Bipedal Species Research Articles

Relationships of mass properties and body proportions to locomotor habit in terrestrial Archosauria

AbstractThroughout their 250 Myr history, archosaurian reptiles have exhibited a wide array of body sizes, shapes, and locomotor habits, especially in regard to terrestriality. These features make Archosauria a useful clade with which to study the interplay between body size, shape, and locomotor behavior, and how this interplay may have influenced locomotor evolution. Here, digital volumetric models of 80 taxa are used to explore how mass properties and body proportions relate to each other and locomotor posture in archosaurs. One-way, nonparametric, multivariate analysis of variance, based on the results of principal components analysis, shows that bipedal and quadrupedal archosaurs are largely distinguished from each other on the basis of just four anatomical parameters (p< 0.001): mass, center of mass position, and relative forelimb and hindlimb lengths. This facilitates the development of a quantitative predictive framework that can help assess gross locomotor posture in understudied or controversial taxa, such as the crocodile-lineBatrachotomus(predicted quadruped) andPostosuchus(predicted biped). Compared with quadrupedal archosaurs, bipedal species tend to have relatively longer hindlimbs and a more caudally positioned whole-body center of mass, and collectively exhibit greater variance in forelimb lengths. These patterns are interpreted to reflect differing biomechanical constraints acting on the archosaurianBauplanin bipedal versus quadrupedal groups, which may have shaped the evolutionary histories of their respective members.

Structure design and traction trafficability analysis of multi-posture wheel-legs bionic walking wheels for sand terrain

Nowadays, the existing walking wheels still have problems with the wheel-legs structure and the traction trafficability on the loose sand. It is commonly believed that African ostrich (Struthio camelus) is a kind of bipedal species with superior running performance on the sandy environment. Being enlightened by this, four bionic walking wheels (herringbone wheel, in-line wheel, V-shaped wheel and combination wheel) were designed and tested by imitating the structure and posture of ostrich’s feet travelling on sand. The results showed that when the wheel load was 20, 30 and 50N respectively and the slip ratio was less than 35%, the herringbone wheel had better traction trafficability than that of other wheels. When the wheel load was 30, 50 and 70N and the slip ratio was more than 35%, the in-line wheel had better performance than that of other wheels. It was shown in this thesis that the bionic walking wheels designed with the multi-posture wheel-legs and the simple structure could reduce the soil resistance and the disturbance to sand, thereby achieving a superior performance of traveling on sand. In addition, a new idea and research method for designing of walking mechanism on soft terrain has been provided in this thesis.

Alginate encapsulation as long-term immune protection of allogeneic pancreatic islet cells transplanted into the omental bursa of macaques.

The transplantation of pancreatic islet cells could restore glycaemic control in patients with type-I diabetes. Microspheres for islet encapsulation have enabled long-term glycaemic control in diabetic rodent models; yet human patients transplanted with equivalent microsphere formulations have experienced only transient islet-graft function, owing to a vigorous foreign-body reaction (FBR), to pericapsular fibrotic overgrowth (PFO) and, in upright bipedal species, to the sedimentation of the microspheres within the peritoneal cavity. Here, we report the results of the testing, in non-human primate (NHP) models, of seven alginate formulations that were efficacious in rodents, including three that led to transient islet-graft function in clinical trials. Although one month post-implantation all formulations elicited significant FBR and PFO, three chemically modified, immune-modulating alginate formulations elicited reduced FBR. In conjunction with a minimally invasive transplantation technique into the bursa omentalis of NHPs, the most promising chemically modified alginate derivative (Z1-Y15) protected viable and glucose-responsive allogeneic islets for 4 months without the need for immunosuppression. Chemically modified alginate formulations may enable the long-term transplantation of islets for the correction of insulin deficiency

A bipedal mammalian model for spinal cord injury research: The tammar wallaby

Background: Most animal studies of spinal cord injury are conducted in quadrupeds, usually rodents. It is unclear to what extent functional results from such studies can be translated to bipedal species such as humans because bipedal and quadrupedal locomotion involve very different patterns of spinal control of muscle coordination. Bipedalism requires upright trunk stability and coordinated postural muscle control; it has been suggested that peripheral sensory input is less important in humans than quadrupeds for recovery of locomotion following spinal injury. Methods: We used an Australian macropod marsupial, the tammar wallaby (Macropus eugenii), because tammars exhibit an upright trunk posture, human-like alternating hindlimb movement when swimming and bipedal over-ground locomotion. Regulation of their muscle movements is more similar to humans than quadrupeds. At different postnatal (P) days (P7–60) tammars received a complete mid-thoracic spinal cord transection. Morphological repair, as well as functional use of hind limbs, was studied up to the time of their pouch exit. Results: Growth of axons across the lesion restored supraspinal innervation in animals injured up to 3 weeks of age but not in animals injured after 6 weeks of age. At initial pouch exit (P180), the young injured at P7-21 were able to hop on their hind limbs similar to age-matched controls and to swim albeit with a different stroke. Those animals injured at P40-45 appeared to be incapable of normal use of hind limbs even while still in the pouch. Conclusions: Data indicate that the characteristic over-ground locomotion of tammars provides a model in which regrowth of supraspinal connections across the site of injury can be studied in a bipedal animal. Forelimb weight-bearing motion and peripheral sensory input appear not to compensate for lack of hindlimb control, as occurs in quadrupeds. Tammars may be a more appropriate model for studies of therapeutic interventions relevant to humans.

A bipedal mammalian model for spinal cord injury research: The tammar wallaby.

Background: Most animal studies of spinal cord injury are conducted in quadrupeds, usually rodents. It is unclear to what extent functional results from such studies can be translated to bipedal species such as humans because bipedal and quadrupedal locomotion involve very different patterns of spinal control of muscle coordination. Bipedalism requires upright trunk stability and coordinated postural muscle control; it has been suggested that peripheral sensory input is less important in humans than quadrupeds for recovery of locomotion following spinal injury. Methods: We used an Australian macropod marsupial, the tammar wallaby (Macropuseugenii), because tammars exhibit an upright trunk posture, human-like alternating hindlimb movement when swimming and bipedal over-ground locomotion. Regulation of their muscle movements is more similar to humans than quadrupeds. At different postnatal (P) days (P7-60) tammars received a complete mid-thoracic spinal cord transection. Morphological repair, as well as functional use of hind limbs, was studied up to the time of their pouch exit. Results: Growth of axons across the lesion restored supraspinal innervation in animals injured up to 3 weeks of age but not in animals injured after 6 weeks of age. At initial pouch exit (P180), the young injured at P7-21 were able to hop on their hind limbs similar to age-matched controls and to swim albeit with a different stroke. Those animals injured at P40-45 appeared to be incapable of normal use of hind limbs even while still in the pouch. Conclusions: Data indicate that the characteristic over-ground locomotion of tammars provides a model in which regrowth of supraspinal connections across the site of injury can be studied in a bipedal animal. Forelimb weight-bearing motion and peripheral sensory input appear not to compensate for lack of hindlimb control, as occurs in quadrupeds. Tammars may be a more appropriate model for studies of therapeutic interventions relevant to humans.

Evidence to suggest that women's sexual behavior is influenced by hip width rather than waist-to-hip ratio.

Waist-to-hip ratio (WHR) is an important ornament display that signals women's health and fertility. Its significance derives from human development as a bipedal species. This required fundamental changes to hip morphology/musculature to accommodate the demands of both reproduction and locomotion. The result has been an obstetric dilemma whereby women's hips are only just wide enough to allow the passage of an infant. Childbirth therefore poses a significant hip width related threat to maternal mortality/risk of gynecological injury. It was predicted that this would have a significant influence on women's sexual behavior. To investigate this, hip width and WHR were measured in 148 women (M age=20.93+0.17years) and sexual histories were recorded via questionnaire. Data revealed that hip width per se was correlated with total number of sexual partners, total number of one night stands, percentage of sexual partners that were one night stands, number of sexual partners within the context of a relationship per year sexually active, and number of one night stands per year sexually active. By contrast, WHR was not correlated with any of these measures. Further analysis indicated that women who predominantly engaged in one night stand behavior had wider hips than those who did not. WHR was again without effect in this context. Women's hip morphology has a direct impact on their risk of potentially fatal childbirth related injury. It is concluded that when they have control over this, women's sexual behavior reflects this risk and is therefore at least in part influenced by hip width.

From bone to plausible bipedal locomotion. Part II: Complete motion synthesis for bipedal primates

This paper addresses the problem of synthesizing plausible bipedal locomotion according to 3D anatomical reconstruction and general hypotheses on human motion control strategies. In a previous paper [Nicolas, G., Multon, F., Berillon, G., Marchal, F., 2007. From bone to plausible bipedal locomotion using inverse kinematics. Journal of Biomechanics 40 (5) 1048–1057], we have validated a method based on using inverse kinematics to obtain plausible lower-limb motions knowing the trajectory of the ankle. In this paper, we propose a more general approach that also involves computing a plausible trajectory of the ankles for a given skeleton. The inputs are the anatomical descriptions of the bipedal species, imposed footprints and a rest posture. This process is based on optimizing a reference ankle trajectory until a set of criteria is minimized. This optimization loop is based on the assumption that a plausible motion is supposed to have little internal mechanical work and should be as less jerky as possible. For each tested ankle trajectory, inverse kinematics is used to compute a lower-body motion that enables us to compute the resulting mechanical work and jerk. This method was tested on a set of modern humans (male and female, with various anthropometric properties). We show that the results obtained with this method are close to experimental data for most of the subjects. We also demonstrate that the method is not sensitive to the choice of the reference ankle trajectory; any ankle trajectory leads to very similar result. We finally apply the method to a skeleton of Pan paniscus (Bonobo), and compare the resulting motion to those described by zoologists.

Estimating dinosaur maximum running speeds using evolutionary robotics

Maximum running speed is an important locomotor parameter for many animals-predators as well as prey-and is thus of interest to palaeobiologists wishing to reconstruct the behavioural ecology of extinct species. A variety of approaches have been tried in the past including anatomical comparisons, bone scaling and strength, safety factors and ground reaction force analyses. However, these approaches are all indirect and an alternative approach is to create a musculoskeletal model of the animal and see how fast it can run. The major advantage of this approach is that all assumptions about the animal's morphology and physiology are directly addressed, whereas the exact same assumptions are hidden in the indirect approaches. In this paper, we present simple musculoskeletal models of three extant and five extinct bipedal species. The models predict top speed in the extant species with reasonably good agreement with accepted values, so we conclude that the values presented for the five extinct species are reasonable predictions given the modelling assumptions made. Improved musculoskeletal models and better estimates of soft tissue parameters will produce more accurate values. Limited sensitivity analysis is performed on key muscle parameters but there is considerable scope for extending this in the future.

Review: After Eden: The Evolution of Human Domination by Kirkpatrick Sale

Review: After Eden: The Evolution of Human Domination By Kirkpatrick Sale Reviewed by Bram Buscher Vrije Universiteit Amsterdam, The Netherlands Kirkpatrick Sale. After Eden. The Evolution of Human Domination. Durham: Duke University Press. 186 pp. ISBN: 0-8223-3938-2. (paperback; acid free paper). US$19.95. In the last decade, several books have come out trying to develop an overview of recent, archaeological, paleontological and historical anthropological evidence on human evolution. One of my favourites so far is John Reader's magnificent Africa, A Biography of the Continent. Although less broad in scope, Kirkpatrick Sale's After Eden now competes for first place. Like Reader, Sale provides a bird's eye view of recent global archaeological and paleontological findings and guides the reader in a mere 138 pages through 65.000 years of modern human evolution. Not being a palaeontologist or archaeologist but rather an interested social scientist, I am not in place to comment on Sale's use of the evidence, although the breadth of material he presents seems extensive. However, what sets After Eden apart from other similar works and what excites me as a social scientist, is Sale's social and critical emancipatory point of departure and the explicit lessons he tries to draw from the ancient past for the present. The central argument of the book revolves around its subtitle: The Evolution of Human Domination. According to Sale, the extraordinary dominance by one single bipedal species [...] has brought us to the present imperilment of the earth, including the extinction of species, the destruction of ecosystems, the alteration of climate, the pollution of waters and soils, the exhaustion of fisheries, the elimination of forests, the spread of deserts, and the disruption of the atmosphere (p.3). The consequence of this dominance of Homo Sapiens and its associated reckless policies and practices towards the earth is unavoidable ecocide (p.3). Our main predicament, so argues the book, is that human dominance is little recognised as a problem because the psychological processes leading up to it have been in the making for many millennia, so becoming accepted wisdom and even religion. In three main chapters, the book outlines how Homo Sapiens started innovating in hunting techniques (chapter one: 70.000 - 50.000 years ago), developed cultural and religious symbols to aid them in their survival (chapter two: 55.000 - 20.000 years ago) and intensified their land use through agriculture (chapter three: 20.000 - 5.000 years ago). Sale

The metabolic cost of force generation.

The purpose of this study was to provide support, based on a review of existing data, for a general relationship between metabolic cost and force generated. There are confounding factors that can affect metabolic cost, including muscle contraction type (isometric, eccentric, or concentric), length, and speed as well as fiber type (e.g., fast or slow) and moment arm distances. Despite these factors, empirical relationships for metabolic cost have been found that transcend species and movements. We revisited the various equations that have been proposed to relate metabolic rate with mass, velocity, and step contact time during running and found that metabolic rate was proportional to the external force generated and the number of steps per unit time. This relationship was in agreement with a previously proposed hypothesis that the metabolic cost to generate a single application of a unit external force is a constant. Data from the literature were collected for a number of different activities and species to support the hypothesis. Running quadrupedal and bipedal species, as well as human cycling, cross-country skiing, running (forward, backward, on an incline, and against a horizontal force), and arm activities (running, cycling, and ski poling), all had a constant metabolic cost per unit external force per application. The proportionality constant varied with activity, possibly reflecting differences in the aspects of muscular contraction, fiber types, or mechanical advantage in each activity. It is speculated that a more general relation could be obtained if biomechanical analyses to account for other factors, such as contraction length, were included.

Asymmetric bipedal locomotion--an adaptive response to incomplete spinal injury in the chick.

The purpose of this study was to compare the asymmetric gait induced by unilateral spinal cord injury in chicks with asymmetric gaits of other bipeds and quadrupeds. After lateral hemisection of the left thoracic spinal cord, kinetic (ground reaction forces) and kinematic (distance and timing) data were recorded as chicks moved overground unrestrained. Ground reaction forces were analyzed to obtain the mechanical energy changes throughout the stride. Kinematic measurements were obtained over a range of speeds to determine the velocity-dependent characteristics of the gait. Hemisected chicks adopted an asymmetric hopping gait in which the animals hopped from the right leg (contralateral to the lesion) onto the left (ipsilateral) leg but then fell forward onto the right leg. Mechanical energy fluctuations throughout a single stride (i.e., two steps) approximated the oscillations that occur during a single walking step of control animals. When examined over a range of velocities, asymmetries in limb timing remained constant, but distance measurements such as step length became more symmetric as speed increased. The results show that, after spinal hemisection, adaptations of the remaining neural circuitry permitted the production of a locomotor pattern that, in addition to providing effective support and propulsion, incorporated some of the energy-conserving mechanisms of the normal walk. Adjustment of this novel locomotor pattern for different velocities further demonstrates the flexibility of locomotor circuitry. Comparisons with other studies shows that this gait shares some temporal and energetic features with asymmetric gaits of several bipedal species, including humans. In particular, hemisected chicks and some hemiplegic humans adopt an asymmetric gait in which maximum energy recovery occurs during the stance of the affected limb; these similarities probably relate to common mechanical constraints imposed on bipedal forms of terrestrial locomotion.

Effects of Artificial Bush Canopies and Illumination on Seed Patch Selection by Heteromyid Rodents

-Bipedal species of seed-eating, desert, heteromyid rodents forage primarily in open spaces while quadrupedal heteromyids forage in structurally complex microhabitats, such as beneath bush canopies. However, both bipeds and quadrupeds use the latter microhabitats relatively more during periods of bright lunar illumination. One explanation for these patterns is that risk of predation is affected by both microhabitat type and illumination, and that microhabitat use is dictated by biped-quadruped differences in vulnerability to predators. I investigated effects of artificial bush canopies and illumination on seed patch selection by three bipedal and three quadrupedal heteromyid species in a laboratory foraging arena. I predicted that, if predation risk affects microhabitat selection, rodents would forage preferentially in seed patches characterized by less risky microhabitat and illumination conditions (i.e., in patches beneath bush canopies rather than open patches, and in dark rather than illuminated patches). Three individual rodent species in addition to species grouped as bipeds and quadrupeds exhibited the predicted preference for dark patches, but only Dipodomys merriami preferred bush patches. No preferences were expressed for open or for illuminated patches. These results and those of previous patch choice experiments that used patches differing in seed distribution and soil properties imply that both predation risk and foraging economics affect heteromyid patch use.

A functional-morphometric analysis of forelimbs in bipedal and quadrupedal heteromyid rodents

The rodent family Heteromyidae contains bipedal hoppers and quadrupedal runners. The possibility that bipedalism is associated with forelimb specialization for nonlocomotory functions, such as burrowing and seed-gathering, motivated a static functional-morphometric and interspecific allometric analysis of 18 metric characters of the forelimb skeleton. A principal-components analysis, across 28 species in six genera, showed that lengths of proximal (scapula, humerus) and distal (ulna, radius, metacarpal) elements were negatively allometric, and widths were positively allometric. Quadrupedal and bipedal species groups showed qualitatively similar allometric patterns, except that scapula width anterior to the spine was positively allometric in quadrupeds and negatively allometric in bipeds; scapula width posterior to the spine was positively allometric in bipeds and isometric in quadrupeds; and olecranon length was isometric in bipeds and positively allometric in quadrupeds. Most morphometric characters varied significantly among species within genera, even when effects of size variation were reduced by reconstructing all species to a common general size (as indicated by their score on the first principal component). These shape differences caused species to vary in the mechanical advantage of the forelimb, of possible importance for digging and seed-harvesting performance. Relative to quadrupeds, bipedal species tended to have greater mechanical advantage for proximal forelimb elements and smaller mechanical advantage for distal forelimb elements, but only the distal pattern remained in reconstructed forms, and no functional character was significantly different when tested over variation among genera nested within locomotion type. Cluster analysis confirmed that forelimb characters related to digging or seed-harvest are not coincident with mode of locomotion. Forelimb characters were, however, associated with digging or seed-harvest performance. Mechanical advantage of the proximal forelimb was positively related to an index of the compaction of soils with which 26 desert-dwelling species are associated, and also to relative use of heavy vs. light soils by nine species in the laboratory. Across 10 species, deviations in seed-harvest rate from expected allometric values were negatively correlated with mechanical advantage of the distal forelimb.

A functional-morphometric analysis of forelimbs in bipedal and quadrupedal heteromyid rodents

The rodent family Heteromyidae contains bipedal hoppers and quadrupedal runners. The possibility that bipedalism is associated with forelimb specialization for nonlocomotory functions, such as burrowing and seed-gathering, motivated a static functional-morphometric and interspecific allometric analysis of 18 metric characters of the forelimb skeleton. A principal-components analysis, across 28 species in six genera, showed that lengths of proximal (scapula, humerus) and distal (ulna, radius, metacarpal) elements were negatively allometric, and widths were positively allometric. Quadrupedal and bipedal species groups showed qualitatively similar allometric patterns, except that scapula width anterior to the spine was positively allometric in quadrupeds and negatively allometric in bipeds; scapula width posterior to the spine was positively allometric in bipeds and isometric in quadrupeds; and olecranon length was isometric in bipeds and positively allometric in quadrupeds. Most morphometric characters varied significantly among species within genera, even when effects of size variation were reduced by reconstructing all species to a common general size (as indicated by their score on the first principal component). These shape differences caused species to vary in the mechanical advantage of the forelimb, of possible importance for digging and seed-harvesting performance. Relative to quadrupeds, bipedal species tended to have greater mechanical advantage for proximal forelimb elements and smaller mechanical advantage for distal forelimb elements, but only the distal pattern remained in reconstructed forms, and no functional character was significantly different when tested over variation among genera nested within locomotion type. Cluster analysis confirmed that forelimb characters related to digging or seed-harvest are not coincident with mode of locomotion. Forelimb characters were, however, associated with digging or seed-harvest performance. Mechanical advantage of the proximal forelimb was positively related to an index of the compaction of soils with which 26 desert-dwelling species are associated, and also to relative use of heavy vs. light soils by nine species in the laboratory. Across 10 species, deviations in seed-harvest rate from expected allometric values were negatively correlated with mechanical advantage of the distal forelimb.

Locomotor Performance of Bipedal and Quadrupedal Heteromyid Rodents

Running endurance and running direction changes of both bipedal (Dipodomys, Microdipodops) and quadrupedal (Chaetotipus, Heteromys, Liomys, Perognathus) heteromyid rodents were measured to determine if locomotor performance is enhanced in bipedal species. Running endurance was significantly higher in bipedal Dipodomys species (kangaroo rats) compared to quadrupedal species of similar size. Bipedal Microdipodops (kangaroo mouse) had even lower endurance than the quadrupedal species as a group. Both running speed and body mass were found to influence running direction changes. The effects of body mass and speed accounted for more running direction changes in Dipodomys species than the quadrupedal species and the bipedal Microdipodops

Laterality in quadrupedal and bipedal prosimians: Reach and whole-body turn in the mouse lemur (Microcebus murinus) and the galago (Galago moholi).

Lateral preferences in food reaching and whole-body turning were assessed in 24 prosimian primates: 16 galagos (Galago moholi) and 8 mouse lemurs (Microcebus murinus). Reach and turn preference in the galago were examined using a single testing procedure; separate procedures were used to evaluate reach and turn preferences in the mouse lemur. The motoric requirements for both species were 1) reach into a Plexiglas container with a single hand for a food item and 2) execution of a whole-body rotation about the long axis of the body. Twenty-three of the subjects tested had a reach preference (15 right, 8 left preferent) and 22 a turn preference (1 right and 21 left preferent). No correlation between the direction of reach and turn preference was found for either species; however an association between right reach preference and female gender was found for the galagos. A species difference in the strength of lateralization was found, with the more bipedal species, the galago, more strongly lateralized in both measures. This result supports the hypothesis that the assumption of upright posture was an important factor in the phylogenetic development of primate lateralization.

Direct Observations of Owls and Heteromyid Rodents: Can Predation Risk Explain Microhabitat Use?

Coexisting heteromyid rodent species of North American deserts differ in habitat use and in locomotory morphology. Quadrupedal species forage primarily in structurally complex microhabitats, such as under bush canopies, while bipedal species forage in open spaces. A common explanation for this morphology—microhabitat association is that species differing in morphology also differ in vulnerability to predators, that microhabitat structure affects predation risk, and that animals preferentially forage in the safest microhabitats. We tested this for two bipedal and two quadrupedal heteromyid species (matched by body size), and one cricetid species, by quantifying effects of habitat and illumination on activity and on risk of predation by Great Horned Owls. Capture frequencies were lower for all heteromyid species than for the cricetid species, Peromyscus maniculatus. Heteromyid activity was lower in open habitat and under bright illumination. Illumination had no significant effect on risk, perhaps because rodents changed activity patterns under full moon to compensate for a potential increment in risk. Habitat, however, did affect risk: all species were attacked and captured more frequently in the open. Bipedal species were attacked relatively more in the open than were quadrupeds. If these results apply to all predators, they indicate that predation alone cannot account for the divergent microhabitat associations of bipedal and quadrupedal species. Bipedal heteromyids, however, escaped owl attacks more frequently than did quadrupeds of equivalent size. It is therefore conceivable that they experience lower overall risk in nature, where owls may preferentially attack more easily captured prey species when given a choice. Under these circumstances, owl predation could reinforce divergent microhabitat specializations based on some other factor, such as foraging economics, by restricting quadrupeds more strongly than bipeds to the safety of bushes.

Use of Artificial Seed Patches by Heteromyid Rodents

We allowed individual heteromyid rodents of nine species to forage singly for millet seeds placed in artificial seed patches that varied in soil texture, soil-bulk density, and seed dispersion. Thirty-five of 45 individuals tested showed nonrandom patterns of patch use, signifi-cantly more than expected if heteromyids as a whole do not distinguish the seed-patch attributes we presented. The nine species differed overall in patch use. Bipedal species did not differ significantly as a group from quadrupedal species. Use of heavy-soil patches was significantly correlated with body size, however, and use of aggregated-seed patches was related to the locality from which individuals were collected. Species from the same locality selected artificial substrates qualitatively similar to those found in microhabitats selected in nature.