Early rice agriculture in Bangladesh: methodological and archaeobotanical perspectives

Thesis

The origin and domestication of Asian rice remains a complex and contentious topic. Among the three main varieties—indica, aus, and japonica—both indica and aus are believed to have originated and been domesticated in India and Bangladesh, respectively. However, a paucity of comprehensive archaeobotanical evidence from South Asia has hindered efforts to elucidate these issues. Additionally, establishing methodological parameters for the taxonomic identification of rice varieties is essential for assessing their origin and domestication. This research uses present-day rice landraces to develop models to investigate an archaeobotanical rice assemblage recovered from Wari-Bateshwar (c. 800-200 BCE) in the Lower Brahmaputra Valley, Bangladesh. The study focuses on three key objectives:

1. A charring experiment to determine the optimal heating regime that produces charred rice resembling well-preserved archaeological specimens (Paper 1);

2. An evaluation of two methods—morphometrics and Geometric Morphometrics (GMM)—for identifying rice varieties using modern accessions of japonica, indica, and aus—and application of these refined techniques to archaeological rice remains from Wari-Bateshwar (Paper 2); and

3. An analysis of rice spikelet base morphology from Wari-Bateshwar to understand the domestication status of local rice and to address hypotheses regarding the origin and domestication of Asian rice varieties, including aus (Paper 3).

The controlled charring experiment reveals that a low-temperature, short-duration heating regime of 230°C for 2-3 hours in a reduced oxygen environment is ideal for producing modern charred rice that closely resembles well-preserved archaeological specimens (Paper 1). ix The morphological study confirms, first, that the morphometric length/width ratio of japonica and aus rice overlaps significantly, complicating their distinction, whereas indica rice shows clear separation. By contrast, a newly derived GMM model achieves an 83% accuracy rate in separating varieties as represented by present-day landraces (Paper 2). When applied to archaeological assemblages from Wari-Bateshwar, the model detects all three Asian rice varieties, japonica, indica, and aus (Paper 2). Furthermore, this study represents a rice chronology in the Bengal frontiers at which japonica and indica arrived by the 6th century BCE, and the aus type became domesticated by the early 4th century BCE.

Finally, the analysis of archaeological rice spikelet bases from Wari-Bateshwar indicates a reduction in shattering and an increase in non-shattering traits through the stratigraphic sequence, indicating a local rice domestication process and hence supporting the multiple domestication hypothesis for Asian rice varieties (Paper 3).

Authors: Rahman, MM

• DOI: 10.5287/ora-eqgnrywy9
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Asian rice varieties; rice domestication; Japonica; Indica; Aus
• Subjects: Plant remains (Archaeology)