medium · Gre Verbal

Passage: For decades, the standard account held that the first inhabitants of the Americas arrived roughly 13,000 years ago, crossing an ice-free corridor that opened between retreating glaciers. Archaeological sites predating that corridor were dismissed as errors of dating or interpretation. But as such sites accumulated—some apparently thousands of years older—the burden of explanation shifted. Rather than explain away each anomalous find, researchers began to ask what alternative route could account for them, and attention turned to a coastal migration by boat along the Pacific rim, feasible even while the interior corridor remained sealed by ice. The corridor model was not so much refuted by a single decisive discovery as eroded by the steady weight of exceptions. The function of the final sentence of the passage is to:

1. Characterize how the older model lost its standing—through cumulative anomalies rather than one refutation
2. Introduce a fresh piece of archaeological field evidence not mentioned anywhere earlier in the passage
3. Concede that, on balance, the corridor model still remains the best-supported explanation available
4. Argue that the alternative coastal migration route along the Pacific rim has now been conclusively proven
5. Question whether any of the anomalous older sites cited in the passage were actually dated correctly

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