Polynesia of the plant in the Cook Islands have been radiocarbon-dated to 1000, and current thinking is that it was brought to central Polynesia c. 700 and spread across Polynesia from there, possibly by Polynesians who had traveled to South America and back. Thor Heyerdahl proposed in the mid-20th century that the Polynesians had migrated from the northwest coast of Canada by large whale-hunting dugouts, and from South America on balsa-log boats. Many anthropologists have criticised Heyerdahl's theory, including Wade Davis in his book "The Wayfinders". Davis says that Heyerdahl "ignored the overwhelming body of linguistic, ethnographic, and ethnobotanical evidence, augmented
Pre-Columbian rafts It was during these trade voyages that South American sailors may have introduced metallurgy to Mexico. The purported trade between Ecuador and Mexico consisted of luxury items, including Spondylus (spiny oyster) and Strombus (conch) shells, which were prominently traded from their origins in the warm ocean waters of Ecuador throughout the Andes and up and down the coasts of South America. Since the voyage of the Kon-Tiki in 1947, there have been numerous crossings of the Pacific Ocean by raft from South America to Polynesia. In the 1990s, four attempts to sail a raft from Ecuador to Mexico failed, although