Will Wilkinson touches on some of the evolutionary aspects of fiction. Alas, the link to the Denis Dutton essay he cites is broken, so I'll just work off his remarks. Any discussion of this sort should break down the different ways in which fiction derives from or conforms to different evolutionary "drives". Steven Pinker, for instance, emphasizes the narrative aspect—we read narratives in order to experience vicariously and derive lessons from possible life scenarios. (Or you could reverse the causality: We enjoy fiction because evolution has given us narrative-oriented minds.) I think you would file the "escapist" aspect of fiction into this category, though that complicates things.

Another aspect of fiction, as related by Dutton and Wilkinson, is the interpersonal aspect—we read fiction in order to learn how to emphasize with people; as Dutton says, "a matter of entering empathically into the minds of our fellows." Again, you can reverse the causal path—we only like fiction because we're empathetic. (Alternatively, some people like fiction because they have no other outlet for expressing empathy. Lack of empathy in real life leads to a retreat into fiction.)

That's interpersonal. There's also the intrapersonal aspect—we read fiction because it helps one develop, not just empathy, but the ability to understand one's own needs and motivations. Most theories of multiple intelligence, like Howard Gardner's, separate this intrapersonal cognition apart from interpersonal empathy. Now admittedly, you get this sort of self-reflecting more in poetry—to be really precise about it, poetry from Wordsworth on down until about the mid-20th century (bear with me, I was also an English major in college)—but it pops up frequently in fiction. I'm simplifying this all by reducing fiction to "needs" and "motivations", so here's an example of what I'm talking about:

His trouble was innocence. All of a sudden he discovered, not what he wanted to do but what he just had to do, had to do it whether he wanted to or not, because if he did not do it he knew that he could never live with himself for the rest of his life, never live with what all the men and women that had died to make him had left inside of him for him to pass on, with all the dead ones waiting and watching to see if he was going to do it right, fix things right…

That's William Faulkner, Absalom, Absolom. Never mind the context; follow my question: What in the hell sort of evolutionary purpose could meditations like the above ever serve? Imagine: You're a hunter-gatherer on the veldt. The ancestral lions approach. And you stop to ask: What's it all mean? Is my trouble... innocence? No! Ridiculous! Lion eat you! No!

At any rate—with the caveat that I don't know a damned thing about evolutionary psychology—I think The Problem With Evolutionary Psychology is this. No doubt there are some first-order drives that developed out of natural selection. The problem was that many of these evolution-given drives conflicted, and then further, second-order evolution was needed. For instance: Emotion, say, is a first-order evolutionary development. (Because those hunter-gatherers on the veldt needed to express pain, glee, whatever, to stay alive and catch food.) But then once emotion was, um, a species-wide characteristic, we needed a second-order evolutionary fix—the ability to control emotions. And so on and so forth, until we finally developed very useless abilities like the ability to write and appreciate introspective fiction, which was only necessary because evolution had bestowed upon us a whole bunch of rampant and conflicting drives that needed to be sorted out. And as society gets more complex, evolution-given attributes pile on top of each other. So it may in theory be possible to give evolutionary explanations for intricate social interactions (what Henry Farrell calls Sad Hominids), but we'll need to figure out which attributes were responses to which. Because we evolved against the self, rather than against nature.

I'm sure that's all bunk, by the way. But it's fun to think about.