การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

The extinction of the woolly mammoth has long been attributed to human overhunting. However, a growing body of evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions aligns closely with the end of the last Ice Age, when global temperatures rose rapidly. As the climate warmed, the mammoth’s steppe-tundra habitat shrank dramatically, fragmenting populations and reducing food availability. Second, genetic studies of ancient mammoth remains reveal a significant loss of genetic diversity before their final disappearance. This bottleneck indicates that populations were already declining due to environmental stress, not sudden human predation. Third, archaeological records show that human hunting of mammoths was sporadic and localized. Most kill sites are concentrated in Eurasia, yet mammoths persisted in North America and Wrangel Island for thousands of years after humans arrived, suggesting that hunting pressure was insufficient to cause extinction. Therefore, while humans may have delivered the final blow, the primary cause of mammoth extinction was climate-driven habitat loss.

🎧 การบรรยาย

The reading argues that climate change, not human hunting, caused woolly mammoth extinction. However, this view is flawed. First, the correlation between warming and extinction is weak. Mammoths survived previous interglacial periods with similar warming, so climate alone cannot explain their demise. In contrast, the arrival of highly skilled human hunters, armed with spears and coordinated strategies, coincides with extinction events on every continent, from Eurasia to North America. Second, the genetic diversity loss cited in the reading may reflect a natural population cycle, not an environmental crisis. More importantly, recent DNA evidence shows that the final surviving populations on Wrangel Island were inbreeding and genetically unhealthy, yet they disappeared only after humans colonized the island—a clear sign of hunting pressure. Third, the archaeological record is biased. Many kill sites have been lost to rising sea levels or remain undiscovered. In North America, for example, Clovis spear points have been found with mammoth remains, and new dating methods suggest that human hunting was more intensive and widespread than previously thought. Thus, the evidence strongly supports human overhunting as the primary cause, not climate change.