The text is about the extinction of diprotodon and hypothetical reasons caused it. The text provide three hypothesis of the diprotodon 's extinction, but the lecture refutes them. The first theory suggests that the diprotodon extinct because of a human 's fire disturb the natural environment of this animal. But the lecture says that Australia is too large and has so many landscape variaty that human 's fire could not have caused so tremendous damage. The second theory suggests that the diprotodon 's extinction is a result of human 's hunting to it. However, human have been hunting to a lot of distinct animals, but they have been living now. Finally, the third theory suggests that the extinction of diprodon connect with a dry and cold