It doesn’t take me 65 billion years to write a novel (though there are Monday mornings when my characters won’t behave and the bottom’s fallen out of my plot, when it feels like it), but thinking about how stories get written in terms of evolution really is helpful. The first thing to recognise is that evolution is inseparable from time, and that's true of writing too, and reading: there are many kinds of time involved. (And if you're wondering why I'm riffing on evolution, click here.)
Survival of the fittest is what's going on in my writing of a crazy first draft. I might have spent a year or two imagining, thinking, reading and researching the stuffs of my story but, as Rose Tremain says, re-imagining is partly a process of forgetting. It's the story (or, rather, my sense of it as an organic whole) that gets to choose - select, if you like - which stuffs get in and in what form. The story is the environment, and it (i.e. my creative sense) naturally selects the best-adapted to its form, plot, themes, voice and so on. So, understanding that, how might you work, so that your materials can evolve and adapt, and you have a chance to work out which have done so best? And how would you exclude things which prevent that "natural selection" operating? Ignore the market? Or your mother-in-law? Or your Inner Critic?
Indeed, one of the damaging things for an author about being on the book-a-year treadmill - which you may need to be on to survive economically - is that this kind of evolution can't be let happen naturally. Too often there isn't time to wait and work and brood, while the stuffs combine and adapt, but only to select the first reasonably suitable material, and hope that it can survive as it is, in this habitat.
There's a similar process going on in revision. The writer revising a novel is always chiefly concerned with survival of the best adapted to the new environment: not with what isn’t useful, but with what is. Yes, some of the early ideas may still show in the final version: some central and essential (the spine, say, or the pentadactyl limbs), while others (like the python’s pelvis or nipples on men) are mere vestiges which have no current function but were not enough of a disadvantage that they were selected against by the evolutionary process of re-drafting. If the essential work of murdering our darlings involves cutting the last remaining links to the Most Recent Common Ancestor, then we get out the knife, and leave the literary palaeontologists of posterity to puzzle out what the links might have been.
And, having murdered your darlings, there is, if you like, an ecological niche. What existing creature could adapt, or what new creature could you evolve, to re-stock the environment and bring it back to its original richness, but without the problem that sent your darling to extinction?
Then there's the strong sense that many writers have that characters evolve on their own: that they have some kind of reality beyond what we might choose to do with them. Sometimes they choose to cooperate, by suddenly doing something which changes everything for the better. Sometimes they seem to be competing with our plans and trying to beat them. This is all a metaphor, of course - and I thought it was pretentious to talk so, till the first time a character of mine couldn't be made to do what I'd planned. And the metaphor is useful: if a character evolves unhelpfully, the author has to choose whether to change the environment to fit the character, or change the origins of character and re-evolve them to fit the environment.
Mind you, if you asked me how a particular part of a story came about, it's a bit like reconstructing a dinosaur from half a jawbone, and a single horn: the conscientious palaeontologist knows it’s provisional, but must make some kind of sense of these grubby brown fragments for those who can't "read" an assemblage of bits into being an animal. If the horn turns out a hundred years later to have been a thumb-spike, then the only sensible option is to shrug, and reckon that in the meantime you’ve kept plenty of PhD students and children’s authors in business.
And of course it's human evolution which has given us our sense of story in the first place. We are conscious of our individual past and of our present, but imagination evolved to stretch beyond that, sideways, backwards and forwards; we imagine shared and other pasts, presents and futures, and make sense of how they're related by constructing a chain of causally related events: a narrative. As the philosopher and novelist Richard Kearney puts it, "we are storied creatures", and even scientists - including evolutionary biologists - have to make their data into a narrative before they can communicate the relationship of cause and effect, and get us to understand.
So I'll choose from all the material I have, and use words to makes the most convincing chain I can of causally-related events for the storied creatures – my readers – who are used to understanding things by following such chains. As Siri Hustvedt says, "Writing a novel is like imagining something that never happened". But all that those readers actually buy is black marks on a page; to read the book they have to re-create those characters, settings and events, using the materials in their own imagination. And that's a different environment, and the process is a re-evolution. Maybe, when someone doesn't like a book, it's just because the characters just couldn't be adapted to that new environment, and so didn't survive.