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Two teeth of a man who lived about 4,000 years ago were discovered to contain abundant bacteria that primarily cause tooth decay and gum disease. The rare find could help scientists better understand how changes in human nutrition have led to the prevalence of cavities today.
The teeth, uncovered during two excavations in 1993 and 1996, were among a large number of human teeth and other remains found in a limestone cave in County Limerick, Ireland. The two molars sampled, dated between 2280 and 2140 B.C., both belonged to the same individual who lived during the Bronze Age, according to the paper published Wednesday in the journal Molecular Biology and Evolution.
One tooth contained surprisingly abundant Streptococcus mutans (S. mutans), a cavity-causing oral bacteria. Lara Cassidy, the paper’s senior author and assistant professor of science, said bacteria are rare in the ancient genomic record, likely because they were not well preserved due to their acid-producing nature, which causes tooth decay and DNA degradation. Genetics at Trinity College Dublin.
Researchers also believe bacteria were not as prevalent in ancient teeth because the human diet contained less refined sugar and fewer processed foods than consumed today, Cassidy said. He added that a significant dietary change was seen with the beginning of agriculture about 10,000 years ago, but major changes were seen with the spread of sugar in the last few hundred years.
Link between dietary changes and tooth decay
It’s unclear why the bacteria in the newly discovered tooth were so well preserved, but Cassidy said the cool, dry conditions of the cave were likely factors.
While caries has been observed in other ancient tooth finds, S. mutans has been discovered in only very low amounts in a handful of remains, such as an older Neolithic tooth or chewed pitch from southwestern France (dated between 3400 and 2900 BC). From the Scandinavian Mesolithic period (dated between 9890 and 9540 BC). According to the article, observations of cavities in other ancient teeth are becoming more frequent following the adoption of grain agriculture, in which grains such as wheat and barley are grown.
By analyzing bacteria found in Bronze Age teeth and comparing it with modern samples, researchers found that the evolutionary tree of ancient S. mutans was more complex than initially thought, and that ancient bacteria had traits such as virulence (the ability to cause disease). It evolved with changes in the human diet, including the popularization of sugar and cereal grains, Cassidy said.
“The past few hundred years have seen a crazy amount of change (in human nutrition), so it’s important to specifically understand how this has affected not only the microbiome (microorganisms such as bacteria that live naturally on and in the human body), the oral microbiome, but also the gut microbiome over the last few centuries.” “It might help us a little bit to understand why some diseases have become so common in Western societies or westernized societies,” he added.
Oral health of the Bronze Age
The Bronze Age teeth showed no signs of tooth decay, but the abundance of bacteria present would have soon developed cavities if the adult male they belonged to had lived slightly longer, Cassidy said.
The two teeth also contained DNA evidence of Tannerella forsythia (T. forsythia), a bacterium implicated in gum disease that is more commonly found in ancient genome records. However, researchers found two different types of bacteria on the teeth; Only one species of the bacterium is common today, implying that ancient microbiomes were much more diverse than modern microbiomes. According to a news release from Trinity College Dublin, biodiversity loss is worrying as it can have negative impacts on human health.
Cassidy said several other teeth found in the cave also showed signs of tooth decay, but it is not known whether these remains belonged to the same individual or other members of the community because they were found fragmented and separate from other skeletal remains. “It’s possible that other teeth in his mouth have decay on them, or that other members of the community are suffering from dental disease.”
Cassidy added that analysis of ancient S. mutans suggests that the bacteria have become more prevalent in recent centuries due to sugar consumption, creating a suitable habitat for the species in the human mouth. Understanding the lineage of modern cavity-causing bacteria helps scientists understand how dietary change may affect oral health today, he said.
Comparative analysis of ancient S. mutans with modern S. mutans “revealed a major change linked to increased sugar consumption over the last few hundred years” and supports previous research that found higher caries rates after the introduction of refined sugar. Natural History Museum, London, which was not involved in the research This invention existed in the 19th century, said Louise Humphrey, research leader at the Center for Research in Human Evolution.
“The oral microbiome has implications for many aspects of human health and disease. … ancient teeth may help us understand how the human oral microbiota (types of microorganisms) evolved over time and the impact of these changes on human health in the past and present,” Humphrey said in an email.
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