The extinction of the woolly mammoth has long been attributed to climate change at the end of the last Ice Age. However, recent archaeological and genetic evidence suggests that human overhunting was the primary driver. First, the timing of mammoth extinctions on different continents correlates with human arrival, not with climate shifts. For example, in North America, mammoths disappeared around 13,000 years ago, shortly after the Clovis people arrived, while climate warming had begun earlier. Second, kill sites with mammoth remains and spear points are widespread, indicating that humans actively hunted these animals. At sites like the Murray Springs in Arizona, researchers have found multiple mammoth skeletons with embedded projectile points, proving direct predation. Third, genetic studies show a rapid decline in mammoth population size beginning around 15,000 years ago, coinciding with human expansion, whereas climate models predict a more gradual decline. Moreover, mammoths survived on isolated Arctic islands like Wrangel Island until 4,000 years ago, long after the Ice Age ended, but only after humans had not yet arrived. This pattern strongly implicates human hunters as the decisive factor in their extinction.
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The reading's claim that human overhunting caused mammoth extinction is flawed. First, the correlation between human arrival and extinction is misleading. In North America, archaeological evidence shows that human populations were sparse and their hunting technology primitive; they could not have killed enough mammoths to cause extinction. Furthermore, many mammoth populations disappeared before humans reached their habitats, such as in Eurasia where mammoths declined 30,000 years ago, long before modern humans arrived in force. Second, the so-called kill sites are rare and often ambiguous. Many mammoth remains found near spear points may be scavenged, not hunted. At Murray Springs, the bones show no cut marks, and the spear points could have been used for defense, not hunting. Third, genetic data actually indicate that mammoth populations were already genetically unhealthy and declining due to inbreeding and habitat fragmentation, not because of hunting. The population crash began 20,000 years ago during a cold snap, before human expansion. Finally, Wrangel Island mammoths survived until 4,000 years ago, but they were dwarfed and genetically impoverished, suggesting they were a relic population doomed by environmental changes, not by humans, since humans reached the island only after 3,500 years ago. Thus, climate and intrinsic factors are more plausible explanations.
📝 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.
