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Record W2903228190 · doi:10.4207/pa.2018.art115

The hand of Australopithecus sediba

2018· article· en· W2903228190 on OpenAlex

Why this work is in the frame

A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.

fundA Canadian funder is recorded on the work.
no affNo Canadian affiliation: this work is invisible to an affiliation-only frame.
No Canadian affiliation. An affiliation-only frame, the usual design, would never have seen this work. It is one of the works that make the case for inverting the frame.

Bibliographic record

VenueKent Academic Repository (University of Kent) · 2018
Typearticle
Languageen
FieldPsychology
TopicPrimate Behavior and Ecology
Canadian institutionsnot available
FundersMax-Planck-Institut für Evolutionäre AnthropologieUniversità degli Studi di FirenzeUniversity of TorontoSmithsonian Institution
KeywordsAustralopithecusHominidaeAnatomyBipedalismPhalanxHomo sapiensPaleoanthropologyBiologyMorphology (biology)ManusPongo pygmaeusThumbEvolutionary biologyBiological evolutionPaleontologyZoologyGeography

Abstract

fetched live from OpenAlex

Here we describe the functional morphology of the Australopithecus sediba hand, including the almost complete hand of the presumed female Malapa Hominin (MH) 2 skeleton and a single, juvenile metacarpal from the presumed male MH1 skeleton. Qualitative and quantitative comparisons with extant hominids and fossil hominins, ranging from Ardipithecus to early Homo sapiens, reveal that Au. sediba presents a unique suite of morphological features that have not been found in any other known hominin. Analyses of intrinsic hand proportions show that the MH2 hand has a thumb that is longer relative to its fingers than recent humans and any other known hominin. Furthermore, the morphology of the hamatometacarpal articulation suggests that the robust fifth metacarpal was positioned in a slightly more flexed and adducted posture than is typical of Neandertals and humans. Together, this morphology would have facilitated opposition of the thumb to the fingers and pad-to-pad precision gripping that is typical of later Homo. However, the remarkably gracile morphology of the first ray and the morphology of the lateral carpometacarpal region suggest limited force production by the thumb. The distinct scaphoid-lunatecapitate morphology in MH2 suggests a greater range of abduction at the radiocarpal joint and perhaps less central-axis loading of the radiocarpal and midcarpal joints than is interpreted for other fossil hominins, while the morphology of the hamatotriquetrum articulation suggests enhanced stability of the medial midcarpal joint in extended and/or adducted wrist postures. The MH2 proximal phalanges show moderate curvature and, unusually, both the proximal and intermediate phalanges have well-developed flexor sheath ridges that, in combination with a palmarly-projecting hamate hamulus, suggest powerful flexion and that some degree of arboreality may have been a functionally important part of the Au. sediba locomotor repertoire. Finally, the MH1 and MH2 third metacarpals differ remarkably in their size and degree of robusticity, but this variation fits comfortably within the sexual dimorphism documented in recent humans and other fossil hominins, and does not necessarily reflect differences in function or hand use. Overall, the morphology of the current Au. sediba hand bones suggests the capability for use of the hands both for powerful gripping during locomotion and precision manipulation that is required for tool-related behaviors, but likely with more limited force production by the thumb than is inferred in humans, Neandertals, and potentially Homo naledi.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.

Full frame distilled prediction

Teacher imitation

Not calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.

metaresearch head score (Codex)0.000
metaresearch head score (Gemma)0.000
Version: codex-gemma-dda1882f352aValidation status: machine_predicted_unvalidated
Candidate categoriesnone
Consensus categoriesnone
DomainCandidate signal: none · Consensus signal: none
Study designCandidate signal: Observational · Consensus signal: Observational
GenreCandidate signal: Empirical · Consensus signal: Empirical
Teacher disagreement score0.341
Threshold uncertainty score0.479

Codex and Gemma teacher scores by category

CategoryCodexGemma
Metaresearch0.0000.000
Meta-epidemiology (narrow)0.0000.000
Meta-epidemiology (broad)0.0000.000
Bibliometrics0.0000.000
Science and technology studies0.0000.001
Scholarly communication0.0000.000
Open science0.0010.000
Research integrity0.0000.000
Insufficient payload (model declined to judge)0.0000.000

Machine scores (provisional)

The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.

Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.

Opus teacher head0.023
GPT teacher head0.276
Teacher spread0.254 · how far apart the two teachers sit on this one work
Validation statusscore_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it