scholarly journals New fossils of Australopithecus sediba reveal a nearly complete lower back

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Scott A Williams ◽  
Thomas Cody Prang ◽  
Marc R Meyer ◽  
Thierra K Nalley ◽  
Renier Van Der Merwe ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Lumbar Vertebrae ◽  
Lumbar Vertebra ◽  
Great Apes ◽  
Geometric Morphometric ◽  
Lower Back ◽  
Pyramidal Configuration ◽  
Fossil Hominins ◽  
Trunk Musculature ◽  
Lower Lumbar

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.

scholarly journals New fossils of Australopithecus sediba reveal a nearly complete lower back

2021 ◽  
Author(s):  
Scott A Williams ◽  
Thomas Cody Prang ◽  
Marc R Meyer ◽  
Thierra K Nalley ◽  
Renier Van Der Merwe ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Lumbar Vertebrae ◽  
Lumbar Vertebra ◽  
Geometric Morphometric ◽  
Lower Back ◽  
Pyramidal Configuration ◽  
Fossil Hominins ◽  
Trunk Musculature ◽  
Lower Lumbar ◽  
Lines Of Evidence

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 demonstrates a lower back consistent with human-like 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”). This contrasts with 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 shape but bears large, cranially-directed transverse processes, implying powerful trunk musculature. We interpret this combination of features to indicate that A. sediba used its lower back in both human-like bipedalism and ape-like arboreal positional behaviors, as previously suggested based on multiple lines of evidence from other parts of the skeleton and reconstructed paleobiology of A. sediba.

scholarly journals Reassessment of the phylogenetic relationships of the late Miocene apes Hispanopithecus and Rudapithecus based on vestibular morphology

2021 ◽  
Vol 118 (5) ◽  
pp. e2015215118
Author(s):  
Alessandro Urciuoli ◽  
Clément Zanolli ◽  
Sergio Almécija ◽  
Amélie Beaudet ◽  
Jean Dumoncel ◽  
...  
Keyword(s):  
Late Miocene ◽  
Phylogenetic Relationships ◽  
Three Dimensional ◽  
Semicircular Canals ◽  
Great Apes ◽  
Great Ape ◽  
Ongoing Debate ◽  
Evolutionary Patterns ◽  
Geometric Morphometric ◽  
Morphometric Analyses

Late Miocene great apes are key to reconstructing the ancestral morphotype from which earliest hominins evolved. Despite consensus that the late Miocene dryopith great apes Hispanopithecus laietanus (Spain) and Rudapithecus hungaricus (Hungary) are closely related (Hominidae), ongoing debate on their phylogenetic relationships with extant apes (stem hominids, hominines, or pongines) complicates our understanding of great ape and human evolution. To clarify this question, we rely on the morphology of the inner ear semicircular canals, which has been shown to be phylogenetically informative. Based on microcomputed tomography scans, we describe the vestibular morphology of Hispanopithecus and Rudapithecus, and compare them with extant hominoids using landmark-free deformation-based three-dimensional geometric morphometric analyses. We also provide critical evidence about the evolutionary patterns of the vestibular apparatus in living and fossil hominoids under different phylogenetic assumptions for dryopiths. Our results are consistent with the distinction of Rudapithecus and Hispanopithecus at the genus rank, and further support their allocation to the Hominidae based on their derived semicircular canal volumetric proportions. Compared with extant hominids, the vestibular morphology of Hispanopithecus and Rudapithecus most closely resembles that of African apes, and differs from the derived condition of orangutans. However, the vestibular morphologies reconstructed for the last common ancestors of dryopiths, crown hominines, and crown hominids are very similar, indicating that hominines are plesiomorphic in this regard. Therefore, our results do not conclusively favor a hominine or stem hominid status for the investigated dryopiths.

Capturing Three-Dimensional In Vivo Lumbar Intervertebral Joint Kinematics Using Dynamic Stereo-X-Ray Imaging

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Ameet K. Aiyangar ◽  
Liying Zheng ◽  
Scott Tashman ◽  
William J. Anderst ◽  
Xudong Zhang
Keyword(s):  
Lumbar Spine ◽  
Three Dimensional ◽  
Lumbar Vertebrae ◽  
Lumbar Vertebra ◽  
Weight Lifting ◽  
Data Set ◽  
X Ray ◽  
Biomechanical Models ◽  
Lifting Task

Availability of accurate three-dimensional (3D) kinematics of lumbar vertebrae is necessary to understand normal and pathological biomechanics of the lumbar spine. Due to the technical challenges of imaging the lumbar spine motion in vivo, it has been difficult to obtain comprehensive, 3D lumbar kinematics during dynamic functional tasks. The present study demonstrates a recently developed technique to acquire true 3D lumbar vertebral kinematics, in vivo, during a functional load-lifting task. The technique uses a high-speed dynamic stereo-radiography (DSX) system coupled with a volumetric model-based bone tracking procedure. Eight asymptomatic male participants performed weight-lifting tasks, while dynamic X-ray images of their lumbar spines were acquired at 30 fps. A custom-designed radiation attenuator reduced the radiation white-out effect and enhanced the image quality. High resolution CT scans of participants' lumbar spines were obtained to create 3D bone models, which were used to track the X-ray images via a volumetric bone tracking procedure. Continuous 3D intervertebral kinematics from the second lumbar vertebra (L2) to the sacrum (S1) were derived. Results revealed motions occurring simultaneously in all the segments. Differences in contributions to overall lumbar motion from individual segments, particularly L2–L3, L3–L4, and L4–L5, were not statistically significant. However, a reduced contribution from the L5–S1 segment was observed. Segmental extension was nominally linear in the middle range (20%–80%) of motion during the lifting task, but exhibited nonlinear behavior at the beginning and end of the motion. L5–S1 extension exhibited the greatest nonlinearity and variability across participants. Substantial AP translations occurred in all segments (5.0 ± 0.3 mm) and exhibited more scatter and deviation from a nominally linear path compared to segmental extension. Maximum out-of-plane rotations (<1.91 deg) and translations (<0.94 mm) were small compared to the dominant motion in the sagittal plane. The demonstrated success in capturing continuous 3D in vivo lumbar intervertebral kinematics during functional tasks affords the possibility to create a baseline data set for evaluating the lumbar spinal function. The technique can be used to address the gaps in knowledge of lumbar kinematics, to improve the accuracy of the kinematic input into biomechanical models, and to support development of new disk replacement designs more closely replicating the natural lumbar biomechanics.

scholarly journals A hominin first rib discovered at the Sterkfontein Caves, South Africa

2016 ◽  
Vol Volume 112 (Number 5/6) ◽  
Author(s):  
Gaokgatlhee Tawan ◽  
Daniel García-Martínez ◽  
Jennifer Eyre ◽  
Markus Bastir ◽  
Lee Berger ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
Fossil Record ◽  
Three Dimensional ◽  
Great Apes ◽  
Small Individual ◽  
Geometric Morphometric ◽  
First Rib ◽  
Morphometric Analyses ◽  
Fossil Hominin

Abstract First ribs – the first or most superior ribs in the thorax – are rare in the hominin fossil record, and when found, have the potential to provide information regarding the upper thorax shape of extinct hominins. Here, we describe a partial first rib from Member 4 of the Sterkfontein Caves, South Africa. The rib shaft is broken away, so only the head and neck are preserved. The rib is small, falling closest to small-bodied Australopithecus first ribs (AL 288-1 and MH1). Given that it was recovered near the StW 318 femur excavation, which also represents a small individual, we suggest that the two may be associated. Three-dimensional geometric morphometric analyses were used to quantify the rib fragment morphology and compare it to extant hominoid and other fossil hominin ribs. While only the proximal end is preserved, our analyses show that South African Australopithecus share derived features of the proximal first rib more closely resembling A. afarensis and later hominins than great apes.

Three-Dimensional Static Modeling of the Lumbar Spine

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Ernur Karadogan ◽  
Robert L. Williams
Keyword(s):  
Experimental Data ◽  
Lumbar Spine ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Lumbar Vertebrae ◽  
Lumbar Vertebra ◽  
Body Motion ◽  
Human Lumbar Spine ◽  
Static Modeling ◽  
Elastic Elements

This paper presents three-dimensional static modeling of the human lumbar spine to be used in the formation of anatomically-correct movement patterns for a fully cable-actuated robotic lumbar spine which can mimic in vivo human lumbar spine movements to provide better hands-on training for medical students. The mathematical model incorporates five lumbar vertebrae between the first lumbar vertebra and the sacrum, with dimensions of an average adult human spine. The vertebrae are connected to each other by elastic elements, torsional springs and a spherical joint located at the inferoposterior corner in the mid-sagittal plane of the vertebral body. Elastic elements represent the ligaments that surround the facet joints and the torsional springs represent the collective effect of intervertebral disc which plays a major role in balancing torsional load during upper body motion and the remaining ligaments that support the spinal column. The elastic elements and torsional springs are considered to be nonlinear. The nonlinear stiffness constants for six motion types were solved using a multiobjective optimization technique. The quantitative comparison between the angles of rotations predicted by the proposed model and in the experimental data confirmed that the model yields angles of rotation close to the experimental data. The main contribution is that the new model can be used for all motions while the experimental data was only obtained at discrete measurement points.

scholarly journals Geometric morphometric investigation of craniofacial morphological change in domesticated silver foxes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Timothy M. Kistner ◽  
Katherine D. Zink ◽  
Steven Worthington ◽  
Daniel E. Lieberman
Keyword(s):  
Three Dimensional ◽  
Cranial Base ◽  
Craniofacial Morphology ◽  
Wild Populations ◽  
Linear Measurements ◽  
Skeletal Morphology ◽  
Geometric Morphometric ◽  
Domestication Syndrome ◽  
Morphometric Investigation ◽  
Unselected Population

AbstractTo test the effects of domestication on craniofacial skeletal morphology, we used three-dimensional geometric morphometrics (GM) along with linear and endocranial measurements to compare selected (domesticated) and unselected foxes from the Russian Farm-Fox Experiment to wild foxes from the progenitor population from which the farmed foxes are derived. Contrary to previous findings, we find that domesticated and unselected foxes show minimal differences in craniofacial shape and size compared to the more substantial differences between the wild foxes and both populations of farmed foxes. GM analyses and linear measurements demonstrate that wild foxes differ from farmed foxes largely in terms of less cranial base flexion, relatively expanded cranial vaults, and increased endocranial volumes. These results challenge the assumption that the unselected population of foxes kept as part of the Russian Farm-Fox experiment are an appropriate proxy for ‘wild’ foxes in terms of craniofacial morphology and highlight the need to include wild populations in further studies of domestication syndrome to disentangle the phenotypic effects of multiple selection pressures. These findings also suggest that marked increases in docility cannot be reliably diagnosed from shape differences in craniofacial skeletal morphology.

scholarly journals A developmentally descriptive method for quantifying shape in gastropod shells

2020 ◽  
Vol 17 (163) ◽  
pp. 20190721
Author(s):  
J. Larsson ◽  
A. M. Westram ◽  
S. Bengmark ◽  
T. Lundh ◽  
R. K. Butlin
Keyword(s):  
Empirical Studies ◽  
Three Dimensional ◽  
Shell Shape ◽  
Large Set ◽  
Littorina Saxatilis ◽  
Shape Variation ◽  
Gastropod Shell ◽  
Geometric Morphometric ◽  
Wide Range ◽  
Descriptive Method

The growth of snail shells can be described by simple mathematical rules. Variation in a few parameters can explain much of the diversity of shell shapes seen in nature. However, empirical studies of gastropod shell shape variation typically use geometric morphometric approaches, which do not capture this growth pattern. We have developed a way to infer a set of developmentally descriptive shape parameters based on three-dimensional logarithmic helicospiral growth and using landmarks from two-dimensional shell images as input. We demonstrate the utility of this approach, and compare it to the geometric morphometric approach, using a large set of Littorina saxatilis shells in which locally adapted populations differ in shape. Our method can be modified easily to make it applicable to a wide range of shell forms, which would allow for investigations of the similarities and differences between and within many different species of gastropods.

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