This decline in oral health over the past 7,500 years is the result of changes in oral bacteria due to human evolution and industrialization, the study authors said. These changes have led to chronic oral and other health problems, according to the report published Feb. 18 in Nature Genetics.
"The composition of oral bacteria changed markedly with the introduction of farming, and again around 150 years ago," explained study leader Alan Cooper, a professor and director of the University of Adelaide's Australian Centre for Ancient DNA, in a center news release. "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 [cavities]-causing strains. The modern mouth basically exists in a permanent disease state."
The international team of researchers examined DNA that had been preserved in tartar -- calcified dental plaque -- found on 34 prehistoric northern European human skeletons. They used these samples to analyze how oral bacteria changed from the Stone Age to the last hunter-gatherers, medieval times and later with the introduction of food manufacturing in the Industrial Revolution.
The evolution of human behavior and diet have had a negative impact on oral health, the investigators said.
"This is the first record of how our evolution over the last 7,500 years has impacted the bacteria we carry with us, and the important health consequences," Cooper said. "Oral bacteria in modern man are markedly less diverse than historic populations and this is thought to contribute to chronic oral and other disease in post-industrial lifestyles," he pointed out.
Study lead author Christina Adler, now at the University of Sydney, added that "dental plaque represents the only easily accessible source of preserved human bacteria." And, she said in the news release, "Genetic analysis of plaque can create a powerful new record of dietary impacts, health changes and oral pathogen genomic evolution, deep into the past."
The researchers said their research is being expanded to include other periods in time, other areas of the world and other species, such as Neanderthals.