การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

The extinction of the woolly mammoth has long been attributed to human hunting, but recent evidence suggests that climate change was the primary driver. First, archaeological sites show that human populations in Siberia and North America were small and scattered during the late Pleistocene, making it unlikely they could have hunted mammoths to extinction. For example, Clovis points, often associated with megafauna hunting, are rare in mammoth kill sites, and many mammoth bones show no signs of butchering. Second, the warming climate at the end of the Ice Age drastically reduced the mammoth’s habitat—the vast steppe-tundra grasslands. As forests and peatlands expanded, the open grasslands shrank, fragmenting mammoth populations into isolated pockets where they struggled to find food. Third, genetic studies of fossil mammoths reveal a steep decline in genetic diversity long before human arrival in their regions, indicating that populations were already shrinking due to environmental stress. This pattern is consistent with climate-driven extinction, not overhunting.

🎧 การบรรยาย

The professor challenges the reading's argument that climate change alone drove woolly mammoth extinction. First, while human populations were small, they were strategically positioned along migration routes and water sources, allowing them to ambush mammoths effectively. Moreover, recent excavations have uncovered more mammoth kill sites with clear cut marks, suggesting that hunting pressure was significant, especially on young and weak individuals. Second, although warming did shrink grasslands, similar climate shifts had occurred earlier in the Pleistocene without causing extinction, and mammoths proved adaptable by browsing on shrubs and trees. Thus, vegetation change alone cannot explain their demise. Third, the genetic decline mentioned in the reading actually predates the last glacial maximum, but mammoth populations recovered during cooler periods, indicating that they could rebound from low numbers. The final extinction coincided precisely with the arrival of advanced human hunters, not with a unique climatic event. Therefore, human hunting, not climate, was the decisive factor.