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As Diets Evolve, Human Teeth Still Cling To The Past

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Ohio State anthropology professor Debbie Guatelli-Steinberg says softer foods are causing problems with teeth and jaws, which evolved on nuts and other harder foods.

The average human diet is a lot different than just a few decades ago, let alone thousands of years ago. Such a drastic change in diet appears to be having some adverse effects on our teeth and jaw, which evolved to chomp nuts and other harder foods.

Ohio State University anthropology professor Debbie Guatelli-Steinberg details some of those issues in her new book, "What Teeth Reveal About Human Evolution."

"Our food has changed dramatically," Guatelli-Steinberg says. "Over the course of our evolutionary history, we ate foods that were much more difficult to chew. This allowed our jaws to grow enough to accommodate third molars when they came in."

Less room for molars means more teeth misalignment. Guatelli-Steinberg says some third-world countries have less teeth misalignment than the U.S. because their current diets are closer to those of their ancestors.

Another major problem with modern diets: Refined sugar.

"You look back in human ancestors and you see very few teeth that had cavities."

Guatelli-Steinberg says it's impossible to say what the relatively-sudden change in diet means for the future of the human smile.

Read their full conversation below. Please excuse minor typos and errors.

Steve Brown: So dental care is obviously light years ahead of where it was even just a few decades ago, but we have much higher cavity rates and misaligned teeth rates now. Is this all because of food?

Debbie Guatelli-Steinberg:  This is primarily because of the kinds of foods that we eat. And also because in different areas of the world, there isn't as much dental care as there may be, say, in Columbus, Ohio. But our food has changed dramatically over a course of evolutionary history. We ate foods that were much more difficult to chew. This allowed our jaws to grow enough to accommodate third molars when they came in, and we had less misalignment of the teeth.

In addition, in our evolutionary history, we didn't have refined sugar so we had very few cavities. You look back in human ancestors and you see very, very few teeth that had cavities.

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Steve Brown: Another way to illustrate, this you wrote that the impaction of the third molar became 10 times more common after the Industrial Revolution?

Debbie Guatelli-Steinberg:  Well not so much impactions, but the misalignments, what are called malocclusion, when the teeth fit together in a way that's not optimal. So there are rotations or things like that.

Steve Brown: Is there anything people can do to stimulate their teeth and jaw to offset these effects?

Debbie Guatelli-Steinberg:  Well some of my colleagues like to make fun that, you know, they could actually have their kids eat beef jerky as they're growing up to stimulate the jaw to grow enough so that they can accommodate.

Steve Brown: Is that true, all jokes aside, is that true? 

Debbie Guatelli-Steinberg:  I don't know that anybody's actually done an experiment to see if that's true, if beef jerky has that effect.

Steve Brown: Or something along those lines though could that help? 

Debbie Guatelli-Steinberg:  It's possible, but I don't know of any experiments, as I say, that have shown that. There are experiments that have been done with baboons, and baboons who have been fed very soft diets, atherosclerosis studies where they're having these very fatty foods and they're very soft, don't grow their jaws large enough. And indeed, they end up with far more malocclusions than other baboons, and they have teeth that are not fitting together correctly.

Steve Brown: In other parts of the world, in, say, third world countries, are teeth better aligned or do they have fewer of these issues caused by soft foods?

Debbie Guatelli-Steinberg:  So in other parts of the world, there are some places where people do have teeth better aligned, where they're eating food that is more mechanically stimulating of jaw growth. Yes.

Steve Brown: Where would you expect the evolution of teeth to go from  here? 

Debbie Guatelli-Steinberg: So this is a difficult question to answer, because certainly what we do is we want to keep people alive, and that's what dentistry is about, is preventing infections and treating them when they do occur and treating malocclusions. So it's hard to say how natural selection might affect dental evolution in the future.

Steve Brown: Are there any theories? Or, I don't know, what's the end game here, what happens? You don't know, no-one knows, right?

Debbie Guatelli-Steinberg:  No, it's hard to know. It's hard to, yeah, it's hard to know where it's going to go.

Steve Brown: And much of your research is possible because teeth hold up much better than the rest of the body, right, they're so mineral heavy and so hard.

Debbie Guatelli-Steinberg:  Exactly. So, teeth are an incredible source of information in the fossil record because they are so heavily mineralized. They resist decomposition, they resist destruction, and so, much of the fossil record consists of teeth. And that's true for human evolution as well as other mammals. And there's a great deal of information that teeth lock into their physical and chemical structure, and that's the information that dental anthropologists try to glean from teeth and to learn about, not only diet but other aspects of human biology.