托福综合写作

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The extinction of the woolly mammoth has long been attributed to human hunting, but recent evidence suggests that climate change was the primary driver. First, the timing of their decline correlates with the end of the last Ice Age, when temperatures rose dramatically. As glaciers retreated, the open grasslands that mammoths depended on were replaced by dense forests and wetlands, reducing their food supply. Second, genetic studies reveal that mammoth populations experienced severe bottlenecks long before humans arrived in their habitats. For example, DNA from Siberian remains shows a sharp decline in genetic diversity starting 20,000 years ago, predating significant human hunting pressure. Third, the survival of dwarf mammoths on Wrangel Island until 2000 BCE, despite human presence nearby, indicates that small, isolated populations could persist. Their eventual extinction there coincided with a period of rapid climate fluctuation, not with increased hunting. Therefore, while humans may have delivered the final blow, the primary cause was environmental change that fragmented habitats and stressed populations beyond recovery.

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The reading’s argument that climate change alone drove mammoth extinction is flawed. First, the correlation with warming is misleading. During earlier interglacial periods, mammoths thrived in warmer conditions, proving they could adapt to climate shifts. The real difference in the late Pleistocene was the arrival of highly skilled human hunters armed with spears and coordinated tactics. Second, the genetic bottlenecks cited actually support human involvement. These bottlenecks occurred as human populations expanded into Siberia and North America, and they coincide with known hunting sites where mammoth bones show butchering marks. The decline in diversity reflects targeted hunting of healthy adults, not gradual habitat loss. Third, Wrangel Island’s dwarf mammoths actually undermine the climate argument. Their extinction around 2000 BCE happened during a stable climatic phase, not a fluctuation. Moreover, archaeological evidence on the island shows human occupation beginning exactly at that time. Thus, the pattern points to overhunting as the decisive factor, with climate playing only a minor, indirect role.