Stories are useful for so much more than just helping us get lucky, however, as Gottschall points out. For listeners (and readers), stories instruct. From Aesop's fables to essays in women's magazines, they encourage us to think about what happens to people (or anthropomorphized animals) who, say, behave more like hares than tortoises or have a threesome with their best friend and her husband. Stories socialize. By demonstrating the intricacies of human relationships, novels and memoirs encourage us to rehearse what we would do and say in a variety of situations—platonic, familial, and maybe especially romantic. Stories—particularly fictional ones—moralize. They help us figure out our values and whet our need for justice.

When we tell stories about ourselves, they also serve another important (arguably higher) function: They help us to believe our lives are meaningful. "The storytelling mind"—the human mind, in other words—"is allergic to uncertainty, randomness, and coincidence," Gottschall writes. It doesn't like to believe life is accidental; it wants to believe everything happens for a reason. Stories allow us to impose order on the chaos.

And we all concoct stories, Gotschall notes—even those of us who have never commanded the attention of a room full of people while telling a wild tale. "[S]ocial psychologists point out that when we meet a friend, our conversation mostly consists of an exchange of gossipy stories," he writes. "And every night, we reconvene with our loved ones ... to share the small comedies and tragedies of our day."

What's more, in private, we're constantly working on far more serious story projects: memoirs that (for most of us) will never be published, or even written down.

Every day of our lives—sometimes with help working things out via tweets or Facebook status updates—we fine-tune the grand narratives of our lives; the stories of who we are, and how we came to be. Those identity tales are usually significantly fabricated, according to Gottschall, no matter how much we might think of ourselves as people who always tell the whole truth, and nothing but the truth. "Scientists have discovered that the memories we use to form our own life stories are boldly fictionalized," he notes. We might, for instance, tell ourselves we had more power over a break-up than we really did, because it's more pleasant to believe that than to face the messier reality that the other person was as much an agent of the split as we were. Or we might convince ourselves that getting fired was what we subconsciously really wanted; how else would we have found time to write that screenplay we've been thinking about for years?