The extinction of the woolly mammoth has long been attributed to human overhunting. However, recent evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions correlates with the end of the last Ice Age, when global temperatures rose rapidly. As the ice retreated, the open grasslands that mammoths depended on were replaced by dense forests and wetlands, shrinking their habitat. Second, genetic studies of mammoth remains show a severe population bottleneck long before humans arrived in their final refuges, indicating that climate-induced habitat loss was already stressing populations. Third, human hunting tools from that era were primarily designed for small game, and there is no direct evidence of large-scale mammoth kills, such as spear points embedded in mammoth bones. Therefore, climate change, not human activity, caused the mammoth's demise.
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The professor argues that the reading's conclusion is flawed. While it is true that climate changed, the timing does not perfectly match. Mammoth populations persisted in isolated Arctic islands for thousands of years after the main climate shift, only disappearing when humans arrived. This suggests climate alone was not sufficient. Regarding the genetic bottleneck, the professor points out that this bottleneck occurred at a time when humans were already present in the same regions, based on archaeological sites. The low genetic diversity could be a consequence of hunting, not just habitat loss. Finally, the claim about hunting tools is misleading. Humans used wooden spears, which decay and leave no marks. Moreover, at sites like the Clovis culture, mammoth bones have been found with butchering marks, indicating that hunting did occur. Thus, human activity likely played a decisive role in the final extinction.
📝 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.
