Ed Yong has a great account today of some research from Alan Cooper's lab on the oral microbiome in pre-agricultural and post-agricultural Europeans: "Prehistoric Plaque and the Gentrification of Europes Mouth".
The hunter-gatherers had a diverse array of bacteria including several groups that are associated with good health. That fits with the relative absence of tooth decay or gum disease among modern or prehistoric hunter-gatherers. They were at the end of a long period of happy co-evolution between us and oral bacteria, says Cooper.
The advent of farming disrupted that tango. After the Agricultural Revolution, as humans began to chow down upon barley, wheat and other domesticated crops, the diversity of the mouth microbes fell, and species associated with oral diseases became more common. Eating all this soft squishy carbohydrate and leaving it lying around the base of your teeth is effectively inviting in a whole new range of bugs to take up permanent residence in your mouth, says Cooper.
I'll have some more comments on this new research when I can sit down to write them up. I've been waiting for this to come out for quite a long time -- I first heard about the research almost three years ago. The potential to characterize oral ecology across time is immense, and we have some excellent data on dental pathologies across the entire timespan. Caries and other dental pathologies are very new in human populations, and although starchy diets have been blamed, very little has been known about how oral bacteria themselves may have become more pathogenic over time. This study is really great because it opens a new door to looking at this evolution across time. We will need to compare this record with the evidence for morphological change in teeth across the same time span. Smaller teeth may have been a consequence of selection associated with dental pathology in agricultural peoples.
Next we will need to compare across space -- including greater sampling of oral microbiome variation among living humans. This is another new area in which we know more about prehistoric people than we do about living human variation!