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 declined dramatically during periods of rapid warming, such as the Bølling-Allerød interstadial (14,700–12,900 years ago), when temperatures rose by several degrees within decades. These warming events shrank the mammoth’s preferred habitat—cold, dry steppe-tundra—by allowing shrubs and forests to expand, fragmenting the open grasslands on which mammoths depended. Second, genetic studies of ancient mammoth remains show a steady loss of genetic diversity and a rise in harmful mutations long before human populations reached high densities in the Arctic. This indicates that populations were already stressed by habitat loss, making them more vulnerable to extinction. Third, the final extinction occurred on isolated islands (e.g., Wrangel Island, St. Paul Island) where human hunting was minimal or absent, yet these populations disappeared around the time of sea-level rise and the arrival of novel vegetation, pointing to environmental causes rather than human predation. Therefore, climate-driven habitat change, not overhunting, was the decisive factor.
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The reading’s claim that climate change alone drove mammoth extinction is unconvincing. While warming did alter habitats, mammoths had survived many previous interglacial warm periods, so why did they not adapt this time? The difference was the arrival of highly skilled human hunters with weapons like spears and later, possibly, projectile points. First, archaeological sites show clear evidence of mammoth hunting, such as cut marks on bones and clusters of carcasses near human camps, dating to periods of population decline. Second, the genetic data cited in the reading actually supports human pressure: the loss of diversity and harmful mutations are consistent with a small, shrinking population caused by overhunting, not just habitat fragmentation. Third, island extinctions actually occurred after humans arrived on those islands; for instance, Wrangel Island was colonized by people around 1700 BCE, and mammoths disappeared shortly thereafter. Moreover, on St. Paul Island, humans arrived even earlier. Thus, while climate may have stressed populations, it was the added pressure of hunting that 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.
