Escritura integrada TOEFL

📖 Texto de lectura

The extinction of the woolly mammoth has long been attributed to human overhunting. However, a more compelling explanation is a combination of climate change and habitat loss. First, the end of the last Ice Age brought rapid warming, which drastically reduced the open grasslands—the mammoth’s primary habitat. As forests and tundra expanded, mammoth populations became fragmented and isolated. Second, climate change also altered migration patterns and breeding cycles. Warmer winters meant less snow cover, but also more frequent thaws and freezes, which created ice layers that prevented mammoths from accessing vegetation beneath. This reduced their food supply and reproductive success. Third, the isolation of small populations on shrinking habitat islands led to inbreeding and genetic decline, making them more vulnerable to disease and environmental stress. While humans did hunt mammoths, archaeological evidence shows that hunting pressure was not consistent across regions and often occurred after populations were already declining. Therefore, climate-driven habitat transformation, not human hunting, was the primary cause of the mammoth’s disappearance.

🎧 Conferencia de audio

The reading’s claim that climate change alone drove mammoth extinction is flawed. First, while grasslands did shrink, mammoths were highly adaptable. Fossil evidence shows they could survive in varied environments, including forest edges and tundra, and their diet included shrubs and other plants. Moreover, during previous interglacial warm periods, mammoths thrived despite similar habitat changes. Second, the ice-layer argument ignores that mammoths had strong tusks and feet adapted to breaking through snow and ice. Modern elephants in similar conditions can dig for food, and mammoth fossils show no signs of starvation. Third, genetic studies reveal that the final surviving populations, such as those on Wrangel Island, did show low genetic diversity, but they persisted for thousands of years. Their extinction coincided with the arrival of humans on the island, not a sudden climate event. In fact, human hunting is supported by kill sites, spear points embedded in bones, and the timing of extinctions—which match human expansion. Thus, while climate may have stressed populations, human overhunting was the decisive factor that pushed them over the edge.