The extinction of the woolly mammoth has long been attributed to human overhunting. However, a closer examination of the evidence suggests that climate change was the primary driver. First, the timing of the mammoth’s decline coincides with the end of the last Ice Age, when global temperatures rose dramatically. This warming caused the mammoth’s grassland habitat, known as the mammoth steppe, to shrink and be replaced by forests and tundra, which offered less nutritious forage. Second, isotopic analysis of mammoth bones shows a sudden shift in diet just before extinction, indicating that they were forced to eat less favorable plants, likely due to habitat degradation. Third, human populations in Siberia and North America at that time were small and sparsely distributed, and their hunting tools—spears and arrows—were unlikely to have caused a rapid extinction of such a large, wide-ranging species. In contrast, the climate-driven loss of the steppe ecosystem would have fragmented mammoth populations, reducing their numbers and making them vulnerable to eventual extinction.
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The reading’s argument that climate change, not human hunting, drove the mammoth’s extinction is unconvincing. First, while the climate did warm, the mammoth steppe did not disappear uniformly. Paleobotanical evidence shows that pockets of grassland persisted in many regions, particularly in northern Siberia and Alaska, until well after the mammoth’s extinction. So mammoths had suitable habitat available. Second, the isotopic shift in bones does not necessarily indicate climate stress. Recent studies of modern elephants show that similar isotopic changes occur when populations are under pressure from hunting, as they alter their ranging behavior and diet. In fact, the isotopic change in mammoths appears abruptly, coinciding with the arrival of humans in each region, not with gradual climate shifts. Third, the claim that human populations were too small to cause extinction ignores the effectiveness of hunting. Even a few humans could drive mammoths to extinction by targeting juveniles and females, as seen in historical overhunting of other megafauna like the moa in New Zealand and the Steller’s sea cow. Moreover, the archaeological record shows numerous kill sites with mammoth bones, indicating that hunting was frequent and impactful. Thus, the evidence points to humans, not climate, as the primary cause.
📝 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.
