Mesopotamia is an intricate example of a river valley civilization complex. It consists of two rivers, the Tigris and the Euphrates, but we can call this a paradigm case of a river valley society. We also know that the earliest origins of civilization happened here, or nearby. The deep history of civilization originating in this region has meant recounted bifurcations in the history of the region, thus cultural and civilizational complexity.
The origins of Mayan civilization are as yet not satisfactorily known to determine whether Mayan civilization was completely autonomous in its lineages, or if the idea of civilization came to Mesoamerica by way of idea dispersal from the earliest sources of settled neolithic agriculture in the Rio Balsas valley (where corn originated in what is now southern Mexico). Whether or not a civilization emerged autonomously is not always a central topic, but in the case of Mayan civilization, it should be a central topic, because one of the most distinct things about Mayan civilization is that it is a civilization of a tropical rainforest. Most autonomously emerging civilizations appeared in river valleys, but Mayan civilization appeared and thrived in the jungles of Mesoamerica. There are few other examples of civilizations of the tropical rainforest in the world, the Khmer civilization being another, but in the case of the Khmer we know that it did not arise autonomously, as it comes much later in history when the idea of civilization was already diffused in Indochina.
