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Abstract ObjectivesThe effects of phylogeny and locomotor behavior on long bone structural proportions are assessed through comparisons between adult and ontogenetic samples of extant gorillas. Materials and MethodsA total of 281 wild‐collected individuals were included in the study, divided into four groups that vary taxonomically and ecologically: western lowland gorillas (G. g. gorilla), lowland and highland grauer gorillas(G. b. graueri), and Virunga mountain gorillas (G. b. beringei). Lengths and articular breadths of the major long bones (except the fibula) were measured, and diaphyseal cross‐sectional geometric properties determined using computed tomography. Ages of immature specimens (n = 145) were known or estimated from dental development. Differences between groups in hind limb to forelimb proportions were assessed in both adults and during development. ResultsDiaphyseal strength proportions among adults vary in parallel with behavioral/ecological differences, and not phylogeny. The more arboreal western lowland and lowland grauer gorillas have relatively stronger forelimbs than the more terrestrial Virunga mountain gorillas, while the behaviorally intermediate highland grauer gorillas have intermediate proportions. Diaphyseal strength proportions are similar in young infants but diverge after 2 years of age in western lowland and mountain gorillas, at the same time that changes in locomotor behavior occur. There are no differences between groups in length or articular proportions among either adults or immature individuals. ConclusionLong bone diaphyseal strength proportions in gorillas are developmentally plastic, reflecting behavior, while length and articular proportions are much more genetically canalized. These findings have implications for interpreting morphological variation among fossil taxa.
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Locomotor signals in the trabecular structure of the hominoid clavicle
Abstract Understanding the functional significance of morphological variation is crucial for investigating locomotor adaptations in fossil primates and early hominins. However, the nuanced form–function relationship in the upper limbs of extant apes is difficult to discern due to their varied locomotor behaviors, complicating the interpretation of similar features in fossil hominins. Trabecular bone, which responds to mechanical strain, reflects the intensity and direction of forces during movement, making it valuable for identifying locomotor adaptations in hominoids. This study examines trabecular bone in the clavicle—a crucial component of shoulder biomechanics—to explore its relationship to mechanical loading patterns and bone functional adaptations in primate locomotion. Using a whole‐bone approach, we analyzed trabecular structure in the clavicle of apes:Gorillaspp. (G. beringei:N = 28;G. gorilla:N = 29),Homo sapiens(N = 19),Hylobatesspp. (H. lar:N = 28;H. concolor:N = 3),Pongospp. (P. abelii:N = 13;P. pygmaeus:N = 24), andPan troglodytes(N = 35), quantifying relative bone volume fraction (rBV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and trabecular number (Tb.N) from high‐resolution micro‐CT scans. Aspects of the clavicular trabecular architecture among ape taxa appear to correspond to differences in locomotor behavior. In most taxa, rBV/TV is highest in regions underlying muscle attachment sites frequently used during upper limb activities, with differences among taxa predominantly reflecting variations in upper limb use and muscle attachment sites. Regions of high rBV/TV beneath entheses and articular surfaces result from different trabecular parameters—higher rBV/TV is achieved primarily via greater Tb.Th under entheses, while in subarticular regions, it is driven by higher Tb.N. However, no consistent differences in sternoclavicular subarticular trabecular bone emerge betweenHomoand the other apes, despite differences in shoulder positioning on the torso. Muscle activity appears to significantly influence trabecular bone structure in the clavicle of living apes, with implications for reconstructing early hominin locomotor behaviors and upper limb use.
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- Award ID(s):
- 2317012
- PAR ID:
- 10576709
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Anatomy
- ISSN:
- 0021-8782
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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