In 1947, Heyerdahl and five fellow adventurers sailed from Peru to the Tuamotu Islands, French Polynesia in a pae-pae raft that they had constructed from balsa wood and other native materials, christened the Kon-Tiki. The Kon-Tiki expedition was inspired by old reports and drawings made by the Spanish Conquistadors of Inca rafts, and by native legends and archaeological evidence suggesting contact between South America and Polynesia. The Kon-Tiki smashed into the reef at Raroia in the Tuamotus on August 7, 1947, after a 101-day, 4,300 nautical mile (4,948 miles or 7,964 km)[11] journey across the Pacific Ocean. Heyerdahl had nearly drowned at least twice in childhood and did not take easily to water; he said later that there were times in each of his raft voyages when he feared for his life.[12]

Kon-Tiki demonstrated that it was possible for a primitive raft to sail the Pacific with relative ease and safety, especially to the west (with the trade winds). The raft proved to be highly maneuverable, and fish congregated between the nine balsa logs in such numbers that ancient sailors could have possibly relied on fish for hydration in the absence of other sources of fresh water. Other rafts have repeated the voyage, inspired by Kon-Tiki. Heyerdahl's book about The Kon-Tiki Expedition: By Raft Across the South Seas has been translated into 70 languages.[13] The documentary film of the expedition entitled Kon-Tiki won an Academy Award in 1951. A dramatised version was released in 2012, also called Kon-Tiki, and was nominated for both the Best Foreign Language Oscar at the 85th Academy Awards[14] and a Golden Globe Award for Best Foreign Language Film at the 70th Golden Globe Awards.[15] It is the first time that a Norwegian film has been nominated for both an Oscar and a Golden Globe.[16]

Anthropologists continue to believe that Polynesia was settled from west to east, based on linguistic, physical, and genetic evidence, migration having begun from the Asian mainland. There are controversial indications, though, of some sort of South American/Polynesian contact, most notably in the fact that the South American sweet potato is served as a dietary staple throughout much of Polynesia. Blood samples taken in 1971 and 2008 from Easter Islanders without any European or other external descent were analysed in a 2011 study, which concluded that the evidence supported some aspects of Heyerdahl's hypothesis.[17][18][19] This result has been questioned because of the possibility of contamination by South Americans after European contact with the islands.[20] However, more recent DNA work (after Heyerdahl's death) contradicts the post-European-contact contamination hypothesis, finding the South American DNA sequences to be far older than that.[21] Heyerdahl had attempted to counter the linguistic argument with the analogy that he would prefer to believe that African-Americans came from Africa, judging from their skin colour, and not from England, judging from their speech.