Polynesia, one of the great geographical subdivisions of Oceania, includes numerous archipelagos scattered in the vast area of the Pacific, New Zealand, Easter Island (Rapa nui) and numerous other small islands. Many cultural elements, together with the fact that many Polynesian idioms belong to the Malayo-Polynesian linguistic family, indicate that the Polynesians reached South East Asia. Skilled navigators, they faced the ocean thanks to a careful observation and deep knowledge of astronomy and natural elements. They prepared detailed "maps" on which the currents were marked with little twigs and islands with shells. The Polynesian social system is based on the transmission by inheritance of the "ranks" that indicated the degree of descent more or less close to the divinities and as a result the possession of a more powerful mana. The traditional religion is based on the cult of the ancestors and of the divinities of a densely populated pantheon.