Another grand and sweeping revision of prehistory on slender evidence, and, like others in the genre -- Jean-Pierre Hallet's recent Pygmy Kitabu or Erich von Daniken's far-out Chariots of the Gods? -- lovable in its enthusiastic excesses and suggestive not so much by its actual claims as by its reminder of how little we really know about the past. James Bailey's conviction is that the world was explored and colonized by sea from about 4000 to 1000 B.C.-- that is, during the Copper and Bronze Ages -- by professional Mediterranean seagoing peoples working for the great empires of Surner-Akkad and the Indus River Valley. The initial motivation: the need for tin ore to make bronze; the extent: all the way to America by both Atlantic and Pacific routes, so that the blond-haired, blue-eyed bringers of civilization deified in Polynesian, Peruvian and Mexican myth were historical figures, the highly cultured god-kings of Sumer and India or their Cretan and Phoenician emissaries. So were the Titans of Greek myth and the builders of Stonehenge; America is Plato's Atlantis, the Sunset Land of Sumerian myth, the western paradise to which Irish hero Cuchulainn (Mayan Kukulcan?) sailed, and all these legends are really fragments of forgotten knowledge. Bailey presents provocative parallels between Meso-American culture and Sumer-Indus Valley -- stepped pyramids, sun worship, irrigation, cotton cultivation, similar gods and design motifs, and much more. He is of course right not to rule out the possibility of ancient contact between the hemispheres, but he does not bother to distinguish between sound and suspect evidence, or between really startling cultural parallels and probable coincidences. His ideas add up to an imaginative new legend which should neither be embraced as true nor written off as utterly groundless.