![]() ![]() It is a fine balancing act, and our species has had 200,000 years to get it right. In this way, diet determines how well jaw length matches tooth size. Selection for jaw length is based on the growth expected, given a hard or tough diet. He showed that the ultimate length of a jaw depends on the stress put on it during chewing. ![]() Higher chewing strains resulted in more growth in the bone that anchors the teeth. The evolutionary biologist Daniel Lieberman at Harvard University conducted an elegant study in 2004 on hyraxes fed soft, cooked foods and tough, raw foods. Its size depends both on genetics and environment and it grows longer with heavy use, particularly during childhood, because of the way bone responds to stress. They cannot change in response to conditions in the mouth.īut the jaw is a different story. So the sizes and shapes of our teeth are genetically pre-programmed. If you’ve ever wondered why your teeth can’t grow or repair themselves when they break or develop cavities, it’s because the cells that make enamel die and are shed when a tooth erupts. The cells that make the cap move outward toward the eventual surface as the tooth forms, leaving a trail of enamel behind. Human teeth are covered with a hard cap of enamel that forms from the inside out. ![]() So why don’t our teeth fit properly in the jaw? The short answer is not that our teeth are too large, but that our jaws are too small to fit them in. The same goes for our fossil forebears and for our nearest living relatives, the monkeys and apes. In other words, the sizes of Hadza teeth and jaws match perfectly. Hadza also typically have a tip-to-tip bite between the upper and lower front teeth and the edges of their lowers align to form a perfect, flawless arch. Most have 20 back teeth, whereas the rest of us tend to have 16 erupted and working. The first thing you notice when you look into a Hadza mouth is that they’ve got a lot of teeth. I am a dental anthropologist at the University of Arkansas, and I work with the Hadza foragers of Africa’s great rift valley in Tanzania. Our distant hominin ancestors did too and so do the few remaining peoples today who live a traditional hunting and gathering lifestyle. Other animals tend to have perfectly aligned teeth. It just doesn’t make sense that such an otherwise well-designed system would be so ill-fitting. It’s as if our teeth are too big to fit properly in our jaws, and there isn’t enough room in the back or front for them all. Do you have impacted wisdom teeth? Are your lower front teeth crooked or out of line? Do your uppers jut out over your lowers? Nearly all of us have to say ‘yes’ to at least one of these questions, unless we’ve had dental work. Nature is truly an inspired engineer.īut our teeth are, at the same time, really messed up. They break food without themselves being broken, up to millions of times over the course of a lifetime and they do it built from the very same raw materials as the foods they are breaking. We rarely consider just how amazing our teeth are. We hold in our mouths the legacy of our evolution. ![]()
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