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 their decline correlates with the warming of the Holocene, not with human expansion. Radiocarbon dating shows that mammoth populations on Wrangel Island survived until 2000 BCE, long after humans arrived on the mainland, yet they vanished shortly after a period of rapid climate warming. Second, their diet, based on dry, nutrient-poor grasses of the steppe-tundra, became scarce as warming led to the encroachment of shrubs and forests, reducing open grassland habitats. Isotopic analysis of mammoth bones reveals a shift to less nutritious plants in their final millennia, indicating dietary stress. Third, genetic studies of the last surviving mammoths show a loss of diversity and an increase in harmful mutations, which weakened their immune systems and fertility, making them more vulnerable to disease and environmental change. These factors, all tied to climate, explain their extinction more convincingly than human hunting, which was sporadic and localized.

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The reading’s argument that climate change drove mammoth extinction is flawed. While it is true that warming occurred, human hunting was not sporadic—it was relentless and targeted. Archaeological sites show systematic kills of juvenile and female mammoths, which would have devastated populations far more than climate stress. Moreover, the dietary shift cited in the reading is misleading: mammoths were generalist feeders and could adapt to shrubs, as evidenced by preserved stomach contents from Siberia containing willow and birch twigs. The genetic decline, too, does not prove climate’s role. Small, isolated populations, whether due to hunting or habitat fragmentation, naturally lose diversity. In fact, the Wrangel Island mammoths survived for thousands of years despite warming, and their extinction around 2000 BCE coincides with the arrival of human hunters on the island—not with any sudden climate event. Thus, the evidence points to humans, not climate, as the decisive factor.