In the Late Quaternary, Australia was home to an array of megafauna. The half-ton Palorchestes azael, the rhinoceros-sized Diprotodon, and even the giant koala, Phascolarctos stirtoni, roamed Australia's interior. However, between 50,000 and 45,000 years ago, they all vanished. Although recent studies indicate human colonization as a potential cause of their extinction, the exact mechanism has never been resolved. Now, geologist Gifford Miller from the University of Colorado at Boulder and his colleagues believe they have uncovered the answer.