PrepTest 150

Topic: Science

Paragraph 1

• Paragraph note
  • Old belief (cooking didn't change our anatomy) vs. new belief (our anatomy evolved to require cooking)
• Views, minor Meta-Structures, and the author's attitude
  • Old view:
    • Cooking didn't lead to any anatomical changes because cooking doesn't require adaptations (first and second sentence)
    • Cooking didn't affect our evolution because the practice is too recent (sixth sentence)
  • New view
    • We can only subsist on raw food in unusual circumstances, which suggests we evolved to need cooking to consume high-calorie diets efficiently (third, fifth, eighth, and last sentences)
    • There's evidence of cooking 250,000 years ago, so cooking is ancient enough to affect our anatomy (seventh sentence)
  • Example of a rare situation in which we could subsist on a raw diet:
    • Relatively sedentary lifestyle in a well-supported urban environment (third sentence)
  • Cause-and-effect relationship:
    • Cooking caused humans to consume high-calorie diets efficiently (eighth sentence)
    • Natural selection for the humans who used high-calorie diets efficiently caused an inability to survive on raw-food diets (last sentence)
  • Author's attitude: "might reasonably have been expected" (first sentence); "Important theoretical obstacles" (fourth sentence); "so evolutionarily constrained" (fifth sentence); "appears to be wrong" (sixth sentence)

Paragraph 2

• Paragraph note
  • Hypothesis: Cooking led to smaller tooth and jaw size
• Views, minor Meta-Structures, and the author's attitude
  • Cause-and-effect relationships, according to the author:
    • Cooking caused smaller tooth and jaw sizes about 100,000 years ago (second through fourth sentences)
    • Also possible that the evolution of Homo ergaster 1.9 million years ago caused smaller tooth and jaw sizes, and new cooking techniques like boiling caused the reduction of tooth and jaw size 100,000 years ago (fifth and last sentences)
  • Author's attitude:
    • "Important questions" (first sentence); "we suggest" (third sentence); "brodly explicable" (fourth sentence); "also posssible" (fifth sentence); "may prove" (last sentence)

Paragraph 3

• Paragraph note
  • Hypothesis: Cooking led to a different digestive system
• Views, minor Meta-Structures, and the author's attitude
  • Comparison:
    • Humans' digestive systems are different from other great apes, traditionally explained as an adaptation to a diet high in raw meat (second sentence)
    • Examples of differences between human and ape digestive systems:
      • Humans have smaller guts, longer small intestines, and smaller colons than other great apes (third sentence)
    • Cause-and-effect relationship, according to the author:
      • A high-calorie diet caused the differences in humans' digestive systems (fourth sentence)
      • Therefore, cooking may have caused the differences in humans' digestive systems (fifth sentence)
    • Author's attitude: "harder to reconstruct" (first sentence); "may therefore be at least as well explained" (fourth sentence); "therefore warranted" (last sentence)

Main Point: Current evidence suggests that cooking changed humans' evolutionary history and led to an inability to survive on a raw-food diet in most circumstances.

Paragraph 1, Sentences 8-9 (P1, S8-9) - Author's central hypothesis

P2, S3 - Author's sub-hypothesis #1

P3, S4 - Author's sub-hypothesis #2

Proposing a Hypothesis: We think this passage best fits the Proposing a Hypothesis Meta-Structure. In such a passage, the author typically makes a prediction or offers an untested explanation of a phenomenon*. The author might also posit questions that need to be addressed before the explanation can be accepted or rejected.

This passage follows this progression closely. The author relays some recent evidence that has overturned old beliefs about cooking and the human anatomy before offering the central hypothesis: cooking changed humans' evolutionary history and led to an inability to survive on a raw-food diet in most circumstances (P1, S5-9). The author uses the remaining paragraphs to describe two sub-hypotheses. The author thinks that cooking may have caused smaller tooth and jaw sizes (P2, S3) and changed the human digestive system (P3, S4). The author also describes some questions that still need to be addressed (P2, S6; P3, S5).

In a Proposing a Hypothesis passage, the main point is generally the author's central hypothesis. This author summarizes the central hypothesis at the end of the first paragraph. We further condensed that main point to: "Current evidence suggests that cooking changed humans' evolutionary history and led to an inability to survive on a raw-food diet in most circumstances."

*Some test-takers may believe this is a Phenomenon/Explanation passage. Such a designation would be OK if they didn't conclude that the author is certain of the explanations in this passage. Typically, we want to reserve the Phenomenon/Explanation Meta-Structures for passages that describe one or more tested explanations that have been accepted or rejected. Note how, in this passage, the author qualifies the explanations with phrases that reveal the explanations have not yet been fully tested or accepted ("we suggest" (P1, S9); "also possible" (P2, S5); "may prove to" (P2, S6); "may therefore be at least as well explained" (P3, S4)).

Causality: As is the case in many science-themed passages, Causality is the predominant minor Meta-Structure in this passage. In fact, the author's main point is causal: cooking caused changes in humans' ability to subsist on raw food. When the main point is causal, we can expect several other causal premises to bolster that main point. We've summarized all the cause-and-effect relationships in the Passage Summary. However, to answer questions quickly and confidently, it's helpful to understand the three central relationships:

• Cooking caused humans to eat high-calorie diets efficiently, which caused an inability to subsist on raw diets (P1, S8-9)
• Cooking may have also caused smaller tooth and jaw sizes around 100,000 years ago (P2, S3)
• Cooking may have also caused changes in humans' digestive systems (P3, S4).

Like the diet that cooking enabled, the first paragraph is dense and hearty. The author gives us a lot of information in that paragraph. If we didn't stop to consider how each of the pieces fit together, we may have had trouble understanding the rest of the passage, which would affect our ability to discern the main point, author's attitude, and Meta-Structure. If you had trouble understanding how the evidence about raw food and "earth ovens" related to the old beliefs about cooking and evolution or to the author's hypothesis, you may have read the first paragraph too quickly.

Remember, these passages want to convey a lot of information in as little space as possible. Each sentence has a vital role in the passage's overall argument. While we don't need to be an expert in every sentence, we should at least understand how the sentences form a coherent whole. If you had trouble appreciating the big-picture in this passage, consider slowing down and pausing to reflect on the passage's overall after each sentence or when you reach "pivot" words (like "However" in the third sentence or "Furthermore" in the sixth).