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 islands in question formed long 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 number of animal species that inhabit the islands are not found in the Americas.', 'Genetic analysis indicates that the iguana species on the islands are different in several respects from those found in the Americas.', 'The lineages of numerous plant and animal species found in Australia or in South America date back to a period prior to the fragmentation of Gondwana.', 'Fossils of iguana species closely related to those that inhabit the islands have been found in Australia.']