Who doesn't love stories? On page, stage or screen, fiction can be as engrossing as sex. But why do we need to explain why we love fiction, any more than why we enjoy sex? Just because the pleasures of fiction, and of art in general, seem so natural does not mean there is nothing to explain. Far from it. We also love 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. On the Origin of Stories asks: Why do we love fiction? How did evolution shape our minds to see the world in narrative terms, and to crave even stories we know to be untrue? Does fiction love us back: does it offer us benefits, or only distraction? In a world of unsparing biological competition, how could a successful species afford an unflagging appetite for stories we know to be untrue? To answer that, we also need to ask, more generally, why do we expend time and resources, across cultures, epochs, classes, life stages and intellectual levels, on music, dance, design, and stories? The arts, and especially the art of fiction, give us pleasure, of course, but does that pleasure reflect biological advantage, or do the arts simply hijack our pleasure buttons, just as drugs or candy do, without offering us real long-term benefit, or even damaging us if we have too much? Art, I argue, is a kind of high play. Play exists in probably all mammals, in most birds and even in intelligent invertebrates like octopi. Flexible behavior and learning allow animals to respond sensitively to their environment but cannot be entirely genetically programmed. If, in times of security, animals practice the behaviors that make the greatest life-and-death difference, like flight and fight, they can then perform better in moments of high urgency. As those more inclined to practice survive more often, the desire to practice intensifies over the generations until practice becomes irresistibly self-rewarding. The sheer fun of play overcomes the deeply-rooted inclination not to expend energy if effort can be avoided. Humans depend not just on physical skills but even more on mental power: we alone inhabit the cognitive niche. Brains cannot understand the welter of information in the world unless it falls into patterns that particular kinds of brains have been shaped to understand. Because we humans depend so much on our cognitive advantages, we especially crave the high yield of patterned information. We chase and tussle, but we also play cognitively, with patterns of the kinds of information that matter most to us: sound (music), sight (the visual arts) and, in our ultrasocial species, social information (story). Art and fiction start here. Because intense repetition and concentrated attention can rewire brains incrementally, the compulsiveness of music, images and story reshapes human minds. We process aural, visual and social information more rapidly, accurately and flexibly through playing in self-rewarding ways with the high-density information of art. On the Origin of Stories proposes, in other words, that evolution has shaped human minds to be partially re-shapable-not least by our predisposition to culture, to art in general, and to the art of fiction in particular. It also shows how evolution makes stories possible by configuring the features of human minds and behavior that literature deploys, represents, appeals to, engages and modifies. Our compulsion for fiction certainly depends on prior capacities for true narrative: on capacities, shared to some extent by many species, for event comprehension; on capacities, shared by fewer species, for event recall; and on capacities, shared to a still more limited extent, and by still fewer species, for event representation. But only humans seem to have a unique species-wide capacity and compulsion for event invention, from pretend play onwards. While I spend half of On the Origin of Stories explaining why we love art and especially fiction, I also want to show how an evolutionary approach can enrich our understanding of particular works of art, and above all, stories. Especially over recent decades, academic criticism of the arts has tended to erase the enjoyment, awe and achievement of art. I want to revive and deepen them. To show that evolutionary criticism can be expansive, not reductive, I focus on two masterpieces as close as possible to the origins of stories, first in human history (Homer's Odyssey), then in individual human development (Dr. Seuss's Horton Hears a Who!). Art cannot produce its effects without engaging minds and feelings. I show how  Homer and Dr. Seuss in their different ways engage audiences over time, space and repeated rereadings by appealing to deep human preferences and capacities;  evolutionary accounts of cooperation, intelligence and creativity help to explain the human nature depicted or implied in the stories;  historical, technological, cultural, political and economic factors interact with evolved features of human nature in different ways in each story;  genius emerges in a perfectly natural way through a Darwinian process of generating, selecting and regenerating, cycle after cycle, in both culture and in the efforts of the individual artist;  life itself has evolved through solving a series of often more complicated and constantly changing problems, and  audiences can tap into the creativity of artists by approaching a work as a network of particular problems and solutions. Many feel that evolutionary explanations of the human must quash culture under biology and freedom under determinism. But if evolution can help explain art-human minds at their most free and creative-then it can surely help explain any feature of human nature. Many also feel that evolution by natural selection robs life of purpose. I argue the converse. Evolution evolves and extends purpose: from life, to emotions, intelligence, cooperation and then also to the creativity that emerged in art and now also feeds into science. Art at its best offers us the durability that became life's first purpose, the variety that became its second, the appeal to the intelligence and the cooperative emotions that took so much longer to evolve, and the creativity that keeps adding new possibilities, including religion and science. We do not know a purpose guaranteed from outside life, but we can add as much as we can to the creativity of life. We do not know what other purposes life may eventually generate, but creativity offers us our best chance of reaching them. Perhaps most rewarding in the reception of On the Origin of Stories has been its appeal to readers of many kinds: to lovers of literature and the other arts ("may have an impact far beyond academic circles...No one thinks on this scale anymore...engrossing," Times Literary Supplement; "Diffusion of Boyd's ideas might even...restore the prestige of the arts and humanities," The Nation); to lovers of science ( "novel...thought-provoking...an impressive mastery of science and an admirable inclination to question orthodoxy," New Scientist) and of E.O. Wilson's vision of a consilient and unified system of explanation linking fundamental science and innovative art ("masterful... entrancing...covers an astonishing range of evolutionary concepts," The Evolutionary Review). On the Origin of Stories has appealed to people in business and in government; to arts administrators, arts educators and art historians; to literary studies from classics to comics, and from writers to critics and those subjecting literary response to experimental analysis; to philosophers and social scientists; to scientists not only in biology and psychology, but even in biochemistry, mathematics and physics. Its afterword was selected for Best American Nature and Science Writing.