TOEFL統合ライティング

📖 読解文章

The extinction of the woolly mammoth, which occurred approximately 4,000 years ago, has long intrigued scientists. While some argue that human hunting was the primary cause, a closer examination of the evidence suggests that climate change was the decisive factor. First, the timing of the mammoth’s extinction aligns closely with the end of the last Ice Age, when global temperatures rose dramatically. This warming transformed the vast, dry steppe grasslands—the mammoth’s primary habitat—into wetter, forested landscapes, reducing their food supply and exposing them to new diseases. Second, archaeological evidence indicates that early human populations, such as the Clovis culture in North America, did not hunt mammoths intensively; only a few kill sites have been found, and these suggest sporadic rather than systematic hunting. Finally, the mammoth’s closest living relatives, elephants, have survived despite being hunted by humans for millennia, implying that hunting pressure alone is insufficient to drive a species to extinction. Thus, the woolly mammoth’s demise was most likely a consequence of environmental shifts that outpaced their adaptive capacity.

🎧 リスニング講義

The lecture challenges the reading’s claim that climate change was the primary cause of woolly mammoth extinction. While climate change may have played a role, the evidence strongly implicates human hunting. First, the timing argument is flawed: the mammoth’s extinction occurred not at the peak of warming but thousands of years later, when climates had stabilized. For example, mammoths survived on Wrangel Island for 5,000 years after the Ice Age ended, indicating they could adapt to warmer conditions. Second, the reading underestimates human hunting pressure. Archaeological findings from Siberia and Alaska show numerous mammoth carcasses with clear signs of spear wounds and butchering marks, and these sites are clustered at times when human populations expanded. Moreover, the lack of extensive kill sites may reflect taphonomic bias—many hunting sites were likely on land that is now submerged due to sea-level rise. Finally, the comparison with elephants is misleading: elephants face severe threats from poaching today, and many populations have been driven to local extinction, demonstrating that humans can indeed decimate large mammals. Therefore, the lecture concludes that overhunting by humans, not climate alone, was the decisive factor in the mammoth’s disappearance.