Agricultural Development in Tongan Prehistory: an Archaeobotanical Perspective
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AGRICULTURAL DEVELOPMENT IN TONGAN PREHISTORY: AN ARCHAEOBOTANICAL PERSPECTIVE A Dissertation by ELLA USSHER A thesis submitted for the degree of Doctor of Philosophy at the Australian National University June 2015 School of Culture, History and Language Department of Archaeology and Natural History i DECLARATION The research presented here is based on original fieldwork, as well as analysis of micro- and macrobotanical assemblages excavated by the author on Tongatapu, Kingdom of Tonga. I certify that, except where it is stated otherwise, this dissertation is the result of my own original investigation. Ella Ussher ii Acknowledgements The completion of this thesis would not have been possible without the contribution and support of a number of people. Firstly, I would like to thank my Chair of Panel Assoc. Prof. Geoff Clark for proposing this project and supporting my fieldwork in Tonga, as well as guiding the final shaping of the written component of my research. My other supervisors, especially Janelle Stevenson and Matiu Prebble, provided me with invaluable technical support over the last four years in both the construction of my comparative collection and the analysis of archaeological material. Many other staff and students at the ANU provided me with specialised advice. These included Dr Jack Fenner (statistics), Dr Frank Brinks (SEM), Dr Anne Prins (histology), Feli Hopf and Jay Chin (microbotanical labwork), Rose Whitau (macrobotanical labwork) and Maxine MacArthur (copy editing). To these people, I am very grateful for their time and sharing of experience and equipment, without which this research could not have been completed. On a more personal level, I wish to give a massive thank you to my partner Josh for being so understanding of the time and effort that needed to go into this PhD project. His love and support ensured that I retained my sanity at the very end and was well looked after as we prepared to welcome our little girl into the world. Thanks and lots of love also needs to go to my family back in NZ who encouraged me to go to Canberra and take my academic career further so that I could follow my passion for archaeobotany. Close friends and colleagues from the ANU such as Katherine Seikel, Stuart Hawkins, Jay Chin, Rebecca Jones, Mirani Litster, Feli Hopf, Christian Reepmeyer, Tim Maloney, Rose Whitau, Ben Shaw, Justin Lewis, and Matthieu Leclerc all helped create a fun and collegial atmosphere both on and off campus. Finally, I would also like to express my gratitude to those who helped distract me from my thesis when I really needed a break by allowing me to follow my other passion in horses, and providing amazing friendships along the way that I will value forever (Maxine, Ann, Wendy, Keryn, Claire, Cathy, Jeremy, Fia, and Kaaren). iii 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 iv 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. Keywords: archaeobotany, starch, parenchyma, microfossils, Tonga, archaeology, agriculture, agroecology, production systems, Lapita v Table of Contents Acknowledgements iii Abstract iv Table of Contents vi List of Tables ix List of Figures xiii List of Abbreviations xvii Chapter 1 Introduction 1 Research aims and objectives 1 Theoretical framework 5 Thesis organisation 6 Chapter 2 Tongan Agriculture in the Pacific Context 9 Research to date 9 Geographic and climatic limitations to agricultural modelling 10 Ethno-historic accounts of plant cultivation in Tonga: 12 Archaeobotany of cultigens in the Pacific 20 Tonga in the Pacific: A summary 30 PART ONE- AN ARCHAEOBOTANICAL COMPARATIVE COLLECTION FOR TONGA 32 Chapter 3 Reviewing Microbotanical Analysis 33 Biology of starch and identification potential 33 Starch taphonomy 35 Modern starch contamination 42 Sampling strategies and extraction techniques 44 Chapter 4 Reviewing Parenchyma 48 Fresh and charred parenchyma morphology 48 Taphonomic factors affecting macrobotanical preservation 49 Collection and sampling of parenchyma 52 Parenchyma identification 54 Chapter 5 Comparative Collection and Morphometric Studies of Pacific Cultigens 57 Species selection 57 Field collection 58 Laboratory processing of samples 59 Starch processing 59 Histology 60 Experimental charring 61 Recording 62 Light microscopy 62 Scanning Electron Microscopy 62 Morphology of native starch 63 Starch morphology 64 Multivariate statistical analysis of starch 76 Morphology of vegetative storage parenchyma 82 Morphological analysis of fresh samples 82 Description of charcoal 100 Development of an Identification Flowchart Key 106 vi PART TWO- DEVELOPMENT OF PREHISTORIC AGRICULTURE IN TONGA 112 Chapter 6 Sites and Field Sampling Strategy 113 Methodology for field sampling of archaeological sediments 113 Site selection 113 Field methods 114 Site descriptions 116 Talasiu (TO-Mu-2) 116 Leka (J17) 117 Heketa (TO-Nt-2) 118 Stratigraphic descriptions 119 Talasiu (TO-Mu-2) 119 Leka (J17) 120 Heketa (TO-Nt-2) 122 AMS dating of cultural contexts 124 Chapter 7 Laboratory Methods 126 Microbotanical analysis: Starch residues 126 Experimentation with starch extraction techniques 126 Laboratory processing: Revised starch extraction protocol 132 Light Microscopy 134 Archaeological starch classification: Assemblage-typology approach 134 Archaeological starch classification: Multivariate statistical analysis 135 Macrobotanical analysis: Charred parenchyma and endocarp 136 Laboratory analysis 136 Chapter 8 Results 138 Macrobotanical analysis 138 Quantification of charcoal 138 Parenchyma distribution and identification: Talasiu TP2 case study 142 Microbotanical analysis 144 Extraction, quantification and distribution 144 Identification: Assemblage-typology approach 147 Identification: Multivariate statistics—Discriminant Function Analysis 150 Comparison of modern Pacific production systems 160 Nutrition 161 Labour investment 178 Outputs 187 Output to input ratios: Efficiency calculation 194 System efficiency comparison and system classification 202 Comparison of prehistoric production systems 209 Nutritional comparison of archaeological species 209 Efficiency comparison of archaeological species and production systems 215 Chapter