Developmental simulation of the adult cranial morphology of Australopithecus sediba

Keely B. Carlson; Darryl J. de Ruiter; Thomas J. DeWitt; Kieran P. McNulty; Kristian J. Carlson; Paul Tafforeau; Lee R. Berger

doi:10.17159/sajs.2016/20160012

Authors

Keely B. Carlson Department of Anthropology, Texas A&M University, College Station, Texas, USA
Darryl J. de Ruiter 1. Department of Anthropology, Texas A&M University, College Station, Texas, USA 2. Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Thomas J. DeWitt Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, USA
Kieran P. McNulty Department of Anthropology, University of Minnesota, Minneapolis, Minnesota, USA
Kristian J. Carlson 1. Department of Anthropology, Texas A&M University, College Station, Texas, USA 2. Department of Anthropology, Indiana University, Bloomington, Indiana, USA
Paul Tafforeau European Synchrotron Radiation Facility, Grenoble, France
Lee R. Berger Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa http://orcid.org/0000-0002-0367-7629

DOI:

https://doi.org/10.17159/sajs.2016/20160012

Keywords:

Malapa, geometric morphometrics, craniofacial morphology, hominin evolution, ontogenetic projection

Abstract

The type specimen of Australopithecus sediba (MH1) is a late juvenile, prompting some commentators to suggest that had it lived to adulthood its morphology would have changed sufficiently so as to render hypotheses regarding its phylogenetic relations suspect. Considering the potentially critical position of this species with regard to the origins of the genus Homo, a deeper understanding of this change is especially vital. As an empirical response to this critique, a developmental simulation of the MH1 cranium was carried out using geometric morphometric techniques to extrapolate adult morphology using extant male and female chimpanzees, gorillas and humans by modelling remaining development. Multivariate comparisons of the simulated adult A. sediba crania with other early hominin taxa indicate that subsequent cranial development primarily reflects development of secondary sexual characteristics and would not likely be substantial enough to alter suggested morphological affinities of A. sediba. This study also illustrates the importance of separating developmental vectors by sex when estimating ontogenetic change. Results of the ontogenetic projections concur with those from mandible morphology, and jointly affirm the taxonomic validity of A. sediba.