The bony labyrinth of StW 573 ("Little Foot"): Implications for early hominin evolution and paleobiology

Amélie Beaudet; Ronald J Clarke; Laurent Bruxelles; Kristian J Carlson; Robin Crompton; Frikkie de Beer; Jelle Dhaene; Jason L Heaton; Kudakwashe Jakata; Tea Jashashvili; Kathleen Kuman; Juliet McClymont; Travis R Pickering; Dominic Stratford

doi:10.1016/j.jhevol.2018.12.002

The bony labyrinth of StW 573 ("Little Foot"): Implications for early hominin evolution and paleobiology

J Hum Evol. 2019 Feb:127:67-80. doi: 10.1016/j.jhevol.2018.12.002. Epub 2018 Dec 22.

Authors

Affiliations

¹ School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa; Department of Anatomy, University of Pretoria, PO Box 2034, Pretoria, 0001, South Africa. Electronic address: beaudet.amelie@gmail.com.
² Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa.
³ School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa; French National Institute for Preventive Archaeological Research (INRAP), Nîmes, France; French Institute of South Africa (IFAS), USR 3336 CNRS, Johannesburg, 2001, South Africa.
⁴ Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa; Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA.
⁵ Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, L7 8TX, UK; Department of Rheumatology, Aintree University NHS Trust, Hospital NHS Trust, Liverpool, L9 7AL, UK.
⁶ South African Nuclear Energy Corporation SOC Ltd. (Necsa), Pelindaba, North West Province, South Africa.
⁷ UGCT Department of Physics and Astronomy, Ghent University, Proeftuinstraat 86/N12, B-9000, Gent, Belgium.
⁸ Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa; Department of Biology, Birmingham-Southern College, Birmingham, AL, 35254, USA.
⁹ Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa; Molecular Imaging Center, Department of Radiology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA; Department of Geology and Paleontology, Georgian National Museum, Tbilisi, 0105, Georgia.
¹⁰ School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa.
¹¹ School of Health Sciences, Aldro Building, University of Brighton, Eastbourne, UK.
¹² Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, WITS 2050, South Africa; Department of Anthropology, University of Wisconsin, Madison, WI, 53706, USA.

PMID: 30777359
DOI: 10.1016/j.jhevol.2018.12.002

Abstract

Because of its exceptional degree of preservation and its geological age of ∼3.67 Ma, StW 573 makes an invaluable contribution to our understanding of early hominin evolution and paleobiology. The morphology of the bony labyrinth has the potential to provide information about extinct primate taxonomic diversity, phylogenetic relationships and locomotor behaviour. In this context, we virtually reconstruct and comparatively assess the bony labyrinth morphology in StW 573. As comparative material, we investigate 17 southern African hominin specimens from Sterkfontein, Swartkrans and Makapansgat (plus published data from two specimens from Kromdraai B), attributed to Australopithecus, early Homo or Paranthropus, as well as 10 extant human and 10 extant chimpanzee specimens. We apply a landmark-based geometric morphometric method for quantitatively assessing labyrinthine morphology. Morphology of the inner ear in StW 573 most closely resembles that of another Australopithecus individual from Sterkfontein, StW 578, recovered from the Jacovec Cavern. Within the limits of our sample, we observe a certain degree of morphological variation in the Australopithecus assemblage of Sterkfontein Member 4. Cochlear morphology in StW 573 is similar to that of other Australopithecus as well as to Paranthropus specimens included in this study, but it is substantially different from early Homo. Interestingly, the configuration of semicircular canals in Paranthropus specimens from Swartkrans differs from other fossil hominins, including StW 573. Given the role of the cochlea in the sensory-driven interactions with the surrounding environment, our results offer new perspectives for interpreting early hominin behaviour and ecology. Finally, our study provides additional evidence for discussing the phylogenetic polarity of labyrinthine traits in southern African hominins.

Keywords: Australopithecus; Cochlea; Inner ear; Semicircular canals; Sterkfontein.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Biological Evolution
Ear, Inner / anatomy & histology*
Fossils / anatomy & histology*
Hominidae / anatomy & histology*
Life History Traits
South Africa