It will be some years before the debate of diffusion versus independent invention comes anywhere near settlement. Much of Gladwin’s evidence for diffusion is striking and not to be laughed aside—particularly the group of Australian traits in our Southwest, and the Polynesian and Melanesian traits in the area around the Gulf of Darien. His injection of Old World voyagers between the northern and southern areas of the New World explains certain puzzling matters; but the theory presents puzzles of its own. Many culture traits of Middle America and Peru are not found in Oceania: the use of cement in masonry and the vigesimal system of numeration in Middle America; the amazingly intricate Maya calendar and hieroglyphics with the first invention of zero; baked brick in two Mexican sites; bronze in Peru; the hammock; the whistling jar; the manioc press. Some of these New World traits must have been invented here, but we are asked to believe that the others were forgotten in Oceania and remembered in the Americas. One argument for trans-Pacific diffusion is clear and cogent, however. It is hard to believe that the men who voyaged as far as the Marquesas and Easter Island stopped there, and so missed our long coast line. Certainly the sweet potato made the ocean crossing in the reverse direction, but was it before Columbus?[18] Other things went with the sweet potato, according to the great chemist Gilbert N. Lewis. Without believing that man originated in South America, he thinks that man first reached the neolithic level in the area east of the Peruvian Andes while his fellow man in the rest of the world was wandering in paleolithic darkness. In the Andean highlands, man developed architecture, numeration, metallurgy, weaving, sculpture, and so forth. He spread these things to Middle America 6,000 or 8,000 years ago, and then carried them across the Pacific to the Old World.[19] As a whole, Lewis’s theory may be unacceptable; but his arguments for diffusion and against independent invention are persuasive. In 1947 six Scandinavians demonstrated the possibility of an east-west crossing by sailing and drifting 4,300 miles in 101 days on a primitive raft of balsa logs from Peru to an atoll not many days from Tahiti.[20]