Keeping our teeth clean has been a pain for thousands of years, with some particularly painful methods historically used to take care of our chompers. Two 4,000-year-old human teeth unearthed in a limestone cave in Ireland were recently found to contain an “unprecedented quantity” of the bacteria that cause tooth decay and gum disease. The genetic analysis of these well-preserved microbiomes reveal how changes in diet shaped our oral health from the Bronze Age to today. The findings are described in a study published March 27 in the journal Molecular Biology and Evolution.
Fossilized dental plaques have been one of the best studied parts of the ancient human body. However, very few full genomes from oral bacteria in teeth prior to the medieval era have been uncovered. This means that scientists have limited data on how the human mouth’s microbiome was affected by changes in diet and from events like the spread of farming about 10,000 years ago.
Sugar-munching, acid producing bacteria
Both of the teeth belonged to the same male individual who lived in present day Ireland during the Bronze Age. The teeth contained the bacteria that cause gum diseases and the first
high quality ancient genome from Streptococcus mutans (S. mutans). This oral bacterium is one of the major causes of tooth decay.
S. mutans is very common in modern human mouths, but is very rare in the ancient genomic record. One potential reason why it’s so sparse may be how the bacterium produces acid. The acid decays the tooth, but also destroys DNA and stops the dental plaque from fossilizing and hardening over time. Most ancient oral microbiomes are found inside these fossilized plaques, but this new study looked directly at the tooth.
[Related: Vikings filed their teeth to cope with pain.]
Another reason why S. mutans may not have been present in ancient mouths may be due to a lack of sugary mouths for it to thrive in. S. mutans loves sugar and an…
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