On the whole, humans seem to be pretty well designed for the things we do. We can get around efficiently on our legs, grasp and manipulate objects with our hands, see fine details with our eyes, and process loads of sensory information with our brains. But if all that makes us feel a bit smug, let’s consider another part of human anatomy that’s often problematic: our four wisdom teeth.
Most of us have these large back teeth (also called third molars), which generally start to erupt (emerge from below the gum line) in young adulthood. But we don’t really need them. In fact, dentists often recommend having wisdom teeth removed before eruption because they can be a source of serious problems. In many cases, that’s because the jaw itself is too small to accommodate all 32 teeth, including these four. So how did we humans end up with more teeth and less jaw than we need?
As it turns out, we weren’t always built that way. Once upon a time, some 100 million years ago, our ancestors used all four limbs for locomotion, and had plenty of room in their jaws for 32 pearly-whites. In fact, their jaws were much larger and more robust than ours are now — and their teeth were more critical for survival. They likely used their teeth for catching prey, as well as tearing it apart and consuming it. Their diet of raw meat, roots and other tough plant material was tough to process, so having plenty of teeth would have been advantageous for their survival.
In time, however, early hominids started walking upright, making tools, growing crops and using fire. Gradually, as brains grew larger and diets became less “raw” (with more grains, vegetables and cooked meats), there was less need for those big back teeth. And as our ancestors’ skulls vastly expanded in size to accommodate the larger brains, their jaws became smaller. But the teeth, which evolve independently, somehow didn’t change; this led to the mismatch in size that we see today.
Will our wisdom teeth eventually disappear? It’s certainly not impossible, given enough time. Right now, perhaps 10 to 25 percent of Americans with European ancestry are lacking at least one; in some groups with Asian ancestry (Inuits, for example), that figure is as high as 45 percent. In fact, having teeth at all is no longer strictly necessary for survival; while it’s far from desirable, some people do manage to live without them. On the other hand, having a bright, healthy smile does seem to enhance a person’s chances of attracting a partner and reproducing – which, in the end, is what evolution is all about.