Prehistoric Humans Didn't Have Cavities. Researchers Think They Know Why

  • While researchers previously thought that human cavities were caused by a change in diet, a new paper suggests another culprit: bacteria.

  • Bacteria found in human teeth thousands of years were much less harmful than the ones lurking around today.

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In the U.S. alone, 90% of adults over the age of 20 have had at least one cavity in their lifetime, according to data from the Centers for Disease Control and Prevention. In other words, they're one of the most common ailments in the country.

Interestingly, cavities are a new occurrence for the human race.

What do you mean by new? Even though oral hygiene is key in our time, humans went without it for thousands of years. Despite this, archeological remains recently examined by researchers show that cavities were almost unknown in prehistoric times.

Historians state that the first signs of oral hygiene practices started appearing among the first great civilizations. The Mesopotamians, for instance, chewed twigs. Others used plants. In fact, scientists have long associated tooth decay with the historical change in diet that occurred with the advent of agriculture.

But if scientists believe our evolving diet gave us cavities, what's the mystery? Recently, a team of researchers from Trinity College in Ireland found several well-preserved teeth with an unusually high amount of bacteria. The bacteria they found happened to be the same ones that are known to cause tooth decay and certain gum diseases, but the enamel was in perfect condition. How was this possible?

The story gets a bit complicated. The teeth were discovered in a limestone cave in County Limerick, Ireland, between 1993 and 1996. They belonged to the same adult who lived more than 2,000 years ago. Under normal conditions, the overabundance of Streptococcus mutans bacteria found in the teeth would have caused problems. But in this case, as stated above, the enamel was fine.

To understand this phenomenon, researchers analyzed the evolutionary history of the bacterium and discovered that the Streptococcus mutans in the teeth isn't the same strain we’re familiar with today. Rather, it was an archaic version of the bacteria, one that's much less virulent than the modern variant.

Diet is only one reason for human cavities. We've known since at least 2013 that our oral flora is losing biodiversity. Now, it looks like we're starting to understand why. When considering the evolution of Streptococcus mutans’ evolution, Lara Cassidy, lead author of the study, told the French outlet GEO the following: “We’ve seen an incredible change in human food habits over the last few centuries. Understanding how this has impacted the microbiome (not just the oral but also the gut microbiome) could help us understand why certain diseases have become so widespread in Western populations.”

In other words, humans have been selecting the most virulent and aggressive strains, which wreak havoc on their teeth, for thousands of years without realizing it. Now, it’s up to us to decide what actions we need to take to prevent this from happening in the future.

Image | Bodgan Condr

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