Relative fibular strength and locomotor behavior in KNM-WT 15000 and OH 35

Objectives: Many primates change their locomotor behavior as they mature from infancy to adulthood. Here we investigate how long bone cross-sectional geometry in Pan, Gorilla, Pongo, Hylobatidae, and Macaca varies in shape and form over ontogeny, including whether specific diaphyseal cross sections exhibit signals of periosteal adaptation or canalization. Materials and methods: Diaphyseal cross sections were analyzed in an ontogenetic series across infant, juvenile, and adult subgroups. Three-dimensional laser-scanned long bone models were sectioned at midshaft (50% of biomechanical length) and distally (20%) along the humerus and femur. Traditional axis ratios acted as indices of cross-sectional circularity, while geometric morphometric techniques were used to study cross-sectional allometry and ontogenetic trajectory. Results: The humeral midshaft is a strong indicator of posture and locomotor profile in the sample across development, while the mid-femur appears more reflective of shifts in size. By comparison, the distal diaphyses of both limb elements are more ontogenetically constrained, where periosteal shape is largely static across development relative to size, irrespective of a given taxon's behavior or ecology. Discussion: Primate limb shape is not only highly variable between taxa over development, but at discrete humeral and femoral diaphyseal locations. Overall, periosteal shape of the humeral and femoral midshaft cross sections closely reflects ontogenetic transitions in behavior and size, respectively, while distal shape in both bones appears more genetically constrained across intraspecific development, regardless of posture or size. These findings support prior research on tradeoffs between function and safety along the limbs.

Section: Methodsmentioning

confidence: 99%

Section: Postcranial Development and Adaptationmentioning

confidence: 99%

Ontogenetic and morphological variation in primate long bones reflects signals of size and behavior

Nadell

Elton

Kovarovic

2020

“…Fibular robusticity (Z p ‐std) depends on age, and this is especially true in the middle part of the fibula. Thus, comparative analyses could be significantly altered given that this part is the only region currently used in paleoanthropological studies (e.g., Marchi et al, 2019; Sparacello et al, 2014). Such phenomena can be considered and discussed by authors based on the sample used and the period to which it belongs.…”

Section: Discussionmentioning

confidence: 99%

“…Reconstructing mobility is a key point in human evolution (Carlson & Marchi, 2014). Recently, fibular bone has been included in functional studies of past populations through assessments of cross‐sectional geometric properties (CSGs) and fibular furrows (Hagihara & Nara, 2016; Marchi, Harper, Chirchir, & Ruff, 2019; Sparacello et al, 2018; Sparacello, Marchi, & Shaw, 2014). However, little is known about the structural changes in the fibula that occur during aging (e.g., Allen, Johnstone, Rice, & Marsh, 2011; McNeil, Raymer, Doherty, Marsh, & Rice, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Allen et al (2011) extended this tibia versus fibula comparison to women and proposed a similar trend: the tibia (weight‐bearing bone) was more prone to age‐related changes in adults, and the fibula was less or not affected by aging. These authors did not include the second moment of areas (and their ratio) and the section modulus, which are commonly used when past populations and their mobility are studied (e.g., Marchi et al, 2019; Shackleford, 2014; Sparacello et al, 2014). Rantalainen, Duckham, Suominen, Heinonen, and Alén (2014) also found age‐related changes in CA based on a comparison of two age groups (<40 vs. > 65 years of age) composed of athletes and referents, although in contrast, the TA was significantly increased at the midshaft, which was the only section studied.…”

Section: Introductionmentioning

confidence: 99%

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Age‐related site‐specific modifications in diaphyseal structural properties of the human fibula: Furrows and cross‐sectional geometry

Chevalier

Tignères

2020

Objectives: Fibular structure is related to locomotor behavior, which allows an exploration of mobility in past human populations with diaphyseal cross-sectional geometry (CSG). However, bone structure depends on age-related changes. Nonmechanical alterations can affect biomechanical investigations. In this study, we examined how the cortical area and the variables used as functional markers in the fibular diaphysis (i.e., CSG and furrows) change with aging. We predict classic and specific modifications, and we discuss functional interpretations based on bone structure. Materials and methods: The sample consisted of 124 individuals of known age in whom the fibular furrow depths were measured with calipers. Microcomputed tomography (micro-CT) scanning of 38 individuals provided CSG (e.g., cortical area, shape index, and robusticity) and fibular furrow indices. CSG was studied at five cross sections taken along the diaphysis. Linear regression analyses and age group comparisons were conducted. Results: The cross-sectional shape summary by fibular furrows and shape index and the total area did not change with aging; in contrast, the cortical area and the robusticity (Z p-std) decreased with age. Discussion: The decrease in robusticity (Z p-std) with aging is due to the maintenance of total area, which is related to the specific mechanical environment of the fibula, and to the loss of cortical bone and not to the decrease in mechanical stress. This finding is consistent with the lower bone modeling capacity in aged individuals, which also explains the lack of significant changes in the diaphyseal shape. Thus, fibular structure in older individuals is due to a combination of early bone adaptations to stress and aging effects.

Gorilla calcaneal morphological variation and ecological divergence

Harper

Ruff

Sylvester

2020

Objectives: The primate foot has been extensively investigated because of its role in weight-bearing; however, the calcaneus has been relatively understudied. Here we examine entire gorilla calcaneal external shape to understand its relationship with locomotor behavior. Materials and methods: Calcanei of Gorilla gorilla gorilla (n = 43), Gorilla beringei graueri (n = 20), and Gorilla beringei beringei (n = 15) were surface or micro-CT scanned. External shape was analyzed through a three-dimensional geometric morphometric sliding semilandmark analysis. Semilandmarks were slid relative to an updated Procrustes average in order to minimize the bending energy of the thin plate spline interpolation function. Shape variation was summarized using principal components analysis of shape coordinates. Procrustes distances between taxa averages were calculated and resampling statistics run to test pairwise differences. Linear measures were collected and regressed against estimated body mass. Results: All three taxa exhibit statistically different morphologies (p < .001 for pairwise comparisons). G. g. gorilla demonstrates an anteroposteriorly elongated calcaneus with a deeper cuboid pivot region and mediolaterally flatter posterior talar facet. G. b. beringei possesses the flattest cuboid and most medially-angled posterior talar facets. G. b. graueri demonstrates intermediate articular facet morphology, a medially-angled tuberosity, and an elongated peroneal trochlea. Discussion: Articular facet differences separate gorillas along a locomotor gradient. G. g. gorilla is adapted for arboreality with greater joint mobility, while G. b. beringei is adapted for more stereotypical loads associated with terrestriality. G. b. graueri's unique posterolateral morphology may be due to a secondary transition to greater arboreality from a more terrestrial ancestor.