Jared Diamond discusses the conflict between the Maori and the Moriori in Chapter 2 of Guns, Germs, and Steel. Both the Maori and the Moriori are Polynesian peoples. However, they settled in very different environments as the Polynesians spread out across the Pacific. Because they settled in such different environments, their societies became very different and the Maori became much more powerful than the Moriori. The Maori were able to conquer the Moriori without much trouble. Diamond devotes a whole chapter to this conflict because in his mind it provides proof of one of the major points he is trying to make in his book.
In Guns, Germs, and Steel, Diamond is trying to explain why Europeans came to be so much more powerful and wealthy than people in places like the Americas, Australia, and New Guinea (before European contact). He says that many people tend to believe that the Europeans became dominant because they were in some way better than the people from the other regions of the world. One suggestion has been that European culture was better-suited to the creation of technology and of advanced civilization than other cultures were. Diamond does not believe this. Instead, he believes that Europeans became more powerful than others because they had better geographic luck. He focuses on the conflict between the Maori and the Moriori to prove that he is right.
Because the Maori and Moriori were both Polynesian, they had the same culture. Therefore, any differences between them in power and wealth could not be caused by differences in culture. So why did the Maori become more warlike and more powerful? Diamond argues that this happened because of the differences in their respective environments. The Maori lived in New Zealand where there were many resources and farming was possible. By contrast, the Moriori lived in the Chatham Islands where the climate was not conducive to farming and resources were relatively few. Because of this, Diamond says, they developed a society that was nothing like the society of the Maori. This happened because of geography, not because of culture.
In this book, Diamond is trying to prove that geographic luck, and not culture, determined which continent’s people would be rich and powerful. He focuses on the Maori and the Moriori because they were people with the same original culture who developed very different societies after being placed in different environments. This is, in his mind, proof that his argument is plausible.