The account of the origin of life that I shall give is necessarily speculative [...] At some point a particularly remarkable molecule was formed by accident. We call it the Replicator. [...] [ The primeval soup ] must have become populated by stable varieties of molecules. [...] The primeval soup was not capable of supporting an infinite number of replicator molecules. [...] There was a struggle for existence among replicator varieties. They did not know they were struggling, or worry about it; the struggle was conducted without any hard feelings, indeed without feelings of any kind. But they were struggling in the sense that any mis-copying that resulted in a new higher level of stability, or a new way of reducing the stability of rivals, was automatically preserved and multiplied. The process of improvement was cumulative. [...] Some of [the replicators] may even have `discovered' how to break up molecules of rival varieties chemically, and to use the building blocks so released to make their own copies. [...] Other replicators perhaps discovered how to protect themselves, either chemically, or by building a physical wall of proteins around themselves. This may have been how the first living cells appeared. Replicators began not merely to exist, but to construct for themselves containers, vehicles for their continued existence. The replicators that survived were the ones that built survival machines for themselves to live in. The first survival machines probably consisted of nothing more than a protective coat. But making a living got steadily harder as new rivals arose with better and more effective survival machines. Survival machines got bigger and more elaborate, and the process was cumulative and progressive.

Was there to be any end to the process of the gradual improvement in the techniques and artifices used by the replicators to ensure their own continuation in the world? There would be plenty of time for improvement. What weird engines of self-preservation would the millenia bring forth? For thousand million years on, what was to be the fate of the ancient replicators? They did not die out because they are past masters of the survival arts. But do not look for them floating loose in the sea; they gave up that cavalier freedom long ago. Now they swarm in huge colonies, safe inside gigantic lumbering robots, sealed off from the outside world, communicating with it by tortuous indirect routes, manipulating it by remote control. They are in you and in me; they created us, body and mind; and their preservation is the ultimate rationale for our existence. They have come a long way, those replicators. Now they come by the name of genes, and we are their survival machines.

Richard Dawkins, The selfish gene.