The circumscription theory is a theory of the role of warfare in state formation in political anthropology, created by anthropologist Robert Carneiro. The theory has been summarized in one sentence by Schacht: “In areas of circumscribed agricultural land, population pressure led to warfare that resulted in the evolution of the state”. The more circumscribed an agricultural area is, Carneiro argues, the sooner it politically unifies. Outline of the theory The theory begins with some assumptions. Warfare usually disperses people rather than uniting them. Environmental circumscription occurs when an area of productive agricultural land is surrounded by a less productive area such as the mountains, desert, or sea. Application of extensive agriculture would bring severely diminishing returns. If there is no environmental circumscription, then losers in a war can migrate out from the region and settle somewhere else. If there is environmental circumscription, then losers in warfare are forced to submit to their conquerors, because migration is not an option and the populations of the conquered and conqueror are united. The new state organization strives to alleviate the population pressure by increasing the productive capacity of agricultural land through, for instance, more intensive cultivation using irrigation. Primary and secondary state development Primary state development occurred in the six original states of the Nile Valley, Peru, Mesoamerican, Yellow River Valley China, Indus River Valley, and Mesopotamia. Secondary state development occurred in states that developed from contact with already existing states. Primary state development occurred in areas with environmental circumscription. The presumption, under the Carneiro Hypothesis, is that agricultural intensification, and the social coordination and coercion necessary to achieve this end was a result of warfare in which vanquished populations could not disperse; the coercive coordination necessary for increased production of surplus is, under Carneiro's hypothesis, a causal factor in the origins of the State. For example, the mountainous river valleys of Peru which descend to the Pacific coast were severely environmentally circumscribed. Amazonian populations could always disperse and maintain sparse contact with other, potentially hostile, neighbors, whereas Andean coastal populations could not. Criticism Carneiro's theory has been criticized by the Dutch "early state school" emerging in the 1970s around cultural anthropologist Henri J.M. Claessen, on the ground that considerable contrary evidence can be found to Carneiro's theory. There are also cases of circumscribed environments and violent cultures which have failed to develop states, for example in the narrow highland valleys of interior