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Bipedalism is a highly specialized and unusual form of primate locomotion that is found today only in modern humans. The majority of extinct taxa within the Hominini were bipedal, but the degree to which they were bipedal remains the subject of considerable debate. The significant discoveries of fossil hominin remains in the last 40 years have resulted in this debate becoming increasingly focused on how bipedal certain fossil taxa were rather than on the overall process. Although the early hominin fossil record remains poor, evidence points to at least two distinct adaptive shifts. First, there was a shift to habitual bipedalism, as typified by certain members of Australopithecus. Such taxa were bipedal, but also retained a number of significant adaptations to arboreal climbing. The second shift was to fully obligate bipedalism, and coincides with the emergence of the genus Homo. By the Early Pleistocene, certain members of Homo had acquired a postcranial skeleton indicating fully humanlike striding bipedalism. The final part of this chapter reviews why bipedalism was selected for. There have been many theoretical explanations, and the most robust remain those linked to the emergence of more open habitats. Such an environmental shift would have involved strong selection for new behavioral strategies most likely linked to the efficient procurement of food.
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... From an orthograde last common ancestor, Hominins and Panins initially diverged into distinct niches, with associated changes in locomotion leading to upright bipedalism in hominins, and knuckle-walking in Pan, similar to Gorillas. Arguably, the shift to bipedalism implies a more terrestrial niche, with different foraging opportunities and predation pressures (Harcourt-Smith, 2007;Almécija et al., 2021). Early hominins likely developed a fluid sociality similar to that characteristic of contemporary hunter/gatherer societies, involving tolerance of, and interaction with, individuals from other small, local, low-density groups (in contrast to chimpanzees and gorillas; more similar in some but not all aspects to bonobos as discussed below), eventually encompassing flexible alliances and coalitions in their fissionfusion context Apicella et al., 2012;Macfarlan et al., 2014;Migliano et al., 2017Migliano et al., , 2020. ...
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Darwin posited that social competition among conspecifics could be a powerful selective pressure. Alexander proposed a model of human evolution involving a runaway process of social competition based on Darwin’s insight. Here we briefly review Alexander’s logic, and then expand upon his model by elucidating six core arenas of social selection that involve runaway, positive-feedback processes, and that were likely involved in the evolution of the remarkable combination of adaptations in humans. We discuss how these ideas fit with the hypothesis that a key life history innovation that opened the door to runaway social selection, and cumulative culture, during hominin evolution was increased cooperation among individuals in small fission-fusion groups.
... During the course of its evolution, the human skeleton has undergone distinctive morphological changes. The most significant of these changes occurred when the first hominids began to stand upright with the emergence of bipedalism (Grabowski and Roseman, 2015;Gruss and Schmitt, 2015;Harcourt-Smith, 2007). The second milestone was the developmental period of anatomically modern humans, during which the morphological characteristics encountered in today's human population developed (Humphrey and Stringer, 2018;Rak, 1990;Svoboda et al., 2003). ...
Article
Introduction: Great variability in shape and size of the bony pelvis can be observed in the current population, but there is not enough data on how long the historical period must elapse to gain changes in pelvic shape and size. The aim of the study was to identify morphological changes in bony pelvis in males and females after a developmentally short period of approximately one thousand years. Material and methods: Seventeen defined external dimensions of pelvic bone from 120 adult individuals (two craniocaudal, two ventrodorsal, six mediolateral, three acetabular dimensions, and four dimension of the auricular surface) were measured. The medieval sample of 60 pelvic bones (30 male and 30 female) was obtained from the Great Moravian site of Mikulčice-Valy (9th-10th century), while the modern collection of 60 pelvic bones (30 male and 30 female) dates from the late 19th and first half of the 20th centuries. Obtained results were evaluated using the independent t-test at a 5% level of significance. Results: A comparison of male and female pelvic dimensions within a single population yielded expected results: the mean male values were greater. In modern population, male pelvis mean values were greater in 15 of defined parameters, while in medieval population, male dimensions were larger in 16 variables. A comparison of modern and medieval female pelvic bones found 11 variables to be greater in medieval sample (one determining the craniocaudal dimension, five the mediolateral, all three the acetabular, and two determining the auricular surface dimensions), but only two were significant (two dimensions determining the mediolateral dimensions). In modern female samples, there were five variables greater (one determining the craniocaudal dimension, one the ventrodorsal, one the mediolateral, and two determining the auricular surface dimensions), but only two were significant as well (one determining the craniocaudal and one the ventrodorsal dimensions). A comparison of male pelvic bones found 13 variables to be greater in medieval pelvis (one determining the craniocaudal dimension, all six the mediolateral, one the ventrodorsal, all three the acetabular, and two determining the auricular surface dimensions), but only four were significant as well (all determining the mediolateral dimensions). In modern male sample, there were only four variables greater (one determining the craniocaudal dimension, one the ventrodorsal, and two determining the auricular surface dimensions), but only one was significant (determining the craniocaudal dimension). Conclusion: Unexpectedly, our study did not find the early medieval population to have a smaller pelvis compared to the modern population. While pelvic bones of the former were somewhat lower, but wider, those of the latter population were a bit higher and narrower. The study allows a very careful statement that one millennium is a time period long enough for measurable morphological deviations of the pelvic bones shape and size to occur.
... There is still disagreement about the significance of the anatomical changes occurred at the transition between australopithecines and Homo, and the locomotor behavior of the early hominins, particularly Homo habilis, is still poorly understood and highly debated (Harcourt-Smith, 2007;Harcourt-Smith & Aiello, 2004;Ruff, 2009). ...
Article
The position (FMP) and orientation (FMO) of the foramen magnum have been used as proxies for locomotion and posture in extant and extinct primates. Several indices have been designed to quantify FMP and FMO but their application has led to conflicting results. Here, we test six widely used indices and two approaches (univariate and multivariate) for their capability to discriminate between postural and locomotor types in extant primates and fossil hominins. We then look at the locomotion of australopithecines and Homo on the base of these new findings. The following measurements are used: the opisthocranion-prosthion (OP-PR) and the opisthocranion-glabella (OP-GL) indices, the basion-biporion (BA-BP) and basion-bicarotid chords, the foramen magnum angle (FMA), and the basion-sphenoccipital ratio. After exploring the indices variability using principal component analysis, pairwise comparisons are performed to test for the association between each index and the locomotor and postural habits. Cranial size and phylogeny are taken into account. Our analysis indicates that none of the indices or approaches provides complete discrimination across locomotor and postural categories, although some differences are highlighted. FMA and BA-BP distinguish respectively obligate and facultative bipeds from all other groups. For what concerns posture, orthogrades and pronogrades differ with respects to OP-PR, OP-GL, and FMA. Although the multivariate approach seems to have some discrimination power, the results are most likely driven by facial and neurocranial variability embedded in some of the indices. These results demonstrate that indices relying on the anteroposterior positioning of the foramen may not be appropriate proxies for locomotion among primates. The assumptions about locomotor and postural habits in fossil hominins based on foramen magnum indices should be revised in light of these new findings.
... 17 Like Neandertals and modern humans, Homo erectus also demonstrates clear post-cranial adaptations for obligate bipedalism, meaning a commitment to terrestrial bipedalism and loss of all unambiguously climbing adaptations. 18 The metatarsal ratios of H. erectus material from Dmanisi are human-like in their proportions to one another; however, the lengths of the pedal phalanges are unknown for this species. 19 Evidence of H. erectus foot morphology has been largely obtained from the Ileret footprints in Kenya, which date to 1.5 million years ago (mya), and appear to have been produced by a more modern-appearing foot architecture than the more ancient Laetoli footprints. ...
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Post-cranial differences between extant apes and humans include differences in the length, shape and size of bone elements relative to each other; i.e. differences in proportions. Foot proportions are influenced by the different functional requirements of climbing and bipedal locomotion. Phalangeal length is generally correlated with locomotor behaviour in primates and there is variation in hominins in relative phalangeal lengths – the functional and evolutionary significance of which is unclear and currently debated. Homo naledi has a largely modern rearfoot (i.e. tarsal skeleton) and midfoot (i.e. metatarsal skeleton). The proximal pedal phalanges of H. naledi are curved, but the relative lengths are unknown, because the phalanges cannot reliably be associated with metatarsals, or in many cases even with ray number. Here, we assess the lengths of the proximal pedal phalanges relative to the metatarsals in H. naledi with resampling from modern human and chimpanzee (Pan troglodytes) samples. We use a novel resampling method that employs two boundary conditions, assuming at one extreme that elements in the sample are associated, and at the other extreme that no elements are associated. The associated metatarsophalangeal proportions from digits 1 and 2 are within the 95% confidence interval of the modern human distribution. However, the associated and unassociated proportions from digits 3–5 fall above the 95% confidence interval of the human distribution, but below and outside of the chimpanzee distribution. While these results may indicate fossil preservation bias or other sample-derived statistical limitations, they potentially raise the intriguing possibility of unique medial versus lateral pedal column functional evolution in H. naledi. Additionally, the relevant associated proportions of H. naledi are compared to and are different from those of H. floresiensis. Both species suggest deep phylogenetic placement so the ancestral condition of the pedal phalanges in the genus Homo remains unclear. Significance: • Modern humans demonstrate straight and relatively short pedal phalanges, whereas H. naledi demonstrates curved phalanges of an unknown relative length. This research analyses the relative length of the proximal phalanges to the metatarsals to determine if naledi has relatively short phalanges similar to modern humans or is distinct from modern humans in both its phalangeal length and curvature. • This analysis further develops a statistical resampling method that was previously applied to large fossil assemblages with little association between bones.
... Bipedal locomotion, either walking, running or jumping has contributed greatly to our evolution as a species. It released our hands for other tasks, changed our visual perspective and contributed to our physical development, motor control ability and dynamic stability [1]. Lower limb force production is a key issue on human gait study with increased interest on muscle, tendon, joint and limb movement optimization [2]. ...
Conference Paper
This study assesses in vivo and noninvasive human lower limb dynamic stiffness at different muscle stretch-shortening cycle (SSC) on maximum vertical jump (MVJ) with long, short and without countermovement. A small sample of n=6 healthy young adult male students of sports and physical education degree without past injuries, specific training or sports record were assessed after informed consent according to the world medical association declaration of Helsinki. Subjects were weighted (76.7 ± 9.3) kg and their height measured (178.9 ± 6.3) cm performing each three trials of MVJ namely squat jump (SJ), countermovement jump (CMJ) and drop jump (DJ) from a step with 40 cm height. Ground reaction forces (GRF) were acquired during impulse phase with AMTI force plate BP2416-4000 CE and Mini Amp MAS-6 amplifier at 1000 Hz. Vertical acceleration (az) of whole body center of gravity (BCG) obtained from resultant vertical ground reaction force (RFz) was time integrated twice for calculation of vertical displacement (Δz) of BCG and dynamic stiffness obtained from slopes at different segmented subphases of RFz mass normalized RFz/m vs Δz plot during impulse phase. Results of vertical dynamic stiffness during impulse phase point for inter-subject similarities at each type of MVJ and statistical significative differences (p<0.05) between SJ, CMJ and DJ with impact on MVJ optimization.
... Natural cobbles have been used by hominins as hammers for more than 3 million years (Harmand et al., 2015). The shift from the use of natural materials to the production of tools by knapping stone, and the presumed reliance on tooling to obtain food, has been linked to changes in the anatomy of the hand (Marzke, 2013), obligate bipedality (Harcourt-Smith, 2007) and enlargement of the brain (Almécija & Sherwood, 2017;Schoenemann, 2006), among other physical changes, in the evolution of the genus Homo. But percussive tooling does not require these specific features of behavior or anatomy. ...
Article
Bearded capuchin monkeys crack nuts with naturally varying stone hammers, suggesting they may tune their grips and muscular forces to each stone. If so, they might use discrete actions on a stone before lifting and striking, and they would likely use these actions more frequently when the stone is larger and/or less familiar and/or when first initiating striking. We examined the behavior of (a) four monkeys (all proficient at cracking nuts) with two larger (1 kg) and two smaller (0.5 kg) stones, (b) 12 monkeys with one 1 kg stone, and (c) one monkey during its first 100 strikes with an initially unfamiliar 1 kg stone. Bearded capuchin monkeys used three discrete actions on the stone before striking, all more often with the larger stones than the smaller stones. We infer that the first discrete action (Spin) aided the monkey in determining where to grip the stone, the second (Flip) allowed it to position the stone on the anvil ergonomically before lifting it, and the third (Preparatory Lift) readied the monkey for the strenuous lifting action. The monkey that provided 100 strikes with one initially unfamiliar stone performed fewer Spins in later strikes but performed Flip and Preparatory Lift at consistent rates. The monkeys gripped the stone with both hands along the sides to lift it, but usually moved one or both hands to the top of the stone at the zenith of the lift for the downward strike. The findings highlight two new aspects of the capuchins’ nut‐cracking: (a) Anticipatory actions with the stone before striking, especially when the stone is larger or unfamiliar, and when initiating striking and (b) shifting grips on the stone during a strike. We invite researchers to investigate if other taxa use anticipatory actions and shift their grips during percussive activity. A wild bearded capuchin monkey uses a stone weighing more than half her own weight to crack a palm nut.
... The positive evolutionary shifts that we found in BFC and in the face, related to the Papionina and the Hominidae, correspond to the disparity peaks found in the diversification through time analyses. These shifts in the BFC and facial shape are present in two primate clades with remarkably different positional behaviors: terrestrial quadrupedalism in the Papionina (except for mangabeys, which are arboreal quadrupeds, partially for Cercocebus and totally for Lophocebus), and bipedalism, knuckle-walking, vertical climbing, and below-branch suspension in the Hominidae (Doran, 1989;Remis, 1998;Schmitt, 1998;Thorpe and Crompton, 2006;Harcourt-Smith, 2007;Schmidt, 2011). This result corroborates our previous finding of a significant correlation between the BFC, the face, and positional behavior (see Objective #2). ...
Article
The basicranium and facial skeleton are two integrated structures displaying great morphological diversity across primates. Previous studies focusing on limited taxonomic samples have demonstrated that morphological integration has a significant impact on the evolution of these structures. However, this influence is still poorly understood. A more complete understanding of craniofacial integration across primates has important implications for functional hypotheses of primate evolution. In the present study, we analyzed a large sample of primate species to assess how integration affects the relationship between basicranial and facial evolutionary pathways across the order. First, we quantified integration and modularity between basicranium and face using phylogenetically-informed partial least squares analyses. Then, we defined the influence of morphological integration between these structures on rates of evolution, using a time-calibrated phylogenetic tree, and on disparity through time, comparing the morphological disparity across the tree with that expected under a pure Brownian process. Finally, we assessed the correlation between the basicranium and face, and three factors purported to have an important role in shaping these structures during evolution: endocranial volume, positional behavior (i.e., locomotion and posture), and diet. Our findings show that the face and basicranium, despite being highly integrated, display significantly different evolutionary rates. However, our results demonstrate that morphological integration impacted shape disparity through time. We also found that endocranial volume and positional behavior are important drivers of cranial shape evolution, partly affected by morphological integration.
Article
Homo erectus s.l. is key for deciphering the origin and subsequent evolution of genus Homo. However, the characterization of this species is hindered by the existence of multiple variants in both mainland and insular Asia, as a result of divergent chronogeographical evolutionary trends, genetic isolation, and interbreeding with other human species. Previous research has shown that cochlear morphology embeds taxonomic and phylogenetic information that may help infer the phylogenetic relationships among hominin species. Here we describe the cochlear morphology of two Indonesian H. erectus individuals (Sangiran 2 and 4), and compare it with a sample of australopiths, Middle to Late Pleistocene humans, and extant humans by means of linear measurements and both principal components and canonical variates analyses performed on shape ratios. Our results indicate that H. erectus displays a mosaic morphology that combines plesiomorphic (australopithlike) features (such as a chimplike round cochlear cross section and low cochlear thickness), with derived characters of later humans (a voluminous and long cochlea, possibly related to hearing abilities)dconsistent with the more basal position of H. erectus. Our results also denote substantial variation between the two studied individuals, particularly in the length and radius of the first turn, as well as cross-sectional shape. Given the small size of the available sample, it is not possible to discern whether such differences merely reflect intraspecific variation among roughly coeval H. erectus individuals or whether they might result from greater age differences between them than currently considered. However, our results demonstrate that most characters found in later humans were already present in Indonesian H. erectus, with the exception of Neanderthals, which display an autapomorphic condition relative to other Homo species.
Article
Objective Although extant nonhuman primates are not habitual bipeds, they are able to walk bipedally from an early age. In humans, children improve their walking skills through developmental processes and learning experience. In nonhuman primates, infants do not routinely experience bipedalism and their musculoskeletal system gradually specializes for other locomotor modes. The aim of this study is to explore the development of occasional bipedal walking in olive baboon and to test whether the postural adjustments change with age. Materials and Methods We collected kinematics and spatiotemporal parameters of bipedal gait in an ontogenetic sample of 24 baboons. Data were collected at the primatology station of the CNRS (France) and a total of 47 bipedal strides were extracted for the present analysis. Results Adults and adolescents walk bipedally in the same way, and the average kinematic pattern is similar across the age-classes. Infants walk bipedally with longer duty factor, they present larger movement amplitude of the thigh and the amplitude of the knee joint decreases with speed. In contrast, older baboons increase the amplitude of the knee and ankle joints with speed. Discussion In a non-adapted biped, the postural adjustments of bipedal walking vary with age. In infant baboons, the balance requirements are likely to be higher and these are solved by adopting a “blocking strategy”. In older baboons, the postural adjustments are focused on the lower limb and the movements increase with speed. These results may echo, in some respects, the developmental sequence of the intersegmental coordination described in the ontogeny of human locomotion.
Thesis
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The bipedal walk is considered as one of the most difficult tasks learned by human beings. The bipedal is more suitable than wheeled robot to work in un-structured terrains due to dexterity and ability to step over uneven surface. This is the reason for considering the bipedal walk though it is inherently unstable and daunting. The human walk is a complex task learned by human. A human baby takes almost a year for a stable gait. The robotic limbs, which imitate the human locomotion, give birth to a bipedal robot. The emergence of humanoid robot has benefited the society due to the benefits in helping the amputee to recover their gait and assistance of elderly people. The modern robots available in the market cannot walk efficiently due to the limitation of flat foot and bending knees. Such robots consume more energy and unstable in unstructured environments. That is the reason we have not seen any robot which can work outside the controlled environments like laboratories. In this research, we have developed the data driven computational walking model to overcome the problem with traditional kinematics based model. Our model is adaptable and can adjust the parameter morphological similar to human. The human walk is a combination of different discrete sub-phases with their continuous dynamics. Any system which exhibits the discrete switching logic and continuous dynamics can be represented using a hybrid system. In this research, the bipedal locomotion is analyzed which is important for understanding the stability and to negotiate with the external perturbations. We have also studied the other important behavior push recovery. The Push recovery is also a very important behavior acquired by human with continuous interaction with environment. The researchers are trying to develop robots that must have the capability of push recovery to safely maneuver in a dynamic environment. The push is a very commonly experienced phenomenon in cluttered environment. The human beings can recover from external push up to a certain extent using different strategies of hip, knee and ankle. The different human beings have different push recovery capabilities. For example a wrestler has a better push negotiation capability compared to normal human beings. The push negotiation capability acquired by human, therefore, is based on learning but the learning mechanism is still unknown to researchers. The research community across the world is trying to develop various humanoid models to solve this mystery. Seeing all the conventional mechanics and control based models have some inherent limitations, a learning based computational model has been developed to address effectively this issue. In this research we will discuss how we have framed this problem as hybrid system. In the first part of the thesis, we have discussed the inherent challenges associated with bipedal robot. We have also presented the overview how computational model are suitable then kinematics based model. In the second chapter of the thesis, we have presented the analysis of the available bipedal robot technology and bipedal model. In chapter third of the thesis, we have given the definition of the bipedal technology. We have presented all the important terminologies used with bipedal gait and push recovery. In chapter fourth of the thesis, we have presented our innovative idea about the data collection for gait and push recovery for different real subjects. The subjects we have considered were students of our institute having 10 left and 25 right handed persons. We have captured data using indigenously developed wearable device HMCD (Human motion capture device) as well as using HLPRDCD (Human Locomotion &Push Recovery Data Capture Device). In chapter fifth we have framed the bipedal walking as hybrid system and developed the vector fields for each seven sub phases of bipedal walk. The major contribution of the research is the development of computational walking model and generation of joints trajectories to each sub phases of gait for all the six joints (hip, knee & ankle). The model has been configured as a rocking block and various parameters have been fitted according to different subjects. We have compared the vector field generated joints trajectories with hybrid automata model and HOAP2 model. Finally we have applied our joints trajectories with HOAP2 robot. We have also presented the cellular automata for state predication of bipedal gait. In the chapter sixthof thesis, we have classified the human gait and push recovery data using various machine learning techniques. In the seventh chapter of thesis, we have proposed a push recovery capable hierarchically type-1 fuzzy logic controller and compared the human push recovery data with model generated data and we have proved that the fuzzy logic based controller is fast to adapt and is more generalised. It is fast and less computational intensive. Useful conclusion based on our research experiment, limitation and future recommendation have been made in the chapter no 8.
Article
The recent discovery of fossil limbs of Australopithecus africanus,(1) including a partial skeleton, makes it possible to compare body proportions of this 3-2.3-million-year-old species with those of A. afarensis (3.9-3 Myr), Homo habilis (2-1.6 Myr), and H. ergaster/erectus (1.9-0.4 Myr). Australopithecus africanus is more similar to H. habilis in having larger forelimbs and smaller hindlimbs than expected from proportions seen in later Home. Curiously the earlier and craniodentally more primitive A. afarensis is more similar to later Home in fore-to-hindlimb proportions. This implies that limb proportions changed back and forth in the hominid lineage or our present view of hominid relationships is too simplified.