The extinction of the woolly mammoth at the end of the Pleistocene has long been attributed to human overhunting. However, a more recent hypothesis suggests that climate change, specifically the rapid warming and associated vegetation shifts, was the primary driver. Proponents of this climate-driven extinction theory point to three main lines of evidence. First, the timing of mammoth decline correlates closely with the Bølling-Allerød warming period, when temperatures rose dramatically and caused widespread habitat loss. Paleobotanical data show that the open steppe-tundra, which mammoths depended on for grazing, was replaced by forest and peatland, reducing their food supply. Second, genetic studies of ancient mammoth remains reveal a significant loss of genetic diversity prior to extinction, indicating population fragmentation and stress. This pattern is consistent with climate-induced habitat fragmentation, not the sudden, selective pressure of hunting. Third, archaeological evidence for human hunting of mammoths is scarce and geographically limited. Most known kill sites are in eastern Europe, while mammoths thrived across North America and Siberia, where such evidence is absent. If overhunting had been the main cause, one would expect more widespread and numerous hunting sites. Thus, while humans may have delivered a final blow, the underlying cause was likely environmental change that weakened mammoth populations long before they disappeared.
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The reading claims that climate change, not human hunting, drove woolly mammoths to extinction, but this argument has several flaws. First, while the Bølling-Allerød warming did alter vegetation, mammoths had survived previous interglacial warm periods with similar temperature increases. For example, the Eemian interglacial about 120,000 years ago was just as warm, yet mammoths persisted. The difference in the late Pleistocene was the arrival of highly efficient human hunters, suggesting that human pressure, not warmth itself, was the new factor. Second, the genetic diversity loss cited in the reading does not necessarily indicate climate stress. Population bottlenecks can also result from overhunting, which would reduce population sizes rapidly and fragment groups. In fact, modern examples of overhunted species, such as elephants, show similar genetic signatures. Third, the scarcity of kill sites is not surprising because mammoth bones were often used for tools and fuel, and many coastal sites are now submerged due to sea-level rise. Moreover, hunting does not require kill sites; humans could have driven mammoths to extinction through indirect effects, such as disrupting migration routes or competing for resources. Therefore, the evidence better supports the overhunting hypothesis, or at least a combination of human and climate factors, but not climate alone.
📝 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.
