Climate change killed off megafauna: study A NEW study has vindicated Aboriginal people over the extinction of Australia's megafauna, finding wild climate fluctuations killed off most of the giant species well before humans arrived. The idea that early Aborigines wiped out the megafauna  which included a ferocious marsupial lion, a hippopotamus-sized wombat, a five-metre goanna and a 230 kilogram kangaroo  was popularised in palaeontologist Tim Flannerys 1994 book Future Eaters.