New Delhi, April 7 -- Newly discovered fossils have given scientists their first real glimpse of when Earth made a crucial transition from plants and unrecognizably simple animals to the complex creatures that took over the world and would eventually lead to us.

And it happened millions of years earlier than researchers thought.

More than 700 fossils found in southwestern China's Yunnan province offer a window into life from 539 million years ago, during the waning end of the Ediacaran period, a time of simple but strange animals that lived two-dimensionally in the oceans, never going up or down, researchers said.

But a study in Thursday's journal Science said many of the fossils in this trove are remnants of more complex animals that ...