Earliest axial fossils from the genus Australopithecus

Meyer, Marc R.; Williams, Scott A.

doi:10.1016/j.jhevol.2019.05.004

Cited by 6 publications

(11 citation statements)

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“…in [4][5][6][7][8]. Combined analysis of the superior and inferior articular facets has the potential to provide essential information about the range of head motions in Australopithecus, which has only been superficially assessed due to the scarcity and fragmentary nature of cervical vertebrae in the hominin fossil record 9,10 . Indeed, a non-human hominoid-like atlas in Australopithecus (e.g., concave superior and inferior articular facets) might suggest a range of head motions that differs from humans 6,7,11,12 , indicating that arboreal activities were fundamental components of the postural and locomotor repertoire of Australopithecus.…”

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confidence: 99%

“…The relative scarcity of the first cervical vertebra in the fossil record of Australopithecus and other hominins and the fragmentary nature of the few specimens that have been discovered thus far mean that extensive speculation is needed when discussing the form of the atlas in human evolution. To date, only four fragmentary atlases attributed to Australopithecus have been described, i.e., the AL 333-83 atlas from Hadar 27 , the atlas of the Australopithecus afarensis infant DIK-1-1 from Dikika 28 and fragments of two first cervical vertebrae attributed to Australopithecus anamensis from Assa Issie 10 . Here we significantly advance this knowledge base by describing the atlas from StW 573 ('Little Foot'), a 3.67 million-year-old Australopithecus prometheus specimen from Sterkfontein Member 2 comprised of a skull and associated postcranial skeleton [29][30][31][32][33][34] .…”

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confidence: 99%

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The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism

Beaudet

Clarke

Heaton

et al. 2020

Sci Rep

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Functional morphology of the atlas reflects multiple aspects of an organism's biology. More specifically, its shape indicates patterns of head mobility, while the size of its vascular foramina reflects blood flow to the brain. Anatomy and function of the early hominin atlas, and thus, its evolutionary history, are poorly documented because of a paucity of fossilized material. Meticulous excavation, cleaning and high-resolution micro-CT scanning of the StW 573 ('Little Foot') skull has revealed the most complete early hominin atlas yet found, having been cemented by breccia in its displaced and flipped over position on the cranial base anterolateral to the foramen magnum. Description and landmark-free morphometric analyses of the StW 573 atlas, along with other less complete hominin atlases from Sterkfontein (StW 679) and Hadar (AL 333-83), confirm the presence of an arboreal component in the positional repertoire of Australopithecus. Finally, assessment of the cross-sectional areas of the transverse foramina of the atlas and the left carotid canal in StW 573 further suggests there may have been lower metabolic costs for cerebral tissues in this hominin than have been attributed to extant humans and may support the idea that blood perfusion of these tissues increased over the course of hominin evolution.

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confidence: 99%

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The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism

Beaudet

Clarke

Heaton

et al. 2020

Sci Rep

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“…Conversely, the dorsally oriented odontoid processes and steeply sloped C2 superior articular facets found in species with more horizontal neck postures may lower energetic requirements of the nuchal musculature by shifting the head dorsally relative to the neck, positioning the weight of the head to be better supported by the vertebral column (Nalley & Grider‐Potter, 2017). Alternatively, the orientation of the odontoid process may be linked with the orientation of the foramen magnum rather than with differences in positional behavior (Meyer & Williams, 2019a, Meyer & Williams, 2019b). According to this argument, a more dorsally oriented foramen magnum would require a more dorsally oriented odontoid process to avoid impingement of the spinal cord as it exits the skull (Meyer & Williams, 2019a, Meyer & Williams, 2019b).…”

Section: Discussionmentioning

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Comparative ontogeny of functional aspects of human cervical vertebrae

Nalley

Scott

McGechie

et al. 2023

American Journal of Biological Anthropology

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ObjectivesDifferences between adult humans and great apes in cervical vertebral morphology are well documented, but the ontogeny of this variation is still largely unexplored. This study examines patterns of growth in functionally relevant features of C1, C2, C4, and C6 in extant humans and apes to understand the development of their disparate morphologies.Materials and MethodsLinear and angular measurements were taken from 530 cervical vertebrae representing 146 individual humans, chimpanzees, gorillas, and orangutans. Specimens were divided into three age‐categories based on dental eruption: juvenile, adolescent, and adult. Inter‐ and intraspecific comparisons were evaluated using resampling methods.ResultsOf the eighteen variables examined here, seven distinguish humans from apes at the adult stage. Human‐ape differences in features related to atlantoaxial joint function tend to be established by the juvenile stage, whereas differences in features related to the nuchal musculature and movement of the subaxial elements do not fully emerge until adolescence or later. The orientation of the odontoid process—often cited as a feature that distinguishes humans from apes—is similar in adult humans and adult chimpanzees, but the developmental patterns are distinct, with human adultlike morphology being achieved much earlier.DiscussionThe biomechanical consequences of the variation observed here is poorly understood. Whether the differences in growth patterns represent functional links to cranial development or postural changes, or both, requires additional investigation. Determining when humanlike ontogenetic patterns evolved in hominins may provide insight into the functional basis driving the morphological divergence between extant humans and apes.

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“…Vertebral remains of Au. anamensis discovered in present‐day Ethiopia also indicate a complicated relationship between the two taxa, as these 4.2‐million‐year‐old axial remains appear to be more derived in certain respects than its successor (Meyer and Williams 2019).…”

Section: New Discoveries Aplentymentioning

confidence: 99%

Revolutionary Fossils, Ancient Biomolecules, and Reflections in Ethics and Decolonization: Paleoanthropology in 2019

Schroeder

2020

American Anthropologist

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Over the past few decades, paleoanthropology has undergone a transformative shift away from studies focused solely on traditional assessments of skeletal anatomy. Prior to this shift, a review highlighting a year of research may have primarily consisted of a description of new fossil discoveries; in 2019, however, this review also incorporates novel subject matters such as ancient DNA, paleoproteomics, and studies applying a wide array of new analytical methods and theoretical frameworks to paleoanthropological questions. Through these new advances, the nonlinearity and complexity of hominin evolution has been illuminated, emphasizing the importance of interdisciplinary work in progressing the field. In addition, similar to the broader discipline of biological anthropology, the topic of decolonization has been reflected on and discussed. Further, researchers in paleoanthropology are grappling with important issues related to open access and data sharing. In light of this widening scope, this review centers on a collection of studies that focus on five key themes: (1) new discoveries; (2) data sharing and ethics; (3) human origins research; (4) paleogenomics, and new advancements in paleoproteomics; and (5) introspection on a colonial history. Paleoanthropology is coming of age, and in 2019 especially, published research has been reflective of this. [Evolutionary anthropology; human evolution; year in review; human origins]

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Earliest axial fossils from the genus Australopithecus

Cited by 6 publications

References 102 publications

The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism

The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism

Comparative ontogeny of functional aspects of human cervical vertebrae

Revolutionary Fossils, Ancient Biomolecules, and Reflections in Ethics and Decolonization: Paleoanthropology in 2019

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