Prehistoric Agricultural Production on Easter Island (Rapa Nui), Chile
Stevenson, Christopher M., Wozniak, Joan, Haoa, Sonia, Antiquity
Traditional Pacific island societies are fundamentally agricultural populations and their production systems have been the focus of extensive ethnographic research (e.g. Barrau 1961; 1965; Brookfield 1972; Kirch 1990; 1994; Malinowski 1935) as well as at the central aspect of scores of archaeological investigations (e.g. Farrington 1985; Kirch 1994; Ladefoged 1990; Ladefoged et al. 1996; Spriggs 1986). The importance of understanding changes in agricultural production over time has been highlighted by the growing consensus that on islands, intensification of agricultural production is required to feed an expanding population and support social competition amongst the elite components of chiefdoms (Kirch 1994; Spriggs 1985; 1986). The form of these productive capabilities has been hypothesized to influence the impetus (or momentum) and level of social stratification in ranked society.
Until recently, information about pre-contact Easter Island (Rapa Nui) agricultural systems has been derived from European ship logs prior to AD 1900 (Beechey 1831; Forster 1777; Lisiansky 1814), early 20th-century descriptions (Routledge 1919; Metraux 1940), ethnobotanical studies (Yen 1988) and the archaeological investigations of a few stone garden features (Ferdon 1961; Skjolsvold 1961). Although numerous bibliographic references make casual observations about field systems, the abundance of crops and lack of irrigation, there is little known about the technology of production for the dryland agricultural system. We believe this is largely due to the difficulty of identifying prehistoric field systems on the contemporary landscape.
It is the goal of this paper to pull together the interim results of several research projects conducted by Wozniak (1996; 1998), Stevenson (1997), Stevenson & Haoa (1998) and Stevenson et al. (1996; 1997) and to present the first detailed, yet preliminary, model of Rapa Nui dryland agricultural production. To accomplish this we first ask the most fundamental of questions: How can agricultural gardens be identified? Second, we examine the role of dryland agriculture in the development of social complexity. Do the lithic mulch gardens on Rapa Nui represent innovations connected with the intensification of production? Lastly, is this a form of capital investment or a developmental feature of continued landscape use?
Hierarchical societies and dryland agriculture
The ethnographic present
In a discussion of contemporary agriculture on the islands of Futuna and Alofi in Western Polynesia, Kirch (1994) contrasts environmental effects, production costs and their social consequences for societies using either irrigation-based agriculture or dryland field systems that rely upon annual rainfall. Kirch's observations about the functioning of dryland agricultural systems form a temporal model that provides a general scenario, presuming a stable environment, for societies which have implemented dryland farming over long periods of time. Here, we summarize these points and present a set of expectations about the agro-political trajectory for Rapa Nui.
There are three fundamental aspects to dryland agriculture (Kirch 1994). First, upon entering a previously uncultivated environment early field systems will be land extensive in nature and the fallow period long in duration. However, with an expanding population the situation can change significantly. Using the supporting observations of Geertz (1963), Kirch (1994) indicates that as a result of over-population, dryland agricultural practices can degrade the landscape and reduce yields. A reduction of the fallow cycle and increased cultivation of the same area can result in significant soil erosion and exhaustion of soil nutrients.
Secondly, all agricultural practices face the requirement of generating a surplus to meet the demands of social production that arise from competitive feasting, alliance exchange and other corporate efforts of the lineage. …