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Difficulty: Very hardApplying the Negation Technique

Paleontologist: The microscopic striations found on the teeth of the recently discovered Thalassodon fossil exactly match the wear patterns produced when modern marine mammals crush hard-shelled mollusks. Although no mollusk shells were found in the same geologic layer as the Thalassodon fossil, we can confidently conclude that the Thalassodon was a mollusk-eater. Consequently, the local marine ecosystem during the epoch in which the Thalassodon lived must have supported large populations of hard-shelled mollusks.

Which of the following statements, if logically negated, would fatally undermine the paleontologist's conclusion? Select all that apply.

  1. The microscopic striations observed on the Thalassodon teeth were not produced by the consumption of a type of hard-bodied prey other than mollusks.Answer
  2. The Thalassodon did not acquire its microscopic tooth striations while inhabiting a distant marine ecosystem prior to migrating to the location where its fossil was discovered.Answer
  3. C
    Modern marine mammals that exhibit identical tooth wear patterns rely on hard-shelled mollusks for the majority of their daily caloric intake.
  4. D
    Every marine species that regularly consumes hard-shelled mollusks develops microscopic tooth striations identical to those found on the Thalassodon.
  5. E
    The Thalassodon consumed exclusively hard-shelled mollusks during its lifespan, avoiding soft-bodied prey that would not leave abrasive marks.

Answer

The statements indicating that the striations were not caused by a different hard-bodied prey, and that the animal did not acquire the striations in a different ecosystem before migrating.
Applying the Negation Technique requires finding statements whose logical opposites destroy the argument's validity. If the option ruling out other hard-bodied prey is negated, it means the striations were caused by something other than mollusks. This severs the link between the tooth wear and the mollusk-eater intermediate conclusion. If the option ruling out migration is negated, it means the animal ate mollusks elsewhere and only died locally. This destroys the final conclusion that the local ecosystem supported the mollusk population.

Step-by-Step Solution

1
Analyze the argument's structure to identify the premises, intermediate conclusion, and main conclusion.
Premise: Striations match mollusk-eaters. Intermediate Conclusion: The animal was a mollusk-eater. Main Conclusion: The local ecosystem supported large populations of mollusks.
Understanding the logical chain is required before identifying the unstated assumptions bridging the gaps.
2
Identify the logical leaps between the evidence and the conclusions.
Gap 1: Assuming no other prey could cause the identical striations. Gap 2: Assuming the animal lived its whole life in the local ecosystem where it was fossilized.
Necessary assumptions operate as 'Defenders' by ruling out alternative explanations for these specific gaps.
3
Apply the Negation Technique to each option by creating its logical contradictory.
Negating the correct options results in: 'The striations WERE produced by another prey' and 'It DID acquire the striations elsewhere before migrating.'
The Negation Technique is the definitive test for evaluating necessary assumptions on the LSAT.
4
Evaluate if the negated statements destroy the argument's main conclusion.
Both negated statements independently sever the logical chain, proving they are logically strictly required for the argument to survive.
If an argument's conclusion falls apart when a statement is false, that statement was an absolutely necessary assumption.

Key Concept

Applying the Negation Technique to Defender Assumptions
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Topics

Applying the Negation Technique

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