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Variability of Australopithecus second maxillary molars from Sterkfontein Member 4
Cinzia Fornai1, Fred L Bookstein2, Gerhard W Weber1
1Department of Anthropology, University of Vienna, Austria.
Journal of Human Evolution
|July 12, 2015
Summary
Determining the number of Australopithecus species is challenging due to poor fossil preservation. This study found no distinct species within Australopithecus using 3D geometric morphometrics of molar shapes.
Area of Science:
- Paleoanthropology
- Evolutionary Biology
- Primatology
Background:
- The classification of hominin fossils from Sterkfontein Member 4 and Makapansgat, particularly Australopithecus species, remains contentious.
- Challenges include poor fossil preservation, complex stratigraphy, and fragmented, unassociated remains, hindering definitive species identification.
Purpose of the Study:
- To investigate the taxonomic diversity within the Australopithecus genus using advanced 3D geometric morphometrics.
- To apply detailed dental analysis to resolve the ongoing debate regarding the number of Australopithecus species present at key South African fossil sites.
Main Methods:
- Utilized 3D geometric morphometrics to analyze the morphology of upper second molars (M(2)s) from fossil hominin samples.
- Examined outer and inner crown surfaces, and crown and cervical outlines using 16 landmarks, 51 curve semilandmarks, and 48 pseudolandmarks.
- Compared dental variation across Australopithecus, Paranthropus, and Homo samples, including Homo sapiens and Homo neanderthalensis.
Main Results:
- Homo species were clearly distinguishable from Australopithecus and Paranthropus based on M(2) morphology.
- No distinct morphological classes were identified within the Australopithecus sample or between Australopithecus and Paranthropus.
- A morphological gradient was observed, with Australopithecus africanus and Australopithecus prometheus at the extremes and Paranthropus overlapping.
Conclusions:
- The M(2) morphology of Australopithecus specimens does not provide stable taxonomic distinctions, suggesting either uninformative morphology or insufficient sample size.
- The high variability within Australopithecus complicates authoritative interpretation, regardless of the analytical method employed.
- Current data suggest a continuous morphological spectrum rather than clearly defined species within the studied Australopithecus fossil record.
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