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 extinctions aligns more closely with climatic shifts than with human expansion. Radiocarbon dating shows that most populations disappeared during the Younger Dryas, a period of abrupt cooling, while human hunters had already been present for millennia without causing major declines. Second, genetic studies of ancient mammoth remains reveal a severe loss of genetic diversity well before human populations reached peak hunting pressure. This bottleneck indicates that climate-induced habitat fragmentation shrank their populations, making them vulnerable to stochastic events. Third, the final refugia of woolly mammoths, such as Wrangel Island, experienced a dramatic warming event shortly before their disappearance, which would have altered vegetation composition and reduced their preferred steppe-tundra habitat. In contrast, human presence on these remote islands was sparse and late, making overhunting an unlikely cause. Therefore, while humans may have delivered a final blow to small, isolated herds, the primary cause of extinction was environmental change.
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The reading's argument that climate change alone drove mammoth extinction is flawed. While the Younger Dryas was cold, mammoths had survived many previous glacial-interglacial cycles, so cooling itself was not fatal. Moreover, the genetic diversity decline cited in the reading actually supports the overhunting hypothesis: as human hunters targeted the largest individuals, they disrupted social structures and reduced breeding success, leading to a rapid genetic bottleneck—not a slow climate-driven decline. The timing of human arrival, not climate, matches the extinction wave across continents: in Eurasia, mammoths vanished as modern humans spread; in North America, they disappeared shortly after Clovis hunters arrived. The Wrangel Island example is misleading: though warming did occur, the island’s vegetation remained suitable for centuries, and the final extinction coincided with the first evidence of human presence on the island, including butchered bones. Furthermore, climate models show that the habitat changes were gradual, giving mammoths time to adapt, whereas human hunting was sudden and unsustainable. Thus, the evidence points to human overhunting as the decisive factor, with climate playing only a minor, secondary role.
📝 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.
