Calcified dental plaque from 34 early European skeletons dating from the Mesolithic period (Stone Age) to the Medieval period has preserved a genetic record of oral bacteria that demonstrates the impacts of evolutionary changes in human diet.

A recent study published in Nature Genetics examined how the transition from hunter-gatherer to farming in the Neolithic period affected oral microbiota and created a shift in disease-associated bacteria. Oral diseases such as caries and periodontitis were rarer in pre-Neolithic hunter-gatherers and early hominins. Farming spawned a more carbohydrate-rich diet associated with an increase in dental calculus and oral pathology.

Researchers found the composition of oral microbiota remained fairly constant into the Medieval period and it was only after the Industrial Revolution that another distinct shift was detected with an increase in caries-associated bacteria, most likely the result of new food processing technology and the production of refined grain and concentrated sugar.

Modern oral microbiotic ecosystems are less diverse than historic populations and dominated by cariogenic bacteria. They are also less likely to be resilient to imbalances and invasions. However, the abundance of periodontal disease-associated bacteria in modern dental calculus is no greater than it was since Neolithic farming. This finding is significant when drawing causal links between periodontitis and other diseases such as heart disease and diabetes. The authors conclude that 'although periodontal disease might contribute to pathogenesis, it is probably not a factor in the rising incidence of these systemic diseases'.