Bipedalism in Homo ergaster: An Experimental Study of the Effects of Tibial Proportions on Locomotor Biomechanics

Gruss, Laura; Schmitt, Daniel

doi:10.1007/978-1-4419-8965-9_8

Cited by 4 publications

(5 citation statements)

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“…Although this variation in limb length and intramembral indices has generally been interpreted as an adaptation to climate in accordance with Bergmann's and Allen's Rules (see Ruff, 1991Ruff, , 1994, the variation in limb proportions within Pleistocene Homo is of potential importance for understanding the continuing evolution of human locomotion over the past two million years. Until recently, however (Polk, 2002(Polk, , 2004Gruss and Schmitt, 2004;Steudel-Numbers and Tilkens, 2004;Pontzer, 2005Pontzer, , 2007, little experimental research has addressed the question of whether, and how, proportional changes actually affect the mechanics of human bipedalism.…”

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confidence: 99%

Limb length and locomotor biomechanics in the genus Homo: An experimental study

Gruss

2007

American J Phys Anthropol

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The striking variation in limb proportions within the genus Homo during the Pleistocene has important implications for understanding biomechanics in the later evolution of human bipedalism, because longer limbs and limb segments may increase bending moments about bones and joints. This research tested the hypothesis that long lower limbs and tibiae bring about increases in A-P bending forces on the lower limb during the stance phase of human walking. High-speed 3-D video data, force plates, and motion analysis software were used to analyze the walking gait of 27 modern human subjects. Limb length, as well as absolute and relative tibia length, were tested for associations with a number of kinetic and kinematic variables. Results show that individuals with longer limbs do incur greater bending moments along the lower limb during the first half of stance phase. During the second half of stance, individuals moderate bending moments through a complex of compensatory mechanisms, including keeping the knee in a more extended position. Neither absolute nor relative tibia length had any effect on the kinetic or kinematic variables tested. If these patterns apply to fossil Homo, groups with relatively long limbs (e.g. H. ergaster or early H. sapiens) may have experienced elevated bending forces along the lower limb during walking compared to those with relatively shorter limbs (e.g. the Neandertals). These increased forces could have led to greater reinforcement of joints and diaphyses. These results must be considered when formulating explanations for variation in limb morphology among Pleistocene hominins.

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Limb length and locomotor biomechanics in the genus Homo: An experimental study

Gruss

2007

American J Phys Anthropol

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“…The runner's high experienced today also reflects this legacy; however, one can only consider the effect 9. See work on ecology (Kramer 2004), dispersal rates out of Africa (Anton, Leonard, and Robertson 2002), energetics (Gruss and Schmitt 2004), social learning and intelligence (Robson and Kaplan 2003), gender roles, reproduction, and foraging (Vitzhum 1997;O'Connell, Hawkes, and Blurton Jones 1999;Aiello and Key 2002), diet (Milton 1999;Ungar et al 2006;Cordain 2006), extant ethnographic analogies of hunting to foraging (Marshall 1976;Shostak 1976;Hilton and Greaves 2004;Draper 1997;Liebenberg 2006), and conceptual abilities inferred from tool making (Wynn 1992;Plummer 2004).…”

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Sands¹,

Sands²

2010

JSRNC

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“…Our Model CFST has a higher-than-average femoral curvature but straighter than average tibial curvature, while our Model SFCT reflects the straightest femur in the overall dataset paired with a much higher than average tibial curvature (see Table 1). Otherwise, the two individuals were both male and similar in estimated body mass, biiliac breadth, and crural index (see Table 1), all parameters that may otherwise influence gait kinematics and muscle kinetics (Gruss and Schmitt, 2004;Polk, 2004;Wall-Scheffler, 2012;Sheehan and Gormley, 2013;Gruss et al, 2017;Law et al, 2021). Body mass was estimated according to population-specific equations (Ruff et al, 2012) when possible (Model CFST), or with the mean of three non-specific equations (Ruff et al, 1997) when no populationspecific equations existed (Model SFCT).…”

Section: Three-dimensional Surface Models and Choice Of Model Morphologymentioning

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Anterior diaphyseal curvature of the femur and tibia has biomechanical consequences during unloaded uphill locomotion

et al. 2023

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The biomechanics of limb bone curvature are complex, and though anterior curvature clearly exhibits some relationship with behavior, the mechanisms shaping it and its biomechanical purpose remain unclear. Among both Neanderthals and humans, anterior limb bone curvature correlates strongly with other limb bone adaptations known to reflect high mobility, particularly in steep variable terrain. We developed a computational musculoskeletal model to test the impact of opposing patterns of human femoral and tibial anterior curvature on muscle kinetics during a proxy for uphill walking: stair-climbing. Femoral and tibial laser scans were used from two archaeological individuals matched for estimated body mass, bi-iliac breadth, and crural index but with reverse patterns of anterior diaphyseal curvature. A default OpenSim musculoskeletal model was modified twice – once to each individual’s anatomy – and the resulting models performed stair-climbing gait simulations with experimentally-collected motion capture data. Both custom MSk models followed the general gait kinematics expected based on stair-climbing gait studies, but differed in muscle kinetics in key areas. When a curved femur was paired with a straight tibia, the opposite pattern of recruitment of bi-articular superficial hamstring muscles was observed compared to the pairing of a straight femur with a curved tibia. Pairing a curved femur with a straight tibia was also associated with reduced soleal recruitment and an increased reliance on secondary ankle plantarflexors. These effects are attributed to variation in muscle moment arms about the knee and the relationships that curvature likely has with other three-dimensional morphological variation within the bone/limb. While the tissue-level mechanisms shaping anterior limb bone curvature remain poorly understood, results of the current study suggest that opposing patterns of variation in long bone curvature within the leg do elicit different kinetic solutions to the problem of achieving the same gait kinematics during uphill locomotion. This is an important first step not just in better understanding the biomechanical impact of anatomical variation in bone curvature on locomotion, but also contributes more broadly to the recognition in biological anthropology of variability in the relationship between locomotor function and underlying skeletal structure.

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Bipedalism in Homo ergaster: An Experimental Study of the Effects of Tibial Proportions on Locomotor Biomechanics

Cited by 4 publications

References 42 publications

Limb length and locomotor biomechanics in the genus Homo: An experimental study

Limb length and locomotor biomechanics in the genus Homo: An experimental study

Running Deep

Anterior diaphyseal curvature of the femur and tibia has biomechanical consequences during unloaded uphill locomotion

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