As we near the conclusion of this survey of American prehistory, it is appropriate that we consider again the questions that have preoccupied theorists since Europeans' first encounter with the Native Americans. How did civilizations, with their cities, stratified social classes, organized religions, markets, and other characteristics that the Spanish invaders could immediately recognize as analogues of their own, arise in Mexico and Peru? Why didn't societies of comparable size and complexity develop elsewhere in the Americas?
One explanation of Old World–New World parallelisms, which was suggested by the first writers to speculate about the matter, is that cultural traits were carried to America by prehistoric travelers from the Old World. Today, no one would seriously suggest that the Indians were simply displaced Israelites, Welshmen, or Atlanteans. However, there are still a few archaeologists, such as George Carter (1977), Betty Meggers (1975), Paul Tolstoy (1974b), and Gordon Ekholm (1964), who contend that particular Old World cultures did have a significant impact on those of the New World, through such mechanisms as trade and religious proselytizing. Arguments for diffusion generally rest on the complexity and arbitrariness of the traits compared, the apparent suddenness with which they occur in the alleged recipient culture, their priority in the supposed donor area, and the existence of a practicable route of transmission.
In previous chapters, we have examined some of the controversies over transoceanic diffusion.