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, the timing of mammoth decline correlates closely with the rapid warming at the end of the last Ice Age, around 10,000 years ago. As temperatures rose, their preferred grassland habitats shrank, replaced by dense forests and wetlands, which were less suitable for large grazing herds. Second, genetic studies of mammoth remains show a dramatic loss of genetic diversity just before extinction, indicating small, isolated populations that struggled to survive—a pattern more consistent with habitat fragmentation than with sudden human predation. Finally, archaeological evidence from human settlement sites shows that mammoth bones are relatively rare compared to other large game like bison or deer, suggesting that humans did not rely heavily on mammoths as a food source. Therefore, while humans may have delivered the final blow, the primary cause of the woolly mammoth’s extinction was climate-driven habitat loss and population collapse.

🎧 リスニング講義

The reading’s argument is flawed. While climate change did play a role, human hunting was far more decisive. First, the correlation with warming is misleading: mammoth populations thrived during earlier interglacial warm periods, so warmth alone cannot explain extinction. What changed at the end of the last Ice Age was the arrival of highly skilled human hunters, not just climate. Second, the loss of genetic diversity can be explained by human hunting, which would have fragmented populations and reduced their numbers rapidly, similar to how overhunting has affected modern elephants. The pattern is not exclusive to habitat loss. Third, the archaeological evidence is incomplete. Mammoth bones may be rare at some sites because humans processed them differently—using them for building materials and tools—or because many kill sites are now submerged due to sea-level rise. In fact, some coastal sites contain abundant mammoth remains, suggesting that hunting was significant. Thus, the lecture shows that the reading ignores the critical role of human predation.