การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

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 factors have been proposed, the most compelling explanation is overhunting by early humans. First, the timing of megafauna extinctions correlates closely with the arrival of humans on each continent. In North America, for example, the disappearance of large mammals around 13,000 years ago coincides with the spread of the Clovis culture, whose distinctive spear points are found at kill sites. Second, megafauna species were particularly vulnerable to hunting due to their slow reproductive rates and large body sizes, which made them easy targets and slow to recover from population losses. Third, archaeological evidence supports human predation: numerous sites contain butchered remains of megafauna alongside human tools, indicating that hunting was not occasional but systematic. Taken together, these lines of evidence strongly suggest that human hunters were the primary drivers of megafauna extinction.

🎧 การบรรยาย

The reading attributes megafauna extinction to human overhunting, but this view is overly simplistic. First, the correlation between human arrival and extinction is not consistent. In Africa and parts of Eurasia, where humans evolved and coexisted with megafauna for hundreds of thousands of years, extinctions were gradual and limited. In contrast, the sudden extinctions in the Americas and Australia occurred after humans arrived, but this could also be explained by climate change. Second, while large animals have low reproductive rates, many species had survived previous climate shifts without human pressure. For example, during earlier interglacial periods, mammoths and giant sloths persisted despite warming events, suggesting that climate change, not human hunting, was the critical factor. Third, the archaeological evidence is sparse and ambiguous. Only a few kill sites have been discovered, and many purported butchered bones may actually have been broken by natural processes like trampling or carnivore activity. Moreover, if hunting were systematic, we would expect far more sites and a more gradual decline, but the fossil record shows a rapid die-off, which is more consistent with a sudden environmental catastrophe such as a comet impact or disease outbreak.