Bioarchaeological sex prediction from central Italy using generalized low rank imputation for cross-validated metric craniodental supervised ensemble machine learning with missing data

Abstract

I use a novel supervised ensemble machine learning approach to verify sex estimation of archaeological skeletons from central Italian bioarchaeological contexts with large amounts of missing data present. Eighteen cranial interlandmark distances and five maxillary metric distances were recorded from n = 240 estimated males and n = 180 estimated females from four locations at Alfedena (600-400 BCE) and two locations at Campovalano (750-200 BCE and 9-11th Century CE). A generalized low rank model (GLRM) was used to impute missing data and 20-fold external stratified cross-validation was used to fit an ensemble of eight machine learning algorithms to six different subsets of the data: 1) the face, 2) vault, 3) cranial base, 4) combined face/vault/base, 5) dentition, and 6) combined cranianiodental. Area under the receiver operator characteristic curve (AUC) was used to evaluate the predictive performance of six constituent algorithms, the discrete algorithmic winner(s), and the SuperLearner weighted ensembles classification of males and females from these six bony regions. This approach is useful for predicting male/female sex from central Italy. AUC for the combined craniodental data was the highest (0.9722), followed by the combined cranial data (0.9644), the face (0.9426), vault (0.9116), base (0.9060), and dentition (0.7421). Cross-validated ensemble machine learning of cranial and dental data shows strong potential for estimating sex in the bioarchaeological record and can contribute additional perspectives to help refine our understanding of human sex estimation. Additionally, GLRMs have the potential to handle missing data in ways previously unexplored in the discipline. The main limitation is that the biological sexes of the individuals estimated in this study are not certain, but were estimated macroscopically using common bioarchaeological methods. However, these methods show great promise for estimation of sex in bioarchaeological and forensic contexts and should be investigated on known-sex reference samples for confirmation.