Around 40,000 years ago, the giant kangaroo disappeared from Australia. So did Diprotodon (rhinoceros-size wombats) and Palorchestes (tapirlike marsupials) as well as supersize birds, reptiles and some 50 other so-called megafauna--big animals. And now a record of fungal spores pulled from the swamp at Lynch's Crater in the northeastern corner of the continent reveals humans as the culprit.

"The megafauna declined soon after the time that we know people arrived in the region," explains zoologist Christopher Johnson of the University of Tasmania, lead author of the report published March 23 in Science. "We conclude that humans, not climate, caused the extinction."