RETHINKING THE GREAT EARTHWORK OF TIKAL: A HYDRAULIC HYPOTHESIS FOR THE CLASSIC MAYA POLITY Jay E. Silverstein, a David Webster, b Horacio Martinez, c and Alvaro Soto c a Joint POW/MIA Accounting Command and University of Hawaii, 94-314 Akia Place, Mililani Honolulu, HI 96789, USA b Department of Anthropology, Pennsylvania State University, University Park, PA 16802, USA c University of San Carlos, Ciudad Universitaria, Zona 12, Ciudad Guatemala, Guatemala Abstract The earthworks of Tikal have long been understood as the most extensive example of defensive architecture in the Maya Lowlands, with the ditch and embankment seen as part of a system of defense anchoring the north and south territorial limits of Tikal to impassable bajos on its flanks. New survey and excavation data suggest that the extent and course of the earthworks are not consistent with the demarcation of the north and south limits of the polity, and that the morphology of the feature is not consistent with a well-conceived or finished defensive construction. Here we present a hypothetical model of the earthworks as a limestone filtration trench that could have been used to collect subsurface water to mitigate the effects of canicular drought or to support off-season agriculture. Since their initial discovery 40 years ago, the earthworks of Tikal, Guatemala, have played an important role in our understanding of patterns of demography, settlement, and militarism at Tikal and in the Maya Lowlands in general. Our recent study of the earthworks has added significant new data, some of which contradicts well- established interpretations concerning the form and defensive func- tion of the earthworks (Webster, Silverstein, Murtha, Martinez, and Straight 2007). Rather than supporting established conclusions about the Maya construction, our current research shows that the feature could not have effectively fulfilled the well-accepted role of a defensive boundary for the hinterlands of Tikal and that the primary function of the feature remains elusive. Water posed an enormous challenge to Tikal’s sociopolitical evolution and maintenance, but hydraulic functions for the earth- works have previously been dismissed based on the porous nature of the limestone bedrock through which water would quickly infil- trate into the subsurface and because the frequent changes in elevation would make a continuous flow along the length of the earthworks impossible (Puleston and Callender 1967; contra Scarborough 2003:80). Keeping in mind that rainfall served as the primary source of water for the polity, we believe that the possibility that the earthworks were in fact constructed for a hydraulic purpose must be reconsidered. We propose that the earthworks might have functioned as a limestone filtration trench built to collect subsurface water in support of lowland agriculture by mitigating risk factors associated with wet season canicular droughts or making possible a late season planting. BACKGROUND The late twentieth century saw a dramatic transformation in our understanding of Maya civilization. Despite the discovery of militar- istic depictions on murals, stelae, and lintels, the idea that the Maya were loosely organized along the lines of a largely peaceful confed- eration of civic-ceremonial centers persisted throughout the early twentieth century. The discovery of an impressive earthwork guard- ing the northern approaches to Tikal in 1966 heralded the demise of the “peaceful Maya” interpretation. The earthwork was found during the University of Pennsylvania Sustaining Area Project directed by Dennis Puleston (1973, 1983). Based on their investi- gation, Puleston and Donald Callender (1967) proposed a model of the earthwork as a defensive barrier and hinterland boundary that has endured for 40 years. Puleston and Calendar first encountered the earthwork 4.5 km north of the central acropolis of Tikal. Using compass and pace, they mapped a 9.6 km long segment of the earthwork running east- west, and with the help of a local guide, they identified a separate earthwork segment approximately 1 km long, running northeast- southwest some 8.25 km southeast of the central acropolis. Their investigation also included the excavation of three trenches to examine the morphology of the ditch and embankment. One trench was placed across one of the numerous gaps that occurred where the ditch seemed to disappear as it traversed one of the many lowland bajos that dot the countryside, another was dug in an area where it appeared that there was a bridge or causeway across the earthwork, and the third was excavated through a well- preserved section of the earthwork (Figure 1). Each of the excavations addressed specific questions about the earthwork. The trench in the well-preserved segment revealed the 45 E-mail correspondence to: drjsilverstein@gmail.com Ancient Mesoamerica, 20 (2009), 45–58 Copyright # 2009 Cambridge University Press. Printed in the U.S.A. doi:10.1017/S0956536109000042