for National Geographic News
An underground trove of fossil skeletons found in Australia suggests humans, not climate change, drove the continent's large land animals to extinction 40,000 to 50,000 years ago.
The conclusion is based on the first scientific analysis of a rare cache of fossils exhumed from three caves in the arid Nullarbor Plain of southern Australia.
First discovered in 2002, the three- to four-million-year-old caverns have yielded fossils of 70 animal species dating from 800,000 to 400,000 years ago.
The menagerie includes 10 intact skeletons of Thylacoleo (lionlike marsupials), a nearly hippo-size giant wombat, and 23 kangaroo species—8 of them new to science.
Gavin Prideaux, a paleontologist at the Western Australian Museum who led the study, said the fossils are remarkable for their diversity and near-perfect condition.
The ancient bones also open an unprecedented window to the environment and climate of that part of Australia during the mid-Pleistocene (800,000 to 200,000 years ago), Prideaux said.
The findings reveal important clues to what eventually drove the plain's large Ice Age animals extinct.
Teeth Tell the Tale
The Nullarbor region receives just 8 to 10 inches (20 to 25 centimeters) of rain a year.
"It's incredibly dry and bleak," said study co-author Richard Roberts, a geologist at the University of Wollongong. "Things don't get much worse than that for an animal in search of free water."
The rich diversity of species found in the ancient caves shows that life was similarly thriving in the region during the Ice Age.
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