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, mammoth populations began to decline around 15,000 years ago, coinciding with a period of significant warming and vegetation shifts. As the ice age ended, grasslands—the mammoths’ primary food source—were replaced by forests and tundra, reducing their habitat and nutritional resources. Second, genetic studies of ancient mammoth remains show a steady loss of genetic diversity before human populations became widespread in their habitats. This genetic decline indicates that populations were already stressed and fragmented due to environmental pressures, not sudden human hunting. Third, on remote islands like Wrangel Island, where humans arrived only after mammoths had disappeared, the last mammoths survived until 4,000 years ago. This suggests that human hunting was not the decisive factor; instead, shrinking island habitats due to rising sea levels and changing plant communities led to their final demise.
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The professor argues that the reading’s climate-change theory is flawed. While it is true that mammoth populations declined during warming periods, human hunting was precisely the added stress that pushed them over the edge. In fact, archaeological sites from that era show clear evidence of mammoth butchery, with cut marks on bones and spear points embedded in carcasses. The genetic diversity argument also misleads: the observed loss of diversity could be a result of human hunting, which reduced population sizes and increased inbreeding, not a pre-existing environmental condition. As for Wrangel Island, the professor points out that mammoths survived there for thousands of years after the climate stabilized, thriving in a small but stable population. Their extinction around 4,000 years ago coincides with the arrival of seafaring humans who hunted them for food and ivory. Thus, the reading’s evidence actually supports the overhunting hypothesis when viewed in full context.
📝 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.
