Center for the Study of Human Origins, Department of Anthropology, New York University, New York, United States; New York Consortium in Evolutionary Primatology, New York, United States; Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa; Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
Western University of Health Sciences, College of Osteopathic Medicine of the Pacific, Department of Medical Anatomical Sciences, Pomona, United States
Renier Van Der Merwe
Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa; Department of Chiropractic, Faculty of Health Sciences, University of Johannesburg, Johannesburg, South Africa
Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa; Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain; Departamento de Biodiversidad, Ecología y Evolución, Universidad Complutense de Madrid (UCM), Madrid, Spain
Center for the Study of Human Origins, Department of Anthropology, New York University, New York, United States; New York Consortium in Evolutionary Primatology, New York, United States
Center for the Study of Human Origins, Department of Anthropology, New York University, New York, United States; Department of Anthropology, Bryn Mawr College, Bryn Mawr, United States
Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa; Department of Human Anatomy and Physiology, Faculty of Health Sciences, University of Johannesburg, Johannesburg, South Africa
Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa; Departamento de Paleobiología, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain
Peter Schmid
Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa; Anthropological Institute and Museum, University of Zurich, Zurich, Switzerland
Steven E Churchill
Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa; Department of Evolutionary Anthropology, Duke University, Durham, United States
Adaptations of the lower back to bipedalism are frequently discussed but infrequently demonstrated in early fossil hominins. Newly discovered lumbar vertebrae contribute to a near-complete lower back of Malapa Hominin 2 (MH2), offering additional insights into posture and locomotion in Australopithecus sediba. We show that MH2 possessed a lower back consistent with lumbar lordosis and other adaptations to bipedalism, including an increase in the width of intervertebral articular facets from the upper to lower lumbar column (‘pyramidal configuration’). These results contrast with some recent work on lordosis in fossil hominins, where MH2 was argued to demonstrate no appreciable lordosis (‘hypolordosis’) similar to Neandertals. Our three-dimensional geometric morphometric (3D GM) analyses show that MH2’s nearly complete middle lumbar vertebra is human-like in overall shape but its vertebral body is somewhat intermediate in shape between modern humans and great apes. Additionally, it bears long, cranially and ventrally oriented costal (transverse) processes, implying powerful trunk musculature. We interpret this combination of features to indicate that A. sediba used its lower back in both bipedal and arboreal positional behaviors, as previously suggested based on multiple lines of evidence from other parts of the skeleton and reconstructed paleobiology of A. sediba.
