The reading material explores the issue of the reasons that lead to the extinction of Steller sea cow. The writer of the article stress that over hunting by native Siberian, the change of ecosystems, and the hunting by the European fur traders are the reasons to blame, however, the speaker of the lecture casts doubt on the arguments and contradict it with the following reaons. First, the speaker disagree with the idea of over hunting by local people because the Steller sea cow is so enormous that can feed the population for several months. Although those local people do hunt Steller sea cow, there is no reason for them to hunt a lot. The speaker identifies the weakness of the reading material by evaluating the reasonability of the action. Therefore, native Siberian's demand of Steller sea cow as food resource weakens the writer's statement. Second, even though the writer suggests that the change of ecosystems shorten the main food resource of Steller sea cow, leading the population of the spices to decline, the speaker argues that if the ecosystems did undergo a dramatic change, this change not only would decrease the population of Steller sea cow, but also would post a great impact on other marine mammal such as whale. The speaker provides the truth that there is no evidence that shows the influence during this period. Third, the writer carelessly concludes that the hunting by the European fur traders is the main reason that causes the extinction of Steller sea cow. Based on the historical information, the speaker disputes the statement by stressing that before the European fur traders arrived, the population of Steller sea cow had declined dramatically already, thus, hunting by fur traders shouldn't be the main reasons of the extinction. In conclusion, although the writer of the reading material provides the reasons which somehow look plausible, the speaker in the lecture provides more convincing and concreted evidences which indicate that the main reasons of the extinction still remain unsure.