The antiquity of aroid pit agriculture and significance of buried A horizons on Pacific atolls

The cultivation of aroids (herbaceous plants with starchy corms) is the foundation of Oceanic societies, yet the study of prehistoric atoll agriculture (utilizing Cyrtosperma chamissonis) has been almost totally neglected. Aroid pit agricultural features, some measuring up to 100 m long and 20 m wide, excavated in the Marshall Islands (center ca. 8°N latitude, 170°E longitude) provide the first chronometric dates (1910 ± 70 B.P., Beta-79576) for this type of cultivation practice associated with coral atolls found throughout the Pacific. Excavations through an aroid pit cultivation pit rim identified a stratigraphic sequence beginning with the sterile subsoil, an A horizon deeply buried under pit spoil dirt, and a prehistoric midden deposit beginning below the surface A horizon. Granulometric analysis of sediments and identification of foraminifers documented the nearshore lagoon as the source for all non-cultural sediments. Anthropophilic land snails (Gastrocopta pediculus and Lamellidea pusilla) in the dated, buried A horizon is a firm basis for confirming the presence of humans near initial colonization (ca. 2000 B.P.) and anchors the culture-historical sequence for the long-term study of human impacts to low coral islands. Consequently, on-going analyses of plant opal phytoliths, starch grains, and charcoal from the buried A horizon, should document the nature of early atoll ecology prior to significant human modification. As aroid pit construction is associated, in many examples, with traditional property boundaries, detailed mapping and dating of these cultivation systems should relate to changes in land tenure and prehistoric social organization. © 1999 John Wiley & Sons, Inc.