LSAT Explanation PT 23, S2, Q6: Prehistoric chimpanzee species used tools similar

LSAT Question Stem

Which one of the following is an assumption on which the argument depends? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

Let's first break down the passage and analyze the argument. The argument states:

1. Prehistoric chimpanzee species used tools similar to those used by prehistoric humans. (premise)

2. Prehistoric tools recently found in East Africa are of a type used by both species. (premise)

3. The area where the tools were found is a savanna. (premise)

4. Prehistoric humans lived in savanna habitats, but prehistoric chimpanzees lived only in forests. (premise)

5. Therefore, the tools must have been used by humans rather than by chimpanzees. (conclusion)

Now, let's create an "Evaluate" question for this argument: "Was the area where the tools were found a forest or a savanna at the time the tools were in use?"

The question type of this problem is Necessary Assumption. We need to identify an assumption on which the argument depends.

a) This answer choice is not necessary for the conclusion to hold. Even if prehistoric humans carried their tools with them, it doesn't mean they carried them from the savanna to the forest or vice versa. The conclusion could still be true even if humans carried their tools.

b) This answer choice is not necessary as well. The argument only concerns the specific area where the tools were found, not the entirety of East Africa.

c) This answer choice is not necessary because the argument doesn't depend on whether humans ventured into the forest inhabited by chimpanzees. The conclusion could still be true even if humans did venture into those areas.

d) This is the correct answer. If we negate this statement and say that the area where the tools were found was a forest at the time the tools were in use, it would destroy the conclusion. If the area was a forest, then chimpanzees could have used the tools, making it impossible to conclude that the tools must have been used by humans.

e) This answer choice is out of scope. We are concerned with the tools that were found, not the capabilities of prehistoric chimpanzees to use more sophisticated tools.

In conclusion, the correct answer is D, as it is a necessary assumption for the argument to hold. The area where the tools were found must not have been a forest at the time the tools were in use in order for the conclusion to be valid.