IT was 70 years ago tomorrow that a raft made of balsa wood, hemp ropes and bamboo set off from the port of Callao in Peru heading westwards to the Polynesian islands. Aboard was the Norwegian anthropologist, ethnographer and writer Thor Heyerdahl, four fellow Norwegians and a Swede plus a green parrot.

They were attempting to prove Heyerdahl’s contention that, contrary to the established theories of the time, the islands of Polynesia could have been settled by people from South America.

Briefly they became the most famous explorers on earth with a voyage that has been re-created many times in reality and modern culture, most notably in a 1951 Oscar-winning documentary.

BALSA WOOD?

INDEED. Many scientists have developed controversial theories about human migration over the millennia, but Heyerdahl was prepared to risk death – he could not even swim — to prove his assertion that the ancient South Americans had the technology and the ability to cross thousands of miles of the Pacific Ocean to make new homes in Polynesia.

He devised his theory after studying the famous stone statues of Easter Island, noticing that they looked more like monuments found in Peru than elsewhere in Polynesia, and also drawing on the folk memory of the inhabitants that there had been conflict between the original inhabitants and invaders from the American continent. For that theory to hold water, the raft needed to be made of the basic materials found by archaeologists and anthropologists during their study of South America in the centuries before the arrival of Christopher Columbus in 1492.

The raft thus consisted of nine balsa tree trunks held together by hemp ropes, across which were lashed further balsa logs that were topped by a mangrove wood mast and a cabin made of bamboo, with the main sail also made from bamboo stems.

A coconut was smashed across its bows and the raft was named Kon-Tiki, ancient name for the Inca peoples’ God of the Sun. On the afternoon of April 28, 1947, Kon-Tiki set sail.

DID THEY TAKE ANY MODERN EQUIPMENT?

NOT being completely daft, the crew took a radio, watches, a sextant and charts, as well as metal knives. None of that equipment was crucial to the making of the journey, however, as was documented in Heyerdahl’s classic account of the project which became a best-seller.

Two of the crew were also rather used to dangerous adventures – Torsteein Raaby was the radioman who had helped target the German battleship Tirpitz in its Norwegian fjord, while Knut Haugland also had radio expertise as he was one of the ‘Heroes of Telemark’, Norwegian resistance fighters who ended the Nazis’ bid to produce heavy water for atomic bombs.

WHAT WAS THE VOYAGE LIKE?

THE authorities insisted on Kon-Tiki being towed beyond the busy sea lanes off Peru and then they were basically set adrift to sail along the Humboldt Current. The sail held up in the prevailing winds and they made remarkable progress, their rations assisted by plenty fresh fish and rainwater.

They had to survive several storms and make repairs to the raft which, in line with Heyerdahl’s theories, actually became a stronger craft after being waterlogged.

Using only the sail and steering oar and navigating by the stars, the crew of Kon-Tiki successfully traversed 4300 nautical miles in 101 days. At times, their biggest problem seems to have been boredom.They actually spotted Polynesian land on the 93rd day but the worst weather of the voyage kept them out to sea for another eight days before they finally made landfall after being tossed on a dangerous reef at Raroia atoll in the Tuamotu Archipelago near Tahiti. All aboard were safe except the parrot who had flown away during a storm and never returned.

THEORY PROVEN THEN?

ALAS no, as even this dramatic voyage failed to convince the anthropologists who claimed that Polynesia was people from Asia, though DNA studies later showed South American genes in some Polynesians.

Nothing daunted, Heyerdahl went even further with his 1960s theory that ancient Egyptians could have been the first people to sail the Atlantic.

It took two attempts, but his second boat made of papyrus, Ra II, made it from Morocco to Barbados in 1970.

He did it again in 1978 with Tigris, a reed boat that sailed from Iraq through the Persian Gulf to Pakistan and then the Red Sea, proving Heyerdahl’s theory that ancient Mesopotamia and the Indus civilisation were linked by sea.

The Tigris was burned at Djibouti in protest at the “inhuman elements” of the world, as Heyerdahl called them.