The extinction of the megafauna—large animals such as mammoths, giant sloths, and saber-toothed cats—at the end of the Pleistocene epoch has long puzzled scientists. While many theories exist, the most compelling explanation is overhunting by early human hunters. First, archaeological sites across North America and Eurasia show a clear temporal correlation between the arrival of humans and the rapid decline of megafauna. For example, at the Clovis sites in North America, spear points are found alongside the remains of mammoths, indicating direct hunting. Second, megafauna species were particularly vulnerable to hunting due to their slow reproductive rates. Animals like the giant sloth gave birth to a single offspring every few years, meaning that even modest levels of hunting could drive populations to extinction. Third, the extinction event was selective, favoring smaller, faster-reproducing species. Fossil records show that while large mammals disappeared, smaller species such as deer and rabbits survived, which aligns with a human hunting preference for large, calorie-rich prey. Collectively, these lines of evidence point to human overhunting as the primary cause of the Pleistocene megafaunal extinction.
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The reading's claim that human overhunting caused megafaunal extinction is problematic. First, the correlation between human arrival and extinction is not consistent. In Africa, where humans evolved and hunted for millions of years, many large mammals like elephants and rhinos survived until recently. In Australia, megafaunal extinctions occurred around 50,000 years ago, but the archaeology shows sparse human populations with simple tools, unlikely to overhunt large animals. Second, the argument about slow reproductive rates is misleading. Many extinct megafauna, such as mammoths, had reproductive rates similar to modern elephants, which have survived despite centuries of hunting. Moreover, some megafauna, like giant kangaroos, had faster reproductive rates yet still went extinct. Third, the selectivity of extinction can be explained by climate change rather than hunting. The end of the Pleistocene saw rapid warming and habitat shifts. Larger animals require more food and space, making them more susceptible to habitat fragmentation. In contrast, smaller species adapted more easily. For instance, during the same period, many large predators like the saber-toothed cat vanished, but they were not typical human prey. Thus, while hunting may have played a minor role, climate change is a more plausible primary cause.
📝 작문 지시 Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
📊 TOEFL Integrated Writing Rubric
Content Accuracy: Accurately capture the relationship between lecture and reading
Information Completeness: Cover all key counter-arguments from the lecture
Structure & Coherence: Logical organization and progression
Language Use: Grammar, vocabulary, expression accuracy
Scored 0-30 based on holistic scoring (original 0-5, scaled to 30).
