If not for a horse, would Alexander have been the Great? William, the Conqueror? Richard, the Lionhearted? If not for their awesome mounts, would the Spaniards have had their way with the New World? Would Paul Revere have spread the word? Would the West have been won?

It is hard to comprehend how far horse power has carried us, difficult to imagine, in our era of mechanical wizardry and speed, what role the horse has played in shaping human history. This is the challenge Juliet Clutton-Brock takes up in her book, a splendid blend of natural and social history that recounts the horse's story as it has figured in—and transfigured—our own.

By drawing on biological, archaeological, and historical evidence, Clutton-Brock describes the wild horse and the wild ass, from their widespread distribution at the end of the last Ice Age to their near extinction today. She shows how these beasts, once hunted for meat, were drafted for work and domesticated as humans began to grasp the possibilities of riding horseback. This discovery, with the speed, distance, and power it offered, transformed the course of history. This elegant tale of the horse and donkey, wonderfully written and handsomely illustrated, revives the true meaning of "horse power."