These life forms exploited the inorganic substrate of the world. 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. Life expanded to fit the meagre niches the world provided. Three billion years passed like motes in a god’s eye. 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. We have some evidence of a few flowerings of more complex life developing. Evolution is inevitable once you have an imperfectly self-replicating system in an environment of limited resources.įor 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. Even without the evidence nestling in the heart of every living cell, the logic itself should be infinitely persuasive. Its offspring faithfully copy the fortuitous error and thereby inherit it.

Here, a mutation can give one minuscule knot of organic chemistry the opportunity to replicate more efficiently than its neighbours. That leads to mutation and the possibility of change, and so to evolution. The replication process is fallible, of course everything is in this world. Imagine life as a manual that includes instructions for replicating itself. We fondly believe there is no reversing that step, however, after a few very basic criteria are satisfied. 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. Life sometimes seems destined, to we fortunate ones who live at the far end of time’s telescope.

They’ve been bustling and thriving and dying and trying to outdo one another in a ferocious, invisible war for survival. For almost half the aeons since its formation, this world has known self-replicating organic entities. 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. Bacteria have been leaching sustenance from strange chemicals in the bowels of the Earth or the depths of the sea.

For three billion years the only life here has been microscopic.

Adrian tchaikovsky the doors of eden