The extinction of the woolly mammoth has long been attributed to human overhunting, but recent evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions correlates more closely with major climatic shifts than with human migration patterns. Radiocarbon dating shows that mammoth populations declined sharply during the Last Glacial Maximum, when human populations in Siberia and North America were still sparse. Second, the dietary habits of mammoths made them vulnerable to habitat loss. Stable isotope analysis reveals that mammoths relied on cold-adapted grasses and sedges, which thrived in the dry, cold steppe. As the climate warmed and became wetter, these plants were replaced by forests and peatlands, reducing the mammoth's food supply. Third, genetic studies indicate a long-term population decline that began well before the arrival of humans in their habitats. DNA from ancient mammoth remains shows a steady loss of genetic diversity over the past 100,000 years, suggesting that environmental stress, not hunting, was the primary factor. These lines of evidence collectively argue that climate change, not human activity, drove the woolly mammoth to extinction.
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The reading's claim that climate change alone drove mammoth extinction is unconvincing. While it is true that climate shifts occurred, they were gradual and allowed mammoths ample time to adapt or migrate, as they had survived previous interglacial periods. In contrast, human hunting, which intensified as humans developed advanced weapons and organized hunting strategies, had a sudden and devastating impact. The radiocarbon dating cited in the reading actually shows that the final extinction pulse occurred at different times on different continents, coinciding with human arrival, not with global climate events. For example, mammoths survived on Wrangel Island until 4,000 years ago, long after the climate had warmed, but soon after humans reached the island. As for diet, while it is true that warming reduced grassland, mammoths were not strictly dependent on grasses; fossilized dung shows they also consumed a variety of shrubs and herbs, so they could have shifted their diet. Finally, the genetic decline mentioned in the reading may reflect natural population fluctuations, not a prelude to extinction. Many species exhibit low genetic diversity yet thrive, and the final extinction was too abrupt to be explained by genetic factors alone. Thus, human hunting remains the more plausible cause.
📝 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.
