TOEFL統合ライティング

📖 読解文章

The extinction of the woolly mammoth, which occurred around 4,000 years ago, has long puzzled scientists. While climate change is often cited as a primary driver, recent evidence suggests that human hunting was the decisive factor. First, archaeological sites on Wrangel Island, one of the last refuges of mammoths, contain stone tools and butchered mammoth bones with cut marks, indicating that humans actively hunted these animals. Second, the timing of extinction coincides with the arrival of humans on the island; mammoths survived there for thousands of years after the mainland populations disappeared, but vanished within a few centuries of human settlement. Third, climate reconstructions show that the environment on Wrangel Island remained stable, with abundant vegetation, during the period of extinction, ruling out climate-induced habitat loss. Therefore, overhunting by humans, not climate change, led to the mammoth's demise.

🎧 リスニング講義

The reading's argument that humans caused the woolly mammoth's extinction is not convincing. First, the cut marks on bones could result from scavenging, not hunting. Humans may have carved meat from carcasses of mammoths that died of natural causes, especially since the island had no large predators. Second, the timing correlation is weak. Radiocarbon dating shows that mammoth populations on Wrangel Island had already declined dramatically before humans arrived, likely due to inbreeding and reduced genetic diversity from small population size. Third, the claim of stable vegetation is misleading. While plant types remained similar, the nutritional quality of the forage declined, as pollen and plant fossil analyses reveal a reduction in high-protein species, which would have weakened the mammoths and made them more susceptible to disease and reproductive failure. Thus, the evidence better supports a combination of genetic and environmental stressors, not human hunting.