Shape analysis of the StW 578 calotte from Jacovec Cavern, Gauteng (South Africa)

Amélie Beaudet; Jean Dumoncel; Jason L. Heaton; Travis R. Pickering; Ronald J. Clarke; Kristian J. Carlson; Lunga  Bam; Luc Van Hoorebeke; Dominic Stratford

doi:10.17159/sajs.2022/11743

Authors

Amélie Beaudet 1.Department of Archaeology, University of Cambridge, Cambridge, United Kingdom; 2.School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa; 3.Catalan Institute of Palaeontology Miquel Crusafont, Autonomous University of Barcelona, Barcelona, Spain https://orcid.org/0000-0002-9363-5966
Jean Dumoncel French National Centre for Scientific Research (CNRS), Paris, France https://orcid.org/0000-0003-0789-7458
Jason L. Heaton 1.Department of Biology, Birmingham-Southern College, Birmingham, Alabama, USA; 2.Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa; 3.Plio-Pleistocene Palaeontology Section, Department of Vertebrates, Ditsong National Museum of Natural History, Pretoria, South Africa https://orcid.org/0000-0001-8039-4748
Travis R. Pickering 1.Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa; 2.Plio-Pleistocene Palaeontology Section, Department of Vertebrates, Ditsong National Museum of Natural History, Pretoria, South Africa; 3.Department of Anthropology, University of Wisconsin-Madison, Madison, Wisconsin, USA https://orcid.org/0000-0001-5369-7807
Ronald J. Clarke Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa https://orcid.org/0000-0003-1759-8937
Kristian J. Carlson 1.Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa; 2.Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, California, USA https://orcid.org/0000-0001-5802-9680
Lunga Bam South African Nuclear Energy Corporation (Necsa), Pelindaba, South Africa
Luc Van Hoorebeke UCGT Department of Physics and Astronomy, Ghent University, Ghent, Belgium https://orcid.org/0000-0002-1943-1359
Dominic Stratford School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa https://orcid.org/0000-0001-9790-8848

DOI:

https://doi.org/10.17159/sajs.2022/11743

Keywords:

Australopithecus, Sterkfontein Caves, cranial morphology, surface-based comparison

Abstract

The fossiliferous deposits within the lower-lying Jacovec Cavern in the locality of Sterkfontein yielded valuable hominin remains, including the StW 578 specimen. Because StW 578 mainly preserves the calotte, the taxonomic status of this specimen has been a matter of discussion. Within this context, here we employed high-resolution microtomography and a landmark-free registration method to explore taxonomically diagnostic features in the external surface of the StW 578 calotte. Our comparative sample included adult humans and common chimpanzees as well as one Australopithecus africanus specimen (Sts 5). We partially restored the StW 578 calotte digitally and compared it to extant specimens and Sts 5 using a landmark-free registration based on smooth and invertible surface deformation. Our comparative shape analysis reveals morphological differences with extant humans, especially in the frontal bones, and with extant chimpanzees, as well as intriguing specificities in the morphology of the StW 578 parietal bones. Lastly, our study suggests morphological proximity between StW 578 and Sts 5. Given the intimate relationship between the brain and the braincase, as well as the integration of the hominin face and neurocranium, we suggest that cranial vault shape differences between StW 578 and extant humans, if confirmed by further analyses, could be either explained by differences in brain surface morphology or in the face. Besides providing additional information about the morphology of the Jacovec calotte that will be useful in future taxonomic discussion, this study introduces a new protocol for the landmark-free analysis of fossil hominin cranial shape.

Significance:

We provide further information on the enigmatic fossil specimen StW 578.
We introduce a new approach for the morphological study of fossil hominin crania.
We highlight morphological similarities between StW 578 and ‘Mrs Ples’.