Logical Reasoning

PT124 · S2 · Q22 Paleontologists recently discovered teeth from

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Paleontologists recently discovered teeth from several woolly mammoths on an isolated Arctic island where no mammoth fossils had previously been found.

Conclusion (Therefore)

Wooly mammoths that lived on the island were smaller on average than those who lived elsewhere.

Evidence

We'll assume that the teeth are representative of wooly mammoths on that island.

The teeth of the wooly mammoths that we found were 25% smaller than average adult mammoth teeth, but they are clearly adult mammoth teeth.

Evaluate

The conclusion is a comparison — we're trying to prove that mammoths on the island were smaller on average than were mammoths off the island.

Our evidence is simply that we collected some teeth, and those were 25% smaller than typical mammoth teeth.

So our author is just assuming,

Goal

Look for something that allows to go from teeth were 25% smaller to being able to conclude the mammoths themselves were smaller

22.

Which one of the following, if assumed, would allow the conclusion to be properly drawn?

  1. Neither tooth size nor overall

    No Impact

    This is like the wishy-washy trap answer on so many Strengthen / Weaken tasks where it states an empty truth like - things differ - things fluctuate - changes happen No one thinks that tooth or body size would every be 100% uniform (i.e. totally identical) across all adult members of any species. So this answer is telling us nothing more than a hollow truth we all know from common sense.

    5% picked this

  2. The tooth wear that naturally

    Unrelated to Goal

    This answer is not allowing us say "smaller teeth proves smaller mammoth", which is our task on this question. The fact that this is ruling out an idea with the word "not" should make us think, "What is this doing, selling us some Necessary Assumption like we don't know what question type we're doing?"

    5% picked this

  3. Unusually small mammoth teeth found

    Weakens, if anything

    All this does is make it seem like usually when we find smaller teeth it's not from an adult. That wouldn't help the author. He has asserted that the small teeth we found on this island are from an adult, and he needs that to be true because he's using it to conclude that adults on the island were smaller mammoths than were adult mammoths elsewhere.

    2% picked this

  4. Correct

    Tooth size among adult woolly

    Why this is right

    This allows us to say that "smaller teeth proves smaller mammoth", since tooth size and overall size are always directly proportional. If the teeth were 25% smaller, than the mammoths were 25% smaller, thus proving the author's conclusion.

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

    84% picked this

  5. Woolly mammoths of the kind

    No Impact: number / variety

    We don't really care whether the island mammoths had the same assortment of teeth that non-island mammoths had. We only care about whether we're allowed to go from noticing "their teeth were smaller" to concluding "their whole bodies were smaller".

    3% picked this

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