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 declines correlates more closely with climatic shifts than with human arrival. In North America, mammoth populations began to dwindle around 14,000 years ago, during a period of rapid warming, whereas humans had already been present for several thousand years. Second, genetic studies of ancient mammoth remains reveal a loss of genetic diversity just before extinction, a sign of population stress caused by habitat fragmentation, not sudden hunting pressure. Third, the ecological niche of mammoths—cold, dry grasslands—shrunk drastically as warming temperatures allowed forests and wetlands to expand, reducing their available habitat. Thus, while humans may have delivered a final blow, climate-driven habitat loss was the fundamental cause of their demise.

🎧 听力讲座

The professor challenges the reading's claim that climate change was the primary cause of woolly mammoth extinction. First, while warming occurred, similar climatic shifts had happened before without causing extinction—mammoths survived previous interglacial periods. The key difference in the latest extinction event was the presence of advanced human hunters, who used sophisticated weapons and cooperative strategies. Second, the genetic diversity loss cited in the reading can be explained by human hunting, which reduces population size rapidly and can lead to inbreeding, not necessarily habitat fragmentation. In fact, habitat fragmentation would take longer to manifest in genetic data than sudden hunting losses. Third, the habitat-shrinkage argument is flawed because mammoths were adaptable; they could migrate to cooler regions or alter their diets. However, human hunting pressure, especially targeting juvenile and female mammoths, would have had a swift and devastating impact, as seen in modern elephant populations. Therefore, overhunting, not climate, was the decisive factor.