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Zorluk: Çok zorCommand of Evidence: Textual

In evolutionary biology, the "expensive tissue hypothesis" posits that the expansion of the hominin brain was metabolically offset by a compensatory reduction in the size of the digestive tract. Conversely, evolutionary anthropologist Dr. Alissa Chen proposes that brain expansion was primarily enabled by a behavioral transition to high-quality, energy-dense diets—such as meat and tubers—which provided the requisite caloric surplus without necessitating any anatomical reduction in gut volume. To test this hypothesis, Chen's team analyzed fossilized skeletal remains of various Pleistocene hominin species, evaluating both dental microwear complexity (where high complexity indicates the consumption of hard, brittle, or tough high-quality foods) and ribcage morphology (used to reconstruct relative gastrointestinal capacity).

Which finding, if true, would most directly support Chen's hypothesis?

  1. A
    Hominin species that showed the greatest reduction in digestive tract size, as indicated by narrow ribcages, also showed the most significant increases in cranial capacity, irrespective of their dental microwear complexity.
  2. B
    Fossils of hominin species with low dental microwear complexity showed a corresponding reduction in cranial capacity and a widening of the ribcage, indicating that low-quality diets directly prevented brain expansion.
  3. Hominin species that exhibited the most rapid increases in cranial capacity also displayed high dental microwear complexity, while their reconstructed ribcage dimensions indicated that gastrointestinal capacity remained constant or expanded.Cevap
  4. D
    Early hominins with large gastrointestinal capacities were able to migrate to diverse new environments because their dental microwear permitted the consumption of highly abrasive fallback foods when high-energy resources were scarce.

Cevap

Hominin species that exhibited the most rapid increases in cranial capacity also displayed high dental microwear complexity, while their reconstructed ribcage dimensions indicated that gastrointestinal capacity remained constant or expanded.
The correct answer directly supports Chen's hypothesis by showing that hominins undergoing rapid brain expansion consumed a high-quality diet (demonstrated by high dental microwear complexity) without experiencing a reduction in gut size (indicated by constant or expanded ribcage dimensions). This aligns perfectly with Chen's argument that dietary shifts, rather than anatomical gut reduction, offset the metabolic costs of brain expansion.

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1
Identify the core claim of Chen's hypothesis.
Chen argues that hominin brain expansion was driven by a behavioral shift to high-energy, nutrient-dense diets (reflected in high dental microwear complexity) and did not require an anatomical reduction in gut size (reflected in stable or larger gastrointestinal capacity).
This establishes the dual criteria needed for supporting evidence: evidence of a high-quality diet AND evidence of a non-reduced gut size in species with expanding brains.
2
Evaluate the relationship between the variables in the passage.
The target finding must link three variables: increasing brain size (cranial capacity), high-quality diet (high dental microwear complexity), and gut size (ribcage morphology indicating constant or expanded volume).
By checking each option against all three variables, we can eliminate options that only address one or two variables, or that show the opposite relationship.
3
Compare the options to identify the one that matches Chen's hypothesis.
The option stating that species with rapid brain growth had high microwear complexity and stable or expanded gut capacity directly supports Chen's model by showing diet quality, not gut reduction, accompanied brain expansion.
This option provides the exact textual evidence required to confirm both parts of Chen's dual claim.

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Command of Evidence: Textual
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