Revisiting mandibular symphyseal shape in juvenile early hominins and modern humans using a deformation-based approach

Abstract

Abstract The juvenile mandible is important in the investigation of ontogenetic and evolutionary changes among early hominins. To more accurately describe complex shape variations, for the first time advanced methods from computational anatomy, and new fossil evidence are used to revisit the ontogeny of the mandibular symphysis in Australopithecus africanus and Paranthropus robustus. We assess which features of the mandibular symphysis best discriminate the growing symphysis in these fossil species, relative to the intraspecific variation observed among modern humans. When compared with more traditional approaches, our results are in line with previous studies and confirm that our approach eliminates potential methodological inconsistencies with the a priori definition of homologous landmarks and the tacit assumption that anatomical shapes are linear. By enabling detailed comparisons of complex shapes in juvenile mandibles, our proposed approach offers new perspectives for more detailed comparisons among Australopithecus, Paranthropus and early Homo in both southern and eastern Africa.