The extinction of the woolly mammoth has long been attributed to overhunting by early humans. This theory, known as the 'Pleistocene overkill hypothesis,' posits that human hunters, arriving in North America and Eurasia around 15,000 years ago, rapidly drove mammoths to extinction. Three key lines of evidence support this view. First, archaeological sites show a clear temporal overlap between the arrival of Clovis hunters and the disappearance of mammoths. Radiocarbon dating indicates that mammoth populations collapsed within a few centuries of human arrival, suggesting a direct causal link. Second, mammoth bones found at kill sites often display cut marks and embedded projectile points, providing direct evidence of hunting. For example, the Waco Mammoth National Monument in Texas contains multiple mammoth skeletons with associated stone tools, indicating a mass kill event. Third, the ecological naivety of mammoths—having evolved without human predators—would have made them easy targets. Modern analogues, such as the rapid extinction of the moa in New Zealand after Polynesian settlement, demonstrate that naive megafauna are highly vulnerable to even low levels of hunting. Collectively, these points argue that human predation was the primary driver of mammoth extinction.
🎧 听力讲座
🎯 模拟考试环境：先点「播放讲座」听完内容，再作答。听力原文默认隐藏。
The reading's overkill hypothesis is appealing but fails to account for several critical facts. First, while it is true that humans arrived around 15,000 years ago, mammoth populations were already in decline long before that. Fossil records from Siberia and Alaska show a gradual decline beginning 30,000 years ago, well before any significant human presence. This pre-human decline points to climate and environmental factors, not hunting. Second, the claim of widespread kill sites is overstated. The Waco site, mentioned in the reading, is actually controversial; many paleontologists argue that the mammoths there died from a flood or other natural catastrophe, and the stone tools may be unrelated or from later occupations. In fact, only a handful of sites worldwide show unequivocal evidence of mammoth hunting, which is insufficient to explain a continental extinction. Third, the comparison to the moa is flawed. Moas were flightless birds with no defense mechanisms, whereas mammoths were massive, intelligent herd animals. Modern studies of elephant behavior show that they are highly adaptable and can learn to avoid human hunters. Moreover, human populations during the Pleistocene were too sparse to exert the pressure needed to wipe out a species that had survived for millions of years. Thus, the weight of evidence suggests that climate change, particularly the loss of open grassland habitats, was the primary cause of mammoth extinction, with hunting playing only a minor role.
📝 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.
