Rethinking Wear Rate Analysis: a New Dentin Exposure Proxy and its Applications to Ancient Chinese Populations

Abstract

Assessing age through dentin exposure often leads to underestimated age due to assumptions of constant molar wear rate. New methods for age-related dentin exposure accrual could facilitate cross-population comparisons independent of dietary habits and sociocultural strategies. We analyzed 3D dentin exposure surfaces in four Chinese archaeological samples to reveal variations in dentin exposure rates linked to socioeconomic practices. Linear regression models of dentin exposure areas across molar rows showed significant correlations, with the first molars exhibiting steeper slopes and smaller intercepts compared to the second molars, which had intermediate values, and the third molars showing the highest intercepts and lowest slopes. The first molar contributed most to overall dentin exposure in the molar quadrant, while the second molar wore faster post-eruption. Among populations, Banlashan, predominantly agriculturalist; Houtaomuga, focused on fishing; and Jiayi, a nomadic hunting society, displayed similar wear rate patterns. In contrast, Dunping, a Bronze Age nomadic settlement situated on a high-altitude plateau, exhibited distinctively lower wear rates. These observed dentin exposure rates aligned with ecological and dietary constraints, enabling interpopulation comparisons using the proposed 3D dentin exposure proxy. Moreover, the statistical model allows for comparing wear rates across populations relative to dietary habits and potentially estimating age at death for isolated archaeological specimens, whether humans or animals. The precision of this physiological age estimation depends on the regression models used, necessitating further research with specimens of known age at death.