The Ediacaran fossils themselves provide evidence of a puzzling leap in biological complexity, though not one nearly great enough (or of the right kind) to account for the Cambrian explosion. Before organisms like Kimberella, Dickinsonia, and sponges appeared, the only living forms documented in the fossil record for over 3 billion years were single-celled organisms and colonial algae. Producing sponges, worms, and mollusks from single-celled organisms is a little like transforming a spinning top into a bicycle.
