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Function, ontogeny and canalization of shape variance in the primate scapula
1Department of Cell Biology and Anatomy, University of Calgary, Alberta, Canada. nmy@stanford.edu
Journal of Anatomy
|October 26, 2006
Summary
Primate shoulder blade shape variation is linked to locomotion. Highly arboreal primates, like apes, show greater scapular shape variance than quadrupeds, suggesting reduced stabilizing selection on non-quadrupedal shoulder evolution.
Area of Science:
- Primate paleontology
- Comparative anatomy
- Evolutionary biology
Background:
- Primate shoulder morphology reflects diverse locomotor behaviors, from quadrupedalism to suspensory postures.
- Previous studies suggested quadrupedal primates exhibit less intraspecific variation in postcranial shape compared to non-quadrupeds.
Purpose of the Study:
- To investigate the correlation between intraspecific scapular shape variance and the degree of quadrupedalism in primates.
- To explore the developmental and selective factors contributing to observed shape variances.
Main Methods:
- Analysis of primate scapular shape variation across different locomotor groups.
- Comparison of shape variance between quadrupedal and non-quadrupedal primates, including infants and adults.
Main Results:
- Intraspecific scapular shape variance is significantly correlated with the degree of committed quadrupedalism.
- Primates with frequent suspensory behaviors (apes, atelines) exhibit twice the scapular shape variance of quadrupeds (Old World monkeys).
- This variance is present early in development and does not change significantly with age, ruling out postnatal factors.
Conclusions:
- The high scapular shape variance in non-quadrupedal primates is likely influenced by embryonic factors or epigenetic modifications related to muscle attachments.
- Heterogeneous functional demands of non-quadrupedal shoulders may reduce stabilizing selection, allowing greater expression of developmental variation.
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