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Mesolithic hunter-gatherers living on a meat-dominated, grain-free diet had much healthier mouths that we have today, with almost no cavities and gum disease-associated bacteria, a genetic study of ancient dental plaque has revealed.

The international team of researchers, led by a group at the Australian Centre for Ancient DNA, University of Adelaide, publish their findings in today’s
Nature Genetics.

The researchers extracted DNA from dental plaque from 34 prehistoric northern European human skeletons, and traced the changes in the nature of oral bacteria from the last hunter-gatherers to Neolithic and medieval farmers and modern individuals.

“Dental plaque represents the only easily accessible source of preserved human bacteria,” says lead author Dr Christina Adler, now associate lecturer in dentistry at the University of Sydney.

The researchers found the composition of bacteria changed with the introduction of farming and again 150 years ago during the Industrial Revolution.

In contrast to the hunter-gatherer and early agriculturist diet, a modern diet full of refined carbohydrates and sugars has given us mouths dominated by cavity-causing bacteria.

“What we found was that the early [hunter-gatherer] groups really had a lot lower frequencies of any of the disease-associated bacteria compared to what you see today [and] that the number of species per person’s mouth, or the diversity, was much higher in the past,” says Adler.

“If they’ve got more [bacterial] diversity that means that those people’s mouths were more resilient to stresses, and probably less likely to develop disease.”