Ancient Irrigation and Buddhist History in Central India: Optically Stimulated Luminescence Dates and Pollen Sequences from the Sanchi Dams

Abstract

This paper presents the results of a recent pilot project aimed at obtaining optically stimulated luminescence (OSL) dates from a group of ancient irrigation dams in central India. The dams are all situated within an area of 750 km2 around the wellknown Buddhist site of Sanchi, the latter established in c. third century B.C. and having a continuous constructional sequence up to the twelfth century A.D. They were documented during earlier seasons of the Sanchi Survey, initiated in 1998 in order to relate the site to its wider archaeological landscape. The pilot project builds upon earlier hypotheses regarding the chronology and function of the Sanchi dams and their relationship to religious and political history in Central India. The principal suggestion is that the earliest phase of dam construction coincided with the rise of urbanization and the establishment of Buddhism in central India between c. third and second centuries B.C.; and that they were connected with wet-rice cultivation as opposed to wheat, the main agricultural staple today. Similarities with intersite patterns in Sri Lanka, where monastic landlordism is attested from c. second century B.C. onward, have also led to the working hypothesis that the Sanchi dams were central to the development of exchange systems between Buddhist monks and local agricultural communities. The pilot project focused on two out of a total of 16 dam sites in the Sanchi area and involved scraping back dam sections created by modern road cuttings. This cast new light on aspects of dam construction and allowed for the collection of sediments and ceramics for OSL dating. The results confirmed the suitability of local sediments to OSL dating methods, as well as affirming our working hypothesis that the dams were constructed-along with the earliest Buddhist monuments in Central India-in the late centuries B.C. Sediment samples were also collected from cores hand drilled in the dried-up reservoir beds, for supplementary OSL dating and pollen analysis, which shed useful insights into land use. KEYWORDS: irrigation, dams, rice agriculture, OSL dating, pollen analysis, ancient India, spread of Buddhism, religious change, theories of state.