of the Palaeolithic times, but also in the Mesolithic, animal protein coming from meat and fish was the main staple food with a very limited role of plant foods," lead researcher Dusan Borić told Business Insider.

Mysteries were revealed from human teeth remains. Dr Dušan Borić / Cardiff People in the Mesolithic period are generally believed to have been hunter-gatherers and lived in vast woodlands. The Neolithic, or New Stone Age, came afterward, and it's then that people were believed to have first planted cereal crops and developed agriculture.

The discovery of domestic cereals in Mesolithic people's diets means that social networks between local foragers and the first Neolithic communities probably extended farther than archaeologists originally thought, given how deep into the Balkan hinterland they were found.

"At the time of the discovery we had the sense that these groups of complex hunter-gatherers were in contact with other more distant locations," Borić said. "We found beads made of marine gastropods that come from coastal areas in Greece and the Adriatic, hundreds of kilometers away from the region for instance."