托福综合写作

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The extinction of the woolly mammoth has long been attributed to overhunting by early humans, but recent evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions correlates more closely with climatic shifts than with human expansion. In North America, mammoths disappeared around 10,000 years ago, during a period of rapid warming and vegetation change, while human populations were already present for millennia. Second, the dietary specialization of mammoths made them vulnerable to climate-induced habitat loss. Stable isotope analyses of mammoth bones reveal a diet composed almost exclusively of cold-adapted grasses and sedges. As temperatures rose, these plants were replaced by shrubs and trees, reducing the mammoth’s food supply. Third, the pattern of extinction across different regions supports a climate cause. Mammoths survived on Wrangel Island until 4,000 years ago, long after humans arrived in nearby mainland areas, but exactly when the island’s vegetation shifted due to sea-level rise. In contrast, human hunting pressure would have been more intense on small islands due to limited escape routes, yet the Wrangel population persisted. Thus, while human hunting may have contributed locally, the overwhelming evidence points to climate change as the decisive factor in the mammoth’s demise.

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The reading’s argument that climate change alone drove the woolly mammoth to extinction is flawed. First, the correlation between climate and extinction is not as tight as claimed. For example, in Eurasia, mammoth populations declined sharply around 15,000 years ago, coinciding with the arrival of highly skilled human hunters, not with a major climatic event. The warming that supposedly killed them occurred later and was gradual, allowing many large herbivores to adapt. Second, the isotope evidence does not prove dietary inflexibility. Modern elephants, close relatives of mammoths, switch their diets seasonally and when food availability changes. In fact, fossilized mammoth dung from Alaska contains pollen from shrubs and trees, indicating that they consumed a broader range of plants when grasses were scarce. Thus, habitat change alone would not have caused starvation. Third, the Wrangel Island case actually undermines the climate argument. The island’s vegetation did not shift drastically until after the mammoths disappeared around 4,000 years ago. Moreover, archaeological evidence shows that humans reached Wrangel Island approximately 3,600 years ago, just a few centuries before the last mammoths vanished. This timing suggests that hunting, not climate, delivered the final blow to a small, vulnerable population. In sum, the reading overstates climate’s role and ignores key evidence that human hunting was the critical factor.