Close but no ingressive
This article blames dental braces for the prevalence of snoring.

Probably a good correlation, but the explanation is all wrong.

Ehrlich and Kahn trace the crooked jumble of teeth many of us develop to the agricultural revolution. (As Stanford paleontologist Richard Klein says, “I’ve never seen a hunter-gatherer skull with crooked teeth.”) When humans turned to farming, food got softer and we stopped chewing so hard. This lack of exercise, Ehrlich and Kahn hypothesize, led to a reduction in Homo sapiens’ face and jaw size. With less room, our teeth have gotten crowded and often jumbled up. It became harder to breathe.

In the first fucking place, you shouldn't be listening to Ehrlich, who is wrong about everything.

Second fucking place, evolution. Tedx. Savannah Sabertooth**. How does lack of exercise lead to reduction in jaw size?

You don't need evolution to explain it, and you need more than jaw strength. The jaw isn't the main factor in this problem.

Breast-feeding babies helps because it takes more effort on the child’s part than sucking on a bottle. Encourage your children to chew thoroughly—Ehrlich and Kahn even advocate gum. They warn that “poor oral posture” contributes to constricting airways. A particular culprit is mouth-breathing, often exacerbated by the fact that we find ourselves indoors so much, where concentrated allergens help stuff up our nasal passages. Mouth-breathing is a sign of a slack jaw and is an indication you are not getting enough oxygen. It’s harder for us to breathe than it was for our jaw-endowed ancestors.

Now we're getting closer, but the explanation still fails. Breast feeding develops the muscles around the mouth, including the tongue and larynx and pharynx. It doesn't involve the jaw.

When you see a serious overbite, it's NOT caused by lack of jaw strength. It's caused by weak or underused facial muscles. (See Treacher Syndrome for an extreme example.) When those muscles are toned up, they hold the teeth inward.

Snoring should depend closely on language. When your language makes heavy use of the pharynx and velum and external larynx muscles, you develop more muscle strength in the relevant areas. More exercise means less slackness.

Data is hard to come by, but here's one comparison of snoring prevalence in Singapore, where culture and environment and wealth are roughly the same across ethnicities:

Chinese, 6.2%; Malay, 8.1%; and Indian, 10.9%.

Agrees with my hypothesis. Chinese, especially the southern version used in Singapore, gives constant exercise to the larynx in forming six tones. Malay doesn't have tones but does have the ingressive consonants typical of that region, which exercise the external larynx muscles. Indian (presumably Hindi) doesn't use tones or ingressives. It's pretty much the same lazy larynx as Euro languages.

Compare Chinese with Korean, which has no tones or ingressives:

The prevalence of self-perceived snoring/apnea was 22.8% (26.4% for males vs. 18.8% for females.

One particular jaw movement is relevant. Protruding the jaw can stop snoring. But this direction isn't exercised or developed by chewing, and isn't a natural part of any phonetic gesture.

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** Footnote: Come to think of it, the Savannah Sabertooth could be a factor, but it would influence muscles rather than skull size, and it doesn't relate to evolution at all. When improved hunting and cooking methods bring in more protein, all muscles are stronger, thus teeth are straighter.

Toenote: And let's not forget the tooth muscles. Or more precisely the periodontal ligament which might as well be a muscle. The PDL responds to the dynamic pressures on its tooth, constantly building and unbuilding connective tissue to take the current stresses. Sort of like a tree building compression wood and tension wood. Braces relieve most of the dynamic strains, letting the PDL atrophy. Chewing more complex fibers creates a wider variety of stresses, improving the PDL's "intelligence" and thus its ability to keep the tooth in position.

Labels: Constants and Variables

  ¶ 1:23 AM