การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

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 reduced the mammoth's grassland habitat. As temperatures rose, forests and tundra expanded, replacing the steppe-tundra that mammoths depended on for food. This habitat loss would have led to population decline regardless of human activity. Second, climate change caused shifts in precipitation patterns, leading to wetter conditions. The increased moisture promoted the growth of mosses and other plants that were less nutritious for mammoths, reducing their overall health and reproductive success. Third, the timing of mammoth extinction correlates more closely with climatic events than with human arrival. On islands like Wrangel Island, mammoths survived until around 2000 BCE, long after humans had arrived, but their extinction there coincides with a period of rapid climate warming. Thus, while humans may have contributed to localized declines, the overriding cause of woolly mammoth extinction was climate-induced environmental change.

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The reading's argument that climate change alone caused mammoth extinction is unconvincing. First, while habitat shifted, mammoths were not inflexible. Fossil evidence shows they could survive in diverse environments, including forested areas. During interglacial warm periods in the past, mammoths persisted despite similar habitat changes, so the warming at the Pleistocene's end was not uniquely devastating. Second, the claim about reduced nutrition from wetter conditions overlooks that mammoths had a broad diet. Isotopic analyses of mammoth bones reveal they consumed a variety of plants, including shrubs and forbs, not just grasses. Furthermore, wetter conditions could have increased overall plant biomass, providing more food, not less. Third, the timing argument is flawed. On the mainland, mammoth populations were already fragmented and declining when humans arrived, but this does not rule out human impact; even small numbers of hunters could have finished off stressed populations. As for Wrangel Island, the mammoths there were dwarfs, and their extinction around 2000 BCE might have been due to inbreeding and human hunting, not climate. In fact, climate models show that the island's environment was stable during that period. Therefore, the evidence points to human overhunting as a significant factor, with climate playing a secondary role.