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Which choice best describes the relationship between the two texts?

Text 1

The "expensive tissue hypothesis" suggests an evolutionary trade-off between brain size and digestive tract mass in primates. Because metabolic energy is strictly limited, maintaining an enlarged brain necessitates a metabolic reduction in other energetically demanding organs. Proponents argue that hominins could afford larger brains only by shifting to higher-quality diets, which allowed the gastrointestinal tract to shrink and freed energy for encephalization.

Text 2

While metabolic constraints certainly shape physiology, broader comparative surveys across non-primate mammals fail to replicate the inverse correlation between brain volume and gut mass. Instead, analyses suggest that encephalization in hominins was primarily subsidized by adaptations in adipose storage and decreased muscular expenditure, which protected brain metabolism during caloric shortages. Thus, dietary-driven intestinal reduction was likely not the principal driver of human brain expansion.

Which choice best describes the relationship between the two texts?

Answer & explanation

Correct answer: C. Text 2 questions the primary mechanism proposed in Text 1 while offering alternative physiological adaptations to explain the same evolutionary outcome.

Text 1 outlines the expensive tissue hypothesis, which posits that hominin encephalization (brain expansion) was made possible by a specific trade-off: a reduction in gut mass driven by higher-quality diets. Text 2 concedes that metabolic constraints exist, but it challenges this specific trade-off by noting that comparative mammal surveys fail to find an inverse link between brain size and gut mass. Text 2 then proposes alternative adjustments (increased adipose storage and reduced muscular expenditure) to explain how hominins energetically accommodated larger brains.

Therefore, Text 2 questions the primary mechanism proposed in Text 1 while offering alternative physiological explanations for brain expansion.

Choice A is incorrect because Text 2 does not support the model in Text 1; rather, it identifies different physiological adjustments and argues that gut reduction was likely not the principal driver.

Choice B is incorrect because Text 2 explicitly concedes that "metabolic constraints certainly shape physiology"; it disputes the specific brain-gut trade-off, not the concept of metabolic constraints entirely.

Choice D is incorrect because Text 2 does not claim intestinal reduction occurred in other mammals; it states that comparative surveys across other mammals failed to find an inverse relationship between brain volume and gut mass.

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Which choice best describes the relationship between the two texts?

Which choice best describes the relationship between the two texts?

Answer & explanation

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