It strikes me as very interesting that the various cultures of these islands (Hawaii, New Zealand, Samoa, etc.) have many striking similarities in language, culture, what have you. My question is how much of this is due to a shared origin, and how much of it is due to interaction between the cultures.
Given that vast distances separated each culture, I was curious if they had significant levels of interaction or otherwise influenced how each society developed. The logistics of making that journey at the time must have been nearly insurmountable! If anyone could suggest further reading into the subject that would be greatly appreciated as well!
A lot of, in fact everything about the similarities in language, culture and even dna is to do with a shared origin/lineage. The continued interaction between the people of the pacific, specifically polynesia and micronesia only helped solidify the already strong similarities. Polynesians descended from Austronesian-speaking mongoloids, as did Island Melanesians, Micronesians, Filipinos, Malaysians, Indonesians and even Malagasy from Madagascar who also share a common linguistic, cultural and genetic lineage.
Some cultural similarities amongst Austronesian-speaking people from Madagascar to Rapa Nui whether still practised today or only in the past include: Animism and veneration of the dead ancestors, tattooing, maritime culture (including their calling cards of outrigger canoes)and similarities in creation stories.
It's well-documented that ancient Austronesians were great navigators and used every technique that they could take from nature to traverse large areas of ocean.Here is a link where I answer how they travelled as far as they did.
Now, after peopling the many islands of the pacific, Polynesians continued to interact with each other dispite the huge distance from each other. We know this from evidence of a stone network based on an ancient Tongan state.
Edit: Found an article here which shows that much of what we know about the Tongan empire is through oral history, linguistics, historical accounts and archaeology.