Escritura integrada TOEFL

📖 Texto de lectura

The extinction of the woolly mammoth has long been attributed to overhunting by early humans. However, recent evidence suggests that climate change was the primary driver. First, the warming climate at the end of the Pleistocene dramatically reduced the mammoth’s grassland habitat. As forests and tundra expanded, the open steppe where mammoths thrived shrank, leading to population fragmentation and decline. Second, climate change altered the timing and availability of vegetation. Warmer temperatures caused shifts in plant communities, with less nutritious and less digestible forage such as woody plants replacing the grasses that mammoths depended on. This nutritional stress likely reduced fertility and increased calf mortality. Third, the timing of extinction varies geographically, which aligns with climate patterns rather than human arrival. In northern Siberia, mammoths survived until about 4,000 years ago, long after humans had arrived, but when the climate became wetter and warmer, they finally disappeared. Similarly, isolated populations on Wrangel Island persisted until 3,700 years ago, only succumbing when environmental conditions deteriorated. Therefore, climate change, not human hunting, was the decisive factor in the mammoth’s demise.

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The reading claims that climate change, not humans, killed the woolly mammoth, but this view is flawed. First, while climate did alter habitat, the loss of grassland was not uniform. Archaeological and paleontological evidence shows that large areas of suitable steppe remained in Beringia and Siberia well into the Holocene. In those regions, mammoth populations persisted until humans arrived with advanced hunting tools. The correlation between human colonization and extinction is striking. Second, the argument about nutritional stress is speculative. Studies of mammoth teeth and coprolites indicate that they could adapt to a wider range of plants than previously thought, including sedges and herbs. Furthermore, modern elephants, their relatives, thrive on varied diets, so a slight vegetation shift would not have caused extinction. Third, the timing argument actually supports human hunting. For instance, on Wrangel Island, mammoths survived for thousands of years after climate stabilized, but they went extinct soon after the first human settlers arrived, around 3700 years ago. In continental areas, the megafauna collapses occur just after human arrival, not during rapid climate shifts. Thus, human predation, not climate, best explains the extinction pattern.