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 extinctions correlates with rapid warming periods, not with human expansion. For instance, populations on Wrangel Island survived until 2000 BCE, long after humans arrived in the region, but disappeared shortly after a dramatic shift in vegetation. Second, genetic studies show that mammoths experienced a severe population bottleneck before human contact, indicating that environmental stress had already reduced their numbers. Finally, stable isotope analyses of mammoth bones reveal a dietary shift toward less nutritious plants, consistent with the loss of productive grasslands due to rising sea levels and increased humidity. These factors collectively point to climate-induced habitat loss as the decisive cause.

🎧 听力讲座

The lecture challenges the reading's claim that climate change alone drove mammoth extinction. While climate shifts did alter habitats, human hunting played a synergistic and more direct role. First, the survival of Wrangel Island mammoths until 2000 BCE actually supports human overhunting—they persisted because the island was inaccessible to early hunters, but when seafaring humans finally arrived, they vanished within a few centuries. Second, genetic bottlenecks can result from many causes, including volcanic eruptions or disease, not necessarily climate; moreover, similar bottlenecks are seen in other megafauna that survived, like bison, so they are not unique indicators of climate stress. Finally, dietary shifts toward less nutritious plants may reflect competition with other herbivores, not climate-driven vegetation loss; in fact, archaeological sites show cut marks on mammoth bones alongside spear points, and population models indicate that even low-level hunting could tip small, climate-stressed populations into extinction. Thus, the reading overlooks the direct evidence of human predation.