Apparently, it doesn't matter if you live a now as an accountant in a major city or a thousand years ago as a hunter and gatherer living in rough shelters - the exactly same bacteria would give you periodontal disease.

Researchers have discovered 1,000 year-old plaque on human skeletons which revealed that despite major changes in diet and oral hygiene over the past millennium, our ancestors suffered from gum disease caused by the same bacteria that still causes gum disease in modern man.

The findings of the study has been published in Nature Genetics. It is an effort that involved the contributions of 32 scientists from twelve different institutions spanning seven countries.

The plaque, which has hardened over time, has preserved bacteria and microscopic particles of food on the surfaces of the teeth. The plaque is also described as a 'microbial Pompeii' because of this. The bacteria that was in the teeth trapped particles of food and debris. Eventually, the calcium phosphate in saliva caused the plaque to calcify into tartar.

Bone rapidly loses its molecular information the moment it is buried, but the mouth's environment stays more stable in comparison, because calculus grows slowly in the mouth and enters the soil in a much more stable state. This helps in the preservation of biomolecules, which, in turn, enabled the researchers to analyze the DNA that was left intact and uncompromised.

The researchers, led by Christina Warinner, an anthropologist at the University of Zurich in Switzerland and the University of Oklahoma in Norman, have found that the species Porphyromonas gingivalis, Tannerella forsythia,Treponema denticola and Filifactor alocis, which causes gum disease in humans today, were also present in the thousand year-old specimens they examined. Gum disease is characterized by chronic inflammation resulting in tooth and bone loss, and is often caused by infections or inflammation of the gums and surrounding bone.

In addition, they found that the ancient human microbiome already contained the basic genetic machinery for antibiotic resistance over 800 years before antibiotics were invented in the 1940s.

The study has also found that the humans at the time hardly cleaned their teeth, and the skeletons showed many years' or decades' worth of plaque buildup on their teeth. Of the skeletons found, only few had noticeably healthy teeth, and older adults showed missing teeth, probably due to wearing, decay, or dental disease.

DNA testing of the tartar was also able to give the researchers a glimpse into what ancient humans had been eating that do not show up in fossil records. The DNA results matched pigs, sheep, bread wheat and vegetables such as cabbage, and also granules from cereals, peas, and beans, not much different from the food one would find at a German restaurant in modern times.

The study's implications that can help add to what science already knows about the evolution of the human oral microbiome and the origins of periodontal disease, which affects more than 10 percent of individuals in the modern world. The Centers for Disease Control and Prevention (CDC) has stated that about 47 percent of adults ages 30 or older in the United States have some form of gum disease.

Periodontal disease is linked to a wide range of systemic disease such as cardiovascular disease, stroke, pulmonary disease, and type II diabetes. Periodontal disease does not develop in wild animals, but it does in domestic pets and zoo animals, prompting scientists to suspect that it is an oral microbiome disease resulting from modern human lifestyles.

The team plans to analyze more ancient populations from other time periods to find out.

"As we learn more about the evolution of this microbiome in response to migration and changes in diet, health and medicine, I can imagine a future in which most archaeologists regard calculus as more interesting than the teeth themselves," said Professor Matthew Collins of the BioArCh research centre in the Department of Archaeology at York.

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