While the anthropogenic impact on global species diversity is clear, the role of ancient human populations in causing extinctions is more controversial. New data presented this week at the Society of Vertebrate Paleontology meetings in Dallas, Texas, implicates early humans in the extinction of large mammals, birds and lizards in Australia. More precise dating of these extinction events places them 14,000 years after the first arrival of humans in Australia... Alroy estimated the likely time-range during which the extinction occurred based on the distribution of radiocarbon dates. He found that the megafauna disappeared between 27 and 40 thousand years ago. Using a similar method, he estimated that the first humans arrived between 50 and 61 thousand years ago. This confidently puts humans on Australia when the megafaunal extinctions occurred. The timings also suggest that there was a 14,000 year lag between the first appearance of humans and their impact on the megafauna.
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!
Abstract: More than 85 percent of Australian terrestrial genera with a body mass exceeding 44 kilograms became extinct in the Late Pleistocene. Although most were marsupials, the list includes the large, flightless mihirung Genyornis newtoni. More than 700 dates on Genyornis eggshells from three different climate regions document the continuous presence of Genyornis from more than 100,000 years ago until their sudden disappearance 50,000 years ago, about the same time that humans arrived in Australia. Simultaneous extinction of Genyornis at all sites during an interval of modest climate change implies that human impact, not climate, was responsible.