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, the timing of mammoth extinctions correlates more closely with rapid warming events than with human expansion. For example, populations on Wrangel Island survived until 2000 BCE, thousands of years after humans arrived, yet disappeared shortly after a period of drastic climate fluctuation. Second, genetic studies show a severe loss of genetic diversity in the last mammoth populations, indicating that they were already struggling due to shrinking habitats and inbreeding before human contact intensified. This genetic bottleneck would have made them vulnerable to disease and environmental stress, not to spear-wielding hunters. Third, stable isotope analyses of mammoth bones reveal dietary shifts toward less nutritious plants in their final millennia, consistent with warming-induced vegetation changes that reduced their preferred steppe-tundra forage. Together, these points argue that climate-driven habitat loss, not human hunting, was the decisive factor in their demise.
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The reading’s claims are plausible but misleading. While climate change did affect mammoths, human hunting was the final blow. First, the Wrangel Island example actually supports human involvement: although humans arrived later, they did not intensify hunting until after 2000 BCE, when the island’s population collapsed—exactly when human pressure increased due to rising sea levels trapping animals and hunters together. Second, the genetic diversity loss cited does not rule out hunting; in fact, small populations are more susceptible to hunting-driven extinction because each individual loss has a greater impact. Furthermore, similar genetic bottlenecks appear in species like the moa, which were definitively hunted to extinction by humans, showing that genetic decline is not unique to climate victims. Third, the dietary shifts observed in isotopes could reflect overgrazing by introduced livestock or competition with humans’ domesticated animals, not solely climate. Moreover, archaeological sites show mammoth bones with cut marks and spear points, proving direct hunting. Thus, while climate stressed the species, human predation pushed them over the edge.
📝 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.
