Maize and Sociopolitical Complexity in the Ayacucho Valley
My research examines the factors influencing the development of human societies, by focusing on one of regions of the world where complex society developed independently, the Central Andes. One of the salient features of Central Andean prehistory is the late development of sociopolitical complexity vis-à-vis other core areas (such as Mesopotamia, China and Mesoamerica). I posit that the primary factors constraining/enabling the emergence of sociopolitical and technological complexity in the Central Andes were economic. It is my theory that the emergence of Andean cities and states in the early first millennium was a direct consequence of the adoption of maize as a dietary staple in this period. Indeed in the prehistory of the Americas, I believe that the shift to intensive maize agriculture was second in importance only to the initial transition to food production. To support this theory, my research seeks to elucidate the role of maize in the development one early Andean state, the Wari Empire of Peru’s Ayacucho Valley (~AD700-1050).
My doctoral research tests the hypotheses that:
1) The Wari state had a maize based economy.
2) The adoption of intensive maize agriculture was responsible for the population growth preceding urbanization in Ayacucho.
I: Corn, Calories, and Cities
The first major goal of my research is the demonstration that maize was the dietary staple of the Wari Empire. At the most basic level, maintaining an urban society and state-level polity is a matter of concentrating calories in order to supply non-food producers, such as elites, administrators, and artisans. In other areas of the Americas, the concentrated calories supporting sociopolitical complexity were supplied in the form of maize. Every urban and state level society in Mesoamerica had an economy based on maize, as did the most complex chiefdoms of the southwestern and eastern North America. However, the dominant reconstruction of Andean economies is one of “splendid isolation”, emphasizing the contributions of indigenous crops, including tubers (particularly potatoes) and relegates maize to the position of ceremonial crop.
I challenge this model of prehistoric Andean economy, which is based not on the archaeological record, but on ethnographic analogy. Maize has several advantages over other American domesticates, including its higher caloric yield per hectare and higher energy: weight ratio. This last feature of the crop is especially relevant in understanding its revolutionary impact upon the Andes, which lacked the wheel and beasts of burden larger than the llama prior to the Spanish Conquest. Concentrating calories is a matter of transportation. In the fragmented, vertical landscape of the semi-arid Andean sierra, maize was simply a more efficient crop than tubers in terms of energy expended in transportation vs. energy derived from consumption.
I seek to refute the tuber theory using archaeological evidence of human reliance on maize gathered from both urban and rural sites associated with the first state to emerge in the Andean sierra, Wari. By demonstrating that maize was the staple of human diet within this polity, I will have shown that the connection between corn and complexity extends to the Andes as well.
II: Agricultural Intensification and Population Growth
The second major aim of my research is to establish what role intensive maize agriculture may have played in the dramatic increase in human population that occurred in Ayacucho during the early first millennium. In this respect, I am attempting to move beyond a mere correlation between maize and urbanism, towards establishing a causative relationship. I advocate the position that technological innovation in general and agricultural intensification in particular, “pulls” population, due to increased fertility and an increase in the carrying capacity of the land, such as occurred during in the “Green Revolution” of the 20th century. In order to test this hypothesis I am analyzing the record of diet deposited in ancient human skeletal remains from different archaeological periods to assess when the transition to intensive maize agriculture occurred. Such analysis should reveal if maize became the staple of human diet preceding, accompanying or postdating the demographic boom in Ayacucho. I hope to show that it was the adoption of intensive cultivation of maize that permitted the growth in population leading to urbanization.
In order to test these hypotheses regarding the prehistoric economy of the Central Andes, I employ the analytical tools of the biological and chemical sciences. I am able to reconstruct human diet using the stable isotope composition of ancient human remains. The study of paleodiet through stable isotope analysis proceeds from the experimental observation that the isotopic composition of animal tissues generally reflects that of the diet they consume (i.e. you are what you eat). Such analyses utilize the variation in the ratios of the stable isotopes of carbon and nitrogen within ecosystems to measure the relative contribution of different resources to animals’ diets. Certain foods, such as maize, have distinct isotopic signatures which are incorporated into the bodies of the animals that eat them.
In addition a new series of radiocarbon measurements made on human bone will provide an absolute chronology for the process of dietary change as well as an improved timeline for sociopolitical developments in the Ayacucho Valley such as the rise and fall of the Wari state.
IV: Preliminary Results
The preliminary results of stable isotope analysis of human and animal remains from the Wari town of Conchopata reveal that maize was the mainstay of both human and animal diet at this site. These findings represent the earliest evidence for maize as a dietary staple in the Central Andean highlands and indicate that the cereal was the staff, rather than the spice of life. The finding that camelids (llamas and alpacas) consumed substantial quantities of maize suggests the use of specialized animal management systems at this site.
Analysis of mummified human remains from a cave near the town of Vinchos reveal that maize remained the staff of life in the Ayacucho Valley during the late prehistoric-early colonial era. These findings are consistent with evidence from other areas of the Andean highlands which indicates that maize agriculture formed the basis of the Inka Empire's domestic economy. The patterning of the nitrogen isotope signatures of the Vinchos mummies is consistent with the use of manure to fertilize maize.
Forthcoming articles will detail the paleodiet of a number of other sites and shed light onto the domestic economy during the period before and after the hegemony of the Wari polity. The results of radiocarbon dating project supported by ther United Kingdom's Natural Environmental Research Council and the Oxford Radiocarbon Accelerator Unit will allow us to refine the prehistoric chronology of the region and better elucidate the processes of cultural evolution and devolution.