The extinction of the woolly mammoth has long been attributed to human hunting, but recent evidence suggests that climate change was the primary driver. Proponents of the climate hypothesis point to three key lines of evidence. First, the timing of mammoth extinction coincides with the end of the last Ice Age, a period of rapid warming and dramatic vegetation shifts. As the cold, dry steppe-tundra gave way to warmer, wetter forests and bogs, the mammoth’s preferred food sources—grasses and sedges—declined, leading to nutritional stress and population decline. Second, genetic studies of ancient mammoth remains reveal a loss of genetic diversity and an increase in harmful mutations in the millennia before extinction, indicating small, isolated populations struggling to survive—a signature of environmental stress rather than sudden overhunting. Third, archaeological sites show that human hunting of mammoths was relatively rare and localized. Most kill sites are concentrated in a few regions, and the number of mammoth bones found at these sites is far too low to account for a species that once spanned three continents. Thus, while humans may have delivered a final blow to a few remnant herds, the overarching cause of extinction was climate-induced habitat loss.
🎧 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 reading presents a compelling case for climate change as the main cause of mammoth extinction, but a closer examination of the evidence reveals serious flaws. First, the timing argument is misleading. Mammoths survived not one but several interglacial warming periods before their final extinction. For example, they persisted through the Eemian interglacial, which was warmer than the Holocene, so warmth alone cannot explain their demise. Second, the genetic evidence actually supports a human role. Small, isolated populations with low genetic diversity are more vulnerable to any additional stress, including hunting. If climate had been the sole factor, we would expect a gradual decline across all populations simultaneously. Instead, genetic data show that some populations, such as those on Wrangel Island, survived for thousands of years after the climate stabilized, only to disappear shortly after humans arrived. This pattern strongly implicates hunting. Third, the claim that hunting was rare ignores the fact that mammoth populations were likely already low due to earlier human expansion. Even a modest hunting pressure on a declining population could have pushed it over the edge. Moreover, new archaeological findings in Siberia have uncovered large-scale kill sites with evidence of mass slaughter, suggesting that hunting was more intensive than previously thought. Therefore, the reading’s conclusion that climate was the primary cause is not supported by the full weight of the evidence.
📝 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).
