54-Million-year-old cavities found by UofT Researchers

The largest sample of cavities in ancient primates have been discovered by two UofT researchers and are believed to be the oldest cavities found in a mammal.

Chloe Tsui, The Mike Contributor

Ouch! Cavities!

Most commonly caused by sweets, cavities are often the result of a carbohydrate rich diet, including but not limited to fruit, honey and gum. Cavities, also known as dental caries, are the little holes that form when bacteria turn carbohydrates (sugar) into acid. This process breaks down tooth enamel and eats at the dentin (yellow, bony tissue hidden beneath the enamel), leaving us with painful tooth decay. 

While there is ever-growing research on human cavities, only a few studies on cavities in other animal species are done. Only recently, University of Toronto researchers Keegan Selig and Mary Silcox have discovered the oldest and largest known sample of cavities in stem primate Microsyops Latidens, a prehistoric mammal that lived almost 54 million years ago. An in-depth understanding of the relationship between dental shape, cavities and diet allows researchers to explore the diets and ecology of extinct animals. Selig explained that “This knowledge can also be used to determine whether or not there has been a change in diet and/ or behaviour over evolutionary time”. 

Confirming Cavities: What to Look For

Using micro-CT scans, Selig and Silcox identified fossilized dental caries in 77 out of 1030 fossilized samples of M. latidens. If the teeth contained smooth, round and wide lesions and/ or mineralized dentine under enamel, they were classified as cavities. Samples not containing cavities were used less, having been more difficult to study; furthermore, colour was excluded as an identifier due to little variation in severity of discoloration. “If these teeth were damaged, the features would likely be jagged and have sharp edges,” says Selig. Additionally, the cavities observed seemed to recur in specific spots, indicative of a rather sugary diet. Food may have been trapped in hard-to-reach places and on top of chewing surfaces. Imagine eating a big bowl of cereal and having a chunk stuck in your teeth (for 54 million years!). 

Care for Some Fruit? What Happened?

Selig & Silcox speculated a shift to a fruit/ sugar rich diet to be the root cause of a higher cavity rate among the younger primates sampled (17% in the more recent group vs 7% in the older group). Additionally, Selig highlighted that that “At certain points in time, the cavities were very frequent, more so than in many living primates”, hinting towards a series of unique events that pushed M. Latidens towards a fruit- based diet. One potential factor that could have contributed to this shift in diet is regional climatic flux, as there has been evidence that points to this possibility. This is further supported by its era- as Early Eocene primates, M. Latidens had survived a time of unstable local climate. 

Although we are still unsure as to why they went extinct, this recent discovery has helped us understand more about their ancient species and life. Who knew cavities were so interesting? Don’t forget to brush your teeth (and limit those sweets- Halloween is coming)!