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
Thor Heyerdahl between widely separated ancient people, notably the "Ra II" expedition of 1970, when he sailed from the west coast of Africa to Barbados in a papyrus reed boat. He was appointed a government scholar in 1984. In May 2011, the Thor Heyerdahl Archives were added to UNESCO's "Memory of the World" Register. At the time, this list included 238 collections from all over the world. The Heyerdahl Archives span the years 1937 to 2002 and include his photographic collection, diaries, private letters, expedition plans, articles, newspaper clippings, original book, and article manuscripts. The Heyerdahl Archives are administered by the Kon-Tiki