Scientists have been unable to agree on the reasons the megafauna became extinct. It is possible when humans came to Australia (around 48,000-60,000 years ago), and began hunting and using fire, they may have caused the extinction of the megafauna. Climate change, which made the country much drier during an Ice Age about 18,000 years ago, may have also have led to the extinction of the megafauna. Some scientists say that climate change alone caused the extinction of the megafauna. This argument does not allow for the fact that the megafaunal species had lived through two million years of climate changes. They had lived through a number of dry times before their sudden extinction.