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 decline correlates closely with the rapid warming at the end of the last Ice Age (around 10,000 years ago), not with the arrival of human hunters, who had coexisted with mammoths for millennia in many regions. Second, warming caused dramatic habitat loss: mammoths relied on dry, cold steppe grasslands, but as temperatures rose, these areas were replaced by dense forests and wetlands, reducing available forage and fragmenting populations. Third, genetic studies of mammoth remains show a severe loss of genetic diversity just before extinction, indicating small, isolated populations that were vulnerable to inbreeding and disease—a pattern consistent with climate-induced habitat fragmentation, not a sudden human onslaught. Therefore, while human hunting may have delivered a final blow in some areas, the overarching cause of extinction was environmental change.

🎧 การบรรยาย

The reading’s argument that climate change alone drove mammoth extinction is unconvincing. First, the timing argument is flawed: humans did not arrive in many high-latitude regions until after the climate had already warmed, but mammoths survived there for thousands of years after that warming. For example, on Wrangel Island, mammoths persisted until 4,000 years ago, long after the warm period began—so warming itself did not immediately kill them. Second, while habitat did change, mammoths were adaptable: fossil evidence shows they could survive in varied environments, including forest edges, and their diet included shrubs and other plants, not solely steppe grasses. Moreover, some of the areas that remained steppe-like still saw extinction when humans arrived. Third, the genetic bottleneck observed can be explained by human hunting: overhunting reduces populations rapidly, causing a genetic crash even without habitat fragmentation. In fact, many island populations that survived climate shifts went extinct soon after human colonization, strongly implicating hunting. Thus, the evidence points to humans as the decisive factor, with climate playing only a minor role.