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Side steps: the erratic pattern of hominin postcranial change through time
Henry M McHenry1, Cassandra C Brown
1Department of Anthropology, University of California, Davis, CA 95616, USA. hmmchenry@ucdavis.edu
Journal of Human Evolution
|June 24, 2008
Summary
Hominin evolution shows brain and craniodental changes toward human-like features. However, postcranial fossils reveal non-linear changes, indicating adaptations rather than a simple march to modern human bodies.
Area of Science:
- Paleoanthropology
- Human Evolution
- Skeletal Biology
Background:
- Hominin fossil record exhibits craniodental changes towards human-like features over time.
- Postcranial skeleton evolution is generally considered to follow a similar trend, but this is not always the case.
Purpose of the Study:
- To investigate the evolutionary trajectory of the hominin postcranial skeleton, specifically the distal humerus.
- To compare the morphology of early hominin postcranial remains with extant hominoids and Homo sapiens.
Main Methods:
- Metrical description and multivariate discriminant analyses of fossil hominin distal humeri.
- Comparison with large samples of extant hominoid humeri, including Homo sapiens.
- Analysis of limb joint proportions, ulnar morphology, and pelvic architecture in fossil specimens.
Main Results:
- Early hominin distal humerus morphology is often more human-like than that of later hominin specimens.
- Multivariate analyses show significant differences (large Mahalanobis distances) between early hominin humeri (1.5-2Ma) and Homo sapiens.
- Postcranial features like limb proportions, ulnar morphology, and pelvic architecture do not display a linear trend of increasing hominization.
Conclusions:
- Hominin postcranial evolution is not a simple linear progression towards modern human form.
- Observed patterns suggest adaptations to specific environmental conditions, constrained by developmental (ontogeny) and historical factors.
- The hominin postcranial fossil record demonstrates "side-steps" and complex evolutionary pathways rather than a straightforward march to human bodies.
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