there's a video series on the book. It's available on google's video. It's really good. Nice description of the migration of man.
Here's a thought, maybe the distinct season change gives people more impact of the necessity of getting things done. If crops arn't harvested by fall, they'll be useless and people would starve. Like the premise of some people buying that reverse clock that determines how much time you have to live, motivating that person to accomplish more.
However; Toro's right, I hate working outside in 30+ weather, and i'd never be able to work on the Equator.