More generally, such beliefs seem to be a popular reflection of the broader theme of degeneracy found in many ancient cultures. Hinduism has its concept of the Yugas, the great ages of the universe which gradually decay into chaos and corruption. Hesiod, writing in Works and Days 109-201, describes the five ages of man, degenerating from the godlike perfection of the Golden Age to the misery of the present. (However, at 156-169 Hesiod’s version contains a heroic race, the only one to improve on its predecessor, meaning that the decline was not inevitable.) That the Greeks viewed the earlier ages as giants comes to us from the story of Talos, the last survivor of the Age of Bronze, who was himself a giant, as recorded on vase paintings and as stated implicitly in Apollonius’ Argonautica 4.1639-1693 and explicitly in the Orphic Argonautica 1358-1360. Ovid repeats the theme as the four ages in Metamorphoses 1.89-150, omitting the heroic age and canonizing the idea of permanent decline.
In Judaism the Ages of Man show up as the dream vision of Daniel 2:31-45, in which the declining value of the materials used to make a great statue symbolize the corruption of each successive kingdom. St. Augustine offered a Christian version, derived from Jewish precedent, in On the Catechizing of the Uninstructed 22, in which he describes the six ages of the world, keyed to Biblical events. Dante, in The Divine Comedy (Inferno 14.103-116), adapts Daniel’s version the Ages of Man.
Apparently under the influence of Hellenic philosophy, the concept of gigantism is bound up in the moral argument of decline, even though it sits uneasily beside the Genesis 6:4 assertion that the “giants” represent moral evil and therefore are an aberration in the scheme of creation.