TOEFL Integrated Writing

📖 Reading Passage

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 decline correlates with the end of the last Ice Age, when global temperatures rose rapidly. Paleontological data show that mammoth populations shrank dramatically as forests replaced grasslands, reducing their primary food source. Second, genetic studies reveal a severe population bottleneck around 20,000 years ago, well before humans migrated into North America, indicating that climate-induced habitat loss was already causing decline. Third, the last known mammoth populations survived on isolated Arctic islands, such as Wrangel Island, where human presence was minimal or absent until much later. If hunting were the main cause, these populations would have disappeared soon after human arrival, but they persisted for thousands of years. Therefore, while humans may have delivered the final blow, the primary cause of mammoth extinction was climate-driven environmental change.

🎧 Listening Lecture

The reading's argument that climate change drove mammoth extinction is problematic. First, while temperatures rose, suitable grassland habitats did not vanish uniformly; in many regions, mosaic landscapes with grasses and herbs persisted, providing ample forage. The decline in mammoth numbers correlates more strongly with the spread of sophisticated human hunting tools, such as Clovis points, which appeared exactly when populations crashed. Second, the genetic bottleneck at 20,000 years ago can be explained by a temporary cold snap, not a warming trend, and mammoths recovered afterward. Their final extinction, however, coincided with human expansion into previously uninhabited areas. Third, the Wrangel Island mammoths are a red herring: their isolation actually protected them from hunters for a time, but when seafaring humans reached the island around 4,000 years ago, mammoths vanished within a few centuries—a pattern consistent with overhunting. Moreover, similar large mammals, like horses and caribou, survived the same climate shifts, proving that climate alone cannot explain mammoth extinction. Thus, the evidence points to humans, not climate, as the decisive factor.