In 1937, fledgling Norwegian zoological researcher Thor Heyerdahl traveled to the South Pacific with his newlywed wife to study the flora and fauna of the isolated Marquesas Islands. As he collected a menagerie of specimens on the tiny Polynesian island of Fatu Hiva, however, Heyerdahl’s curious mind drifted from thoughts of living creatures to those of ancient civilizations.

Aware of the prevailing scholarly wisdom that people from Southeast Asia had arrived from the west to first populate Polynesia, the Norwegian couldn’t help but notice the trade winds and breakers rolling across the Pacific Ocean from the east. Heyerdahl noted the presence of South American plants such as the sweet potato in Polynesia and the similarities between stone figures on Fatu Hiva and the monoliths erected by ancient South American civilizations. He saw parallels in the physical appearances, rituals and myths of Polynesians and South Americans, and around the glow of a fire, he listened as an elder spoke of a demigod named Tiki who brought his ancestors to the island from a big country beyond the eastern horizon.

Heyerdahl on board Kon-Tiki. (Credit: Archive Photos/Getty Images)

Heyerdahl returned to Norway with fish, jars of beetles and a new dream—to challenge conventional wisdom and demonstrate that the first people who settled Polynesia came from the east, not the west. He abandoned his zoology studies and developed an ethnological theory that two waves of people from the Americas populated the South Pacific. The first wave, Heyerdahl said, arrived around A.D. 500 from pre-Incan Peru by way of Easter Island on rafts that drifted on the currents of the Pacific Ocean; the second came approximately 500 years later from the coast of British Columbia by way of Hawaii. Critics thought the theory impossible and said the open rafts of South America’s pre-Incan civilizations were hardly seaworthy enough to make an oceanic crossing.

Heyerdahl, however, was determined to prove that such a voyage was possible—even if it meant risking his life. Although the Norwegian had no sailing experience and couldn’t even swim, he announced plans to make the perilous crossing on a log raft built only with tools available to pre-Columbian South Americans. “Your mother and father will be very grieved when they hear of your death,” one skeptical diplomat told Heyerdahl when hearing of his plan. Promising “nothing but a free trip to Peru and the South Sea islands and back,” Heyerdahl recruited a five-man crew who built a 30-by-15-foot raft made of nine balsawood logs harvested from the Ecuadorian jungle lashed together with hemp ropes. An open bamboo cabin with overlapping banana leaves covering the roof provided the only protection from the elements.

With a smash of a coconut against the bow, the vessel was christened Kon-Tiki after the legendary Peruvian sun god who had vanished westward across the sea, a mythical figure who served as the mirror image to the Polynesian demigod Tiki who had arrived from the east. On April 28, 1947, Kon-Tiki departed Callao, Peru, with six men and a Spanish-speaking green parrot aboard. Borne along by the northeast-east trade winds that billowed the massive square sail bearing the image of the bearded Kon-Tiki, the raft groaned and creaked as it drifted across the vast blue desert of water.

Although the vessel carried a radio that the crew used to provide daily meteorological and oceanographic observations, a rescue would have been nearly impossible given their remote location in the ocean. They navigated with just the sun, stars, currents and winds as their guides. They maneuvered the raft with only the sail, paddles and a temperamental steering oar as they beat against waves that in stormy conditions towered higher than their masts.

Kon-Tiki on display in Oslo, Norway. (Credit: Getty Images)

Each morning the cook collected the flying fish that flopped onto the deck overnight. The seaweed and shellfish that grew on Kon-Tiki’s underside lured sardines, tuna, dolphins and at least one unwelcome visitor. One day when crewmember Knut Haugland leaned over to wash his hands, he came face-to-face with a 30-foot whale shark, the world’s largest fish species. “Its body rose to the surface like a small mountain,” he recalled in his diary. After circling the vessel for an hour, the enormous sea monster thankfully found other ocean prey.

On the voyage’s 93rd day, Heyerdahl and his crew finally spotted palm trees on the horizon. The winds and currents, however, kept the vessel out at sea. More than a week later, as dawn broke on August 7, they spotted a reef on the starboard side. As the fragile timber raft approached the jagged reef, the cresting waves grew and sent tons of water splashing over Kon-Tiki. The crew clung to whatever they could as the mast snapped and the swells heaved them onto the Raroia atoll in the Tuamotu Archipelago near Tahiti.

All arrived safely—except for the parrot that had vanished during a storm out at sea—after covering 4,300 nautical miles in 101 days, an average speed of 42.5 miles per day. Heyerdahl had proved that an ancient voyage from South America to Polynesia was possible. However, he could not prove that it had actually occurred, and most scholars continue to dismiss his theory and believe the first Polynesian settlers arrived from Southeast Asia.

Heyerdahl poses in front of Kon-Tiki display, 1990. (Credit: AGNETE BRUN/AFP/Getty Images)

Heyerdahl recounted the epic voyage in the bestselling 1950 book “Kon-Tiki: Across the Pacific by Raft” and in a documentary the following year that won the Academy Award. He continued to conduct research expeditions to Easter Island, the Galapagos Islands and South America until his death in 2002, and he led voyages across the Atlantic and Indian Oceans in primitive vessels similar to Kon-Tiki to prove how other ancient civilizations may have been interconnected. The raft he sailed across the Pacific Ocean in 1947 is now on display at the Kon-Tiki Museum in Oslo.