The desserts and jungles are littered with abandoned ancient cities from civilizations that failed without explanation. The synopsis on the back of the book says that it analysis why the great civilizations declined in terms of changes in their environment. The book starts off at Easter Island where explorers found evidence of an advanced culture demonstrated by the huge statues but the current inhabitants were living in caves and had no idea how the statues got there. The theory of the book is that the people cut down the trees to form a runner network to move the 20foot statues around. The inhabitants cut down all the trees to move statues leaving nothing for building, cooking or building canoes.
The main theme of the book is that once humans progressed past small groups of hunter gathers they began to strain the ability of the land to repair itself. Even today the few peoples who still forage have a daily calorie intake of 2100 calories on three days work a week leaving four days a week for leisure.
In foraging cultures food was seen as common resource available to all. The move to farming allowed people to produce a surplus of food from a limited but at a cost of more labour and less free time. The benefit of the surplus was that the society could support specialists such as potters and craftsmen. Later adding clerics, administrators and a military to the list of specialist. The First use of writing was to record crop movements into and out of central stores not as a means of communication or archiving knowledge.
Initially the world was covered in trees. Areas of forest were cleared for farming in a slash and burn style. Sometimes the forest would recover first by turning to scrub then...