The Terror Birds of South America may be the most unusual predators ever to roam the face of the Earth. Until about five million years ago, the continent of South America was totally isolated by water from the rest of the world. A water gap separated the South from North America, and as a result, evolution had a chance to experiment. After the dinosaurs died out 65 million years ago, they left an ecological gap. The role of top predators in their world was left empty when they were no longer around. In the rest of the world, mammals filled in that gap the creatures that would evolve into sabre tooth cats, wolves and bears. But in South America, large, flightless birds evolved into the Top Predator role. These were the Terror Birds the only birds ever to become Top Predators on an entire continent.