托福综合写作

📖 阅读文章

The extinction of the woolly mammoth has long been attributed primarily to human hunting, a theory known as the 'overkill hypothesis.' Proponents argue that early human migrants, armed with advanced hunting tools, rapidly decimated mammoth populations upon their arrival in new territories. First, archaeological sites across North America and Eurasia show a correlation between human settlement and mammoth decline, with kill sites containing mammoth bones and spear points. Second, the timing of extinction aligns with human expansion: mammoths disappeared from mainland regions shortly after humans appeared, while isolated populations on remote islands (e.g., Wrangel Island) survived for thousands of years longer. Third, the mammoth's slow reproductive rate made it especially vulnerable to even modest hunting pressure, as females gave birth to a single calf every few years, limiting population recovery. Thus, the overkill hypothesis presents a compelling, human-driven explanation for the mammoth's demise.

🎧 听力讲座

The lecture challenges the overkill hypothesis, arguing that climate change, not human hunting, was the primary driver of woolly mammoth extinction. First, the correlation between human arrival and mammoth decline is misleading. Many archaeological sites with mammoth bones lack clear evidence of hunting, such as cut marks or butchering tools; bones may have been scavenged from animals that died naturally. Second, the timing argument fails because climate data show that the mammoth's habitat—cold, dry steppe—shrank dramatically during the warming period at the end of the last Ice Age. This habitat loss, not human presence, coincided with extinction on the mainland. Moreover, Wrangel Island's mammoths survived longer because the island's cooler, isolated environment preserved suitable vegetation, not because humans were absent—indeed, humans did not reach Wrangel until after the mammoths died out. Third, while slow reproduction made mammoths vulnerable, climate-induced habitat fragmentation would have reduced food quality and quantity, further lowering birth rates and increasing mortality, a more plausible cause than sporadic hunting. Therefore, the lecture concludes that climate-driven environmental change, not overhunting, best explains the mammoth's extinction.