A collection of 2.1-billion-year-old fossil organisms may be the earliest known example of complex life on Earth. The fossils are flat discs almost 5 inches across, and have scalloped edges and radial slits. Paleobiologists think they were either complex colonies of single-celled organisms or early animals.
The specimens predate the first truly multicellular organism, called Grypania spiralis, which appeared in the fossil record 1.4 billion years ago. But they don’t beat single-celled organisms that emerged about 3.4 billion years ago.