Monday, October 01, 2007

New Wisdom on Wisdom Teeth
Now, a study detailed in the Sept. 27 issue of the journal Nature finds these annoying teeth may only exist because of a weakness in a developmental mechanism that allows them to cram their way into the back of the jaw.

Molars are the rearmost teeth in the mouth of most mammals. Adult humans have 12 molars (three on each side of the upper and lower jaws), and the last of each group is called the wisdom tooth.

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One thing about molars that has perplexed scientists is why some people have very large wisdom teeth, while others (lucky for them) might not have any at all.

This is an interesting topic, but one that I never looked into in any detail. The basics one gets from one's undergrad anthropology courses are that the mandible has gotten smaller over time, that the switch to agriculture has meant more dental disease, and that, because of the former, wisdom teeth become more problematic. This study seems to indicate that among "early humans" (unclear what age they're referring to; the provided link goes to an article on a Magdalenian specimen), all 3 molars were about the same size. Nowadays, the 3rd molars tend to be smaller, which suggests that natural selection is favoring smaller 3rd molars (perhaps in response to smaller mandibles?).

Are 3rd molars usually normally erupted without problem in. . .early modern humans? Neanderthals? Is there any real evidence for problematic 3rd molar eruption tied to a shortening of the mandible? As a matter of fact, I've never really checked what the evidence is for the "agriculture = more tooth decay" maxim. Was it ever really established quantitatively, or has it passed into cliché status more on general observation than rigorous analysis?