A huge marine mammal known as Steller s sea cow once lived in the waters around Bering Island off the coast of Siberia It was described in 1741 by Georg W Steller a naturalist who was among the first Europeans to see one In 1768 the animal became extinct

Both reading and lecture discuss extinction of Stellar's sea cow. The reading passage implies that there are three possibilities. However, the professor disagrees with the reading passage. Accordingly, he presents three refutations.

First of all, the reading mentions that the sea cows could have been over-hunted by native Siberian people. Yet, the lecturer challenging the theory by arguing that sea cows are massive and population of Siberian people is not large. In fact, he states Siberian people have no reason to over-hunt the sea cow because sea cow can feed them for months. As a result, being over-hunted by Siberian people cannot be a factor that cause extinction of sea cows.

Secondly, the passage suggests that sea cow population might have become extinct due to ecosystem disturbances which cause decline of food supplies. Nevertheless, the scholar seriously contradicts the hypothesis by asserting that other marine animals like whales did not been affected by ecosystem disturbances. Furthermore, he contends that kelp might just be fine and sea cows did not experience food shortage. Therefore, the second hypothesis is unconvincing.

Last but not least, the reading article indicates that European fur traders might responsible for extinction of sea cows. Once again, the speaker opposes evidence revealed in the reading by assuming that sea cow population were already quite small when European fur traders came to the island. Moreover, he points out that there must be something which caused sea cow to decline before European arrived. Thus, extinction of sea cows cannot attribute to European fur traders.

To conclude, the professor argues against the theories in the reading article. That is to say, he maintains that none of the explanations of extinction is achievable.