The extinction of the woolly mammoth has long been attributed to human hunting, but a more recent theory suggests that climate change at the end of the last Ice Age was the primary driver. Three main arguments support this view. First, the warming climate drastically altered the mammoth's habitat. As temperatures rose, the vast steppe-tundra, which provided nutritious grasses and sedges, was replaced by forest and boggy tundra, reducing the available food supply. Second, increased precipitation and rising sea levels led to the flooding of coastal plains, which were key migration routes and lowland feeding grounds. This fragmentation of habitats isolated small populations, making them more vulnerable to local extinction. Third, the timing of the mammoth's decline correlates more closely with the climatic shifts than with human expansion. Fossil records show that mammoth populations began to decline around 15,000 years ago, well before the arrival of sophisticated hunting tools and large-scale human settlement in many regions. Even on isolated islands like Wrangel Island, where humans were absent until 4,000 years ago, mammoths survived until about 3,700 years ago, suggesting that human hunting was not the decisive factor in their mainland extinction.
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The lecture challenges the climate-based explanation for woolly mammoth extinction. While acknowledging that climate change played a role, the professor argues that human activity was the critical factor. First, the claim about habitat loss is overstated. Mammoths were adaptable grazers that could survive on a variety of vegetation, including shrubs and tree bark, as evidenced by their survival in forested refuges in Siberia and Alaska. Second, the flooding of coastal plains did not necessarily isolate populations. In fact, many mammoth populations migrated inland to higher elevations, and there is no evidence that these inland areas lacked sufficient food or caused population bottlenecks. Third, the timing argument is flawed. Human hunting pressure was intense in the very regions where mammoths disappeared earliest, such as North America and Europe, and archaeological sites show clear evidence of mammoth butchery. Moreover, the Wrangel Island example actually supports the hunting hypothesis: when humans finally arrived there around 4,000 years ago, the last mammoths vanished within a few centuries, which is too rapid to be explained by the gradual climate change alone. Thus, the lecture concludes that human hunting, not climate, was the primary cause of the mammoth's extinction.
📝 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.
