How Evolution Is Making Our Wisdom Teeth Disappear

New mathematical formula explains why we have certain teeth—and predicts that we'll soon lose our wisdom teeth

The human mouth is due for an evolutionary update, study suggests — (REUTERS)
Mar 26, 2016 at 3:04 PM ET

Wisdom teeth are more than just an annoyance—if they become impacted, they can cause gum disease and eventually shove the rest of your pearly whites out of your mouth at embarrassing angles. So why do we have them?  Each of our teeth has a mathematical formula that guides its growth, which gradually changes as humans evolve, according to a recent study in the journal Nature,

But the formula behind wisdom teeth is only now catching up with the rest of our mouth. When it does, the study suggests, humanity will eventually evolve its way out of wisdom teeth entirely.

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For the study, researchers worked with mouse and human teeth to demonstrate that a mammalian tooth’s growth is governed by straightforward rules and a relatively simple mathematical equation. They found that jaw tissue activates the growth of one molar, and that this molar then sends a chemical signal to the next molar so that it knows how large it can grow without encroaching on the first molar’s territory.

Even better—the entire process happens in an orderly fashion, with one molar tipping off the next in a cascade of strategic tooth growth. “There’s been a big debate about how the jaw or the adjacent teeth interact during development,” coauthor Jukka Jernvall of the University of Helsinki in Finland told Science Nordic. “We show that the first molar inhibits the next, and the second molar inhibits the third, in what we call an inhibitory cascade.”

Further, we can use the same mathematical model to predict what will happen to our teeth as time moves on—and our pesky wisdom teeth appear likely to get the boot. “The new study also explains why we are now losing our wisdom teeth,” Jernvall told Science Nordic. “It’s simply a pattern that was already established at the beginning of our family tree.”

That’s because our ancestors had very large wisdom teeth near the back of their jaws that instructed all of the teeth in front to make room by remaining smaller. But with the rise of the Homo genus, the molar closest to the front of our mouths began to grow larger. Over time, the model predicts that the system should self correct—since we now have a larger molar near the front, the molars near the back (such as the wisdom teeth) should shrink and disappear accordingly.

One of the most interesting aspects of the model, however, is its ability to predict the size and shape of any tooth based on the size and shape of one well-placed tooth. Using this model, archaeologists who discover the timeworn skulls of ancient humans can easily predict what their teeth probably looked like—which would be a real boon for researchers who are trying to reconstruct our history from bones and teeth.

“Teeth can tell us a lot about the lives of our ancestors, and how they evolved over the last 7 million years,” said coauthor Alistair Evans of Monash University in Australia in a press statement. “What makes modern humans different from our fossil relatives? Paleontologists have worked for decades to interpret these fossils, and looked for new ways to extract more information from teeth.”