As late as 1900, the prehistory of Mexico was accounted for very neatly by three successive words, Toltec, Chichimec, and Aztec. Now we know other words, and we know that other peoples and other cultures—Olmec, Zapotec, Mixtec, Totonac, Tarascan, Teotihuacan—also played an important part. We divided the Maya just as neatly into the Old Empire and the New, one south and the other north. Now we know that there were no empires, and that the Maya culture grew widely and steadily towards fruition and decay. Once we thought that the Itzá were the Maya that founded Chichén-Itzá in Yucatan. Now we give the name Itzá to the Toltec or Toltec-influenced invaders that came hundreds of years later. Once scientists disputed whether culture and agriculture began in the highlands of Mexico or in the highlands of Peru. Now certain of them believe that the American became a farmer in the lowlands east of the Andes, while others think he began to till the soil in many spots at the same time. Only a few years ago, we thought that a fairly recent Indian culture—which is called the Woodland Pattern of the eastern United States—had its roots in Middle America. Now its pottery is being traced back through northwestern Canada and northern Asia to the Baltic and even perhaps to Africa.[1] The Mound Builders were once thought an ancient people. Now some of them seem barely to antedate the discovery of America. Bernal Díaz del Castillo—best of the chroniclers of the conquest of Mexico—may have observed that the Mexicans, along with all the Indians of the New World, were ignorant of the principle of the wheel; certainly this has been repeated over and over again for many years. Yet in 1888 Désiré Charnay reported and pictured a Mexican pottery toy with wheels, and since then more of these toys have been found.[2] Throughout his life Roland B. Dixon denied the possibility of productive transpacific migration from Polynesia to South America; yet at the end he accepted the transfer of the sweet potato from South America to Polynesia. From important matters to trivia, the list is long; we have hardly touched it. Obviously, prehistory is not a field where truth is easily and quickly come upon. The student, quite as much as the scientist, must keep an open mind. He must neither cherish dogma nor refuse speculation. Truth still lies afar off.