The researchers, from the University of Adelaide's Australian Centre for Ancient DNA (ACAD), the University of Aberdeen (Dept of Archeology), Scotland, and the Wellcome Trust Sanger Institute, Cambridge, England, published their study in Nature Genetics.
The authors say that analyzing the DNA of calcified bacteria on the teeth of humans throughout modern and ancient history "has shed light on the health consequences of the evolving diet and behavior from the Stone Age to modern day".
The scientists explained that there were negative changes in oral bacteria as our diets altered when we moved from being hunter-gatherers to farmers. Further changes were observed when humans started manufacturing food during the Industrial Revolution.
Study leader Professor Alan Cooper, ACAD Director, said, "This is the first record of how our evolution over the last 7500 years has impacted the bacteria we carry with us, and the important health consequences."
The introduction of processed sugar may have completely changed the composition of oral bacteria in humans.
The scientists extracted DNA from calcified dental plaque (tartar) from 34 prehistoric human skeletons from northern Europe. They examined the changes in the nature of oral bacteria that were first present in prehistoric hunter-gatherers, through to the Bronze Age when farming became established, then to Medieval times and finally to the Industrial Revolution and later.
Dr Christina Adler, lead author, who was a PhD student at the University of Adelaide during the study, said "Genetic analysis of plaque can create a powerful new record of dietary impacts, health changes and oral pathogen genomic evolution, deep into the past." Dr. Adler now works at the University of Sydney.
The modern mouth exists in a permanent disease stateProfessor Cooper said:
"The composition of oral bacteria changed markedly with the introduction of farming, and again around 150 years ago. With the introduction of processed sugar and flour in the Industrial Revolution, we can see a dramatically decreased diversity in our oral bacteria, allowing domination by caries-causing strains. The modern mouth basically exists in a permanent disease state."
Professor Cooper has been working with Professor Keith Dobney from the University of Aberdeen on this for the last 17 years. Professor Dobney said "I had shown tartar deposits commonly found on ancient teeth were dense masses of solid calcified bacteria and food, but couldn't identify the species of bacteria. Ancient DNA was the obvious answer."
Scientists examined tartar deposits found on ancient teeth in their study. (Photo: Alan Cooper/University of Adelaide)
In an Abstract in Nature Genetics, the authors wrote that "modern oral microbiotic ecosystems are markedly less diverse than historic populations, which might be contributing to chronic oral (and other) disease in postindustrial lifestyles."
It was not until 2007 that the team could control background levels of bacterial contamination properly. This became possible when ACAD's super-clean labs and stringent decontamination and authentications protocols became available.
The scientists are now expanding their studies geographically and chronologically, and including other species, such as Neanderthals.
There is some evidence that beeswax was used 6,500 ago in dentistry, scientists from Abdus Salam International Centre for Theoretical Physics, Italy, explained in the open access journal PLoS ONE on 19th September, 2012.