Agriculture in Tongan Prehistory: An Archaeobotanical Perspective

Abstract

This thesis presents the results of an archaeobotanical study of agricultural development in the Kingdom of Tonga. Prior to this study, there has been no direct archaeological evidence for agriculture in Tongan prehistory. Through the implementation of systematic archaeobotanical techniques, this study aimed to fill this gap and address two key research questions: 1) whether early colonisers were dependent on introduced crops, or if human dispersal was fuelled predominantly by the exploitation of natural resources; and 2) whether archaeobotanical data can provide new evidence to examine the role of agriculture within the development of the maritime chiefdom in Tonga through agroecological modelling. This research was divided into two main phases. The first involved the construction of a comprehensive comparative collection for macrobotanical (vegetative storage and fruit parenchyma and endocarp), and microbotanical (starch) components of economic and supplementary plant taxa from Tonga. As part of this, a study of the morphological attributes of starch and parenchyma was conducted that incorporated multivariate statistical analyses of diagnostic attributes. Two methods for taxonomic classification were suggested: automated classification using Discriminant Function Analysis (DFA) of starch, and the use of an Identification Flowchart Key for parenchyma. In the second phase of research, archaeobotanical data from three sites on Tongatapu, representing three different time periods in Tongan prehistory, is presented. Macrobotanical and microbotanical remains were extracted from these sites using flotation, wet-sieving and bulk stratigraphic sampling and compared to a comprehensive reference collection using a combination of SEM and light microscopy. Sampled cultural deposits at Talasiu (2750-2650 cal BP), Leka (1300-1000 cal BP) and Heketa (800-600 cal BP) present new insights into the role of plant taxa within late-Lapita, the Formative Period, and early stages of the Classic Tu’i Tonga chiefdom. Modelling using techniques from Human Ecology, specifically agroecology, replicated past production systems using measures of system efficiency such as nutritional value of taxa, labour investment and productivity in terms of yields. These were compared to expectations based on current literature, and a revised chronology for agricultural development and links to social complexity is presented. This study demonstrates that multivariate statistical analysis and identification flowcharts enable the discrimination of starch and vegetative storage parenchyma from most Tongan plant taxa based on metric and nominal morphological attributes. When applied to archaeobotanical data these techniques indicate that most staple cultigens and some supplementary or famine foods were brought to Tonga within a few hundred years of initial Lapita colonisation. Late prehistoric introductions likely included the sweet potato (Ipomoea batatas) by 600 BP, transported via East Polynesia through the extensive trade networks of the developing Tongan state. Modelling past production systems linked decreased system nutritional efficiency over time to horticultural specialisation in primary crops and increasingly centralised government on Tongatapu. Critically, this analysis modelled the high nutritional efficiency of Lapita subsistence, and linked this to the division of labour investment between both economic and supplementary species within a decentralised social hierarchy.