OSLO, Norway – Explorer Thor Heyerdahl, whose 1947 Kon-Tiki expeditions captured the world’s imagination, slipped into a coma Tuesday, a week after he started refusing food, water or medical treatment.

At the time, doctors gave the 87-year-old Norwegian, recently diagnosed with brain cancer, hours or at most days to live. A week later, Heyerdahl, who made a career of challenging the views of the scientific mainstream, was still alive but comatose, his son said.

“He is so strong that he warned us that it could take a long time,” Thor Heyerdahl Jr. said.

“The doctor said he does not think he will ever open his eyes again,” he said by telephone from Lillehammer, Norway.

The scientist and adventurer was taken to the Santa Conora hospital on the Italian Riviera nearly three weeks ago after becoming ill during a family gathering at Colla Michari, an ancient Italian village he bought and restored in the 1950s.

At his request, he was released from the hospital and brought back to his beloved Colla Michari to spend his final days surrounded by family.

Experts scoffed at Heyerdahl when he set off to cross the Pacific aboard a balsa raft in 1947, saying it would get waterlogged and sink within days.

After 101 days and 4,900 miles, he proved them wrong by reaching Polynesia from Peru, in a bid to prove his theories of human migration.

His later expeditions included voyages aboard reed rafts, Ra, Ra II and Tigris. His wide-ranging archaeological studies were often controversial and challenged accepted views.

Heyerdahl became associated with the University of Maine and its Institute for Quaternary and Climate Studies through his work with Professor Daniel Sandweiss at an excavation of a pyramid complex in Peru in the late 1980s.