The extinction of the woolly mammoth, which occurred roughly 4,000 years ago, has long been attributed primarily to human hunting. However, recent evidence suggests that climate change and habitat loss were the decisive factors. Three key arguments support this view. First, the last known populations of mammoths survived on isolated Arctic islands, such as Wrangel Island, where human hunters were absent or arrived only after the mammoths had already declined. This indicates that climate-driven shifts in vegetation, not hunting pressure, caused their final disappearance. Second, paleoclimatic data show that the end of the Pleistocene was marked by rapid warming and increased precipitation, which transformed the dry, grassy steppe-tundra—the mammoth’s preferred habitat—into wet, boggy tundra and forest. Such habitat fragmentation would have reduced food availability and increased vulnerability to disease and starvation. Third, genetic studies of ancient mammoth remains reveal that late populations exhibited low genetic diversity and signs of inbreeding, consistent with small, isolated groups struggling to adapt to a changing environment. These genetic bottlenecks likely weakened their immune systems and reproductive success, making extinction inevitable even without human interference.
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The professor argues that the reading’s conclusion is flawed, and that human hunting played a more significant role than climate change. First, while early human presence on Wrangel Island is debated, archaeological evidence now shows that humans did reach the island before the mammoth’s final extinction, and they likely hunted them. Even if hunting pressure was low, the arrival of a new predator could have pushed an already vulnerable population over the edge. Second, the climate change argument overlooks the fact that mammoths had survived many previous warming periods. For example, they thrived during the interglacial periods before the last Ice Age, when temperatures were similar to or warmer than those at their extinction. Thus, climate alone cannot explain their demise. Third, the genetic diversity data cited in the reading actually supports the hunting hypothesis. Small, isolated populations are more susceptible to extinction from any additional stress, including hunting. Moreover, the low genetic diversity may have been a result, not a cause, of the population decline—humans could have reduced the population size, leading to inbreeding and further decline. Therefore, the reading’s dismissal of human hunting is unjustified.
📝 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.
