The extinction of the woolly mammoth has long been attributed to overhunting by early humans, but recent evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions aligns with the end of the last Ice Age, when global temperatures rose dramatically. As the ice retreated, the mammoth's preferred habitat—cold, dry steppe—shrank, reducing available forage. Second, genetic studies of mammoth remains show a significant population decline that began well before the arrival of humans in many regions, indicating that environmental stress, not hunting, initiated the collapse. Third, the survival of relict populations on remote islands, such as Wrangel Island, until around 2000 BCE, long after humans had arrived but during a period of stable climate, suggests that hunting pressure alone was insufficient to cause extinction. Instead, these final populations died out due to inbreeding and genetic drift, which are consequences of small population size exacerbated by climate-driven habitat loss. Therefore, while humans may have delivered the final blow in some areas, the overarching cause of woolly mammoth extinction was climate-induced habitat degradation.
🎧 听力讲座
🎯 模拟考试环境：先点「播放讲座」听完内容，再作答。听力原文默认隐藏。
The professor challenges the reading's claim that climate change was the primary cause of woolly mammoth extinction. First, while the timing of extinction does correlate with post-glacial warming, it also coincides with the expansion of human hunters into new territories. The reading ignores the fact that mammoths had survived previous interglacial warm periods, so warming alone cannot explain their demise. Second, the genetic evidence of early population decline is misinterpreted. The reading assumes this decline was due to climate, but it could equally reflect human hunting pressure, as human populations were present in the same regions during those early declines. Moreover, the populations that persisted the longest, like those on Wrangel Island, were isolated and small, which made them more vulnerable to stochastic events—but their final extinction around 2000 BCE occurred during a period of stable climate, which the reading acknowledges. This suggests that non-climatic factors, such as hunting by newly arrived humans or disease, were decisive. Third, the survival of island populations actually undermines the climate hypothesis: if climate were the main driver, these cold-adapted mammoths should have thrived in their cold island environments. Instead, their extinction on islands, where human presence was limited, points to other pressures. In sum, the evidence better supports the view that human activities, not climate, were the critical factor in woolly mammoth extinction.
📝 Writing Prompt Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
📊 TOEFL Integrated Writing Rubric
Content Accuracy: Accurately capture the relationship between lecture and reading
Information Completeness: Cover all key counter-arguments from the lecture
Structure & Coherence: Logical organization and progression
Language Use: Grammar, vocabulary, expression accuracy
Scored 0-30 based on holistic scoring (original 0-5, scaled to 30).
