TOEFL Integrated Writing

📖 Reading Passage

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 extinction coincides with the rapid warming at the end of the last Ice Age, around 10,000 years ago. As temperatures rose, the open grasslands that mammoths depended on were replaced by dense forests and wetlands, reducing their primary food source. Second, genetic studies show a severe population bottleneck in mammoths long before humans arrived in their final habitats, such as Wrangel Island. This indicates that populations were already declining due to environmental stress, not sudden human predation. Third, archaeological records from Siberia and North America reveal that early human hunters primarily targeted smaller, easier prey like reindeer and bison, and mammoth kill sites are extremely rare. Even where human and mammoth remains coexist, the evidence of hunting is often ambiguous, such as broken bones that could result from scavenging. Therefore, while humans may have delivered a final blow to isolated populations, the overwhelming cause of mammoth extinction was climate-driven habitat loss.

🎧 Listening Lecture

The professor argues that the reading’s claims are not convincing. First, although warming occurred 10,000 years ago, similar warming events had happened earlier in the Pleistocene without causing mammoth extinction. For instance, mammoths survived interglacial periods with warmer temperatures, so climate alone cannot explain their demise. Second, the genetic bottleneck on Wrangel Island actually supports human involvement: the island was isolated, and mammoths there survived until about 4,000 years ago, long after the main extinction. This suggests that mainland populations were wiped out by humans, while the island population only succumbed when humans finally reached it, likely through hunting. Third, the scarcity of mammoth kill sites is not surprising because early humans would have processed large carcasses at kill sites, leaving few articulated bones, and the lack of such sites may reflect poor preservation rather than no hunting. Moreover, recent discoveries in Siberia show mammoth bones with embedded spear points and cut marks, proving active hunting. Thus, the lecture contends that human overhunting, not climate, was the decisive factor in mammoth extinction.