托福综合写作

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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 extinctions correlates with the end of the last Ice Age, when global temperatures rose rapidly. As the ice retreated, mammoth habitats—cold, dry grasslands known as steppe-tundra—shrank dramatically. Pollen records from Alaska and Siberia show that these grasslands were replaced by forests and wetlands, which provided unsuitable forage for mammoths. Second, genetic studies reveal a severe population bottleneck among mammoths long before human hunters arrived in their final refuges. DNA from mammoth remains on Wrangel Island indicates that the population there had already declined to fewer than 300 individuals by 7,000 years ago, likely due to shrinking food supplies. Third, human hunting pressure was minimal in the regions where mammoths survived longest. Archaeological sites from the Paleolithic period show that humans primarily hunted smaller game, such as reindeer, and mammoth bones found at these sites are often from natural carcasses, suggesting scavenging rather than active hunting. Therefore, climate-induced habitat loss, not human predation, drove mammoths to extinction.

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The reading’s argument that climate change alone caused mammoth extinction is flawed. While it is true that habitats shrank, this does not explain why mammoths disappeared entirely, whereas other large herbivores like bison and horses survived. In fact, mammoths were highly adaptable and could have migrated to new areas, but they did not—why? Because human hunters followed them. First, the timing argument cuts both ways: the end of the Ice Age also saw an expansion of human populations into the Americas and Siberia. The last mammoths vanished exactly when human hunters arrived in their final refuges, such as Wrangel Island—around 4,000 years ago, not 7,000 as the reading claims. That 7,000-year date is from a single fossil, not a population census. Moreover, the genetic bottleneck the reading cites may have been caused by hunting, not climate, as overhunting reduces populations just as effectively. Second, the claim that humans only hunted small game is contradicted by new evidence: spear points embedded in mammoth ribs have been found in sites in Siberia and North America, and kill sites with butchered mammoth remains are now documented. Even scavenging would have disrupted mammoth social structures, as humans competed for the same carcasses. Third, climate change was not uniform; many regions remained suitable for mammoths, yet they died out only where humans were present. For example, mammoths survived on uninhabited islands like Saint Paul until humans arrived, then went extinct within a few centuries. Thus, human activity, not climate, was the decisive factor.