It is my understanding that civilization (permanent settlements, rudimentary systems of government, the establishment of laws, etc) is considered to have arisen independently in six separate spots around the globe: Mesopotamia, India, China, Egypt, Mesoamerica and Peru. At the time, there were still humans living all over the rest of the globe, but they weren't "civilized"; they were hunter-gatherers who lived in small tribes or individual family units.

So how did the idea of "civilization" spread? How did these early civilizations lead to civilizations in different parts of the world, like the Greeks and Carthaginians, the Mayans, the Polynesians, the Japanese and the Navajo? Was it just travelers from one area meeting people in another and going "hey, you should check out this agricultural permanent settlement thing, it's pretty awesome"?