PrepTest 119, Section 3, Question 26
Fossilized teeth of an extinct species of herbivorous(36 more words not shown)
The argument assumes which one(3 more words not shown)
- ANone of the(13 more words not shown)
- BPlants of every(10 more words not shown)
- CEach of the(16 more words not shown)
- DPhytoliths have also(12 more words not shown)
- EMost species of(15 more words not shown)
Reading the argument
Those are the plants we found evidence of. Were they the only plants the apes ate?
The phytoliths are tiny petrified plant remains found on the fossilized teeth. They give us evidence of some foods, but the author treats them as a complete menu. Maybe other plants didn't leave these traces. Maybe only some foods left remains that stayed on the teeth. If a plant could be eaten without leaving the evidence we're examining, its absence from the teeth wouldn't establish its absence from the diet.
What we’re looking for
For the required assumption, we need that missing link between eating a plant and leaving a trace. The author must assume that every type of plant in the diet left phytoliths on the teeth. Otherwise, an unrecorded food could be missing from the proposed menu. Notice that this concerns all the evidence taken together, not whether every individual tooth carries every plant.
Working the answers
- A
Whether a plant species still exists doesn't tell us whether the traces cover the apes' entire diet. A plant could have become extinct after leaving phytoliths, or it could still be around today. Either situation is compatible with the evidence. The argument doesn't need every identified plant to have survived until now.
- BCorrect
Every type of plant the apes ate left phytoliths on their teeth. That is needed to use the absence of other kinds of phytoliths to rule other plants out of the diet.
If some eaten plants left no phytoliths, the apes could have consumed those plants without our finding them in this evidence. B rules out that missing-trace possibility. It doesn't say how much of each plant the apes ate or require the same foods to appear on every tooth.
- C
The teeth can contribute different pieces of the dietary record. One tooth might carry traces of one plant and another tooth traces of another. Taken together, they could still reveal all the types eaten. The argument needs complete coverage across the evidence, not an identical set of traces on each tooth.
- D
The argument concerns this extinct ape species. Phytoliths on other species' teeth might be interesting, but their presence isn't required to interpret these teeth as a complete dietary record. Finding them elsewhere wouldn't establish that every food eaten by these apes left a trace.
- E
Living great apes might eat a narrow range of plants without this extinct species having done so. Even a narrow diet could include a plant that left no phytoliths. We need evidence that the particular traces capture the entire diet, not a general description of different species alive today.
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