You are in the desert lands of Australia, 50,000 years ago.

The air in the eastern savanna was thick, carrying the scent of dry eucalyptus and approaching rain that never seemed to fall. You sat perfectly still behind the shielding branches of a saltbush, watching a migration.

They moved like a slow-moving, living mountain range—a herd of Diprotodon.

There were maybe twenty of them, massive marsupials the size of modern rhinoceroses, plodding through the mudflats. Their skin was thick and dusty brown, with coarse, sparse hair covering their barrel-shaped bodies. They looked like wombat giants, but with strangely delicate, large heads.

Up close, the sound was overwhelming—a rhythmic, heavy thump-swish, thump-swish of their pillar-like legs moving through the dry, cracking clay. One massive adult walked within twenty paces of you. Its head was down, scanning the stunted shrubs, its snout working to tear away branches with its blunt, powerful teeth. From its lower jaw, two long, forward-pointing tusks—the "two forward teeth"—gleamed in the sun, perfectly designed for foraging.