Since the last Ice Age, the reindeer's extraordinary adaptation to cold has sustained human life over vast tracts of the earth's surface, providing meat, fur, and transport. Images carved into rocks and tattooed on the skin of mummies hint at ancient ideas about the reindeer's magical ability to carry the human soul on flights to the sun. These images pose one of the great mysteries of prehistory: the reindeer revolution, in which Siberian native...