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 dramatically reduced the mammoth’s habitat. As glaciers retreated, grasslands were replaced by forests and tundra, which provided less forage. Fossil pollen records show a sharp decline in grass species that mammoths depended on, coinciding with their population decline. Second, the timing of mammoth extinctions varies by region, which contradicts a single human-driven event. In some areas, such as Wrangel Island, mammoths survived until 2000 BCE, thousands of years after humans arrived. This suggests that local climate conditions, not human presence, determined their fate. Third, human hunting pressure was likely too low to cause extinction. Archaeological sites with mammoth kill evidence are rare, and early human populations were small. Even if hunting occurred, it was probably opportunistic rather than systematic. Thus, the most plausible explanation is that climate-induced habitat loss, not human activity, led to their demise.

🎧 リスニング講義

The reading claims that climate change, not human hunting, caused mammoth extinction. However, this view overlooks key evidence. First, while grasslands did decline, mammoths were adaptable. Isotopic analyses of their teeth show they could consume a variety of plants, including shrubs and tree bark, which were available in forests. Therefore, habitat change alone does not explain their extinction. Second, the survival of mammoths on Wrangel Island actually supports human involvement. That island was isolated and had no human inhabitants until after 2000 BCE, which is exactly why mammoths persisted there. In contrast, on the mainland where humans arrived earlier, mammoths vanished sooner. This pattern aligns with human hunting pressure. Third, the rarity of kill sites is misleading. Early humans likely used mammoth carcasses without leaving clear butchery marks, as they may have scavenged or used only certain parts. Moreover, even low hunting intensity can drive slow-reproducing species like mammoths to extinction. Thus, the lecture shows that the reading’s arguments are not convincing.