TOEFL統合ライティング

📖 読解文章

The extinction of the woolly mammoth has long been attributed to human overhunting. However, recent evidence suggests that climate change was the primary driver. First, the warming period at the end of the Pleistocene drastically reduced the mammoth's grassland habitat. Pollen records from Siberia and Alaska show a shift from dry steppe to wet tundra, which would have diminished the food supply. Second, the timing of extinction varies by region, with populations persisting on remote islands like Wrangel Island until 4,000 years ago—thousands of years after humans arrived. If overhunting were the main cause, these isolated populations would have been wiped out quickly. Third, climate models indicate that increased precipitation and snow depth would have made it harder for mammoths to forage, as their thick fur would become waterlogged and they would struggle to dig through deep snow. These factors, rather than human activity, best explain the pattern of decline.

🎧 リスニング講義

The reading's argument for climate change is flawed. While habitat changes did occur, they were not uniform. In many areas, such as the Great Plains of North America, grassland actually expanded during the same period, yet mammoths still vanished there. The island survival example is misleading: Wrangel Island was a refuge because it was too small and remote for humans to find easily, but once humans did arrive—around 4,000 years ago—the mammoths disappeared within a few centuries. This timing strongly implicates hunting. Moreover, the climate model's emphasis on snow depth is speculative. Modern elephants in snowy regions, like those in zoos, cope well with cold and snow, and mammoths had specialized adaptations, such as smaller ears and a hump of fat, that would have mitigated such stress. In fact, archaeological sites show clear evidence of mammoth butchery, with cut marks on bones and spear points embedded in carcasses, which directly demonstrates human hunting. These findings undermine the climate-only explanation.