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 mammoth population began to decline around 15,000 years ago, well before human hunters arrived in large numbers in Siberia and North America. Fossil records show a gradual decrease in population size, which aligns with the warming climate that reduced the mammoth's cold-steppe habitat. Second, mammoths were highly specialized for cold environments, with thick fur, small ears, and a hump of fat for insulation. As temperatures rose, the grasslands they depended on were replaced by forests and wetlands, shrinking their food supply and forcing them into isolated pockets. Finally, genetic studies of late-surviving mammoths reveal low genetic diversity, indicating small, inbred populations that were vulnerable to disease and environmental stress. This pattern is consistent with a species struggling against habitat loss, not one being actively hunted by humans, who would have targeted healthy, dispersed herds.
🎧 听力讲座
The reading's argument that climate change alone caused the mammoth's extinction is flawed. While climate change did play a role, human hunting was the decisive factor. First, the timeline is misleading: human hunting of mammoths began at least 20,000 years ago, and archaeological sites show extensive mammoth bone piles with cut marks, indicating sustained hunting pressure. The population decline after 15,000 years ago actually coincides with improved human hunting technology and population expansion, not just warming. Second, mammoths were not as fragile as the reading claims. They had survived previous warm interglacial periods without going extinct, and their diet was more flexible—they could eat shrubs and tree bark, not just grass. In fact, fossilized dung from late mammoths shows they adapted to forest environments. Finally, the low genetic diversity observed is a result of the population crash, not its cause. When humans wiped out local populations, the survivors were isolated and inbred, which made them more susceptible to extinction. If climate were the main cause, we would expect a more gradual decline across all regions, but instead, extinction occurred on islands shortly after humans arrived, while mainland populations vanished earlier—a pattern that matches hunting pressure.
📝 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.