Two teeth from a man who lived approximately 4,000 years ago were discovered with an abundance of bacteria that mainly cause cavities and gum disease. The rare discovery could help scientists better understand how changes in the human diet have led to the prevalence of cavities today.
Discovered during two excavations in 1993 and 1996, the teeth were among several other human teeth and other remains found inside a limestone cave in County Limerick, Ireland. The two molars, dated between 2280 and 2140 BC, were from a single person who lived during the Bronze Age, according to the article published March 27 in journal Molecular Biology and Evolution.
One of the teeth had a surprising abundance of Streptococcus mutans (S. mutans), an oral bacteria that causes cavities. The bacteria is rare in the ancient genomic record, likely because it does not preserve well due to its acid-producing nature that causes degradation and degradation of DNA in teeth, said Lara Cassidy, senior author of the paper and assistant professor in the department of genetics at Trinity College. Dublin.
Researchers also believe that the bacteria is not commonly found in old teeth because the human diet included less refined sugar and fewer processed foods than are consumed today , Cassidy said. A significant dietary shift was observed with the beginning of agriculture about 10,000 years ago, but the last few centuries have seen significant changes with the popularization of sugar, she added.
Connection between dietary changes and cavities
It's unclear why the bacteria on the newly discovered tooth was extremely well preserved, but Cassidy said the cave's cool, dry conditions are likely factors.
Although cavities have been observed in other ancient tooth finds, S. mutans has only been discovered in very low quantities in a few remains, such as an older Neolithic tooth from southwestern France (dated between 3400 and 2900 BC) or a resin chewed from the Scandinavian Mesolithic (dated between 9,890 and 9,540 BC). Observations of cavities in other old teeth become more frequent after the adoption of cereal agriculture, the cultivation of grains such as wheat and barley according to the article.
By analyzing bacteria found in Bronze Age teeth and comparing them to modern samples, researchers discovered that the ancient evolutionary tree of S. mutans was more complex than originally thought — and they had found traces of ancient bacteria, such as virulence (the ability to cause harm), evolving along with changes in the human diet, including the popularization of sugar and grains, Cassidy said.
“The last few centuries have seen a huge amount of change (in the human diet), so understanding particularly how this has impacted the microbiome (the microorganisms, like bacteria, that naturally live in and on the human body), not just the oral microbiome, but also the intestinal microbiome, can help us understand a little why certain diseases have become so prevalent in Western or Westernized populations in recent centuries”, he added.
Bronze Age oral health
No signs of cavities were found in the Bronze Age teeth, but if the adult man they belonged to had lived a little longer, the abundance of bacteria present suggests he would have soon developed cavities, Cassidy said.
The two teeth also contained DNA evidence of Tannerella forsythia (T. forsythia), a bacteria involved in gum disease that is most commonly found in the ancient genomic record. But researchers found two distinct strains of the bacteria in the teeth — today, only one strain of the bacteria is commonly seen, implying that ancient microbiomes were much more diverse than modern microbiomes. Biodiversity loss is concerning as it can have negative impacts on human health, according to a press release from Trinity College Dublin.
Several other teeth found inside the cave showed signs of tooth decay, but it is unknown whether these remains are from the same person or other members of the community as they were found disarticulated, separated from other skeletal remains, Cassidy said. “It is possible that other teeth in his mouth had cavities, or other members of his community were suffering from dental disease.”
Analysis of ancient S. mutans suggests that the bacteria became more prevalent in recent centuries due to sugar consumption, which created a favorable habitat for the species inside human mouths, Cassidy added. By understanding the strains of modern bacteria that cause cavities, this further helps scientists understand how changing diets can impact oral health today, she said.
Analysis of ancient S. mutans compared to modern S. mutans “revealed a significant change in the last few centuries linked to increased sugar consumption ” and supports previous research that found higher rates of cavities after refined sugar became widely available in the 19th century, said Louise Humphrey, research leader at the Human Evolution Research Center at the Natural History Museum in London, who was not involved. in the study.
“The oral microbiome has implications for many areas of human health and disease. Ancient teeth can help us understand how the human oral microbiome (range of microorganisms) has evolved over time and the impact of these changes on human health in the past and today,” Humphrey said in an email.
Source: CNN Brasil
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