When did you last immerse yourself in the pool of make-believe? In a television drama, or a film, watched from the sofa or a cinema seat? A story you just read to your children? The comic strip you read in this morning’s newspaper? A joke you heard at work or around the table? The novel you read last night? A love song on your iPod? Chances are that the last fictional story you encountered was not long ago, and the previous one not long before that.

Why do we spend so much of our time in story worlds, from pretend play and fairy tales to novels, comics, TV sitcoms and vampire series, movies from Hollywood to Bollywood and arthouse, and the stories in poems, song lyrics and computer games? Wouldn’t you expect a successful species, as we seem to be, to spend its time focusing on what’s true in the world? But we, uniquely, often distract ourselves with what we know to be untrue.

I teach literature, and fictions beat at the heart of literature. I don’t want to take fictions for granted, even if they give us such pleasure. We also get pleasure from ice cream and fresh butter. Explaining why we enjoy such treats by answering, “Because they are delicious,” only takes us around in circles. Dung beetles find delicious the smell and taste of dung. We need to explain why we find pleasing the pleasures we happen to have. To a dung beetle, or to any species we know but our own, our taste for stories would be perverse.

In 1859, in On the Origin of Species, Darwin explained the variety of life on earth in terms of natural selection. His explanation has been confirmed and deepened in ways even he could never have anticipated. In a world of finite resources, nature selects relentlessly, over the generations, in favour of those variations that offer some advantage, however small, in terms of survival and reproduction. Over time those variations become established as adaptations, as bodily or behavioral features across a species.

Natural selection selects stringently, weighing benefits against costs. Storytelling is comparatively cheap, except that it takes time, and a little energy, to invent, tell, and listen to stories. But we could use that time for activities with immediate biological advantage, like gathering resources or competing with others for resources already stockpiled.

Biologist Richard Dawkins notes that if building dams were not beneficial to beavers, beavers with less inclination to pursue such a useless activity would have outbred those who wasted energy this way. But since dam-building persists, it must offer beavers benefits. In the same way, if fiction offered no benefits in terms of reproductive success, those of us with less inclination to engage in it would thrive, and fiction would fade away as a human behavior. Manifestly, it has not. What benefits does it offer?

It’s no puzzle at all why we tell true stories. If we can comprehend events, and if we have language, and if we are highly social animals, then, without needing to add anything else, we will tell true stories. Chimpanzees monitor each other intensely, and one chimp will even bring to the attention of another the fact that this male and that female are copulating behind that tree. Biologists see humans as not just social, like chimps, but as uniquely ultrasocial. We have even more reason than chimps to want to know who’s doing what to whom. And with true narrative we can also point who has done you-know-what to whom, or who has had done this or that successfully, and where, and how.

But how could we afford an unflagging appetite for stories we know to be untrue? To answer that I think we have to explain why we expend time and resources, across cultures, epochs, classes, life stages and intellectual levels, on the arts in all their forms: music, dance, design, and stories.

I say this because it seems highly likely that the literary arts were the last of the arts to emerge. Analogues of music and dance exist in many species, in birds, in intelligent non-primates like whales and dolphins, and in primates like gibbons and chimpanzees. Chanting and rhythmic movement and perhaps rhythmic stick- or rock-banging—in other words forms of proto-song, proto-dance and proto-drumming—seem to stretch back millions of years. And the earliest signs of the visual arts in hominins date back hundreds of thousands of years.

Many Acheulean stone handaxes (which date from over 1.5 million to 100,000 years ago) have been found in impractical sizes, too large or too small, or with an unnecessary degree of symmetry, and without the usual microscopic signs of wear and tear, as if they have been painstakingly shaped for purely ornamental reasons. Ocher seems to have been mined for human bodily adornment for perhaps 240,000 years. Although the matter is far from being decided, a full modern language adequate for telling stories seems to date back only to a hundred thousand years ago, or half as long again. Other proto-arts had probably been developing for hundreds of thousands of years before the first full-scale fictions. Why did the arts become established across human cultures and life stages?

In On the Origin of Stories I explain art as deriving from play. Play occurs in all mammals where it has been looked for, in birds, and even in octopi, the most intelligent of invertebrates. For good evolutionary reasons, animals normally try to exert the least effort to accomplish their goals. Animals conserve resources—except in play, where they, and we, happily expend energy. Why?

The amount of play in a species correlates with its flexibility of behavior. If behavior is not built in genetically, it needs to be learned to maximize flexibility. If a behavior is hardwired, there would be no point in exercising it in a way as expensive in energy and risk as play. But if there is room for flexibility, then individuals who can improve their execution of complicated behaviors and their judgment of situations in which they are needed, will fare better. This is especially the case in critical behaviors such as flight or fight.

If in secure situations animals practice the behaviors that make the greatest life-and-death difference, they can then perform better and with more context-sensitivity in moments of high urgency. Recent work on brain plasticity shows that brains can be rewired incrementally through repeated activity, so long as it engages full attention. For that reason play has developed in many species, especially those like birds and mammals, which enjoy the security parental care provides. Over generations, the motivation to practice has evolved and strengthened until play becomes compulsive, self-rewarding, irresistible. And the forms of play most popular in other animals and even ourselves are chasing or racing (flight) and rough-and-tumble (fight).

We, uniquely, gain most of our advantages over other species, and even over one another, not from physical but from mental strength and speed. Information matters for any species, but for no others is it so decisive as for ours.

Minds can process information rapidly only when it falls into patterns for which those kinds of minds have been prepared. Detecting patterns within information enables minds to understand their environment efficiently. When recording devices track acoustic frequencies to analyze speech sounds objectively, they show continuous variation between distinct but related phonemes (b and p, for instance) and continuous sound production across what we hear as syllable and even word breaks. Yet even infants, even children not yet born, filter out the informational noise that tape recorders cannot help registering and begin to extract the patterns of phonemic distinctions in the language of their birth environment.

All animals have preferences for particular kinds of patterns that can yield rapid rich inferences for their species. But because we particularly crave information, because we have a much more open-ended curiosity than other animals, we have a wide and intense appetite for pattern, for clear information, crisp outlines, bold colors, pure sounds: we therefore find beauty in flowers or butterflies, paintings or photographs, birdsong or music. We find pattern beautiful even in things we don’t recognize, like images of electron flow or light diffraction at minute scales, or nebulae at vast ones.

Unlike other animals, therefore, we not only chase and tussle, we not only play physically, but we also play cognitively. Art, I suggest, is open-ended cognitive play with pattern, with patterns of intersecting patterns, in the information modes that matter most to us: sight, in the visual arts; sound, especially in music; and social information, in fiction.

Minds, as recent neuroscience has discovered, can be plastic: they can be reshaped. But not easily or rapidly, as we know from learning a new language later in life. It takes much repetition and focused attention, as first some new neural connections are made, then more on top of those, then still more on top of those. As the most successful connections strengthen, mental processing becomes more efficient, until the whole network is established and increasingly efficiently tuned and fast-tracked.

Play can reshape minds to become more efficient and flexible in particular kinds of response because it is compulsively self-rewarding. We take part in it again and again, our minds fully focused. So too with the uniquely human cognitive play of art, including the art of fiction. The compulsiveness of music, images and story reshapes human minds just as physical play shapes animal bodies and minds. “Research suggests,” writes Melvin Konner in his magisterial The Evolution of Childhood (2010) that in positive and playful moods we “are more open to experience and learn in better and more varied ways.”

We process aural, visual and social information more rapidly, accurately and flexibly through playing in a self-rewarding way with the high-density information patterns of art. Without instruction or prompting, children engage eagerly in song, dance, drawing or shape-making. They adore pretend play and want stories told again and again.

Reshaping minds requires focused attention, yet minds evolved to monitor the immediate environment, not the unreal. To compete for attention with the real and immediate, fictional stories therefore tend to offer high-intensity information, with striking characters, often with unusual powers, facing high stakes and extreme situations. Even a bright four-year-old concocting his own story knows how to hook and hold his own attention and that of listeners:

Once there was a dragon who went poo poo on a house and the house broke then when the house broke the people died and when the people died their bones came out and broke and got together again and turned into a skeleton and then the skeletons came along and scared the people out of the town and then when all the people got scared out of the town then skeleton babies were born and then everyone called it skeleton town and when they called it skeleton town the people came back and then they got scared away again and then when they all got scared away again the skeletons died no one came to the town so there was no people ever in that town ever again.

This boy’s social cognition has not yet become sophisticated enough to incorporate intention into his story, yet he already perfectly understands attention—as of course do mothers telling fairy tales, or professional storytellers aiming at their larger audiences.

The account of art, and especially of fiction, that I propose involves no unique morphological traits. In the case of fiction, I assume we had already developed both systems of event comprehension, like the psychological capacities known as theory of mind—understanding others in terms of not just actions but also of intentions, desires and even beliefs—that make it possible to track the full complexity of social events, and the capacity for language that makes it possible to communicate events. But our predilection for art, and especially the art of fiction, involve motivational traits.

Humans have the same compulsion as other animals to play at physical activities, and like them, too, especially at activities associated with flight and fight. Children, especially boys, also have a special motivation, cross-culturally, to throw stones, sticks, balls, darts, Frisbees, fruit, and much more, presumably in reflection of a developmental preparation for our unique human tendency to use projectiles for attack and defense. In the same way, we extend ordinary animal play into our play with patterned information, in preparation for our unique tendency to use information for attack, defense and everything else.

Fiction takes minds that first evolved to deal with the here and now away from the here and now. Ape minds grew in order to deal with complex social relations, and human minds developed still further as we became ultrasocial. Our minds are most finely tuned for understanding agents, that is, any creatures who can act: animal, human, and by extension, monsters, gods and spirits.

In ancient environments, the agents we evolved to track were other animals as well as people, and even in modern urban environments children have a compulsive desire to learn the names of animals and to play with or make up or listen to stories about animals. Our minds want to and easily can track and differentiate agents, since other agents, human or not, offer the most complex, volatile and high-stake information we regularly encounter. We carry that motivation and capacity into pretend play and story.

Minds naturally evolved to focus on the here and now, and very young children do not readily think offline, away from the here and now. They don’t even easily recall their recent past, but they can easily use the present props of toys, with a stick or a rag that can be an animal or a baby, or with a modern handmade or manufactured toy, to conjure up scenarios involving agents that hook their attention. (My ten-month old granddaughter just said her first word: “Angela,” the name of the doll her mother too had as a child.)

Through our appetite for social information, children’s object play gradually becomes social and pretend play. We increasingly learn to dispense with the physical props and enactments of pretend play as we master the cultural props of local stories and myths. As we move into completely offline fictions, we continue to try out new possibilities and roles, testing social options and social emotions. The compulsiveness of story helps us improve our skills of social cognition, of switching perspectives, of seeing from other points of view, of imagining alternative or counterfactual scenarios.

As psychologist and novelist Keith Oatley remarks, fiction works as a social simulator, allowing us to stretch our scope beyond the actual to the possible or the impossible. We need not be confined to the given, but can turn actuality around within the much larger space of possibility to explain how things are or to see how they could have been or might be. By building on our sociality, pretend play and fiction extend our imaginations, taking us from the here and now along tracks we can easily follow even offline because they are the fresh tracks of agents.

The long perspective of evolution offers us a new dimension on ourselves. It lets us see ourselves not in 2-D but in 3-D, and see what we have taken for granted with a new sense of depth, curiosity and wonder. Science can enrich rather than impoverish our sense of art. They complement each other rather than compete: where science helps explain human nature, art’s role is not to explain but to engage and to evoke.

Scientists now offer a fascinating evolutionary explanation of why laughter developed in humans, and a neurophysiological explanation of how laughter operates, but they will not make us laugh by doing so, or find a formula for being funny, or make us laugh less in future because we understand better why or how we laugh.

In the same way we have been shaped to savor art and stories more immediately, more viscerally, more emotionally than we can respond to new scientific explanations. Science may help explain why and how art and fiction have come to matter, but that will not give science their emotional impact, nor allow it to find a formula for art or fiction, nor make them matter less. If anything, it will only clarify why and how they matter so much.