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Difficulty: Very hardRuling Out Alternate Explanations (Defender)

Archaeologist: The abandonment of the thriving ancient settlement of Kelior is generally attributed to a century-long regional drought. However, isotopic analysis of soil strata indicates that less than a decade before the abandonment, Kelior's farmers abruptly transitioned from cultivating teff, a highly drought-resistant grain, to a variety of water-intensive marsh-rice. Therefore, it was actually this ill-advised agricultural pivot, rather than the drought alone, that precipitated the settlement's collapse by engineering a catastrophic famine.

The archaeologist's argument relies on which one of the following assumptions?

  1. The regional drought was not so extreme that it would have caused a catastrophic famine at Kelior even if the farmers had continued cultivating teff exclusively.Answer
  2. B
    If the farmers of Kelior had maintained their cultivation of teff, the settlement would not have been abandoned during the century-long drought.
  3. C
    The farmers of Kelior did not transition to cultivating water-intensive marsh-rice in a desperate, albeit misguided, attempt to counteract the early effects of the drought.
  4. D
    The variety of marsh-rice adopted by the Kelior farmers did not yield significantly more calories per acre than teff during periods of adequate rainfall.
  5. E
    The catastrophic famine that precipitated the settlement's collapse began immediately following the first failed harvest of the water-intensive marsh-rice.

Answer

The assumption that the drought was not severe enough to destroy the drought-resistant teff crops.
In this argument, the author attempts to shift the blame for a historical famine from an external factor (a drought) to an internal factor (an agricultural pivot). To successfully argue that the pivot, 'rather than the drought alone', was the cause, the author must inherently assume that the drought was not independently capable of causing the exact same catastrophic outcome. If the drought would have decimated the highly resistant teff anyway, the farmers' ill-advised pivot to rice was irrelevant to their ultimate fate. Therefore, the argument depends on the assumption that the drought was not extreme enough to destroy the original crops.

Step-by-Step Solution

1
Identify the main conclusion of the argument.
The conclusion is that the agricultural pivot to marsh-rice, rather than the drought alone, precipitated the settlement's collapse by causing a famine.
Understanding the exact causal claim is necessary to evaluate what the author must assume to make this claim.
2
Identify the premises supporting the conclusion.
1. Kelior faced a century-long drought. 2. Shortly before abandonment, farmers switched from drought-resistant teff to water-intensive marsh-rice.
Premises provide the foundation; the assumption must bridge the gap between these facts and the causal conclusion.
3
Anticipate alternate explanations (weaknesses) in the causal claim.
What if the drought was incredibly severe—so apocalyptic that no crop, not even the highly resistant teff, could have survived? If that were true, the crop pivot didn't matter; the drought alone caused the famine.
A 'Defender' assumption works by explicitly ruling out a potential weakness or alternate explanation that would destroy the argument.
4
Apply the Negation Technique to the correct option.
Negated correct answer: The drought WAS so extreme it would have caused a famine even if they cultivated teff. This directly contradicts the conclusion that the pivot, rather than the drought alone, caused the famine.
The Negation Test is the definitive proof for a Necessary Assumption question. If negating the choice destroys the argument, it is the correct answer.

Key Concept

Necessary Defender Assumptions in Causal Arguments
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Topics

Ruling Out Alternate Explanations (Defender)

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