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 timing of mammoth decline correlates closely with the end of the last Ice Age, when global temperatures rose rapidly. As the ice retreated, the mammoth’s preferred habitat—cold, dry steppe grasslands—shrunk dramatically, replaced by forest and wetland. This habitat loss would have reduced food availability and fragmented populations, making them vulnerable to extinction. Second, genetic studies show that mammoth populations experienced a severe bottleneck long before humans arrived in large numbers in North America and Siberia. DNA analysis from fossil remains indicates a steady decline in genetic diversity over the past 20,000 years, which points to environmental stress rather than sudden hunting pressure. Third, archaeological evidence for human hunting of mammoths is scarce; only a few kill sites have been found, and these are insufficient to explain the extinction of a species that ranged across three continents. In contrast, climate models accurately predict the timing and pattern of extinction, aligning with known changes in vegetation and temperature. Therefore, while humans may have delivered a final blow to isolated populations, the overarching cause was climate-driven habitat loss.

🎧 Conferencia de audio

The reading’s argument that climate change alone drove the woolly mammoth to extinction is flawed. While it is true that temperatures rose and habitats changed, this does not exclude human hunting as the decisive factor. First, the correlation between habitat loss and extinction is weak. Mammoths had survived previous interglacial periods with similar warming, so they were capable of adapting to warmer climates if not for human pressure. In fact, mammoths persisted on isolated islands like Wrangel Island for thousands of years after the mainland extinctions, despite similar climate shifts—what differed was the absence of humans. Second, the genetic bottleneck cited in the reading actually supports the hunting hypothesis: a sudden population crash, consistent with overhunting, would also reduce genetic diversity. The gradual decline seen in the DNA data may reflect the final stages after humans had already decimated populations, not a slow climate-induced attrition. Third, the scarcity of kill sites is misleading. Archaeological evidence is often biased toward well-preserved, accessible sites; many hunting grounds may have been on now-submerged coastal plains or destroyed by glacial activity. Moreover, even if direct evidence is rare, indirect evidence—such as the development of sophisticated hunting tools and the simultaneous extinction of other large megafauna in regions where humans appeared—strongly implicates human activity. Thus, the lecture argues that climate change was a background factor, but human hunting was the critical trigger.