CHARRED TUBERS : INTRODUCTION
Archaeobotanical studies of charred plant macroremains have traditionally focused on seeds, fruits, nuts and wood, the above ground sexual reproductive organs and structural tissue of plants. What is rare in the archaebotanical record however, are findings of vegetative storage organs – roots and tubers.
What are Roots and Tubers?
Roots and tubers will be used as a collective term used to describe vegetative parenchymateous storage organs, including rhizomes, tubers, stolons, roots, corms, and bulbs, found underground or at the base of the stem. The term ‘roots and tubers’ is used and accepted as a convenient collective term to describe all types of vegetative storage organs in archaeobotany, (Hather 1994, Kubiak-Martens 2002). These organs are composed of starch-rich parenchyma cells that store plant energy for vegetative regeneration.
Roots and tubers are a common part of the human diet. Wild roots and tubers are known ethnographically to be a plant staple in hunter gather societies. Canadian Indians gathered, roasted, stored and traded roots and tubers, gaining 50% of their carbohydrates from underground storage organs (Hunn, Turner, French 1998). Over winter, perennial and biennial plants store sugars in the form of starch in their roots and tubers ready for spring regrowth. For hunter gatherer societies dormant storage organs filled with sugars can be a valuable food resource over the lean winter months. Some roots and tubers are available all year round and once collected can be dried and stored for extended periods. Indeed today - carrots, onions, potatoes, cassava, garlic, ginger, sweet potato, yam, beet – are all important human foods cultivated across the world. Yet, roots and tubers are rarely identified in the archaeological record.
The scarcity of archaeological roots and tubers is partly due to problems in preservation. Soft tissued roots and tubers tend to have a high water or oil content which, during charring, often volatilises and distorts the tissue, sometimes reducing organs into fragments or destroying them completely. The fragmentary nature of these remains makes identification difficult especially since they are often not recognised as tuber or root material. Parenchymateous storage tissues, if they are not preserved whole, can easily be mistaken for wood charcoal or categorised as indeterminate or damaged plant remains on initial examination. New techniques and identification criteria based on microscopic anatomical features provided by Hather (1991, 1993, 2000) has succeed in expanding research into roots and tubers from archaeological sites. Where gross morphological characteristics are preserved, root and tuber fragments are more visible in the archaeobotanical record and easier to identify. However, the lack of comprehensive identification criteria restricts the level of identifications possible at present. A recent survey of archaeobotanical studies of UK sites determined that only 40% of root and tubers found were able to be identified to genera. The remainder were either categorised as indeterminate or to family level (Thank you to Allen Hall for information from the Archaeobotanical Computer Database (ABCD)).
This tutorial therefore aims to further publicise roots and tubers in archaeobotany and assist with the identification of root and tuber remains, particularly focusing on organ morphology and features.
Finds of Archaeological Roots and Tubers
Finds of archaeological roots and tubers are limited. In Europe and the Near East, most root and tuber material has been found in pre-agrarian sites. Clarke (1976) and Zvelebil (1994) hypothesised that prior to the adoption of agriculture hunter-gatherers were gaining most of their carbohydrates from plant foods, specifically starch rich roots and tubers. Investigations into Palaeolithic and Mesolithic plant remains, some purposely targeting archaeological parenchyma using Hather’s analytical techniques, have found a range of edible roots and tubers in Denmark, the Nederlands, Czech Republic, Spain, Scotland, Poland and Egypt (Bakels and van Beurden 2001, Hillman et al 1989, Holden et al 1995, Kubiak-Martens 1996, 1999, 2002, Mason and Hather 2000, Mason et al 1994, Mithen et al 2001, Perry 1999, 2002 and Preiss et al 2005). Identification of roots and tubers from later periods is more sporadic with finds in Neolithic Nederlands (Bakels 1988, Kubiak-Martens 2006, 2008) Egypt (Hather 1995) and Syria (Willcox et al 2007), Chalcolithic Turkey (Hather 2000), Bronze Age Britain (Moffet 1991, Allison and Godwin 1949, Hather 2000) and Egypt (Fahmy 2005, Van Zeist 1983) Roman France (Priess et al 2005) and Byzantine Sparta (Hather et al 1992). A summary of archaeological root and tuber finds can be found here. These findings are all thought to be of non-cultivated roots and tubers. In tropical and sub tropical regions archaeobotanical research has focused on cultivated roots and tubers such as yams, sweet potato, cassava and taro.
Hillman, G. Madeyska, E. Hather, J. 1989. Wild plant foods and diet at Late Paleolithic Wadi Kubbaniya: The evidence from charred remains. in The Prehistory of Wadi Kubbaniya.
Holden, T Hather, J. Watson,J. 1995 Mesolithic plant exploitation at the Roc del Migdia, Catalonia, Journal of Archaeological Science, 22, 769-778.
Kubiak-Martens, L. (2002) New evidence for the use of root foods in pre-agrarian subsistence recovered from the late Mesolithic site at Halsskov, Denmanrk. Vegetation History and Archaeobotany 11: 23-31
Kubiak-Martens, L. 1996. Evidence for possible use of plant foods in Palaeolithic and Mesolithic diet from the site of Calowanie in the central part of the Polish Plain .Vegetation History and Archaeobotany 5: 33-38
Mason SL, Hather JG, Hillman GC (1994) Preliminary investigation of the plant macro-remains from Dohi Vestonice II and its implications for the role of plant foods in the Palaeolithic and Mesolithie of Europe. Antiquity 68:48-57
Mason, S. Hather, J. (2000) Parenchymatous plant remains from Staosnaig. In Mithen, S. (ed) Hunter-gatherer landscape archaeology. The Southern Hebrides Mesolithic Project 1988 - 1998. McDonald Institute Monographs Cmbridge pp. 415 - 425.
Moffett, L. (1991) Pignut tubers from a Bronze Age cremation at Barrow Hills, Oxfordshire, and the importance of vegetable tubers in the prehistoric period Journal of Archaeological Science, Volume 18, Issue 2, March 1991, Pages 187-191
Mithen S / Finlay N / Carruthers W / Carter S / Ashmore P (2001) Plant use in the Mesolithic: evidence from Staosnaig, Isle of Colonsay, Scotland. J Archaeol Sci 28: 223-234
Perry, D. 1999. Vegetative tissues from Mesolithic sites in the northern Netherlands. Current Anthropology 40: 231 - 237.