The expeditions have been many and adventurous!

Fatu Hiva
The events surrounding his stay on the Marquesas, most of the time on Fatu Hiva, were told first in his book På Jakt efter Paradiset (Hunt for Paradise) (1938), which was published in Norway but, following the outbreak of World War II, never translated and largely forgotten. Many years later, having achieved notability with other adventures and books on other subjects, Heyerdahl published a new account of this voyage under the title Fatu Hiva (London: Allen & Unwin, 1974). The story of his time on Fatu Hiva and his side trip to Hivaoa and Mohotani is also related in Green Was the Earth on the Seventh Day (Random House, 1996).

The Kon-Tiki expedition
In the Kon-Tiki Expedition, Heyerdahl and five fellow adventurers went to Peru, where they constructed a pae-pae raft from balsa wood and other native materials, a raft that they called 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. After a 101 day, 4,300-mile (6,900 km) journey across the Pacific Ocean, Kon-Tiki smashed into the reef at Raroia in the Tuamotu Islands on August 7, 1947.

Heyerdahl, who had nearly drowned at least twice in childhood, admits that he did not take easily to water. "There were moments during every one of my experimental raft voyages that I was momentarily deadly afraid and - like seafarers throughout the ages in similar situations - I felt that I survived through my faith in some superior invisible power. Gradually, I got familiar with the friendly partnership between the dancing ocean and its gentle playmate - the flexible, wash-through aboriginal raft ship. My companions knew I loved life and assumed I had founded my unshakable faith in my scientific theories on solid facts."

Kon-Tiki demonstrated that it was possible for a primitive raft to sail the Pacific with relative ease and safety, especially to the west. 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. Inspired by Kon-Tiki, other rafts have repeated the voyage. Heyerdahl's book about the expedition, Kon-Tiki, has been translated into over 67 languages. The documentary film of the expedition, itself entitled Kon-Tiki, won an Academy Award in 1951.

Anthropologists continue to believe, based on linguistic, physical, and genetic evidence, that Polynesia was settled from west to east, 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 served as a dietary staple throughout much of Polynesia. Heyerdahl attempted to counter the linguistic argument with the analogy that, guessing the origin of African-Americans, he would prefer to believe that they came from Africa, judging from their skin colour, and not from England, judging from their speech.

Studies of HLA genes from "blood samples from Easter Islanders whose ancestors had not interbred with Europeans and other visitors" (collected in 1971 and 2008), led Erik Thorsby (professor of Medicine) to conclude (in 2011) that there was "evidence to support elements of Heyerdahl's hypothesis".

Heyerdahl's theory of Polynesian origins
Heyerdahl claimed that in Incan legend there was a sun-god named Con-Tici Viracocha who was the supreme head of the mythical fair-skinned people in Peru. The original name for Viracocha was Kon-Tiki or Illa-Tiki, which means Sun-Tiki or Fire-Tiki. Kon-Tiki was high priest and sun-king of these legendary "white men" who left enormous ruins on the shores of Lake Titicaca. The legend continues with the mysterious bearded white men being attacked by a chief named Cari who came from the Coquimbo Valley. They had a battle on an island in Lake Titicaca, and the fair race was massacred. However, Kon-Tiki and his closest companions managed to escape and later arrived on the Pacific coast. The legend ends with Kon-Tiki and his companions disappearing westward out to sea.

When the Spaniards came to Peru, Heyerdahl asserted, the Incas told them that the colossal monuments that stood deserted about the landscape were erected by a race of white gods who had lived there before the Incas themselves became rulers. The Incas described these "white gods" as wise, peaceful instructors who had originally come from the north in the "morning of time" and taught the Incas' primitive forefathers architecture as well as manners and customs. They were unlike other Native Americans in that they had "white skins and long beards" and were taller than the Incas. The Incas said that the "white gods" had then left as suddenly as they had come and fled westward across the Pacific. After they had left, the Incas themselves took over power in the country.

Heyerdahl said that when the Europeans first came to the Pacific islands, they were astonished that they found some of the natives to have relatively light skins and beards. There were whole families that had pale skin, hair varying in color from reddish to blonde. In contrast, most of the Polynesians had golden-brown skin, raven-black hair, and rather flat noses. Heyerdahl claimed that when Jakob Roggeveen first discovered Easter Island in 1722, he supposedly noticed that many of the natives were white-skinned. Heyerdahl claimed that these people could count their ancestors who were "white-skinned" right back to the time of Tiki and Hotu Matua, when they first came sailing across the sea "from a mountainous land in the east which was scorched by the sun." The ethnographic evidence for these claims is outlined in Heyerdahl's book Aku Aku: The Secret of Easter Island.

Heyerdahl proposed that Tiki's neolithic people colonized the then-uninhabited Polynesian islands as far north as Hawaii, as far south as New Zealand, as far east as Easter Island, and as far west as Samoa and Tonga around 500 AD. They supposedly sailed from Peru to the Polynesian islands on pae-paes--large rafts built from balsa logs, complete with sails and each with a small cottage. They built enormous stone statues carved in the image of human beings on Pitcairn, the Marquesas, and Easter Island that resembled those in Peru. They also built huge pyramids on Tahiti and Samoa with steps like those in Peru. But all over Polynesia, Heyerdahl found indications that Tiki's peaceable race had not been able to hold the islands alone for long. He found evidence that suggested that seagoing war canoes as large as Viking ships and lashed together two and two had brought Stone Age Northwest American Indians to Polynesia around 1100 AD, and they mingled with Tiki's people. The oral history of the people of Easter Island, at least as it was documented by Heyerdahl, is completely consistent with this theory, as is the archaeological record he examined (Heyerdahl 1958). In particular, Heyerdahl obtained a radiocarbon date of 400 AD for a charcoal fire located in the pit that was held by the people of Easter Island to have been used as an "oven" by the "Long Ears," which Heyerdahl's Rapa Nui sources, reciting oral tradition, identified as a white race which had ruled the island in the past (Heyerdahl 1958).

Heyerdahl further argued in his book American Indians in the Pacific that the current inhabitants of Polynesia migrated from an Asian source, but via an alternate route. He proposes that Polynesians traveled with the wind along the North Pacific current. These migrants then arrived in British Columbia. Heyerdahl called contemporary tribes of British Columbia, such as the Tlingit and Haida, descendants of these migrants. Heyerdahl claimed that cultural and physical similarities existed between these British Columbian tribes, Polynesians, and the Old World source. Heyerdahl's claims aside, however, there is no evidence that the Tlingit, Haida or other British Columbian tribes have an affinity with Polynesians.

Heyerdahl's theory of Polynesian origins never gained acceptance among anthropologists. Physical and cultural evidence had long suggested that Polynesia was settled from west to east, migration having begun from the Asian mainland, not South America. In the late 1990s, genetic testing found that the mitochondrial DNA of the Polynesians is more similar to people from southeast Asia than to people from South America, showing that their ancestors most likely came from Asia. Easter Islanders are of Polynesian descent.

Anthropologist Robert Carl Suggs included a chapter titled "The Kon-Tiki Myth" in his book on Polynesia, concluding that "The Kon-Tiki theory is about as plausible as the tales of Atlantis, Mu, and 'Children of the Sun.' Like most such theories it makes exciting light reading, but as an example of scientific method it fares quite poorly."

Anthropologist and National Geographic Explorer-In-Residence Wade Davis also criticised Heyerdahl's theory in his book The Wayfinders, which explores the history of Polynesia. Davis says that Heyerdahl "ignored the overwhelming body of linguistic, ethnographic, and ethnobotanical evidence, augmented today by genetic and archaeological data, indicating that he was patently wrong."

Expedition to Rapa Nui
In 1955-1956, Heyerdahl organized the Norwegian Archaeological Expedition to Rapa Nui (Easter Island). The expedition's scientific staff included Arne Skjølsvold, Carlyle Smith, Edwin Ferdon, Gonzalo Figueroa and William Mulloy. Heyerdahl and the professional archaeologists who traveled with him spent several months on Rapa Nui investigating several important archaeological sites. Highlights of the project include experiments in the carving, transport and erection of the notable moai, as well as excavations at such prominent sites as Orongo and Poike. The expedition published two large volumes of scientific reports (Reports of the Norwegian Archaeological Expedition to Easter Island and the East Pacific) and Heyerdahl later added a third (The Art of Easter Island). Heyerdahl's popular book on the subject, Aku-Aku was another international best-seller.

In "Easter Island: the Mystery Solved" (Random House, 1989), Heyerdahl offered a more detailed theory of the island's history. Based on native testimony and archaeological research, he claimed the island was originally colonized by Hanau eepe ("Long Ears"), from South America, and that Polynesians Hanua momoko ("Short Ears") arrived only in the mid-16th century; they may have come independently or perhaps were imported as workers. According to Heyerdahl, something happened between Admiral Roggeveen's discovery of the island in 1722 and James Cook's visit in 1774; while Roggeveen encountered white, Indian, and Polynesian people living in relative harmony and prosperity, Cook encountered a much smaller population consisting mainly of Polynesians and living in privation.

Heyerdahl speculates there was an uprising of "Short Ears" against the ruling "Long Ears." The "Long Ears" dug a defensive moat on the eastern end of the island and filled it with kindling. During the uprising, Heyerdahl claimed, the "Long Ears" ignited their moat and retreated behind it, but the "Short Ears" found a way around it, came up from behind, and pushed all but two of the "Long Ears" into the fire.

The boats Ra and Ra II
In 1969 and 1970, Heyerdahl built two boats from papyrus and attempted to cross the Atlantic Ocean from Morocco in Africa. Based on drawings and models from ancient Egypt, the first boat, named Ra (after the Egyptian Sun god), was constructed by boat builders from Lake Chad using papyrus reed obtained from Lake Tana in Ethiopia and launched into the Atlantic Ocean from the coast of Morocco. After a number of weeks, Ra took on water after its crew made modifications to the vessel that caused it to sag and break apart. The ship was abandoned and the following year, another similar vessel, Ra II, was built of totora by Demetrio, Juan and Jose Limachi from Lake Titicaca in Bolivia and likewise set sail across the Atlantic from Morocco, this time with great success. The boat reached Barbados, thus demonstrating that mariners could have dealt with trans-Atlantic voyages by sailing with the Canary Current.

A book, The Ra Expeditions, and a film documentary Ra (1972) were made about the voyages.

Apart from the primary aspects of the expedition, Heyerdahl deliberately selected a crew representing a great diversity in race, nationality, religion and political viewpoint in order to demonstrate that at least on their own little floating island, people could cooperate and live peacefully. Additionally, the expedition took samples of marine pollution and presented their report to the United Nations.

The Tigris
Heyerdahl built yet another reed boat, Tigris, which was intended to demonstrate that trade and migration could have linked Mesopotamia with the Indus Valley Civilization in what is now modern-day Pakistan. Tigris was built in Iraq and sailed with its international crew through the Persian Gulf to Pakistan and made its way into the Red Sea. After about 5 months at sea and still remaining seaworthy, the Tigris was deliberately burnt in Djibouti, on April 3, 1978, as a protest against the wars raging on every side in the Red Sea and Horn of Africa. In his Open Letter to the UN Secretary-General Kurt Waldheim, he explained his reasons:

"Today we burn our proud ship... to protest against inhuman elements in the world of 1978... Now we are forced to stop at the entrance to the Red Sea. Surrounded by military airplanes and warships from the world's most civilized and developed nations, we have been denied permission by friendly governments, for reasons of security, to land anywhere, but in the tiny, and still neutral, Republic of Djibouti. Elsewhere around us, brothers and neighbors are engaged in homicide with means made available to them by those who lead humanity on our joint road into the third millennium.

To the innocent masses in all industrialized countries, we direct our appeal. We must wake up to the insane reality of our time.... We are all irresponsible, unless we demand from the responsible decision makers that modern armaments must no longer be made available to people whose former battle axes and swords our ancestors condemned.

Our planet is bigger than the reed bundles that have carried us across the seas, and yet small enough to run the same risks unless those of us still alive open our eyes and minds to the desperate need of intelligent collaboration to save ourselves and our common civilization from what we are about to convert into a sinking ship."