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Demography, Cultural change, and the Diffusion of Rice and Millet during the Jomon-Yayoi transition in prehistoric Japan

Periodic Reporting for period 1 - ENCOUNTER (Demography, Cultural change, and the Diffusion of Rice and Millet during the Jomon-Yayoi transition in prehistoric Japan)

Reporting period: 2019-04-01 to 2020-09-30

Human history is punctuated by episodes of large-scale diffusion of new ideas and people that lead to era-defining transitions in past societies. Investigating what promotes these events, how societies react to these, and what long-term consequences they induce is a key to understanding the fundamental drivers of cultural change. The ENCOUNTER project pushes this agenda forward by investigating the timing and the mode of the dispersal of rice and millet farming in the Japanese archipelago during the 3rd millennium BP. This is a pivotal moment in Japanese prehistory that marks the transition between the so-called Jomon and Yayoi periods, and its ultimate consequences are still detectable in the genetic, linguistic, and cultural variation of present-day Japan. The event was triggered when migrant groups from the Korean peninsula brought a package of novel cultural traits that spread, via demic and cultural diffusion, in different parts of Japan. At the time, the Japanese archipelago was occupied by an incumbent population (known as Jomon) predominantly based on hunting, fishing, and gathering economies. Jomon communities, however, responded differently to the new cultural and economic traits from mainland Asia. Some regions adopted the entire cultural package almost immediately, while in other instances the archaeological record suggests episodes of hybridisation, selective adoption of traits, resistance, and even reversion. In other words, the Jomon/Yayoi transition was a profoundly heterogeneous process. The overall aim of the ENCOUNTER project is to identify and explain such variation by synthesising the rich but unstructured archaeological record in Japan. It will seek to determine the extent by which such variation can be explained by environmental conditions (e.g. suitability to rice and millet farming), cultural connectivity, and demographic processes, and explore the subsequent pathways undertaken by different regions to the origins of early states. In pursuing this endeavour, the ENCOUNTER project provides an exceptional case study for studying the topical theme of the relationship between migration and cultural change, offering a deep-time perspective on a phenomenon that has long, and still does characterise pivotal moments of human history.
The first 18 months of the project has been primarily dedicated to data collection and the development of novel quantitative and computational methods, although some work packages have already achieved preliminary results.

Work Package 1 (Demography) has collected several proxy data for population change, namely radiocarbon dates from the entire archipelago (currently over 30,000 dates) and dwelling data from selected case studies (currently over 3,000 units). The collection of radiocarbon dates is scheduled to be completed by the 1st quarter of 2021, while the dwelling data has been completed from one case study (Yamanashi prefecture) and the current target is to complete the remaining 4 case studies by 2021. WP1 has also focused on methodological development, in particular statistical techniques for inferring population dynamics from the density of radiocarbon dates (published in DOI: 10.1017/RDC.2020.95) and handling different forms of chronological uncertainties of artefacts dated via attribution to ceramic-typology based phases (published in DOI: 10.1016/j.jas.2020.105136). The WP has also exploratored, via simulation, potential caveats and challenges for demographic inference based on archaeological data (published in DOI: 10.1098/rstb.2019.0726). These new techniques are currently being applied to the collected data, and preliminary results (see fig1) have already confirmed the demographic impact of the transition, with a rapid population increase in the first few centuries of the 3rd millennium BP.

Work Package 2 (Subsistence and Food Technology) has so far focused on the sampling, extraction, and preparation of an initial set of 300+ potsherds from eight archaeological sites for organic residue analyses. Initial analyses of these and additional samples will commence with the start of the PDRA1 position in January 2021.

Work Package 4 (Environment) focused on the collection of historical (e.g. 19th-century yield records) and environmental data for modelling regional variations in the suitability and the productivity of rice and millet farming at the onset of the Yayoi period. Initial modelling of the thermal niche has already revealed key geographic variation, and a manuscript revealing initial insights in relation to the spatial variation of macro-botanical evidence (see fig.2) is currently under preparation.

Work Package 3 (Material Culture), Work Package 5 (Spread of Rice and Millets), & Work Package 6 (Integration and Synthesis) have primarily focused on preliminary set-up work (data collection, method development) before the appointment of relevant team members.
The primary goal of the ENCOUNTER project is to investigate how incumbent populations responded to the introduction of new cultural elements brought in by migrant groups. Studies on hunter-gathering to farming transition have traditionally focused less on the dynamics of cultural adoption of incumbent populations, and neglected how different pathways such as resistance, hybridisation, and reversion after an initial adoption emerge. By examining these different dynamics within the confines of the Japanese archipelago, the project will provide new insights from one of the richest archaeological records available globally, contributing both to the understanding of a defining moment in Japanese history and more generally to the relationship migration and cultural change. ENCOUNTER is also expected to introduce an array of significant methodological advances, including new molecular techniques to identify specific taxa, and statistical approaches to infer past population dynamics, model the tempo and the mode of dispersal dynamics, track the evolution of cultural boundaries and reconstruct the productivity of different crops. The relevance of many of these advances are beyond the remits of the contextual goals of the project, and ENCOUNTER will facilitate the application of these new methods by making all research fully reproducible and where possible, develop software packages to promote reuse.
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Relative risk surface of rice remains showing area of high/low densities in the Yayoi period
Summed Probability of Radiocarbon Dates as Proxy of Jomon and Yayoi population dynamics (n=12,808)