Agriculture, carbohydrates, and archaeological evidence of tooth decay

A gives us a way to learn about ancient diets: look at people's teeth. Caries means tooth decay. If a population started eating more sticky, carbohydrate-rich agricultural staples, its teeth may show the change. That could help archaeologists identify a shift from hunting and gathering toward farming.

The proposed link is about the food, not farming magically damaging teeth. Tooth structure and bacteria also matter, but carbohydrate texture and composition affect how readily food sticks. So before treating a cavity as a sign of agriculture, we should ask what people were eating and how they obtained it.

The meat-versus-maize comparison illustrates the usual pattern. The Sioux sample showed almost no decay; the Zuni sample, from a population heavily dependent on cultivated maize, showed decay in 75 percent of the teeth. Other researchers have repeatedly found the same general relationship: greater reliance on agriculture tends to go with more decay.

Then A gives us exceptions. People can gather carbohydrate-rich foods without growing them. The acorns weren't farmed, but they were processed into stone-ground flour, and people eating large amounts had substantial tooth decay. The Hopi also collected wild foods with high potential to cause decay. The diet can produce the dental effect even without the farming.

A's main point: Agricultural diets generally produce more tooth decay because of their carbohydrate-rich foods, but gathered foods can produce high decay rates too.

B takes us to Ban Chiang, where skeletal remains cover 2,000 years. The early inhabitants combined hunting, gathering, and cultivation, and later became more dependent on agriculture. Given A, I expect their tooth-decay rate to increase. Let's see whether that happens.

First, B adds another mechanism: tooth wear. Some wear removes the fissures that trap food and therefore reduces decay. Less fiber or grit can mean less wear, leaving more of those food traps. But severe wear creates a different problem by exposing the pulp cavity. So less wear isn't automatically better, and more wear isn't automatically better either. We need to know what the wear does.

Rice and yams were already part of Ban Chiang's varied early diet, alongside wild plants and animal foods. Greater reliance on these carbohydrate sources should, under the usual expectation, bring more cavities.

But the early group actually had slightly more decay than the late group. That's the reverse of what I expected. Can changes in tooth wear explain it? The observed wear patterns don't support that explanation here.

Instead, B offers two dietary possibilities. The later diet may have remained varied enough that no single food dominated. There may also have been a shift from sweeter yams toward rice, which is less likely to cause decay. These are proposed explanations for the unexpected finding, not proof of exactly what everyone ate.

B's main point: Ban Chiang's increasing reliance on agriculture did not bring more tooth decay, possibly because diets remained varied and shifted toward less decay-producing rice.

Together, the accounts show both the value and the limits of using teeth as clues. The general dietary pattern matters, but the actual foods and their effects can prevent farming and cavity rates from moving together.