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Difficulty: MediumPrimary Purpose of the Whole Text

For years, evolutionary biologists assumed that the domestication of dogs (*Canis lupus familiaris*) from wolves was driven primarily by shared hunting behaviors and social bonding. However, recent genomic analyses have revealed a crucial genetic shift: domestic dogs possess significantly more copies of the *AMY2B* gene, which codes for amylase, an enzyme that breaks down starch. While wolves carry only 22 copies of this gene, domestic dogs can have up to 3030. This genetic expansion suggests that the transition of dogs from wild carnivores to domesticated companions was heavily dependent on their ability to digest starch-rich agricultural waste. By highlighting this metabolic adaptation, geneticists have reframed dog domestication not just as a behavioral alignment, but as an evolutionary response to the rise of human agriculture.

Which choice best states the main purpose of the text?

  1. A
    It argues that behavioral alignment between wolves and humans was the primary driver of canine domestication.
  2. B
    It suggests that early agricultural societies intentionally bred wolves with high amylase levels.
  3. It discusses genomic research suggesting dog domestication was facilitated by a metabolic adaptation to agricultural diets.Answer
  4. D
    It explains the biochemical mechanism by which the AMY2B gene produces amylase in domestic dogs.

Answer

The correct answer explains that the text discusses genomic research suggesting dog domestication was facilitated by a metabolic adaptation to agricultural diets.
The correct answer accurately states the main purpose of the text. The passage describes how genomic research has identified a significant increase in the copies of the AMY2B gene in domestic dogs compared to wolves, and explains that this metabolic adaptation allowed dogs to digest starch-rich agricultural waste, thereby reframing the narrative of dog domestication as an evolutionary response to agriculture.

Step-by-Step Solution

1
Analyze the passage structure and identify the transition.
The text begins with a traditional assumption (behavioral alignment) and introduces new genomic evidence (multiplication of the AMY2B gene) to argue that dog domestication was linked to dietary adaptation.
Recognizing the shift from the old assumption to the new genomic findings helps identify the primary message the author wants to convey.
2
Evaluate the choices against the overall argument.
The option concerning genomic research and metabolic adaptation captures the synthesis of the genetic findings and their evolutionary implications for domestication. Other options either repeat the old assumption, focus on narrow biochemical details, or make unsupported speculations.
The correct option must summarize the entire text's main purpose rather than a supporting detail or introductory premise.

Key Concept

Primary Purpose of the Whole Text
Estimated Time:1m 30s
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Primary Purpose of the Whole Text

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