The extinction of the woolly mammoth has long been attributed to human overhunting. However, recent evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions aligns closely with the end of the last Ice Age, when temperatures rose rapidly. Paleoclimatic data show that the warming caused dramatic shifts in vegetation, reducing the open grasslands that mammoths depended on. Second, genetic studies of mammoth remains reveal a severe population bottleneck beginning around 20,000 years ago, well before humans developed advanced hunting tools. This decline matches the onset of a cold, dry period, not human activity. Third, archaeological evidence indicates that human hunting of mammoths was sporadic. Sites with mammoth bones and tools are rare, and many bones show no cut marks, suggesting that humans scavenged rather than actively hunted. Therefore, climate-induced habitat loss, not human predation, was the decisive factor in their disappearance.
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The reading’s claim that climate change caused mammoth extinction is unconvincing. First, although warming reduced grasslands, mammoths were adaptable. Fossil pollen shows that they also fed on shrubs and herbs that expanded during interglacial periods. Moreover, mammoths survived previous warm periods, such as the Eemian, when temperatures were even higher than in the late Pleistocene. Second, the population bottleneck cited in the reading occurred at 20,000 years ago, but this was a time of global cooling, not warming. If climate were the issue, the decline should have coincided with the later warming. Instead, the final extinction occurred around 4,000 years ago on Wrangel Island, where humans arrived only shortly before the mammoths vanished. Third, the scarcity of kill sites is misleading. Humans may have used perishable weapons or hunted in ways that left few traces. In North America, the Clovis culture left distinctive spear points associated with mammoth remains, and dating shows these sites coincide with the last mammoth populations. Thus, human hunting, not climate, best explains the extinction.
📝 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.
