To answer this question, you need to look at Chapter 2 of Guns, Germs, and Steel. There, Diamond describes the “natural experiment of history” that the Polynesians underwent. People from the same culture spread out across the Pacific and populated many islands with very different environments. Starting on p. 58, Diamond discusses six environmental variables that helped make the Polynesian societies different. They were “island climate, geological type, marine resources, area, terrain fragmentation, and isolation.”
- Island climate. Some of the Polynesian islands were warm and rainy. Others were cold and dry and others were in between.
- Geological type. Some of the islands were atolls. New Zealand is part of an ancient continent that broke up. There were also volcanic islands of different elevations and sizes.
- Marine resources. Most of the islands have many marine resources near to shore in shallow waters. However, some have steep drop-offs and lack reefs and therefore have fewer resources.
- Area. Obviously, some of the islands were bigger and some were smaller. The biggest was New Zealand while the smallest permanently inhabited island was 100 acres in size.
- Terrain fragmentation. Some of the islands were divided up by valleys that made it hard to travel from one place to another. Others had fewer divisions and so travel was easy.
- Isolation. Some of the islands were relatively near to one another while some were very far away from any other islands. This made a difference in how often the people who settled on those islands were able to have contact with the outside world.
These are Diamond’s six environmental factors that were relevant to Polynesian societal development. Please look in the book for more details.