Half a billion years before human hands would one day unearth them, creatures were quietly rehearsing what it means to be an animal on the floor of a deep, ancient ocean. Fossils recovered from Canada's Mackenzie Mountains — some 567 million years old — now suggest that the earliest complex life did not emerge in the sun-warmed shallows we long imagined, but in the stable, dark depths of the Ediacaran sea. The discovery, led by researchers from the American Museum of Natural History and Dartmouth College, pushes back key evolutionary milestones by up to ten million years and places North Ameri