A brief 250 million years of History from hadosaurus to hairy humans 250 million years ago there wasn't an upright two-legged human primate in sight. So who were the real first settlers in america? Thanks giant cockroaches scaly spiny scary dinosaurs Rats the size of cows and mammoths with 10 foot Tusk and all kinds of prehistoric animals that crawled lumbered and stalked across North America even before we evolved America's Horrible Histories find out what you've missed