I was watching Moana with my nephew when I started thinking about the extent of contact they had with other civilizations, which led to the question of if they thought they were the only humans on Earth, and even if the Hawaiian islands were the only pieces of land on Earth.
Their religion has clear ties to other Polynesian religions, which shows their descent, but did they know that they were descendants of people from other islands, or did they have a creation story where the gods placed humanity on the Hawaiian islands and that's it?
Sorry for the repetitiveness in this; I'm just trying to be as clear as possible.
Great questions. First though, Moana is not a story about ancient Hawaii and culturally the film pulls much more from cultural advisors with links to Tahiti and Samoa than it does to Hawaii. If we had to imagine a time setting for Moana it would be sometime between 500 BCE to 100 CE during a period archeologists refer to as the “Polynesian Pause.” A time when a unique, decidedly Polynesian cultural complex arises from its origin in the eastern most island groups of the Lapita cultural complex (Fiji-Tonga-Samoa). This is a brief epoch during which settlement further east seems to pause— it doubtful long distance voyaging stopped altogether, certainly short leg voyaging between islands in the same group did not stop. However, this is a gap in material evidence attesting to a pause on the settlement of new island groups to the east during this time. I specify east, because it’s quite likely some of the western Polynesian islands, sometimes referred to as Polynesian Outliers as they aren’t within the neat boundaries of the “Polynesian Triangle,” were settled.
As to Hawaiian Religion; yes there is a creation myth centered around the creation of the islands, all life in the sea, air, and land around the islands, and the establishment of royal genealogies. So yes, there are ideas about creation in situ.
As to knowledge of outside groups; that varies. Yes, there are genealogies that trace themselves back to the Society Islands (Tahiti) and in some cases to specific valleys there. There are oral traditions that speak to voyaging between Tahiti and Hawaii and back to Tahiti till at least the 15th century with some potentially a bit more recent in nature. There are also traditions; though I can not speak to their exact antiquity as they may be the product of a 19th century political context, that link Hawaii with cast offs from both Japan and North America. Not to mention traditions about a ship wrecked Spanish galleon and the odd inclusion in that myth of some Tahitian language terms instead of Hawaii, perhaps indicating a different source for the myth or the continue contact between Tahiti and Hawaii.
So to briefly sum up; yes there is a creation mythos, but yes there was knowledge of other island groups.