The extinction of the woolly mammoth has long been attributed to human overhunting, a theory supported by the presence of spear points near mammoth remains and the timing of their disappearance on continents. However, a more compelling explanation is climate change. First, the warming climate at the end of the Pleistocene reduced the mammoth’s grassland habitat, known as the mammoth steppe, which was replaced by forests and tundra. This vegetation shift drastically reduced their food supply. Second, climate change also altered migration patterns and breeding cycles, as warmer winters and unpredictable seasons disrupted the mammoths' ability to store fat and reproduce successfully. Finally, rising sea levels from melting glaciers isolated populations on islands, where limited space and resources led to inbreeding and eventual extinction, as seen in the Wrangel Island population that survived until 4,000 years ago but showed signs of genetic defects.
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The lecture challenges the idea that climate change was the primary cause of woolly mammoth extinction. First, while the habitat did change, mammoths were adaptable grazers, and fossil evidence shows they could survive on a variety of plants, including sedges and herbs found in tundra. Moreover, their range overlapped with new habitats, and they did not disappear until much later, suggesting they could cope with vegetation shifts. Second, the claim about disrupted breeding is speculative; no direct evidence links climate warming to reduced fertility. In fact, mammoth populations thrived during earlier warm interglacial periods, indicating they could reproduce successfully in warm conditions. Third, island dwarfing and genetic defects, as seen on Wrangel Island, occurred only after sea levels rose, but this does not explain the extinction on mainland continents, where mammoths vanished thousands of years earlier. The lecture concludes that human hunting, not climate, best explains the rapid extinction, as it aligns with the arrival of advanced hunters and the pattern of die-off.
📝 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.
