Thor Heyerdahl (Norwegian pronunciation: [tu:r 'haei@da:l]; October 6, 1914 - April 18, 2002) was a Norwegian adventurer and ethnographer with a background in zoology, botany, and geography. He became notable for his Kon-Tiki expedition in 1947, in which he sailed 8,000 km (5,000 mi) across the Pacific Ocean in a hand-built raft from South America to the Tuamotu Islands. The expedition was designed to demonstrate that ancient people could have made long sea voyages, creating contacts between separate cultures. This was linked to a diffusionist model of cultural development.

In 1955-1956, Heyerdahl organized the Norwegian Archaeological Expedition to Rapa Nui (Easter Island). The expedition's scientific staff included Arne Skjolsvold, Carlyle Smith, Edwin Ferdon, Gonzalo Figueroa and William Mulloy. Heyerdahl and the professional archaeologists who travelled 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 Polynesian Hanau 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 notes the oral tradition of 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. This moat was found by the Norwegian expedition and it was partly cut down into the rock. Layers of fire were revealed but no fragments of bodies.  As for the origin of the people of Easter Island, DNA tests have shown a connection to South America, critics conjecture that this was a result of recent events, but whether this is inherited from a person coming in later times is hard to know. If the story that (almost) all Long Ears were killed in a civil war is true, as the islanders story goes, it would be expected that the statue-building South American bloodline would have been nearly utterly destroyed, leaving for the most part the invading Polynesian bloodline.

Answer the following question by taking a quote from the article: Why is that
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.