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 mammoth decline correlates with the end of the last Ice Age (approximately 10,000 years ago), when global temperatures rose dramatically. This warming caused the replacement of their preferred steppe-tundra habitat with dense forests and wetlands, reducing their food supply. Second, mammoths had low genetic diversity, as revealed by ancient DNA studies, making them vulnerable to diseases and environmental shifts. This lack of variation would have hindered their adaptation to rapid climate change. Third, human populations at the time were small and sparsely distributed, with limited hunting technology (e.g., spears), making it unlikely they could have driven such a widespread species to extinction. Instead, the melting of ice and changes in vegetation align more closely with the mammoth’s disappearance, as seen in similar megafauna extinctions in other regions.

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The lecture challenges the reading’s claim that climate change alone caused mammoth extinction. While the warming trend did alter habitats, it was not uniform; some regions retained suitable steppe-tundra until later, and mammoths could have migrated. However, archaeological evidence shows that human hunting was more intense than the reading suggests. For example, kill sites with mammoth bones and spear points date to the exact period of their final decline, and human populations were larger and more organized than previously assumed, with evidence of cooperative hunting drives. Moreover, the genetic diversity argument is misleading: mammoth populations in the late Pleistocene had relatively high diversity, and low diversity only appeared in isolated, shrinking populations—likely a consequence, not a cause, of extinction. Finally, the reading ignores that mammoths survived earlier warm interglacial periods without going extinct, implying that warming alone was not sufficient. Instead, the combination of human pressure and climate stress, with humans as the decisive factor, explains the rapid extinction.