托福综合写作

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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 the mammoth’s decline correlates more closely with the warming period at the end of the Pleistocene than with human migration patterns. Radiocarbon dating shows that mammoth populations began to shrink significantly around 15,000 years ago, when temperatures rose and habitats shifted, whereas humans had already been present in Siberia for over 5,000 years without causing major declines. Second, the warming climate led to the replacement of the mammoth’s preferred steppe-tundra vegetation with forests and wetlands, which provided poor forage. Fossil pollen records indicate a rapid transition to birch and spruce forests in regions where mammoth fossils disappear, suggesting that habitat loss—not hunting—was the critical factor. Third, isolated populations of mammoths survived on remote islands like Wrangel Island until about 4,000 years ago, long after humans had arrived in the area. If hunting were the main cause, these small populations would have been easy targets, yet they persisted for thousands of years, implying that climate, not human activity, was the decisive influence.

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The professor challenges the reading’s claim that climate change alone drove the woolly mammoth to extinction. While the timing of decline does correlate with warming, the professor points out that human hunting was not constant; instead, human populations expanded dramatically precisely when climate shifted, because warmer conditions allowed humans to move into new regions. Thus, the correlation with climate does not rule out hunting. Second, the reading argues that habitat change was critical, but the professor notes that mammoths were adaptable generalists. They did not rely exclusively on steppe-tundra; fossil evidence shows they also ate grasses and sedges in wetlands. Moreover, the vegetation shift was gradual, giving mammoths time to adapt, whereas the sudden appearance of highly efficient human hunters with advanced weapons would have been devastating. Third, the survival of mammoths on Wrangel Island actually supports the hunting hypothesis. Because the island was small and isolated, human hunters may not have reached it until later, or the harsh conditions limited human settlement. Once humans did arrive—around 4,000 years ago—the mammoths disappeared within a few centuries. This pattern fits overhunting, not climate, since climate on the island remained stable during that period. Therefore, the professor concludes that human activity was the primary cause.