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Occipital Condyle Development in Extant Hominids and Australopithecus afarensis
Neysa Grider-Potter1,2, Thierra K Nalley3, Jeremiah E Scott3
1Department of Biomedical Sciences, Northeast Ohio Medical University, Rootstown, Ohio, USA.
American Journal of Biological Anthropology
|June 23, 2025
Summary
The study found that condylar curvature increases with age in all hominids, but adult human and gorilla condyles are flatter than chimpanzees and orangutans. Australopithecus afarensis shows a chimpanzee-like pattern, suggesting convergent evolution in humans and gorillas.
Area of Science:
- Paleoanthropology
- Comparative Anatomy
- Developmental Biology
Background:
- Occipital condyle morphology varies across hominids, influencing positional behavior and upright posture.
- The ontogeny and curvature of condylar joint surfaces remain less understood.
- This research investigates condylar curvature development in extant hominids and Australopithecus afarensis.
Purpose of the Study:
- To examine the ontogenetic changes in occipital condylar curvature.
- To compare condylar curvature across different hominid species and developmental stages.
- To correlate changes in condylar curvature with cranial synostosis fusion.
Main Methods:
- Quantified condylar curvature in 147 individuals across five species: chimpanzees, gorillas, humans, orangutans, and A. afarensis.
- Categorized specimens into juvenile, adolescent, and adult dental age groups.
- Employed resampling methods to analyze inter- and intra-generic differences and recorded synostotic fusion timing.
Main Results:
- Condylar curvature increases with ontogeny in all studied taxa.
- Adult Homo and Gorilla exhibit flatter condyles compared to Pan and Pongo.
- Australopithecus afarensis displays a Pan-like morphology and developmental trajectory.
Conclusions:
- The observed patterns of condylar curvature do not directly correlate with postural or locomotor differences.
- The flatter condyles in humans and gorillas appear to be a result of convergent evolution.
- The Pan-like morphology in A. afarensis supports the idea of a retained plesiomorphic cervico-occipital region in early hominins, even after the evolution of bipedality.
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