The extinction of the woolly mammoth (Mammuthus primigenius) at the end of the Pleistocene has long intrigued scientists. While climate change and human hunting are often cited, a compelling theory attributes their demise to a hyperdisease—a highly virulent pathogen spread by humans or their domesticated animals. This hypothesis is supported by three key observations. First, the timing of mammoth extinctions correlates with human migration into Siberia and North America, suggesting that humans introduced the pathogen to naïve populations. Second, the rapid disappearance of mammoths, often within a few thousand years of human arrival, is more consistent with a swift disease outbreak than with gradual climate shifts or sustained hunting pressure. Third, genetic evidence from mammoth remains shows a sharp decline in genetic diversity just before extinction, which is a typical signature of a population bottleneck caused by an epidemic, as seen in modern examples like the rabbit calicivirus. Thus, the hyperdisease hypothesis offers a plausible explanation for the enigmatic extinction of this megafauna.
🎧 听力讲座
🎯 模拟考试环境：先点「播放讲座」听完内容，再作答。听力原文默认隐藏。
The reading’s hyperdisease hypothesis is intriguing, but it suffers from several critical flaws. First, the correlation between human arrival and mammoth extinction is not consistent. In some regions, such as Wrangel Island, mammoths survived for thousands of years after humans arrived, which would be impossible if a highly lethal pathogen had been introduced. Second, other megafauna, like horses and camels, went extinct at the same time, yet they would have been equally susceptible to a hyperdisease. If a pathogen were the cause, we would expect to see many species affected, but genetic and fossil evidence shows that some species, such as bison, survived with little impact. Third, the purported genetic bottleneck is not unique to epidemics; it can also result from habitat fragmentation due to climate change, which reduced mammoth populations gradually. Moreover, no ancient pathogen DNA has ever been identified in mammoth fossils, whereas we have found DNA of other diseases in ancient remains. Therefore, the evidence better supports non-disease explanations like climate-driven habitat loss and human hunting.
📝 คำแนะนำการเขียน 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).
