WEaning Age FiNder (WEAN): a tool for estimating weaning age from stable isotope ratios of dentinal collagen

Abstract

Nitrogen stable isotope ratios (δ15N) of incremental dentine collagen have been extensively used for the study of breastfeeding and weaning practices in ancient populations. The shifts in δ15N values reveal the duration of exclusive breastfeeding, the onset and completion of weaning. Despite the significant progress in sampling precision protocols, the weaning estimation is still performed by visual observation of δ15N individual profiles, a time-consuming, labor-intensive, and error-prone task. To fill this gap, we generated WEAN, a tool that enables automated estimation of weaning age based on δ15N measurements from incremental dentine collagen. WEAN generates a refined age assignment based on regression analysis and calculates the knee/elbow point of the δ15N curvature as the individual’s weaning age. We tested the accuracy of the tool by re-estimating 130 weaning ages from published datasets with the calculation of the root mean square error (RMSE). The results show a strong agreement between the visual observation and the elbow method underlining that an automatic mathematical framework can be used for the accurate estimation of weaning age. The tool can estimate the weaning age of a single or many individuals and produces visually appealing graphics (scatter and line plots) and output files. WEAN introduces a novel and robust method that streamlines the assessment of δ15N values for the exploration of breastfeeding and weaning patterns in antiquity.