Two teeth, from the same man, were excavated from Killuragh Cave, County Limerick and studied by archaeologists from the Atlantic Technological University and University of Edinburgh. The teeth showed advanced dental decay and had a high amount of Streptococcus mutans DNA, a strain of bacteria that is linked to gum disease tooth decay. Though S. mutans is common in modern mouths, it is very rare for the strain to be seen in ancient teeth, which makes this finding in these teeth vital for creating a truer version of the lineage of mouth bacterias. More and more dental cavities have become common due to sugary foods being introduced in masses, which may explain why the presence of S. mutans is so rare in ancient teeth. Scientists also found that other streptococcal strains were missing from the teeth while other divergent bacterias common in gum disease, like Tannerella forsythia, was found. Dr. Cassidy, an author of the study, explains, "a single lineage of T. forsythia has become dominant worldwide. this is the tell-tale sign of natural selection..." (ScienceDaily). T. forsythia being present added evidence of natural selection for this strain and answered other questions about gum disease bacteria's history.
I think analyzing fossils, and finding answers from something thousands of years old is always worth reading about. The thought of the evolution of the microbiome of the mouth is not something usually thought about but, these findings are vital for gum disease history and human mouth health. Learning more about what sweets can do to human teeth and how tooth decay affected people from up to 4000 years ago was very interesting and thought provoking, considering the age of these teeth. It's also interesting to see how the microbiome has changed, how some strains are missing while others are that are present now, are missing then. I also thought it was important to mention how these findings were considered to support "loss in biodiversity" which supports the "disappearing microbiome hypothesis". This hypothesis proposes that "modern microbiomes are less diverse that those of our ancestors" (ScienceDaily). Overall, I thought it was an interesting read and sparked a hope that more research about the history of tooth decay and gum disease is done.
