Reading Comprehension

PT132 · S1 · P3 · Q20 Dental Caries

A free, expert breakdown of this official LSAT Reading Comprehension question.

  • Save & drill this skill — build targeted practice sets from questions like this one

  • Video walkthroughs — watch every question solved step by step

  • 81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

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.

Topic

The relationship between dental caries (cavities) and carbohydrate consumption — used as a clue to the transition from hunter-gatherer to agricultural diets.

Framework

Dual Passage. Both passages discuss the caries-agriculture link. Passage A presents the prevailing view (more agriculture = more caries) plus exceptions; Passage B applies that view to a specific archaeological site (Ban Chiang, Thailand) and finds an unexpected result.

Main Point

The prevailing view is that increased agricultural (carbohydrate-rich) diets cause more caries — but Passage B's Ban Chiang study found caries decreasing as agriculture increased, likely because the diet remained varied and shifted toward less cariogenic carbohydrates.

Passage A: The prevailing view, with exceptions

Caries strongly linked to sticky carbohydrates of agricultural diets. Leigh's North American study: meat-eating Sioux had almost no caries; maize-dependent Zuni had 75% caries — and But there are exceptions: nonagricultural populations eating processed acorn flour or wild plants high in cariogenic potential (Hopi pinyon nuts, wild tubers).

Passage B: Ban Chiang's anomaly

Ban Chiang, Thailand, transitioned from hunter-gatherer-cultivator to increasing agriculture over 2,000 years. Research generally says agricultural intensification declines health, including dental health. Caries is uncommon in pre-agricultural populations; tooth-wear (which removes fissures and reduces caries) is also a factor. Ban Chiang's diet included rice and yams from the start. Yet caries was slightly greater in the Early Group than the Late Group — opposite the expected pattern. Tooth-wear didn't explain it. Likely explanations: the late-period diet remained varied (no single food dominated), and there may have been a shift from yams (sweeter, more cariogenic) to rice (less cariogenic).

20.

Each passage suggests which one of the following about carbohydrate-rich foods?

  1. Varieties that are cultivated have

    Trap

    Opposite of Passage A Unsupported Passage B In the final sentence of Passage A, it talks about wild carbs such as pinyon nuts and tubers that have high cariogenic potential. Passage B doesn't even really comment on cultivated vs. wild varieties of carbs.

    7% picked this

  2. Those that require substantial processing

    Unsupported Passage B Opposite Passage A

    Highly processed carbs are never discussed in passage B. They are talked about in the final paragraph of passage A, in which we hear about an "early nonagricultural (i.e. still hunter-gatherer) population who consumed large amounts of highly processed flour".

    3% picked this

  3. Correct

    Some of them naturally have

    Why this is right

    This is somewhat close to our predicted overlap: both passages linked carb-rich foods to higher rates of caries. In Passage A, the final sentence provides support. If we identify certain wild plants (such as pinyon nuts and wild tubers) as having high cariogenic potential, then we're implying that there is a variety to the cariogenic potential of foods. In passage B, the final sentence says that the Ban Chiang group shifted from yams toward rice, which is a less cariogenic carb. So once again, the comparative modifier is telling us that carbs can vary in terms of their potential to cause caries. p.s. Carcinogenic = cancer-causing Cariogenic = caries-causing

    Skill tested: Inference · how this choice captures the passage's function is the move to repeat next time.

    81% picked this

  4. Some of them reduce caries

    Opposite, if anything

    We thought the overlap was that both passages linked carb-rich foods to an increased potential for caries. This answer is saying some carb-rich foods reduce caries formation. In the 2nd paragraph of Passage A, they're saying that as people started eating more sticky carbs, they had less fiber/grit in their diet, so their teeth didn't wear down as much, which is why it was easier for caries (cavities / little spaces) in their teeth to form.

    4% picked this

  5. The cariogenic potential of a

    Unsupported Passage B Opposite Passage A

    This seems like functionally the same idea as answer choice (A). And once again, we would say that Passage B never makes a wild vs. cultivated distinction. And in Passage A, the only time they talk about wild carbs is to provide an example of a food with high caries potential (whereas this answer choice is saying wild carbs should have less cariogenic potential).

    4% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill
LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free