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Difficulty: HardIdentifying Necessary Assumptions

Biologist: The prehistoric canid *Aetocyon* must have lived and hunted in large social groups. The recent discovery of fossilized *Aetocyon* reveals that these animals had highly specialized jaw structures adapted exclusively for crushing large bones. In the modern world, bone-crushing predators such as spotted hyenas hunt in large, coordinated packs in order to take down large prey.

Which of the following are necessary assumptions on which the biologist's argument depends? (Select all that apply.)

  1. *Aetocyon* did not rely predominantly on scavenging the kills of other animals to obtain the large bones it crushed.Answer
  2. B
    *Aetocyon* lived in social groups that were identical in size and structure to those of the modern spotted hyena.
  3. A single *Aetocyon* was physically incapable of taking down the large prey animals from which the crushed bones were derived.Answer
  4. D
    Any extinct predator that possessed jaw structures adapted exclusively for crushing large bones lived and hunted in large social groups.
  5. E
    Any modern predator that hunts in a large, coordinated pack possesses jaw structures adapted for crushing large bones.

Answer

The correct statements are that the animal did not rely predominantly on scavenging, and that a single individual was incapable of taking down the large prey.
The biologist argues that because modern bone-crushing predators hunt in large packs to take down large prey, the prehistoric canid must have done the same. This reasoning relies on bridging two distinct logical gaps. First, it assumes the canid acquired large bones by hunting rather than scavenging. By applying the Negation Technique, if the animal DID rely predominantly on scavenging, the need for a large pack to take down prey is eliminated, destroying the argument. Second, the argument assumes a single animal could not take down large prey on its own. If one individual WAS physically capable of taking down large prey alone, there would be no requirement for them to hunt in large, coordinated packs, which also causes the conclusion to collapse.

Step-by-Step Solution

1
Deconstruct the argument into its core components.
Conclusion: The prehistoric animal must have lived and hunted in large social groups. Premises: It had bone-crushing jaws; modern bone-crushers hunt in large packs to take down large prey.
Identifying the exact conclusion and the supporting evidence is necessary to locate the logical gaps.
2
Identify the unstated logical leaps.
The argument leaps from 'bone-crushing jaws' to 'hunting in packs'. It assumes the animal actually hunted its own large prey instead of scavenging, and that the prey was too large for a solitary hunter.
A necessary assumption is an unstated premise that bridges a gap and must be true for the conclusion to stand.
3
Apply the Negation Technique to test the options.
Negating the correct statements causes the argument to fail. If the animal scavenged predominantly, or if it could hunt large prey alone, the conclusion that it MUST have hunted in large packs is destroyed.
The Negation Technique definitively proves whether an assumption is logically required by the argument.

Key Concept

Identifying Necessary Assumptions using the Negation Technique
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Topics

Identifying Necessary Assumptions

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