Viết tích hợp TOEFL

📖 Đoạn văn

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 decline correlates closely with the end of the last Ice Age, when global temperatures rose dramatically. As the ice retreated, the vast steppe grasslands that mammoths depended on were replaced by dense forests and wetlands, reducing their food supply. Second, genetic studies show that mammoth populations experienced a severe bottleneck around 20,000 years ago, well before human hunters arrived in large numbers in Siberia and North America. This population crash aligns with a period of rapid climate fluctuation, not with human activity. Third, isolated mammoth populations on Wrangel Island survived until about 4,000 years ago, long after humans had colonized the island. If human hunting were the main cause, these small, vulnerable populations would have been wiped out quickly, but they persisted for thousands of years, suggesting that habitat loss due to climate was the critical factor.

🎧 Bài giảng

The reading’s claim that climate change alone drove mammoth extinction is unconvincing. First, while temperature increases did alter habitats, mammoths had survived previous interglacial periods with similar warming. They were adaptable animals, capable of shifting their range. In contrast, human hunting introduced a novel pressure that mammoths had never faced. Second, the genetic bottleneck cited actually supports the hunting hypothesis: a rapid decline in population starting around 15,000 years ago coincides with the expansion of Clovis hunters, who left abundant spear points at mammoth kill sites. The earlier bottleneck at 20,000 years was not as severe as claimed, and populations recovered before the final collapse. Third, the Wrangel Island population is a red herring. These mammoths were dwarfed and genetically unhealthy due to inbreeding, making them vulnerable to any small disturbance. Archeological evidence shows humans did visit Wrangel Island during the period of their final extinction. Moreover, the island’s shrinking area due to rising sea levels would have reduced resources, but human presence likely delivered the final blow, as seen in other island extinctions where hunting and habitat disruption combined.