The surface of the Proterozoic Earth

Abstract

In the imagination of the geologist, the ‘Proterozoic’ — the two billion years between 2500 million years ago and about 570 million years ago — is the time of great but shadowy events. The dark beginnings were closing: the world was starting to take its modern shape. In the late Archaean, we see the biosphere in its medieval morning, dispelling the Dark Ages. Then, at some time in the Proterozoic the bacteria give rise to the eukaryotes, with their cellular nucleus and sexual reproduction: courtship begins, and jousting between males — the High Middle Ages of our planet. At the end of the Proterozoic come hard skeletons and high-tech predators with good eating equipment: strong animals with manifest destiny. The modern ‘Phanerozoic’ world has begun. Such is the teaching of the geological textbooks. It may be true, or it may not. Perhaps evolution is not inevitably bound to follow a single path — there may have been many other pathways that, by accident, were not chosen. Had one of these alternative paths been followed, life today might have been very different. The history of life is rich in dividing points where chance or the hand of the deity prevailed. Perhaps we owe more than we can imagine to our bacterial predecessors during the Dark Ages.