การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

The extinction of the woolly mammoth has long been attributed to human hunting, but recent evidence suggests that climate change was the primary driver. First, the timing of mammoth decline coincides with the end of the last Ice Age, when global temperatures rose rapidly. As the climate warmed, the vast grasslands known as the mammoth steppe shrank, reducing their primary food source. Second, genetic studies of ancient mammoth remains show a severe population bottleneck around 20,000 years ago, well before the peak of human hunting activity. This suggests that environmental stress, not hunting, caused the population to crash. Third, human populations in the Arctic were sparse and relied mainly on small game, as evidenced by archaeological sites that contain few mammoth bones. If humans had been the main predators, we would expect more evidence of mammoth hunting, such as spear points embedded in bones or butchery sites.

🎧 การบรรยาย

The reading's claim that climate change alone drove mammoth extinction is flawed. While warming did alter habitats, humans played a decisive role. First, the timing argument is misleading: mammoth populations survived several earlier interglacial warm periods, so warming alone cannot explain their final extinction. In contrast, the arrival of humans in the Americas and Siberia correlates precisely with extinctions. Second, the genetic bottleneck cited actually occurred when humans first entered the region, not before—recent DNA evidence places the bottleneck at 15,000 years ago, matching human expansion. Third, the scarcity of mammoth bones at archaeological sites does not prove negligible hunting. Humans likely used mammoth carcasses efficiently, leaving few traces, or hunted younger animals that were easier to kill, whose bones are less likely to be preserved. Moreover, known kill sites, such as the Clovis sites in North America, show clear evidence of mammoth hunting, including projectile points embedded in ribs. Thus, human hunting, not climate, was the critical factor.