TOEFL統合ライティング

📖 読解文章

The extinction of the woolly mammoth has long been attributed to overhunting by early humans. This 'Pleistocene overkill' hypothesis rests on three main pillars. First, archaeological evidence shows that human hunters, equipped with sophisticated projectile weapons, arrived in North America and Eurasia around the same time that mammoth populations began to decline dramatically. The timing of human arrival and mammoth extinction aligns closely, suggesting a causal link. Second, mammoths were slow-reproducing animals, with a long gestation period and single offspring, making them highly vulnerable to even modest levels of hunting pressure. Even small human populations could have driven them to extinction by selectively killing juveniles and females. Third, the fossil record reveals that mammoth bones often bear cut marks and other signs of butchering, providing direct evidence that humans actively hunted and consumed these animals. Taken together, these points suggest that human predation, not climate change, was the primary driver of the woolly mammoth's demise.

🎧 リスニング講義

The reading's overkill hypothesis is appealing but flawed. While it is true that human arrival and mammoth decline overlapped, correlation does not equal causation. Climate change at the end of the Pleistocene dramatically altered mammoth habitats, shrinking the open grasslands they depended on and replacing them with forests and tundra. This habitat loss would have caused population declines even in the absence of human hunting. As for the reproductive vulnerability argument, many slow-reproducing species, such as elephants, have coexisted with human hunters for millennia without going extinct. The mammoth's extinction likely required a combination of factors, not just hunting. Finally, the cut marks on mammoth bones are not conclusive evidence of hunting; they could result from scavenging. Early humans may have opportunistically butchered animals that had already died from starvation or disease, especially during periods of climate stress. In fact, many mammoth bone sites show no signs of human activity at all. Thus, the reading overstates the role of humans while ignoring the powerful impact of environmental change.