托福综合写作

📖 阅读文章

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 more closely with the end of the last Ice Age (about 10,000 years ago) than with the arrival of human hunters in North America, who appeared around 13,000 years ago. If humans were the main cause, mammoth populations should have crashed immediately after human arrival, yet they persisted for thousands of years. Second, the habitat of the mammoth—the mammoth steppe—was replaced by dense forests and wetlands as the climate warmed, reducing the open grassland that mammoths depended on for food. Fossil pollen records show that this vegetation shift occurred rapidly, and mammoth fossils are rare in post-glacial forest layers. Third, mammoth teeth and bones from the late Pleistocene show signs of nutritional stress, such as decreased tooth size and increased enamel defects, indicating that food scarcity, not hunting, weakened the populations before their final disappearance. Therefore, although humans may have delivered the final blow, the ultimate cause of extinction was the climate-induced loss of their grassland ecosystem.

🎧 听力讲座

The reading's argument that climate change alone drove the woolly mammoth to extinction is flawed. While it is true that human hunters arrived in North America long before the mammoths disappeared, this does not rule out overhunting. In fact, archaeological sites show that human hunting increased dramatically after 12,000 years ago, exactly when mammoth populations began to collapse. The reading also claims that habitat loss was critical, but this ignores the fact that smaller pockets of grassland persisted in refuges, and fossil evidence shows that mammoths could survive in mixed woodland environments if not overexploited. For example, mammoth remains found on islands like Wrangel Island, where climate changed but humans were absent until later, survived for thousands of years after the mainland extinctions—proving that climate alone was not sufficient. Finally, the signs of nutritional stress cited in the reading are not conclusive; similar stress markers appear in populations that are overcrowded or hunted heavily, because hunting disrupts social structures and forces animals into suboptimal feeding areas. Thus, the lecture argues that human hunting, not climate, was the decisive factor, and the reading's evidence is interpretable in a way that supports overhunting.