New fossils of Australopithecus sediba reveal a nearly complete lower back

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 . We show tha...

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Bibliographic Details
Published in:eLife 2021-11, Vol.10
Main Authors: Williams, Scott A, Prang, Thomas Cody, Meyer, Marc R, Nalley, Thierra K, Van Der Merwe, Renier, Yelverton, Christopher, García-Martínez, Daniel, Russo, Gabrielle A, Ostrofsky, Kelly R, Spear, Jeffrey, Eyre, Jennifer, Grabowski, Mark, Nalla, Shahed, Bastir, Markus, Schmid, Peter, Churchill, Steven E, Berger, Lee R
Format: Article
Language:English
Subjects:
20th century
Adaptation
Animals
Australopithecus sediba
Back - anatomy & histology
bipedalism
Evolutionary Biology
Female
Fossils - anatomy & histology
Hominidae - anatomy & histology
Hominidae - physiology
human evolution
Hypotheses
Locomotion
lordosis
Mining
Morphology
paleoanthropology
Pelvis
Posture
upright posture
Vertebrae
vertebral column
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Summary: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 . 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 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 .
ISSN:2050-084X
2050-084X
DOI:10.7554/eLife.70447