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 the mammoth’s decline coincides with the end of the last Ice Age, around 10,000 years ago, when global temperatures rose rapidly. This warming caused dramatic shifts in vegetation, replacing the cold-adapted steppe grasslands—the mammoth’s primary food source—with forests and tundra, which could not support large herds. Second, archaeological records show that human hunting pressure was relatively low. Sparse population densities and limited hunting technology, such as spears and pitfalls, would have been insufficient to drive a species as widespread and fecund as the mammoth to extinction. Third, genetic studies of ancient mammoth remains reveal a severe loss of genetic diversity in the final millennia before extinction, a signature of population fragmentation and habitat loss, not of sudden overhunting. This genetic bottleneck indicates that the remaining populations were isolated in small, shrinking refugia, struggling to survive as their environment deteriorated.
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The reading’s argument that climate change alone drove the woolly mammoth to extinction is not convincing. First, while the climate warmed, similar warming events had occurred in previous interglacial periods without causing mammoth extinction. In those earlier warm phases, mammoths survived because they could migrate to cooler northern regions or adapt to new vegetation. However, the key difference in the late Pleistocene was the arrival of highly efficient human hunters. Second, the claim that human hunting was insignificant ignores evidence from kill sites, where mammoth bones show cut marks and are associated with stone tools. Moreover, even low-density human populations could exert a disproportionate impact on large, slow-reproducing animals like mammoths, whose gestation period is 22 months and who produce single offspring. Third, the genetic diversity loss cited in the reading actually supports the overhunting hypothesis. As humans expanded, they preferentially hunted mammoths in the most favorable habitats, breaking populations into small, isolated groups. This fragmentation, not climate, would reduce gene flow and cause the genetic bottleneck. In fact, the last known mammoth populations survived on remote islands for thousands of years after the climate warmed, suggesting they could persist if not for human interference.
📝 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.
