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, but recent evidence suggests that climate change was the primary driver. First, archaeological sites show that human populations in Siberia and North America were sparse and lacked advanced hunting technologies capable of consistently killing large megafauna. Second, paleoclimatic data indicate that the last glacial period ended with rapid warming and vegetation shifts, which reduced the open grasslands that mammoths depended on, replacing them with forests and tundra. Third, genetic studies of mammoth remains reveal a severe population bottleneck before human arrival in many regions, implying that numbers were already declining due to environmental stress. Therefore, climate-induced habitat loss, not hunting, caused their extinction.

🎧 リスニング講義

The lecture challenges the reading's claim that climate change alone drove mammoth extinction. First, while human populations were small, they were highly effective hunters, using spears with Clovis points and driving herds over cliffs, as evidenced by mass kill sites with mammoth bones. Second, although vegetation changed, mammoths were adaptable and could consume a variety of plants, including shrubs and grasses, as shown by analysis of fossilized dung, which contains remains of non-grass species. Third, the genetic bottleneck cited in the reading actually occurred much earlier, during an interglacial period, and mammoth populations recovered before humans arrived, only to collapse again coinciding with human expansion. Thus, the timing of human arrival matches extinction events more closely than climate shifts, implicating hunting as the decisive factor.