Victoria Fossil Cave, as the cavern is now known, warehouses the bones of something like 45,000 animals. Some of the oldest bones belonged to creatures far larger and more fearsome than any found today in Australia. They were the ancient Australian megafauna—huge animals that roamed the continent during the Pleistocene epoch.
In boneyards across the continent, scientists have found the fossils of a giant snake; a huge flightless bird; a wombat-like creature the size of a rhinoceros; and a seven-foot-tall kangaroo with a strangely short face. They've found the remains of a tapir-like creature; a hippo-like beast; and a lizard, 20 feet long, that ambushed its prey and swallowed everything down to the last feather.
The Australian megafauna dominated their ecosystems—and then were gone in an extinction spasm that swept away nearly every animal that weighed a hundred pounds or more. What, exactly, killed them off?
Given how much ink has been spilled on the extinction of the dinosaurs, it's a wonder that even more hasn't been devoted to the megafauna of the Pleistocene, creatures that had the dual virtues of being dramatically large and coexistent with humans. Prehistoric humans never threw spears at Tyrannosaurus rex, except in cartoons. Humans, however, really did hunt mammoths and mastodons.
The disappearance of American megafauna—mammoths, camels, giant short-faced bears, giant armadillos, stag moose, glyptodonts, saber-toothed cats, dire wolves, giant ground sloths, and horses, among others—happened relatively soon after the arrival of human beings, about 13,000 years ago. In the 1960s, paleoecologist Paul Martin developed what became known as the blitzkrieg hypothesis. Modern humans, Martin said, created havoc as they spread through the Americas, wielding spears tipped with stone points to annihilate animals that had never faced a technological predator. But the extinction spasm wasn't comprehensive. North America kept its deer, pronghorn, black bears, and a small type of bison; brown bears and newly arrived elk and moose expanded their ranges. South America retained jaguars and llamas.
In Australia the largest indigenous land animals are red kangaroos.