Although some say the Moriori were a Polynesian people who settled on the Chatham Islands via an independent migration from the equatorial Polynesian islands, many scholars now say Moriori were simply Maori from the lower South Island who migrated to the Chathams.
In the Chathams, they would've found a colder and harsher environment than the one they would have left behind; one that barely supported them. The Moriori couldn't cultivate any plants they may've carried with their migration, and hencely had to live as hunter-gatherers.
The Moriori embraced a pacifistic culture which rigidly avoided warfare. Ritual fights and conciliation substituted for warfare. Maori from the North Island of New Zealand chartered a ship and settled the Chathams in 1835, and went on to slaughter, cannibalised and enslave the Moriori whom did not wish to fight. The notion that the Moriori were completely wiped-out by Maori is untrue. However, the last fully-blooded Moriori, Tommy Solomon, died in 1933. There are thousands of Moriori descendants alive today, and indeed, some of them have made claims through the Waitangi Tribunal.