TOEFL Integrated Writing

📖 Reading Passage

The extinction of the woolly mammoth has long been attributed to human overhunting, but a growing body of evidence suggests that climate change was the primary driver. First, the timing of mammoth decline correlates more closely with climatic shifts than with human expansion. Radiocarbon dating shows that mammoth populations began to dwindle drastically around 15,000 years ago, during a period of rapid warming, whereas human hunters had already been present in Siberia and North America for thousands of years without causing major declines. Second, the habitat preference of mammoths—cold, dry steppe grasslands—was highly sensitive to climate. As temperatures rose, these grasslands were replaced by forests and wetlands, reducing the available forage and fragmenting populations. Paleobotanical data from sediment cores reveal a sharp decline in steppe vegetation exactly when mammoth numbers fell. Third, isolated populations survived longer in refugia with stable cold climates, such as Wrangel Island, where humans did not arrive until much later. This pattern suggests that climate, not hunting, was the limiting factor. If humans had been the main cause, these remote populations would have vanished soon after human contact, but they persisted for thousands of years after mainland extinctions.

🎧 Listening Lecture

The reading’s argument that climate change alone drove mammoth extinction is unpersuasive. First, the correlation with warming is misleading. While temperatures rose 15,000 years ago, similar warming episodes had occurred earlier in the mammoth’s history without causing extinction. What was different this time was the presence of highly efficient human hunters with advanced weapons and coordinated hunting strategies. Archaeological sites show mass kill sites with butchered mammoth remains, indicating that humans actively targeted them. Second, the habitat change argument overlooks the fact that mammoths were adaptable. Fossil evidence shows they could consume a variety of vegetation, including shrubs and grasses, and they could migrate to new areas. The replacement of steppe by forests did not eliminate all food sources; other large herbivores, such as bison and horses, survived these habitat changes. Third, the Wrangel Island example actually undermines the climate hypothesis. Mammoths on Wrangel survived for 7,000 years after the mainland extinctions, but they died out around 1700 BC—shortly after the first human settlers arrived on the island. This timing is far more consistent with hunting pressure than with climate, as the island’s climate had remained stable. Thus, while climate may have stressed populations, human hunting was the decisive factor in their final demise.