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Pelvic dimensions in female modern Homo sapiens (left) and female Au. afarensis specimen A.L. 288-1 ( " Lucy, " right). The two pelves are shown in in superior/anterior view and drawn to the same scale. The red arrows indicate bi-acetabular breadth, which is very similar in the two species despite the great difference in overall body size. Modified from Rosenberg and Trevathan (2002).
Source publication
A broad pelvis is characteristic of most, if not all, pre-modern homi-nins. In at least some early australopithecines, most notably the female Australopithecus afarensis specimen known as " Lucy, " it is very broad and coupled with very short lower limbs. In 1991, Rak suggested that Lucy's pelvic anatomy improved locomotor efficiency by increasing...
Context in source publication
Context 1
... pelvic anatomy of early australopithecines has been particularly well-studied in two partial skeletons: Australopithecus africanus Sts 14 and Au. afarensis A.L. 288-1 ("Lucy"), which share a mediolaterally broad, ante- roposteriorly compressed pelvic inlet and outlet and notable iliac flare ( Fig. 1; Tague and Lovejoy, 1986;Ruff, 1994;H€ ausler and Schmid, 1995). Estimates of the medio-lateral diameter of Lucy's pelvic inlet, which is approximately equal to bi-acetabular breadth, range between 123 mm and 132 mm (Tague and Lovejoy, 1986;Abitbol, 1991;H€ ausler and Schmid, 1995), within 10mm of that of an average modern human woman ...
Citations
... Foetal station and position can interfere with the progression of labour, while extrinsic pelvic exercises (anteversion and retroversion) promote intrinsic movements of the sacrum (nutation and counternutation) and this can facilitate cervical effacement, descent and foetal rotation. [27][28][29][30] None of the previously published clinical trials on the use of the Swiss ball during labour 17-20,26 used a protocol of exercises targeted at pelvic biomechanics and this may have precluded any effect on the duration of the first stage of labour. Most of those studies failed to report the amount of time during which the ball was used. ...
... Evidence shows that the vertical position and freedom to move around during labour can improve the quality and effectiveness of contractions, reducing the likelihood of an instrumental delivery and the need for epidural analgesia or episiotomy, and improving foetal conditions. [28][29][30][31] The use of the present protocol was expected to have a positive effect on these outcomes, since the ball enables labouring women to remain in a vertical position; however, these expected results were not found in this study. Adding other non-pharmacological methods to the management of labour could have improved these outcomes. ...
... 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). ...
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.
... Holowka et al. (2017) investigated chimpanzee and human bipedal walking and found that humans had a greater range of motion through stance, because of dramatic midfoot plantarflexion and adduction which they thought prepared the foot for push-off. Gruss et al. (2017) assessed 3D kinematics of walking in humans and found that those with wider pelves take longer strides at different velocities, but with less hip-extension, than others. They concluded that the wide australopith pelvis could have offset short legs and enhanced efficiency. ...
Motion analysis, as applied to evolutionary biomechanics, has experienced its own evolution over the last 50 years. Here we review how an ever-increasing fossil record, together with continuing advancements in biomechanics techniques, have shaped our understanding of the origin of upright bipedal walking. The original, and long-established hypothesis held by Lamarck (1809), Darwin (1859) and Keith (1934), amongst others, maintained that bipedality originated in an arboreal context. However, the first field studies of gorilla and chimpanzees from the 1960's, highlighted their so-called 'knucklewalking' quadrupedalism, leading scientists to assume, semi-automatically, that knucklewalking must have been the precursor to bipedality. It would not be until the discovery of skeletons of early human relatives Australopithecus afarensis and Australopithecus prometheus, and the inclusion of methods of analysis from computer science, biomechanics, sports science and medicine, that the knucklewalking hypothesis would be most robustly challenged. Their short, but human-like lower limbs and human-like hand indicated that knucklewalking was not part of our ancestral locomotor repertoire. Rather, most current research in evolutionary biomechanics agrees it was a combination of climbing and bipedalism, both in an arboreal context, which facilitated upright, terrestrial, bipedal walking over short distances.
... Vidal-Cordasco et al. (2017) similarly detected slightly higher, albeit statistically non-significant, massadjusted walking costs in their sample of Spanish women compared to men. Moreover, greater pelvic breadth in females has been shown to yield additional speed flexibility and greater stride length, partly compensating for elevated locomotor costs owing to lower hip mechanical advantage (Gruss et al., 2017;Rak, 1991;Wall-Scheffler, 2022;Wall-Scheffler & Myers, 2017;Whitcome et al., 2017). These results led several authors to reject the hypothesis that efficient bipedal locomotion has restricted the evolution of a more spacious birth canal (e.g., Dunsworth, 2016Dunsworth, , 2018Warrener et al., 2015, Warrener, 2018Gorman et al., 2022). ...
Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the "obstetrical dilemma." Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic dimensions is sometimes interpreted as empirical support for discarding an obstetrical dilemma. Here we explain why these points are important but do not invalidate evolutionary explanations of human childbirth. We present robust empirical evidence and solid evolutionary theory supporting an obstetrical dilemma, yet one that is much more complex than originally conceived in the 20th century. We argue that evolutionary research does not hinder appropriate midwifery and obstetric care, nor does it promote negative views of female bodies. Understanding the evolutionary entanglement of biological and sociocultural factors underlying human childbirth can help us to understand individual variation in the risk factors of obstructed labor, and thus can contribute to more individualized maternal care.
... AL 288-1 is predicted to have been approximately 1.05 m tall [26] with a body mass range of 13-42 kg [27][28][29], although the AL 288-1 specimen is typically considered to be on the lower end of the body mass spectrum of the species [30]. Today, it is generally agreed among researchers that the postcranial skeleton displays morphological features indicative of bipedality [31][32][33][34][35], and has thus been the focus of previous biomechanical assessments of muscle recruitment during movement [5,7,8]. ...
To understand how an extinct species may have moved, we first need to reconstruct the missing soft tissues of the skeleton, which rarely preserve, with an understanding of segmental volume and muscular composition within the body. The Australopithecus afarensis specimen AL 288-1 is one of the most complete hominin skeletons. Despite 40+ years of research, the frequency and efficiency of bipedal movement in this specimen is still debated. Here, 36 muscles of the pelvis and lower limb were reconstructed using three-dimensional polygonal modelling, guided by imaging scan data and muscle scarring. Reconstructed muscle masses and configurations guided musculoskeletal modelling of the lower limb in comparison with a modern human. Results show that the moment arms of both species were comparable, hinting towards similar limb functionality. Moving forward, the polygonal muscle modelling approach has demonstrated promise for reconstructing the soft tissues of hominins and providing information on muscle configuration and space filling. This method demonstrates that volumetric reconstructions are required to know where space must be occupied by muscles and thus where lines of action might not be feasible due to interference with another muscle. This approach is effective for reconstructing muscle volumes in extinct hominins for which musculature is unknown.
... Nonetheless, gait mechanics can be adapted to accommodate variation in form to produce similar function. Specifically, wider hips allow for a longer stride length relative to leg length [29,30] and are associated with increased stability, which necessitates less mediolateral force development [23]. Hence, while wide hips potentially increase hip coronal plane moment and abduction muscle forces (e.g., [14]), wide hips also create mechanisms that use less energy to move [23]. ...
Despite a paucity of physiological evidence, simplistic biomechanical analyses have led researchers to assume that humans who have wider hips use more energy to walk. Pitting biomechanical first principles against physiological data has led to little deepening of our understanding of bipedalism and its evolution. Both approaches, however, use proxies for the energy used by muscles. We decided to approach the question directly. Using a musculoskeletal model of the human body that estimates the metabolic energy expenditure of muscle activation for 48 people (23 women), 752 trials were evaluated. Metabolic energy consumption for the abductor muscles was summed over a stride to create total abductor energy expenditure. We calculated the maximum hip joint moment acting in the coronal plane and the functional distance between the hip joint centers. We hypothesize that wider hips would be correlated with both maximum coronal plane hip moment and increased total abductor energy expenditure when mass and velocity were controlled. Linear regressions with multiple independent variables, clustered by participant to control for the non-independence of the data points, were performed in Stata. We found that hip width does not predict total abductor energy expenditure, although mass and velocity combine to predict 61% of the variation (both p<0.001). Maximum hip joint coronal plane moment is predicted by pelvic width (p<0.001) and, in combination with mass and velocity (both p<0.001), explains 79% of the variation. Our results indicate that people use their morphology in ways that limit differences in energy expenditure. Consistent with recent discussion, intraspecific variation might not be useful to understand differences among species.
... According to this theory, a birth ball supports the perineum and decreases pressure. Besides, some studies indicate that compared to the supine position, movement freedom and upright positions assisting gravity like sitting on a swinging chair during labor, sitting on a birth ball or toilet enhance the fetus descent, decrease contractions and labor pain, and increase the quality and efficiency of the labor (5,6,12,17,42,43). In this way, women's being in comfortable positions helps them to cope with uterus contractions during the labor process. ...
Objective: This study aimed to determine the effectiveness of different birth balls used at the first stage of labor on fetal head descent, pain intensity, and maternal satisfaction. Methods: This study used a single-blind, randomized controlled experimental design. It was conducted with 180 primipara women in a maternity hospital in Erzurum, Turkey between October 2018 and December 2019. Women were randomized into 3 groups: A=Control group (n=60), B=Spherical birth ball group (n=60), and C=Peanut ball group (n=60). Birth balls were initiated in the active phase in the first stage of labor when cervical dilatation was 4 cm. Data were collected using the Personal Information Form, the Visual Analogue Scale (VAS), the Verbal Rating Scale (VRS), Partograph, and the Scale for Measuring Maternal Satisfaction in Birth (SMMSB). Results: In the active and transitional phases of labor, the VAS and VRS scores for labor pain perception of Group B were statistically significantly lower than the scores of Group A and C (p
... Specifically, work on auditory-motor entrainment in walking (Thaut, 2008(Thaut, , 2015, in which researchers examine the impact on gait of different forms of auditory information (i.e., metronome beats at different tempos) have generally found that such input has its most robust impact on temporal and spatiotemporal variables of gait, with less consistent effects on spatial properties (Lim et al., 2005;Willems et al., 2006;Rochester et al., 2007). 4 Such an effect is understandable when considered from a biomechanical vantage point, in which the principle determinants of stride length in bipedal locomotion derives from pelvic width, and the degree of flexion and extension at the hips leading to grater pelvic rotation (Rak, 1991;Gruss et al., 2017). Because the current manipulations do not place significant demands on, or require modification of the fundamental biomechanics of walking (indeed, backward walking has often been characterized as requiring comparable biomechanics to forward walking, Winter et al., 1989;Grasso et al., 1998;van Deursen et al., 1998), it is thus not surprising that little impact was observed on stride lengths. ...
Multitasking is a critical feature of our daily lives. Using a dual-task paradigm, this experiment explored adults’ abilities to simultaneously engage in everyday motor and cognitive activities, counting while walking, under conditions varying the difficulty of each of these tasks. Motor difficulty was manipulated by having participants walk forward versus backward, and cognitive difficulty was manipulated by having participants count forward versus backward, employing either a serial 2 s or serial 3 s task. All of these manipulations were performed in single-task conditions (walk only, count only) and dual-task conditions (walk and count simultaneously). Both motor performance variables (cycle time, stride length, walking velocity) and cognitive variables (counting fluency, counting accuracy) were assessed in these conditions. Analyses of single-task conditions revealed that both motor and cognitive manipulations predictably influenced performance. Analyses of dual-task performance revealed influences of motor and cognitive factors on both motor and cognitive performance. Most centrally, dual-task costs (normalized difference between single- and dual-task conditions) for motor variables revealed that such costs occurred primarily for temporal or spatiotemporal gait parameters (cycle time, walking velocity) and were driven by cognitive manipulations. Dual-task cost analyses for cognitive measures revealed negative dual-task costs, or dual-task benefits, for cognitive performance. Finally, the effects of dual-task manipulations were correlated for motor and cognitive measures, indicating dual-task performance as a significant individual difference variable. These findings are discussed with reference to theories of attentional allocation, as well as the possible role of auditory–motor entrainment in dual-task conditions.
... To date, this method has not yet been applied to humans nor the hominin fossil record, but offers poten-tial to address questions regarding the bipedal gait of early hominins, such as the probable biped Australopithecus afarensis ( Gruss et al. 2017 ). The specimen AL 288-1 (commonly known as "Lucy") is one of the most complete hominin specimens, dated to 3.2 million years ago (Ma) from the Hadar region of Ethiopia ( Johanson et al. 1982 ;Kimbel et al. 1994 ). ...
... The specimen AL 288-1 (commonly known as "Lucy") is one of the most complete hominin specimens, dated to 3.2 million years ago (Ma) from the Hadar region of Ethiopia ( Johanson et al. 1982 ;Kimbel et al. 1994 ). Researchers generally agree that the postcranial skeleton displays morphological features indicative of bipedality ( Rak 1991 ;Kramer 1999 ;Ward 2002 ;Wang et al. 2004 ;Lovejoy 2005 ;Nagano et al. 2005 ;Gruss et al. 2017 ), despite numerous morphological differences to modern humans, such as a wide pelvis and relatively shorter lower limbs ( Jungers 1982 ;McHenry 1986 ;Tague & Lovejoy 1986 ;Kramer 1999 ;Wall-Scheffler & Myers 2017 ). These and other skeletal differences ( Brassey et al. 2018 ) have underpinned two schools of thought: Au. afarensis as a facultative biped that exploited other locomotory avenues such as arborealism ( Senut 1980 ;Stern 2000 ) versus Au. afarensis as a habitual biped, mostly exploiting bipedalism as the main form of locomotion ( Preuschoft & Witte 1991 ;Rak 1991 ;Lovejoy 2007 ). ...
- English
The postcranial skeleton of Australopithecus afarensis (AL 288-1) exhibits clear adaptations for bipedality, although there is some debate as to the efficiency and frequency of such upright movement. Some researchers argue that AL 288-1 walked with an erect limb like modern humans do, whilst others advocate for a “bent-hip bent-knee” (BHBK) gait, although in recent years the general consensus favours erect bipedalism. To date, no quantitative method has addressed the articulation of the AL 288-1 hip joint, nor its range of motion (ROM) with consideration for joint spacing, used as a proxy for the thickness of the articular cartilage present within the joint spacing which can affect how a joint moves. Here, we employed ROM mapping methods to estimate the joint spacing of AL 288-1’s hip joint in comparison to a modern human and chimpanzee. Nine simulations assessed different joint spacing and tested the range of joint congruency (i.e., ranging from a closely packed socket to loosely packed). We further evaluated the sphericity of the femoral head and whether three rotational degrees of freedom (DOFs) sufficiently captures the full ROM or if translational DOFs must be included. With both setups, we found that the AL 288-1 hip was unlikely to be highly congruent (as it is in modern humans) because this would severely restrict hip rotational movement and would severely limit the capability for both bipedality and even arboreal locomotion. Rather, the hip was more cartilaginous than it is in modern humans, permitting the hip to rotate into positions necessitated by both terrestrial and arboreal movements. Rotational-only simulations found that AL 288-1 was unable to extend the hip like modern humans, forcing the specimen to employ a BHBK style of walking, thus contradicting 40+ years of previous research into the locomotory capabilities of AL 288-1. Therefore, we advocate that differences in the sphericity of the AL 288-1 femoral head with that of a modern human necessitates all six DOFs to be included in which AL 288-1 could osteologically extend the hip to facilitate a human-like gait.
... The human configuration allows the lesser gluteal muscles, which run from the outside of the iliac blades to the top of the femur, to efficiently balance the pelvis and upper body over a single support leg during locomotion. The orientation of the iliac blades in humans also permits rotation of the pelvis counter to the rotation of the thorax during locomotion and thus allows the pelvis to contribute to a long stride length (Inman et al. 1981;Rak 1991;Gruss et al. 2017). Chimpanzees, in contrast, limit counterrotation of the pelvis and thorax and walk with a swaying gait and/or with their upper limbs to the side for balance (see O'Neill et al. 2018). ...
