Thor Heyerdahl was a Norwegian explorer and ethnographer who is best known for his Kon-Tiki expedition in 1947. Heyerdahl sailed 8, 000 km across the Pacific Ocean on a wooden raft to prove that ancient people could have traveled from South America to Polynesia. Heyerdahl's other expeditions included the Ra and Tigris expeditions, which explored the origins of early civilizations in the Middle East. Heyerdahl also wrote several books about his travels and experiences.