Global patterns of dental morphological variation: Revisiting ASUDAS trait frequencies

Dental morphological traits provide valuable insights into global human variation and population structure. The Arizona State University Dental Anthropology System (ASUDAS) has long been a cornerstone for documenting crown and root morphology, yet recent discussions have questioned its reliability for characterising population differences. This study aimed to (i) identify the ASUDAS traits most commonly analysed in recent research, and (ii) compare their reported frequencies with those documented in the foundational work of Turner and Scott. A systematic review identified 43 eligible studies comprising 36,919 individuals representing all major subdivisions of humankind. Thirty variants across 27 distinct traits were recorded most frequently, and 29 of these were subjected to meta-analysis using random-effects models. Nearly all traits showed significant between-group and within-group heterogeneity, indicating strong discriminatory potential but also substantial population-level variability. While broad patterns remain consistent with classic ASUDAS expectations, several traits exhibited expanded regional ranges, reflecting both greater sample diversity and admixture effects. These findings reaffirm the value of ASUDAS traits for describing broad-scale morphological patterns while underscoring the need for multi-trait, population-specific, and context-specific approaches when interpreting dental morphology in anthropological research.