The extinction of the woolly mammoth has long been attributed to overhunting by early humans. However, recent evidence suggests that climate change was the primary driver. First, the warming period at the end of the Pleistocene reduced the mammoth’s preferred habitat—cold, dry grasslands known as steppe-tundra. As temperatures rose, forests and wetlands expanded, fragmenting the open landscapes on which mammoths depended. Pollen records from Siberia and Alaska show a sharp decline in grass pollen and an increase in tree pollen exactly when mammoth populations dwindled. Second, climate change would have disrupted the mammoth’s food supply. Warmer, wetter conditions favored less nutritious plants like mosses and sedges over the high-protein grasses that sustained large herds. Studies of mammoth dung and stomach contents reveal a shift toward lower-quality forage in their final millennia. Third, the timing of extinction aligns more closely with climate events than with human arrival. In isolated locations like Wrangel Island, mammoths survived until about 4,000 years ago, long after humans had arrived in nearby mainland areas, but they died out soon after a period of dramatic environmental change. Thus, while human hunting may have delivered a final blow, climate-driven habitat loss and nutritional stress were the fundamental causes.
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The reading's claim that climate change alone drove mammoth extinction is unconvincing. While it is true that habitats shifted, human hunting played a decisive role, as shown by archaeological and genetic evidence. First, the habitat change was not as abrupt as the reading suggests. Mammoths had survived previous interglacial warm periods with similar habitat shifts, proving their adaptability. However, the arrival of highly skilled human hunters, armed with spears and coordinated strategies, was unprecedented. Kill sites with mammoth remains and butchering tools are found across Eurasia and North America, directly linking human activity to their demise. Second, the dietary argument is flawed. Fossilized mammoth feces from the late Pleistocene contain remains of diverse plants, including shrubs and herbs, not just grasses. This indicates they were generalist feeders capable of adapting to changing vegetation. Moreover, other large herbivores, such as bison and horses, thrived during the same period despite similar vegetation changes, suggesting that food availability was not limiting. Third, the Wrangel Island example actually supports human-driven extinction. Mainland mammoths vanished around 10,000 years ago, coinciding with human expansion. The Wrangel population survived only because it was isolated on a remote island with no human presence. When humans finally reached Wrangel around 4,000 years ago—likely by boat—the mammoths disappeared within a few centuries. Therefore, the pattern of extinction tracks human arrival, not just climate shifts.
📝 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.
