The extinction of the woolly mammoth has long been attributed to overhunting by early humans. However, recent evidence suggests that climate change was the primary driver. First, the mammoth’s habitat—the mammoth steppe—was a vast, dry grassland that thrived during the cold, arid conditions of the last Ice Age. As the climate warmed and became wetter, this grassland was replaced by forests and bogs, which were unsuitable for mammoths. Paleobotanical data from sediment cores show a dramatic shift in vegetation around 10,000 years ago, coinciding with the mammoth’s decline. Second, the warming climate caused a significant rise in sea levels, which flooded the Bering Land Bridge and isolated mammoth populations on islands. Such isolation reduced genetic diversity and made populations more vulnerable to disease and inbreeding, as seen in the dwarfed mammoths of Wrangel Island, which eventually died out. Third, the timing of human arrival does not align with mammoth extinctions in many regions. For example, in Siberia, humans arrived over 30,000 years ago, yet mammoths persisted until about 10,000 years ago—a lag of 20,000 years. If overhunting were the cause, extinction should have followed more quickly. Together, these points indicate that climate-induced habitat loss, not human predation, was the decisive factor.
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The reading’s argument that climate change alone drove the mammoth’s extinction is flawed. While it is true that warming altered the vegetation, this change was gradual, giving mammoths time to adapt or migrate. However, human hunting added a sudden, unsustainable pressure. Archaeological sites in North America show kill sites with mammoth bones and spear points, dated precisely to the period of final extinction. These are not isolated—over a dozen such sites exist. Second, the island isolation point actually supports human involvement. The Wrangel Island mammoths survived until 4,000 years ago, long after the mainland extinctions, but they disappeared soon after the first humans arrived on the island. Radiocarbon dating of human artifacts on Wrangel coincides exactly with the mammoth’s last known remains. This is a classic pattern of overhunting on islands. Third, the timing objection ignores that human hunting was not constant. Early human populations were small and used simple weapons, but around 15,000 years ago, human populations surged and hunting technology improved, with the invention of the atlatl (spear thrower). This increased hunting efficiency dramatically. In Siberia, the 20,000-year lag is explained by the fact that mammoth populations were already stressed by climate, and it was the combination of climate stress and intensified hunting that finally pushed them over the edge. Thus, the reading overlooks the synergistic effect of both factors, and human hunting was the final, decisive blow.
📝 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.
