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Postcranial robusticity in Homo. I: Temporal trends and mechanical interpretation
C B Ruff1, E Trinkaus, A Walker
1Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
American Journal of Physical Anthropology
|May 1, 1993
Summary
Postcranial robusticity in Homo has exponentially declined over time due to reduced mechanical loading, linked to brain size and technology. This trend shows a decrease in bone shaft strength but not joint size.
Area of Science:
- Paleoanthropology
- Human Evolution
- Biomechanics
Background:
- Postcranial robusticity in the genus Homo exhibits temporal trends.
- Understanding these trends provides insights into human evolution and adaptation.
Purpose of the Study:
- To analyze temporal changes in postcranial bone properties within the genus Homo.
- To compare diaphyseal and articular robusticity across different Homo species and time periods.
Main Methods:
- Developed scaling relationships between bone structural properties and length using mechanical models and Recent human data.
- Standardized structural properties to compare Recent and pre-Recent Homo samples (Homo sp., H. erectus, archaic H. sapiens, early modern H. sapiens).
Main Results:
- Observed a consistent, exponential decline in diaphyseal (shaft) robusticity from the early Pleistocene to Recent humans.
- Found no similar temporal decline in articular robusticity; relative femoral head size remained constant.
- Early modern H. sapiens showed shaft robusticity closer to archaic H. sapiens than to Recent humans.
Conclusions:
- The decline in postcranial robusticity is attributed to reduced mechanical loading, primarily through developmental rather than genetic changes.
- Environmental and behavioral factors, including increased brain size and technological advancements, are linked to this decline.
- Changes in robusticity lag behind cognitive and technological developments in human evolution.