TOEFL Integrated Writing

📖 Reading Passage

The extinction of the woolly mammoth at the end of the Pleistocene has long been attributed to human overhunting. However, a more nuanced cause—climate change—offers a compelling alternative. This essay argues that climate change, not human activity, was the primary driver of mammoth extinction, based on three lines of evidence. First, the timing of extinction correlates with a major climatic event, the Younger Dryas, a sudden return to glacial conditions around 12,900 years ago. This rapid cooling drastically reduced the open grasslands that mammoths depended on, replacing them with forests and tundra, which provided insufficient forage. Human populations at that time were sparse and lacked advanced hunting technology, making it unlikely they could have driven such a widespread species to extinction. Second, genetic evidence from fossil remains indicates a severe population bottleneck long before humans arrived in high numbers. DNA analysis shows that mammoth populations began to decline around 20,000 years ago, during a period of warming and habitat fragmentation, not during periods of intense human hunting. This suggests that environmental stress, not hunting, initiated the decline. Third, modern examples of megafauna extinction, such as the Irish elk, show that climate-driven habitat loss can cause extinction even when human hunting is absent. The Irish elk disappeared during a period of climatic warming, and its large antlers, which required abundant minerals, could not adapt to the changing vegetation. This parallel demonstrates that climate shifts alone can be sufficient to cause extinction of large herbivores.

🎧 Listening Lecture

The professor challenges the reading's claim that climate change was the primary cause of woolly mammoth extinction. While acknowledging climate shifts, the lecture argues that human hunting played a decisive role, offering counterpoints to each of the reading's arguments. First, the timing argument is flawed. The Younger Dryas cooling did not cause immediate extinction; mammoths survived for thousands of years after this event in isolated refugia. Instead, their final extinction occurred around 4,000 years ago, exactly when human populations expanded into their last remaining habitats, such as Wrangel Island. This correlation between human arrival and extinction is far more striking than any climate event. Second, the genetic bottleneck cited in the reading is actually evidence of human impact, not climate. The decline starting 20,000 years ago coincides with the spread of modern humans across Eurasia, who were skilled hunters. Genetic data also show a loss of diversity that is typical of populations subjected to intense hunting pressure, not just habitat fragmentation. Third, the Irish elk analogy is misleading. The Irish elk went extinct during a period of warming, but recent studies indicate that human hunting was a significant factor there as well. Moreover, mammoths had a broader diet and could adapt to varied environments, unlike the specialized Irish elk. Thus, the reading's reliance on this analogy fails to prove that climate alone could kill mammoths. In sum, the lecture insists that human hunting, especially in combination with climate stress, was the decisive factor, and the reading's dismissal of human agency is not supported by the evidence.