Polynesian navigation snow. In the mid-20th century, Thor Heyerdahl proposed a new theory of Polynesian origins (one which did not win general acceptance), arguing that the Polynesians had migrated from South America on balsa-log boats. The presence in the Cook Islands of sweet potato that is a plant native to the Americas (called "kūmara" in Māori), which have been radiocarbon-dated to 1000 CE, has been cited as evidence that Americans could have traveled to Oceania. The current thinking is that sweet potato was brought to central Polynesia circa 700 CE and spread across Polynesia from there, possibly by Polynesians who had traveled
Frogner century Scandinavian sea vessels - including the fully intact Oseberg ship - which were used as high status tombs. A collection of Viking weapons, utensils and talismans, buried with the ships, is also on display. The Kon-Tiki Museum is named after the raft on which Norwegian adventurer Thor Heyerdahl crossed the Pacific Ocean in 1947. Alongside the raft, the museum houses various artefacts related to Heyerdahl's other expeditions and a changing program of temporary exhibitions explores his life and work. Oslo City Museum is situated at Frogner Manor in the Vigeland park (Frognerparken). It is a museum of cultural history