When I was a teenager, a dentist extracted my unemerged wisdom teeth. He said they were impacted and were crowding my other teeth. Recently I found out why. It was a childhood of not chewing forcefully enough, which caused my jawbone to slightly undergrow, enough that there was no room left to accommodate my third molars, which are the last ones to erupt during growth (a dental version of musical chairs). Studies show that at least three-fourths of modern humans are similarly affected.

courtesy Coronation Dental Specialty Group, Wikimedia Commons

Our fossil ancestors did not have impacted wisdom teeth, and their occlusion was dead on—their upper and lower front teeth contacted each other precisely, which allowed for efficiency in cropping twigs and gnawing gristle off bones. These hunter-gatherers then had to chew long and hard to make these raw, tough foods digestible. Their progeny eventually quit the nomadic life and changed to a diet of roasted meat and boiled grain. Since as children these “civilized” folk did not have to gnaw and grind forcefully to nourish themselves, they developed overbites, because their jawbones failed to achieve their full growth potential. Apparently a modern diet of mashed potatoes, ground beef, boiled peas, and ice cream is not conducive to the development of a jawbone capable of comfortably housing all of our 32 teeth.

Multiple observations support this use-it-or-lose-it concept. As far back as 1871, Charles Darwin in his book, The Descent of Man, made the association between oral stress and jaw size. In recent times, anthropologist Robert Corruccini noted that elders in rural Kentucky, who grew up eating hard-to-chew foods, had better bites, despite the near absence of professional dental care, than did younger residents who grew up eating more processed foods. He observed similar bite differences in the Pima Indians before and after they had access to grocery stores and in rural and urban dwellers in India who ate diets of hard millet and tough vegetables vs. soft bread and lentils, respectively. Studies on mice (see comparative images) and monkeys have also indicated that soft diets result in smaller jaws.

Does this make you want to begin eating bark and jerky? If you are out of high school, sorry, it is too late. Like me, you can see your dentist or accept having crooked teeth, an overbite, or both. But the overbite does offer an advantage—the ability to efficiently make words starting with “f” or “v”. The linguists call these sounds labiodentals, and computer modeling says that they are 29% easier to say with an overbite than with edge-to-edge occlusion. About 4000 years ago, development of an overbite among our gruel-sipping ancestors helped spur the diversification of languages in Europe and Asia. A linguist has suggested that in ancient Rome and India using labiodentals was a status symbol, indicating wealth associated with a soft diet. Even for the poor about 1500 years ago, the Proto-Indo-European patēr, which carried over into Latin, changed to the Old English faeder. Today, labiodental consonants are present in 76% of Indo-European languages.

Perhaps I am belaboring the obvious, but as a bone lover I must extol bone. Isn’t it amazing that bone cells can respond to the presence or absence of mechanical stresses encountered during chewing and that leads to job security for dentists and to the sounds we make when speaking? Happy Fathers’ Day.

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