Expert: John Shea - 11/5/2009

Question
As an art student I've studied anatomy, including examining skulls of people of different ethnicities, as well as drawing all kinds of people. I've noticed that western Europeans and many Japanese people often have small jaws full of crowded, crooked teeth while the native peoples of Australia and New Guinea often have large jaws full of perfect, straight white teeth-yet they're much less likely to have seen a dentist. The dental arch in Europeans is narrow and rounded while in native Australians it's almost square. While looking at photos of people from around the world I came across photos taken by Weston Price. Regardless of whether you agree with his conclusions, he did document how indigenous people who ate their traditional diets of unprocessed foods had large jaws full of perfect teeth, but that when these same groups adopted a western style diet their jaws shrank within a few generations and they too had crowded, crooked teeth. That's too fast for genetic evolution. Could a diet of soft, refined foods fail to provide the jaws with enough work for them to develop to their full size, sort of like how a diet low in protein can make people grow shorter than their genes could have allowed?

Answer
Lee,
You've pretty much answered your own question.  The articulation between teeth and the mandible is very labile (flexible).  So, if it gets stressed firmly and regularly, it reinforces itself by bone growth and remodeling.  Preindustrial and preagricultural diets have more fiber and thus stressed teeth more than recent diets do.  This is likely why you see well-aligned, healthy teeth and robust  mandibles among hunter-gatherers and people who eat minimal processed foods.  Agricultural and Industrial diets have less fiber, stress the teeth/jaw less.  In the absence of such stress, teeth grow less regularly.  In Chinese prehistory, according to the late K.C. Chang, we can tell exactly the point where chopsticks came into use because dental variation and pathology just goes wild.
For more information, look up papers by C.Loring Brace, who has written extensively about this subject.
Sincerely,
John Shea


In reply to your comment:  People who take public funds for their education and research have a moral obligation to share their expertise and the results of their research with the public.  I have to be conservative with my time, for there are many claims on it; but when I get an intelligent question like yours, I don't mind giving a thorough answer.
Cheers,
John Shea