TOEFL統合ライティング

📖 読解文章

The extinction of the dodo bird, a flightless bird native to Mauritius, is often attributed solely to human activities such as hunting and habitat destruction. However, a closer examination suggests that natural factors played a more significant role in its demise. First, the dodo had no natural predators before human arrival, which led to a lack of fear and an inability to escape from introduced species like rats, pigs, and monkeys that raided their nests. This vulnerability was not a result of human hunting but of evolutionary naivety. Second, the dodo's reproductive rate was extremely low—females laid only one egg per year—making the population highly susceptible to any environmental stress, including natural climate fluctuations. Cyclones and droughts that occurred regularly in Mauritius could have devastated the small population even without human interference. Third, volcanic activity on the island, which was geologically active, may have periodically destroyed dodo habitats and food sources, further reducing their numbers. Thus, while humans certainly contributed, the dodo's extinction was largely driven by pre-existing biological and environmental weaknesses.

🎧 リスニング講義

The reading presents a view that natural factors were primarily responsible for the dodo's extinction, but this interpretation is flawed. First, while the dodo lacked fear of predators, this trait only became fatal after humans introduced invasive species. Historical records indicate that Dutch sailors and their domesticated animals arrived in 1598, and within 80 years the dodo was gone. The timing directly correlates with human arrival, not with any natural predator. Moreover, studies of other island birds show that they can develop fear quickly if natural predation occurs, but no such native predators existed on Mauritius, so the dodo's naivety was not an adaptive failure but a pre-human condition. Second, the claim about low reproductive rates overlooks that many long-lived birds with single-egg clutches thrive for centuries if undisturbed. For example, the albatross also lays one egg per year and remains extant. The real issue was that introduced pigs and monkeys ate the eggs, which humans brought. Third, volcanic activity on Mauritius was minimal during the dodo's existence; the last major eruption occurred millions of years before the dodo evolved. In contrast, human deforestation for sugar plantations directly destroyed the dodo's forest habitat, a fact documented in colonial records. Therefore, the evidence strongly points to human actions as the decisive cause.