Perkins: According to an article I read, the woolly mammoth's extinction in North America coincided with a migration of humans onto the continent 12, 000 years ago, and stone spearheads from this period indicate that these people were hunters. But the author' s contention that being hunted by humans contributed to the woolly mammoth's extinction is surely wrong since, as paleontologists know, no spearheads have ever been found among the many mammoth bones that have been unearthed. Which of the following, if true, provides the strongest reason for discounting the evidence Perkins cites in arguing against the contention that being hunted by humans contributed to the North American extinction of woolly mammoths? ['Cave paintings in North America that date from 12, 000 years ago depict woolly mammoths as well as a variety of other animals, including deer and buffalo.', 'Because of the great effort that would have been required to produce each stone spearhead, hunters would have been unlikely to leave them behind.', 'At sites where mammoth bones dating from 12, 000 years ago have been unearthed, bones of other mammals have rarely been found.', 'The stone from which stone spearheads were made is unlikely to have disintegrated over the course of 12, 000 years.']