TOEFL Integrated Writing

📖 Reading Passage

The Extinction of the Megafauna: A Climate-Driven Event During the Pleistocene epoch, large terrestrial mammals such as woolly mammoths, saber-toothed cats, and giant ground sloths roamed across North America and Eurasia. Their sudden disappearance around 12,000 years ago has long puzzled scientists. While some have proposed human overhunting as the primary cause, a closer examination of the evidence suggests that climate change was the dominant factor. First, the timing of megafaunal extinctions aligns closely with the end of the last Ice Age, a period of dramatic warming and shifting vegetation patterns. As glaciers retreated and grasslands gave way to forests, the open habitats that these animals depended on shrank, reducing their food sources and leading to population declines. Second, climate models and fossil pollen records show that many megafaunal species experienced significant range contractions prior to human arrival in their habitats, indicating that environmental stress was already underway. Finally, archaeological evidence reveals that early human populations were sparse and their hunting tools relatively primitive, making it unlikely that they could have driven such large and widespread animals to extinction. Together, these points strongly support climate change as the principal cause of the megafaunal demise.

🎧 Listening Lecture

Now listen to a lecture on the same topic from a professor of paleontology. While the reading attributes the extinction of Pleistocene megafauna to climate change, this view is fundamentally flawed. First, the timing argument is misleading. In many regions, such as Australia and the Americas, megafaunal extinctions occurred after human arrival but did not coincide with major climatic shifts. For instance, in North America, the most significant extinction pulse happened about 12,000 years ago, just as the Clovis culture emerged, not at the peak of warming. Second, the claim that vegetation changes shrink habitats is too simplistic. Many megafaunal species, like mammoths, were generalist feeders that could adapt to diverse environments. Fossil evidence shows that some populations survived in forested areas by altering their diet. Moreover, the range contractions mentioned in the reading were often localized and did not necessarily lead to extinction; similar contractions occurred during earlier interglacials without such dramatic losses. Third, the dismissal of human hunting is unsupported. Recent studies have demonstrated that Clovis points and other advanced weapons were highly effective, and even low-density hunter-gatherer populations could exert immense pressure on slow-reproducing large animals. In fact, simulation models show that a modest hunting rate could drive megafauna to extinction within centuries. Thus, the reading’s climate-centric explanation fails to account for the full evidence.