Diffusion
The book talks a lot about diffusion theory but does not really explain it. It was an early archaeological theory (the most widely held) that all civilizations (state-level societies) came from one source and then diffused out through trade and migration. It was actually thought that all technologies were also invented once and diffused (bow and arrow, wheel, calendar, agriculture etc).
Today we know that many technologies development independently many times and that state-level societies developed independently in Europe, Asia and the Americas with no contact between them.