GMAT Critical Reasoning (CR) | Scientist: A small group of islands near Australia is inhabited

Scientist: A small group of islands near Australia is inhabited by several species of iguana; closely related species also exist in the Americas, but nowhere else. The slands in question formed Jong after the fragmentation of Gondwana, the ancient supercontinent that included present-day South America and Australia. Thus, these species' progenitors must have rafted on floating debris across the Pacific Ocean from the Americas.

Which one of the following, if true, most weakens the scientist's argument?

(A)
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