การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

The extinction of the woolly mammoth has long been attributed to human overhunting, but recent evidence suggests that climate change was the primary driver. First, the timing of mammoth extinctions correlates more closely with major climatic shifts than with human expansion. Radiocarbon dating shows that mammoth populations declined sharply during the Bolling-Allerod warming (14,700-12,900 years ago), well before humans reached high densities in northern Eurasia. Second, mammoths were adapted to cold, dry steppe-tundra environments. As the climate warmed, forests and wetlands replaced these grasslands, shrinking their habitat and food sources. Isotopic analyses of mammoth bones reveal a shift to less nutritious plants during this period, indicating nutritional stress. Third, human hunting alone cannot explain the simultaneous extinction of other large mammals, such as the steppe bison and Irish elk, which also declined due to vegetation changes. In contrast, species like reindeer and moose, which thrived in warmer habitats, survived. Thus, climate-induced habitat loss, not hunting, was the decisive factor.

🎧 การบรรยาย

The lecture challenges the reading's claim that climate change alone drove mammoth extinction. While climate shifts were important, the professor argues that human hunting was the critical final blow. First, the reading overlooks evidence that human populations were present and actively hunting mammoths in many regions before their extinction. For example, at sites in Siberia and North America, spear points have been found embedded in mammoth bones, and kill sites show systematic butchering. Second, the claim that climate change caused habitat loss ignores the fact that mammoths were resilient and adaptable. They survived previous interglacial warm periods with similar vegetation changes, suggesting they could cope unless additional stress, such as hunting, was added. Third, the reading's comparison with other species is misleading. Steppe bison and Irish elk had different ecological niches, and their declines may have involved other factors, such as disease or competition. Moreover, humans did not hunt those species as intensively as mammoths, which provided abundant meat and ivory. The professor concludes that while climate change weakened mammoth populations, it was the arrival of skilled human hunters that pushed them over the edge, as evidenced by the correlation between human migration and extinction timelines in each region.