I keep telling people that when it comes to Polynesian DNA, we lack genetic diversity. People erroneously use “pedigree collapse”, or the more blunt “inbred” when referring to endogamous groups. But both terms are not specific to our type of DNA situation, and research supports what Polynesians have gone through with their migratory patterns over the past few thousand years.
From oral tradition, we know that Tahiti, at one point in time was the center of religion. From Taputapuatea, a sacred marae on Ra’iatea (old name was Havai’i) was where Polynesians from other island countries came and they worshiped. They did this for a few centuries, while they started emigrating to the far parts of the pacific ocean, to as far south east to Rapa Nui (Easter Island), to the south west to Aotearoa (New Zealand) and north as far as the Hawaiian islands. These three points define the Polynesian triangle and for the most part islands within these zones are known to be Polynesian.
Around 1200 A.D. is when migration ceased among these groups. It would not be until about 500 years later when Europeans would travel within the Pacific, people such as Captain Cook who noticed that as far and isolated these islands are, that the people had similar cultures and languages. DNA confirms that. When Captain Cook arrived in the Hawaiian islands in 1778, he estimated a population of 300,000. Other historians say that he under-estimated the number of Hawaiians based on what he could see from his ship, and did not take into consideration the inhabitants inland. So they say it was about 800,000 to one million Hawaiians in 1778. The 1890 Hawaiian Kingdom Census counted 40,622 aboriginal Hawaiians. The 2000 US census counted about 460,000 Native Hawaiians. The current Hawaiian population came out of the 40,000 Hawaiians from 1890, which was the last bottle neck occurrence.
Now that Polynesians are getting DNA tested, we come up as 1st, 2nd or 3rd cousins for the most part, usually sharing more than 50cM, sometimes as high as 500cM and with multiple segments, which they say is consistent with an endogamous group. In particular are the high shared percentages among Maoris of New Zealand and Kanaka (Maoli) of Hawai’i. But given the history of migration it is understandable why eastern Polynesians would be much more genetically similar to each other compared to the older, western Polynesians. As Polynesians migrated further east, they became genetically closer.