Between 50,000 and 10,000 years ago, many of the world's largest mammals disappeared. Picture creatures like saber-toothed cats with 7-inch fangs and elephant-sized sloths. Woolly mammoths whose curved tusks grew longer than 12 feet. Even a three-ton wombat the size of a car. After roaming Earth for millions of years, most large-bodied mammals—especially those weighing over a ton—were wiped out. Vanished.