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 shrank the mammoth’s habitat—the cold, dry steppe-tundra. As temperatures rose, forests and wetlands replaced these grasslands, reducing the available forage and fragmenting populations. Second, genetic studies of mammoth remains show a severe population bottleneck well before humans arrived in high numbers in North America and Eurasia, indicating that climate stress had already weakened the species. Third, the timing of extinction varies across regions: on isolated islands like Wrangel Island, mammoths survived until about 4000 years ago, long after human hunters had arrived, but only after sea-level rise had shrunk their island habitat. This pattern is inconsistent with a human-driven extinction, as hunter pressure would have remained constant or increased over time. In contrast, climate-driven habitat loss explains why the last mammoths disappeared in the most climate-affected refugia.
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The reading’s claim that climate change alone caused mammoth extinction is unconvincing. While habitat loss did occur, human hunting played a decisive role, especially in the final extinctions. First, the habitat shrinkage argument is overstated: mammoths were adaptable grazers, and they coexisted with forests and wetlands in earlier interglacial periods. What changed in the late Pleistocene was the arrival of highly skilled human hunters who used spears and drives, and archaeological sites show mammoth kill sites with butchery marks. Second, the genetic bottleneck cited actually supports human hunting: the population decline accelerated exactly when human populations expanded across Beringia, not merely when climate warmed. The DNA data show a sharp drop around 30,000 to 15,000 years ago, a period of human migration. Third, the island survival case backfires. On Wrangel Island, mammoths survived longer not because climate was stable, but because humans did not colonize the island until later. Once humans arrived around 4000 years ago, the mammoths went extinct within a few centuries—a pattern replicated on other islands. Thus, hunting delivered the final blow, even if climate stress weakened populations earlier.
📝 写作提示 Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
