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 coincides with the end of the last Ice Age, when global temperatures rose rapidly. As the glaciers retreated, the vast steppe grasslands that mammoths depended on were replaced by dense forests and wetlands, reducing their available habitat. Second, genetic studies of mammoth remains show a dramatic loss of genetic diversity just before extinction, indicating small, isolated populations that were vulnerable to inbreeding and disease. This pattern is more consistent with habitat fragmentation than with rapid hunting pressure, which would not necessarily reduce genetic variation so severely. Third, archaeological sites with mammoth bones and hunting tools are relatively rare, and many such sites show signs of scavenging rather than active hunting. If humans had been the main cause, we would expect more widespread evidence of large-scale kills. Therefore, while human activity may have contributed, the overwhelming evidence points to climate-induced habitat loss as the decisive factor in the mammoth’s disappearance.
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The professor argues that the reading’s claims about climate change are not convincing, and that human hunting was indeed the main cause. First, the habitat change theory fails because mammoths were highly adaptable. Fossil evidence shows that mammoths survived in various environments, including forests and wetlands, during earlier interglacial periods when temperatures were similar to those at the end of the Ice Age. If they could cope with such changes before, why did they suddenly die out when humans appeared? Second, the genetic bottleneck mentioned in the reading is actually a sign of overhunting. When humans arrive in a region, they kill the largest and healthiest individuals, disrupting social structures and causing rapid population decline. This leads to small, isolated groups and inbreeding, exactly what the genetic data shows—not the slow fragmentation from climate change, which would have taken thousands of years. Third, the scarcity of hunting sites is misleading. Many mammoth bones have been found with cut marks, but these sites are often destroyed by natural processes like river erosion or later human activity. Also, hunters may have used wooden spears that decayed, leaving no trace. In fact, at some sites, the pattern of bone breakage and tool marks clearly indicates deliberate hunting of young or weak individuals. Thus, the evidence actually aligns with human predation, not climate.
📝 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.
