托福综合写作

📖 阅读文章

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 mammoth population declines correlates closely with the warming period known as the Bølling-Allerød interstadial (about 14,700 years ago), not with the arrival of humans. Radiocarbon dating of mammoth remains shows a sharp drop in numbers during this warm phase, while human hunting pressure was still low in many regions. Second, climate change altered the mammoth’s habitat. As temperatures rose, the dry, grassy steppe-tundra that mammoths depended on was replaced by wet, forested landscapes with less nutritious vegetation. This habitat loss would have reduced the carrying capacity of the land, making mammoth populations more vulnerable to any additional stress. Third, genetic studies of fossil mammoths reveal a significant decline in genetic diversity before the species disappeared, indicating a small, fragmented population that was likely struggling to survive due to environmental stress, not a sudden overkill by hunters. These lines of evidence challenge the overhunting hypothesis and point to climate as the main cause of mammoth extinction.

🎧 听力讲座

The reading argues that climate change, not human hunting, drove the woolly mammoth to extinction, but this view is flawed. First, the correlation with the Bølling-Allerød warming is misleading. Human populations also expanded during that period, and archaeological sites show increased mammoth hunting as human groups moved into new areas. The decline in mammoth numbers actually coincides with the spread of sophisticated hunting tools, such as spears with stone points, which made hunting more efficient. Second, while habitat change did occur, mammoths were adaptable. Fossil evidence shows that some mammoth populations survived in refugia with mixed vegetation, and they could have shifted their diets to shrubs and other plants. In fact, the last surviving mammoths on Wrangel Island lived for thousands of years in a similar post-glacial environment, proving that habitat change alone was not fatal. Third, the genetic diversity decline is also consistent with overhunting. When human hunters target the largest and healthiest individuals, they remove the most genetically fit animals, leading to a rapid loss of diversity and population fragmentation. This pattern is seen in other species that were overhunted by humans, such as the moa in New Zealand. Therefore, the evidence better supports human overhunting as the primary cause, with climate playing only a secondary role.