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 exti

Both the article and the lecture talk about the possible theories for extinction of sea cows in the Bering Island of Siberia. The reading passage claims that although there are no clear reasons why they become extinct, some theories hypothesis the reasons, and provides three reasons of support. In contrast, the lecturer gives strong arguments from a rather different perspective. He casts doubt on all the author's reasons by explaining that there are major problems with all these theories and they cannot be the reasons for this extinction.

First, the author posits that over-hunting is one reason of decreasing in the populations. The professor refutes this point by stating that the sea cows are usually massive creatures, as mentioned in the passage, with about "9 meter long, and weight about 10 tones". Therefore, a single sea cow could feed an entire village for about a month. He also points out that since the region of Siberia didn't have many populations, the reason for hunting this number of animals are something more than just for food.

As the second point, the article explains that the vanishing of their main food sources, which is a sea plant named Kelp, due to ecosystem disturbance are the main reason for decreasing in populations. The lecturer, however, disputes this argument. He contends that since Kelp are the main source of food for other animals, such as Wales, the disappearance of these plants should also lead to the reduction of the wales population. Since no reports are published regarding a reduction in the population of wales, the Kelp are growing well and this is not a reasonable theory for the extinction of sea cow populations.

Finally, the author avers that the main reason of their extinction are European fur traders which tend to kill these creatures for their financial values and pose many developed weapons for killing them. The professor casts doubt on this statement by expressing that sea cow populations are decreased long before even the European traders reached the region. Thus, another reason should be responsible for the extinction of these animals, and as the professor states, "the traders are the ones who arrived last".