The island was most likely populated by Polynesians who navigated in canoes or catamarans from the Gambier Islands (Mangareva, away) or the Marquesas Islands, away. According to some theories, such as the Polynesian Diaspora Theory, there is a possibility that early Polynesian settlers arrived from South America due to their remarkable sea-navigation abilities. Theorists have supported this through the agricultural evidence of the sweet potato. The sweet potato was a favoured crop in Polynesian society for generations but it originated in South America, suggesting interaction between these two geographic areas. However, recent research suggests that sweet potatoes may have spread to Polynesia by long-distance dispersal long before the Polynesians arrived. When James Cook visited the island, one of his crew members, a Polynesian from Bora Bora, Hitihiti, was able to communicate with the Rapa Nui. The language most similar to Rapa Nui is Mangarevan, with an estimated 80% similar vocabulary. In 1999, a voyage with reconstructed Polynesian boats was able to reach Easter Island from Mangareva in 19 days.