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Forelimb segment length proportions in extant hominoids and Australopithecus afarensis
Michelle S M Drapeau1, Carol V Ward
1Département d'Anthropologie, Université de Montréal, Montréal, QC, Canada H3C 3J7. m.drapeau@umontreal.ca
American Journal of Physical Anthropology
|December 13, 2006
Summary
Australopithecus afarensis forelimb proportions are similar to modern humans, not elongated like apes. This suggests reduced metacarpals and possibly humerus length compared to ancestral conditions.
Area of Science:
- Paleoanthropology
- Comparative Anatomy
- Functional Morphology
Background:
- Forelimb proportions are crucial for understanding locomotor adaptations in fossil hominoids.
- Limited data exists on individual forelimb segment proportions in extant and fossil hominoids.
Purpose of the Study:
- To analyze relative lengths of arm, forearm, wrist, and palm in Australopithecus afarensis.
- To compare forelimb bone scaling and element lengths to body size in extant hominoids and A. afarensis.
Main Methods:
- Comparative analysis of forelimb bone scaling relationships.
- Assessment of individual forelimb element lengths relative to a body size surrogate.
- Examination of fossil hominoid skeletons (A.L. 438-1 and A.L. 288-1) and extant hominoid species.
Main Results:
- Hylobatids and orangutans exhibit the longest relative forelimb bones; carpal variation is minimal.
- Pan species show unique long metacarpals relative to ulnar length.
- Australopithecus afarensis forelimb bones are not significantly longer than human proportions for their size.
Conclusions:
- Australopithecus afarensis falls within human variation for most forelimb proportions, differing slightly in brachial index.
- A. afarensis possesses short metacarpals, similar to humans, unlike Pan.
- Forelimb proportions in A. afarensis suggest a reduction in metacarpal and possibly humerus length relative to body size from the ancestral state.
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