As human diets began to modernize, as we began cooking and cleaning more of our daily foodstuffs, a strange thing happened: The bacterial colonies in our mouths became far less diverse. Hunter-gatherers from seven thousand years ago had far more microbial diversity in their mouths than did Stone Age agriculturalists. Bacteria that had coexisted and coevolved with our bodies and diets, that had adapted, were crowded out by a new environment, and our mouths became colonized by nastier bacteria. We further repopulated our mouths with the ever more widespread use of processed sugars. The incidence of cavities exploded. We began to suffer chronic oral disease, something that became most bothersome, and sometimes even deadly, in the pre-antibiotic, pre-brushing, pre-dentist era.

As human diets began to modernize, as we began cooking and cleaning more of our daily foodstuffs, a strange thing happened: The bacterial colonies in our mouths became far less diverse. Hunter-gatherers from seven thousand years ago had far more microbial diversity in their mouths than did Stone Age agriculturalists. Bacteria that had coexisted and coevolved with our bodies and diets, that had adapted, were crowded out by a new environment, and our mouths became colonized by nastier bacteria. We further repopulated our mouths with the ever more widespread use of processed sugars. The incidence of cavities exploded. We began to suffer chronic oral disease, something that became most bothersome, and sometimes even deadly, in the pre-antibiotic, pre-brushing, pre-dentist era.