Viết tích hợp TOEFL

📖 Đoạn văn

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 drastically reduced the mammoth’s grassland habitat, replacing it with forests and tundra that could not support large herds. Fossil pollen records from Siberia and Alaska show a rapid shift from steppe-tundra to shrub tundra around 10,000 years ago, coinciding with mammoth population declines. Second, climate-induced changes in food availability led to nutritional stress and reduced fertility. Isotopic analysis of mammoth bones from this period reveals elevated nitrogen levels, indicating starvation, while female mammoths showed lower rates of pregnancy compared to earlier periods. Third, the timing of extinction supports a climate cause: mammoths survived on isolated Arctic islands, such as Wrangel Island, until around 4,000 years ago—long after humans had arrived in mainland North America and Eurasia. If human hunting were the main factor, these island populations would likely have been wiped out quickly once humans reached them, but instead they persisted for thousands of years. Thus, environmental change, not human predation, was the decisive factor in the woolly mammoth’s demise.

🎧 Bài giảng

The reading argues that climate change, not human hunting, killed the woolly mammoth, but this conclusion is flawed. First, while grasslands did shrink, mammoths were not strictly grassland specialists. Their diet included a variety of plants, and they could adapt to shrub tundra. In fact, studies of mammoth dung from the last glacial period show they consumed willow and birch, which thrived in warmer conditions. So habitat change alone cannot explain their extinction. Second, the evidence of nutritional stress is misleading. The elevated nitrogen levels in bones could be due to aridity, not starvation, and low pregnancy rates might reflect natural population cycles or the effects of inbreeding as populations became small and fragmented, not a direct climate impact. Third, the survival on Wrangel Island actually supports the hunting hypothesis. When humans finally reached Wrangel around 1700 BCE, the mammoths disappeared within a few centuries—a rapid extinction event that matches overhunting, not gradual climate change. Moreover, the mainland mammoths vanished exactly when human populations expanded and developed advanced hunting tools, such as Clovis points. The coincidence is too strong to ignore. In sum, the reading misinterprets the data; human hunting was likely the primary cause.