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 with the end of the last Ice Age, when global temperatures rose dramatically. As glaciers retreated and vegetation shifted from grasslands to forests and tundra, the mammoths’ preferred habitat—open steppe—shrank, reducing their food supply. Second, genetic studies of ancient mammoth populations show that their numbers began to dwindle thousands of years before the arrival of humans in key regions like Siberia and North America. This pre-human decline indicates that climatic factors, not hunting, initiated the population crash. Third, mammoths that survived longer on isolated islands, such as Wrangel Island, exhibited signs of genetic defects and reduced fertility, consistent with a shrinking, stressed population caused by environmental deterioration rather than human pressure. These islands had no human predators until much later, yet the mammoths still went extinct. Therefore, climate-induced habitat loss and genetic decline, not human hunting, were the decisive causes of mammoth extinction.
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The reading’s argument that climate change alone drove mammoth extinction is flawed. First, while temperature rise did alter habitats, humans also played a critical role by hunting mammoths at their water sources and using fire to modify landscapes. Archaeological sites in North America contain mammoth bones with spear points embedded, proving direct human predation. Second, the genetic data cited in the reading is misinterpreted. The pre-human decline in Siberia may reflect natural population fluctuations, not a trend toward extinction. Indeed, mammoth populations rebounded during brief cold periods, only to crash when humans with advanced weapons appeared. Third, the Wrangel Island case actually supports human involvement: the island’s mammoths survived until about 4,000 years ago, well after the mainland extinctions, but they disappeared shortly after the first humans arrived on the island. The genetic defects observed are more likely the result of a small founding population, not a slow climate-driven decline. In fact, paleoclimate records show that Wrangel Island’s environment remained stable and suitable for mammoths during their final centuries. Thus, the timing of human arrival, not climate, best explains the final extinction of these isolated populations.
📝 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.
