A huge marine mammal became extinct

The author of the reading believes that the Steller's sea cow has been extinct and provides three theories of support. However, the lecturer rejects the claim made in the reading, casting doubt on all the three theories presented in the passage. First, the author claims that overhunting in the past caused to sea cow extinction. This point is challenged by the lecturer. He says that these animals were really massive creatures with approximately ten tones weight. Also, one of them was enough for native Siberian people for months, and settlers did not need a lot of those large animals. Second, the author of the reading states that sea cow population has been extinct due to some ecosystem disturbances. Indeed, these disturbances caused to food shortage. The lecturer rebuts this. He points out that if these disturbances had responded for sea cow extinction, other marine animals would have extinct. He elaborates on this by mentioning that some marine animals such as whales did not extinct. Also, he mentions that there is no evidence of food shortage. Finally, the writer believes that European fur traders were responsible for sea cow extinction. The lecturer, on the other hand, says that when those traders arrived to the island, sea cow population was small. He puts forth the idea that those animal's population has been extinct before traders arriving.