The extinction of the woolly mammoth has long been attributed to human overhunting, but recent evidence suggests that climate change was the primary driver. First, the timing of mammoth decline correlates closely with the end of the last Ice Age, when global temperatures rose rapidly. As the ice retreated, the steppe-tundra habitat that mammoths relied on shrank dramatically, reducing their food supply. Second, genetic studies show that mammoth populations experienced severe bottlenecks long before humans arrived in their final refuges, indicating that climate-driven habitat loss had already weakened the species. Third, on Wrangel Island, where mammoths survived until 4,000 years ago, the population was isolated and small, yet human presence was minimal. This suggests that even without significant hunting, the changing climate—such as increased precipitation and shrub encroachment—doomed the island population.
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The lecture challenges the reading's claim that climate change alone caused mammoth extinction. While climate change may have contributed, human hunting was decisive. First, the correlation between habitat loss and extinction is weak. Mammoths had survived multiple interglacial warm periods before, so warming alone cannot explain their demise. Instead, the rapid expansion of human hunters across Eurasia and North America precisely matches the timing of mammoth disappearances. Second, the genetic bottlenecks mentioned in the reading actually occurred after humans had already begun hunting mammoths, not before. Moreover, bottlenecks can result from overhunting, not just habitat fragmentation. Third, the Wrangel Island case is misleading. Although human population was small, even occasional hunting by a few hunters could have pushed a tiny, already stressed population over the edge. In fact, archaeological evidence shows that humans did visit Wrangel Island during the mammoth's final centuries, and their hunting may have been the final blow.
📝 写作提示 Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
