The reading passage argues that the primary reason for the extinction of Megatherium, the giant ground sloth, was excessive hunting by early humans. However, the professor in the lecture disputes this claim, presenting alternative explanations such as climate change and habitat loss. First, the reading claims that as humans arrived in South America, they hunted Megatherium intensively for food and other resources, leading to a sharp decline in its population. However, the professor challenges this idea by stating that there is very little direct evidence of human hunting. He explains that very few Megatherium fossils have been found with signs of butchering, making it unlikely that hunting was the main cause of their extinction. Second, the reading suggests that the slow reproductive cycle of Megatherium made it particularly vulnerable to overhunting. Since these animals reproduced at a slow rate, even moderate hunting could have led to population collapse. In contrast, the professor argues that climate change played a more significant role. He explains that at the time of Megatherium’s decline, the climate was shifting rapidly, leading to changes in vegetation. Since these giant sloths relied on specific plants for food, the loss of these plants likely contributed to their extinction. Finally, the reading proposes that Megatherium disappeared around the same time humans expanded their presence in the region, further supporting the idea that hunting was the main cause. However, the professor refutes this by stating that Megatherium populations had already been declining before significant human expansion. He suggests that environmental changes, including habitat destruction and shifts in food sources, had a greater impact on their survival than human activity. In conclusion, while the reading attributes the extinction of Megatherium to human hunting, the professor disagrees by arguing that a lack of evidence for hunting, climate change, and habitat loss were more likely the true causes.