The same thing was said about North America when the humans got here 12,000 years ago.
Now that we've found 30-40,000 year old human foot prints in Mexico, what killed the large mammals off 12,000 year ago, huh?
In the middle of Australia there is a group of three or four meteorite craters called the Henley craters. They're like the Arizona meteorite crater -- not so big, but there are several of them -- and, like in Arizona, the land was scattered with pieces of iron meteorite. I think the [inaudible] dating very slow growing desert plants. They believe that the date is about 5000 years ago -- the formation of the craters. The Aboriginal name for this area is the "Place Where The Sun Walked on the Earth" -- they must have seen it!