While the issue both the reading and listening focus on is the possible causes of sea cows’ extinction, which are the huge marine mammal lived around Bering Island, the listening casts doubt at three main points.
At the first point, the reading states that overhunting by Siberian people is a possible reason which contribute to sea cows’ extinction. According to the listening, sea cows are massive animals. They can be up to nine meters long and weight ten tons. Therefore, a single sea cow can feed Siberian people for months. In addition, the Siberian population was quite small, so there was no need for them to hunt a lot sea cows. As a result, sea cows were not likely to go extinct due to overhunting by Siberian people. This is a direct contradiction to what is indicated in the reading.
At the second point, the reading believes that their food source was negatively affected by ecosystem disturbance. It resulted in the decline in kelp population, which sea cows feed on. On the contrary, the listening argues that if the ecosystem became severe before 1768, it not only affected kelp population but other part of the marine life, like mammals. However, there was no report of decline in whale population, which indicates that the marine life was growing just fine. Accordingly, the shortage of food is not the convincing reasons for the sea cows extinction. This is an important point that was not considered by the author of the reading passage.
At the last point, the reading mentions that European fur traders, who had the destructive weapon that can kill sea cows on large kill, are the reasons leading to sea cows extinction. However, the listening confirms that reports have shown that by the time the European arrived, the population of sea cows was quite small. Their population was larger 100 years before 1700, which is long before the European arrival. Therefore, no matter what had happened before, the European was the last to arrive when it came to sea cows extinction. This is yet another example of how the professor and the author of the reading passage contradict one another.