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Difficulty: Very hardIdentifying Underlying Assumptions

Dendrochronological analysis of 14th-century oak timber beams extracted from agricultural granaries across Northern Europe demonstrates a pronounced, three-decade narrowing of annual growth rings between 1315 and 1345. Historians argue that this growth contraction indicates a severe, region-wide prolonged drought during those decades, which directly triggered the widespread grain harvest failures and subsequent famines recorded in monastic chronicles of the era.

Which of the following is an assumption on which the historians' argument depends?

  1. The oak trees harvested for the granary timbers were not grown predominantly in specialized microclimates where annual ring width was determined primarily by environmental factors other than regional precipitation levels.Answer
  2. B
    Monastic chronicles from the early 14th century provide a more reliable quantitative account of agricultural yields than do dendrochronological records from nearby living trees.
  3. C
    Severe grain harvest failures in 14th-century Northern Europe occurred exclusively in regions where oak growth rings exhibited a marked reduction in width during the same decade.
  4. D
    The prolonged drought between 1315 and 1345 was caused by atmospheric circulation shifts that simultaneously altered precipitation patterns across Southern Europe.
  5. E
    The construction rate of agricultural granaries increased significantly throughout Northern Europe during the period of narrow ring formation between 1315 and 1345.

Answer

The argument depends on the assumption that the oak trees used for granary timbers were not grown predominantly in specialized microclimates where ring width was governed primarily by factors other than precipitation levels.
The correct answer isolates a fundamental unstated premise: that narrow ring width in the analyzed timbers actually reflects regional rainfall deficits rather than local non-precipitation variables. Under the Negation Test, if the harvested trees grew in microclimates controlled by temperature, frost, or soil conditions, the narrow rings would cease to serve as evidence of drought, completely invalidating the historians' conclusion.

Step-by-Step Solution

1
Identify the argument's premises and conclusion.
Premise: Granary oak timbers show narrow rings between 1315 and 1345. Conclusion: This ring narrowing indicates a severe regional drought that caused grain harvest failures.
Establishing the explicit premise-to-conclusion path reveals the unstated logical gap.
2
Identify the core logical gap in the causal leap.
The author assumes that ring width in these specific harvested trees directly measures regional precipitation, assuming no confounding environmental factors caused the narrow rings.
If non-precipitation factors caused the narrow growth rings, the inference connecting narrow rings to drought collapses.
3
Apply the Negation Test to the correct choice.
Negating the statement yields: 'The oak trees WERE grown predominantly in microclimates where ring width was determined primarily by factors other than precipitation.'
If this negated premise is true, narrow rings reflect temperature or soil anomalies rather than drought, completely undermining the historians' argument.

Key Concept

Identifying Necessary Assumptions via the Negation Test
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Topics

Identifying Underlying Assumptions

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