Logical ReasoningDifficulty: Medium

PT23 S2 Q6 Explanation

Prehistoric chimpanzee species

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsNecessary Assumption

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Stimulus

Prehistoric chimpanzee species used tools similar to those used by prehistoric humans; prehistoric tools recently found in East Africa are of a type used by both species. The area where the tools were found, however, is a savanna, and whereas there were prehistoric humans who lived in savanna habitats, must have been used by humans rather than by chimpanzees.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
6.

Which one of the following is an assumption on which the

Answer choices

  1. Too Strong8% picked this

    Prehistoric humans did not carry their tools with them when they traveled from one

    Too Strong: never carried tools Chimps vs. Humans The author hasn't committed herself to the extreme and unlikely idea that prehistoric humans never carried tools with them when traveling from one place to another. The reason this answer might feel tempting to some, though, is because one possible objection we had was, "What if this tool they found was used by a chimp, who lived in a forest, and just dropped it in the savannah as it was traveling from one forest to another". So a 'corrected' version of this answer would say (A) Prehistoric chimpanzees did not carry tools with them as they traveled through a savannah

  2. Too Strong: predominantly5% picked this

    Since the evolution of the first primates, East Africa has been

    The author hasn't committed herself to the idea that most of East Africa was savanna. She is only saying this area where the tools were found was savanna. Savannas might be 7% of East Africa's habitats or 70%. It doesn't make any difference to the argument.

  3. Too Strong: never10% picked this

    Prehistoric humans never ventured into areas of the forest that were inhabited

    This looks off-putting because of how extreme it is. Based on this paragraph, the author is now committed to believing that a prehistoric human never ever when into a forest in habited by chimps? Why would it matter if there were at least one human who ventured into a chimp-controlled area of the forest? Would that hurt the author's argument and allow us to argue that the tools found in the savanna really belonged to chimps? No, not unless we think "human venturing into chimp-controlled forest = human leaves with a chimp tool in his possession and drops it in the savanna", but that's way too big a stretch.

  4. Correct75% picked this

    The area where the tools were found was not a forest at the time the

    Why this is right

    This has that lovable "ruling-out" language (not) that's present in so many correct Defender answers. If we negate this, does it weaken? Yes! The author is saying, "They found the tools in a savanna. Chimps didn't live in savanna habitats. They lived in the forest." The negation says, "Yes, author, but the area where the tools were found was a forest back in prehistoric times, so there might have been chimps living there, so these tools we found might have belonged to chimps." In arguments that are based on found artifacts, the author is normally assuming that "where we found it = where it came from", as well as "what this area is like now = what this area was like then".

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

  5. Out of Scope: sophistication1% picked this

    The prehistoric ancestors of modern chimpanzees were not capable of using tools more sophisticated than those found

    This also has the lovable ruling-out "not", so we should see whether the negation weakens the argument. If we say, "Hey, author, those prehistoric chimps were capable of using tools more sophisticated than the tools we found", that would not weaken. The argument had nothing to do with how simple or sophisticated the found tools were. The author didn't decide on human-user vs. chimp-user based on the tools' sophistication. He decided based on the habitat where the tools were found.

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