Water, Soy Sauce, Feces, and Death: A Geometric Morphometric and Machine Learning Analysis of Edo-Period Ogame Jars, Japan

Abstract

The stoneware ‘Ogame’ (“large jar”) produced in Hizen Province, Kyushu, during Japan’s Edo period (1603–1868) served diverse domestic and mortuary functions, from storing water, soy sauce, and fertilizer to containing human remains in burial contexts. Previous scholars have suggested that key historical developments, including the Qing Dynasty ‘sea ban’ (1647–1684) and the rise of mass-produced porcelain in Hizen, contributed to increasing morphological standardization in both porcelain and stoneware. However, no prior morphometric study has tested this hypothesis for Ogame jars. This study applies two-dimensional, outline-based Geometric Morphometrics (GMM) and machine learning-based ‘Random Forest’ classification to assess shape variability in a dataset of 243 jars from kiln and mortuary contexts across Hizen and Chikuzen Provinces (present day Saga and Fukuoka prefectures). Results show (1) a statistically significant negative trend in within-stage dispersion across the Edo period, and (2) a pronounced morphological divergence between mortuary and kiln-associated jars. These findings reveal how Edo-period Ogame shape was influenced by temporal processes of standardization and context-specific demands for mortuary and domestic use. By integrating quantitative morphometric tools with machine learning classification, this exploratory study provides a replicable framework for investigating shape change in historical ceramics with limited chronological resolution.