Revenants have a long history in literature, one that far predates the better-known twelfth-century medieval tradition. Many of our earliest revenant stories come from ancient Greece and Rome, dating to between the fifth century BCE and the fourth century CE, and from such disparate literary sources such as the historian Herodotus, the natural scientist Pliny the Elder, the Roman novelist Apuleius, and the paradoxographer Phlegon of Tralles. Although the flesh-eating revenant is extremely rare in classical antiquity, the dead return for other reasons, especially to procreate and to prophesize. In some cases, the force behind the revivification is made clear, such as in necromantic rituals performed by witches, or when revenants specifically say that the chthonic gods allowed their return to the living. In other cases, principally those of resurrections rather than corpse reanimation, the reasons behind the return to life often remain mysterious. Throughout the literature, revenants represent a reversal of the natural order and thus often serve as metaphors for societal or political unrest.