การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

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 the end of the last Ice Age, when global temperatures rose dramatically. As the ice retreated, the vast, dry steppe grasslands that mammoths depended on were replaced by dense forests and wetlands, reducing their food supply. Second, genetic studies of mammoth populations show a severe decline in genetic diversity long before humans arrived in their final strongholds, such as Wrangel Island. This bottleneck indicates that populations were already stressed by habitat fragmentation, not by sudden hunting pressure. Third, archaeological records reveal that human hunting of mammoths was sporadic and localized. Clovis spear points, for example, are found at only a few kill sites, and these sites are concentrated in North America, whereas mammoths also vanished from unpopulated regions like the Arctic islands. Thus, climate-driven habitat loss, not human hunters, best explains their demise.

🎧 การบรรยาย

The reading's argument that climate change alone drove mammoth extinction is flawed. While it is true that warming altered habitats, mammoths were highly adaptable and had survived previous interglacial periods with similar temperature rises. The crucial difference in their final extinction was the presence of modern humans. First, the genetic bottleneck the reading cites actually supports the overhunting hypothesis: populations were already small and vulnerable, and even modest hunting could push them over the edge. On Wrangel Island, mammoths persisted for thousands of years after the climate stabilized, only disappearing around 4,000 years ago—coinciding with the arrival of human settlers. Second, the reading downplays the efficiency of human hunting. Kill sites may be rare because mammoth bones were often transported for tool making, and hunting could have been focused on juveniles or vulnerable individuals, leaving few archaeological traces. Third, the correlation between human expansion and mammoth extinction is striking: mammoths vanished from every continent shortly after humans arrived, including Siberia and the Americas, while regions like the Arctic islands, which the reading claims were unpopulated, actually show evidence of early human occupation. Therefore, overhunting, perhaps in combination with climate stress, was the decisive factor.