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 their decline coincides with the end of the last Ice Age, when global temperatures rose dramatically. As the glaciers retreated, the open grasslands that mammoths depended on were replaced by dense forests and wetlands, reducing their food supply and fragmenting their habitat. Second, genetic studies of mammoth remains show a steady loss of genetic diversity before their final disappearance, indicating a gradual population decline due to environmental stress, not a sudden overkill by humans. Finally, the last known mammoths survived on remote Arctic islands, such as Wrangel Island, where human hunters were absent until much later. If overhunting were the main cause, these isolated populations would have vanished earlier, yet they persisted for thousands of years after the mainland populations were gone.

🎧 Listening Lecture

The reading claims that climate change was the primary cause of woolly mammoth extinction, but this view is flawed. First, while climate warmed, mammoths had survived previous interglacial periods with similar temperature increases. Their specialized diet was not as inflexible as assumed; fossilized dung shows they could consume a variety of plants, including shrubs and sedges, when grasses were scarce. Second, the alleged loss of genetic diversity is not evidence of climate stress. Small populations naturally lose genetic variation over time, and the DNA samples may have come from already declining groups. In fact, the sudden disappearance of healthy, genetically diverse populations in many regions is more consistent with rapid human hunting. Third, the persistence on Wrangel Island is actually a strong argument against climate change. If climate were the killer, these cold, isolated islands would have been among the first to become unsuitable, yet they supported mammoths for millennia. The only factor that changed on the mainland but not on Wrangel was the arrival of human hunters, which occurred after the island populations died out—likely due to inbreeding and small numbers, not climate.