Prelude: The Ediacaran Period Excerpt from Other Edens: Speculative Evolution and Intelligence by Professor Ruth Emerson of the University of California For three billion years the only life here has been microscopic. Bacteria have been leaching sustenance from strange chemicals in the bowels of the Earth or the depths of the sea. Ice comes, ice goes; the atmosphere for most of this time is a heady mix of chemicals either toxic to life or simply useless to it. There is life, though. For almost half the aeons since its formation, this world has known self-replicating organic entities. They’ve been bustling and thriving and dying and trying to outdo one another in a ferocious, invisible war for survival. Life sometimes seems destined, to we fortunate ones who live at the far end of time’s telescope. But what were the chances of success? Hard to say, and the no man’s land between inorganic process and organic existence is a region, not a hard dividing line. We fondly believe there is no reversing that step, however, after a few very basic criteria are satisfied. Imagine life as a manual that includes instructions for replicating itself. The replication process is fallible, of course; everything is in this world. That leads to mutation and the possibility of change, and so to evolution. Here, a mutation can give one minuscule knot of organic chemistry the opportunity to replicate more efficiently than its neighbours. Its offspring faithfully copy the fortuitous error and thereby inherit it. Even without the evidence nestling in the heart of every living cell, the logic itself should be infinitely persuasive. Evolution is inevitable once you have an imperfectly self-replicating system in an environment of limited resources. For the longest time, all the dramas of this particular world could have played out in a drop of water, life was of so small a scale. We have some evidence of a few flowerings of more complex life developing. But either the ice came back, acidity rose or oxygen levels fell – and these early signs collapsed like enlightened empires before the tides of barbarism. Three billion years passed like motes in a god’s eye. Life expanded to fit the meagre niches the world provided. And a constantly changing cast of life forms fled from one another, devoured their fellows like miniature tigers and traded genetic material like shady black marketeers hiding contraband in their trench coats. These life forms exploited the inorganic substrate of the world. Later, they exploited the organic matrix that was the graveyard of a million billion fast-lived generations of their forebears. Then in this Archaean microbial age, some unicellular visionary made an explosive discovery – akin to mankind’s discovery of fire, in terms of its impact. A volatile, poisonous chemical was tamed. Since the dawn of the Earth, this chemical had voraciously attacked any element it came into contact with; now it became the servant of developing life. This first metabolizing of oxygen might have been a defence mechanism. A process that incorporated the dangerous substance rather than falling prey to it. Perhaps your ancient ancestors took wolf cubs from their mothers with a similar goal. And what a world of opportunity opened up! Oxygen is a shortcut to a higher energy lifestyle, a ticket to getting out of the bacterial ghetto to live the high life. Our cast of characters becomes more complex as a result. Life gets a new paint job, alloys and go-faster stripes, now there is something more powerful under the hood. Next, single cells find advantage in numbers. Simple bacterial mats carpet the floors of every sea, shore to shore, washing up on lifeless beaches in a scummy slick of organic matter that cannot even decay properly yet. Then cells cling to each other, sharing the work so enough of them might even resemble some larger coherent being. But the next storm or riptide breaks them down again, to reform slowly, later. Some developing cells cling to those bacterial mats and rocks and sieve the water for organic detritus; some drift in the current. Cells evolve that can only survive in the company of their fellows, doing some small specialist role like an office worker who only deals with form G. But because the rest of the alphabet is also monitored, the paycheque still comes through every month. Multicellular life evolves exponentially, now it has that hard, oxygenated liquor to fuel it. Everywhere, a garden of life arises – the very first Eden. But it doesn’t support life like ours, or even our ancestors’. This is life of another caste entirely. A world of quilt-bodied things that lie supine upon the sea floor, or inch slowly across the bacterial mats without limbs or muscles, feeding upon them without mouths. They are a global community of organisms alien to us, and they live without tooth or claw, without eyes, without organs. Our world was like this once. Go back six hundred million years and you wouldn’t know the difference. But this is not our world. In this world, something awoke.