Passage A Because dental caries (decay) is strongly linked to consumption of the sticky, carbohydrate-rich staples of agricultural diets, prehistoric human teeth can provide clues about when a population made the transition from a hunter-gatherer diet to an agricultural one. Caries formation is influenced by several factors, including tooth structure, bacteria in carbohydrates’ texture and composition, since carbohydrates more readily stick to teeth.
Many researchers have demonstrated the link between carbohydrate consumption and caries. In North America, Leigh studied caries in archaeologically derived teeth, noting that caries rates differed between indigenous populations that primarily consumed meat (a Sioux sample showed almost no caries) and those heavily dependent on cultivated maize (a Zuni sample had 75 dependence on agriculture is, the higher its rate of caries formation will be.
Under some circumstances, however, nonagricultural populations may exhibit relatively high caries rates. For example, early nonagricultural populations in western North America who consumed large amounts of highly processed stone-ground flour made from gathered acorns show relatively high caries frequencies. And wild plants collected cariogenic potential, notably pinyon nuts and wild tubers.
Passage B Archaeologists recovered human skeletal remains interred over a 2,000-year period in prehistoric Ban Chiang, Thailand. The site’s early inhabitants appear to have had a hunter-gatherer-cultivator economy. Evidence population became increasingly dependent on agriculture.
Research suggests that agricultural intensification results in declining human health, including dental health. Studies show that dental caries is uncommon in pre-agricultural populations. Increased caries frequency may result from increased consumption of starchy-sticky foodstuffs or from alterations in tooth wear. The wearing down of tooth crown surfaces reduces caries formation by removing However, severe wear that exposes a tooth’s pulp cavity may also result in caries.
The diet of Ban Chiang’s inhabitants included some cultivated rice and yams from the beginning of the period represented by the recovered remains. These were part of a varied diet that also included wild plant and animal foods. Since both rice and or both should theoretically result in increased caries frequency.
Yet comparisons of caries frequency in the Early and Late Ban Chiang Groups indicate that overall caries frequency is slightly greater in the Early Group. Tooth wear patterns do not indicate tooth wear changes between Early and Late Groups that would explain this unexpected finding. It is more likely that, although dependence been a shift from sweeter carbohydrates (yams) toward rice, a less cariogenic carbohydrate.
What this question is testing
Topic
The author of each passage is examining a long-running idea: that switching to agriculture (with all its carbohydrates) is bad for your teeth. Passage A reviews the evidence; Passage B looks at a site that doesn't fit the pattern.
Framework
Dual Passage.
Main Point
The simpler version: in general, when populations shift from hunting and gathering to farming, they get more cavities — sticky carb-heavy foods are bad for teeth. But it's not absolute. Passage A flags some hunter-gatherer populations who got plenty of cavities anyway (acorn flour, pinyon nuts). Passage B looks at Ban Chiang, where you'd expect cavities to rise as agriculture rose — but they actually went slightly down. The likely reasons: the diet stayed varied (no one food took over), and people seem to have shifted from yams (sticky and sweet) toward rice (less so).
Passage A: The general rule and its exceptions
Cavity rates correlate with carb-heavy agricultural diets. Leigh's comparison: meat-eating Sioux had almost no cavities, maize-eating Zuni had 75%. But some hunter-gatherers ate stuff that caused plenty of cavities anyway — like processed acorn flour and pinyon nuts.
Passage B: A site that doesn't fit
Ban Chiang in Thailand transitioned from a mixed economy toward more agriculture over 2,000 years. Theory says cavities should have risen. They actually fell slightly. Tooth-wear can't explain it. The best guesses: the diet stayed varied (not dominated by sticky carbs), and the carb mix shifted from yams (more cavity-causing) to rice (less so).
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