Escritura integrada TOEFL

📖 Texto de lectura

The extinction of the woolly mammoth has long been attributed to overhunting by early humans, but recent evidence suggests that climate change was the primary driver. First, the warming period at the end of the Pleistocene dramatically reduced the mammoth’s grassland habitat. As forests and tundra replaced steppe, the open landscapes that mammoths depended on for foraging shrank, leading to population fragmentation and decline. Second, genetic studies of fossil remains show a significant loss of genetic diversity in mammoth populations well before the arrival of humans in many regions. This bottleneck indicates that populations were already stressed by environmental pressures, not by hunting. Third, the timing of mammoth extinction varies by region, often coinciding with local climate shifts rather than human expansion. For example, on Wrangel Island, mammoths survived until about 4,000 years ago, long after humans had arrived, but they disappeared shortly after a period of rapid climate fluctuation. Therefore, while human hunting may have delivered the final blow to some isolated populations, the overarching cause was climate-driven habitat loss.

🎧 Conferencia de audio

The reading presents a compelling case for climate change as the main cause of mammoth extinction, but it overlooks key counterevidence. First, while warming did alter habitats, mammoths were highly adaptable and had survived previous interglacial periods with similar temperature increases. In contrast, the rapid expansion of human hunters across continents correlates more precisely with extinction events. For instance, in North America, mammoths vanished within a few centuries of the arrival of Clovis hunters, a pattern too abrupt to be explained by gradual habitat change. Second, the genetic diversity decline mentioned in the reading may not predate human impact. Recent DNA analyses from Siberia show that the sharpest drop in diversity occurred after humans entered the region, not before. This suggests that hunting, not climate, drove populations to small, isolated groups. Third, the Wrangel Island case actually supports human involvement. Although humans reached the island later, they arrived around 4,000 years ago, and the mammoth’s final extinction coincided with human settlement, not just climate fluctuation. In fact, archaeological evidence shows mammoth bones with cut marks from human tools on the island. Thus, the reading’s arguments fail to refute the strong link between human hunting and mammoth extinction.