Gait Transitions in Human Infants: Coping with Extremes of Treadmill Speed

Spinal pattern generators in quadrupedal animals can coordinate different forms of locomotion, like trotting or galloping, by altering coordination between the limbs (interlimb coordination). In the human system, infants have been used to study the subcortical control of gait, since the cerebral cortex and corticospinal tract are immature early in life. Like other animals, human infants can modify interlimb coordination to jump or step. Do human infants possess functional neuronal circuitry necessary to modify coordination within a limb (intralimb coordination) in order to generate distinct forms of alternating bipedal gait, such as walking and running? We monitored twenty-eight infants (7–12 months) stepping on a treadmill at speeds ranging between 0.06–2.36 m/s, and seventeen adults (22–47 years) walking or running at speeds spanning the walk-to-run transition. Six of the adults were tested with body weight support to mimic the conditions of infant stepping. We found that infants could accommodate a wide range of speeds by altering stride length and frequency, similar to adults. Moreover, as the treadmill speed increased, we observed periods of flight during which neither foot was in ground contact in infants and in adults. However, while adults modified other aspects of intralimb coordination and the mechanics of progression to transition to a running gait, infants did not make comparable changes. The lack of evidence for distinct walking and running patterns in infants suggests that the expression of different functional, alternating gait patterns in humans may require neuromuscular maturation and a period of learning post-independent walking.     

The pattern of restriction enzyme-induced banding in the chromosomes of chimpanzee,gorilla, and orangutan and its evolutionary significance

Summary The pattern of banding induced by five restriction enzymes in the chromosome complement of chimpanzee, gorilla, and orangutan is described and compared with that of humans. The G banding pattern induced by Hae III was the only feature common to the four species. Although hominid species show almost complete chromosomal homology, the restriction enzyme C banding pattern differed among the species studied. Hinf I did not induce banding in chimpanzee chromosomes, and Rsa I did not elicit banding in chimpanzee and orangutan chromosomes. Equivalent amounts of similar satellite DNA fractions located in homologous chromosomes from different species or in nonhomologous chromosomes from the same species showed different banding patterns with identical restriction enzymes. The great variability in frequency of restriction sites observed between homologous chromosome regions may have resulted from the divergence of primordial sequences changing the frequency of restriction sites for each species and for each chromosomal pair. A total of 30 patterns of banding were found informative for analysis of the hominid geneaalogical tree. Using the principle of maximum parsimony, our data support a branching order in which the chimpanzee is more closely related to the gorilla than to the human.     

Pliocene hominid gait: New interpretations based on available footprint data from Laetoli

Normative trends in the gait patterns of modern man can be used to reconstruct crucial characteristics of the bipedal behaviour of Pliocene hominids from their fossilized footprints. In this reconstruction the interrelated parameters of velocity, stride-length, and cadence are determined from imprints made in damp volcanic ash some 3.7 million years ago. When early hominid footprint data is fitted to regression equations of high predictability for the interrelationship of these locomotor parameters in modern man, a pattern of gait emerges that contradicts previous reconstructions.     

The distal femoral anatomy of Australopithecus

The anatomy of the distal femoral fragments from Sterkfontein is reviewed, including its orthopaedic and biomechanical implications with respect to locomotion pattern. Comparisons are made with other hominids and a number of quadrupedal primates. Items which are considered are the obliquity and robustness of the shaft, the anterior intercondylar groove, the intercondylar notch, and the contour of the medial and lateral articular surfaces. The distinctive hominid status of these specimens is shown by their extensive adaptation to bipedal locomotion. No feature is found which is not fully commensurate with completely bipedal locomotion; rather, their distinctive hominid character points to a need for a reanalysis of the gait pattern in these early Pleistocene hominids.     

Some comments on the case for Early Pleistocene hominids in South-Eastern Spain

Several sites in the Orce Basin have revealed evidence of the presence of hominids in the Early Pleistocene. These remains are dated to over 1.0 million years, while they may be as old as 1.6 million years. The skeletal remains from Venta Micena in the Orce Basin show a molecular “fossil protein” pattern which aligns them with hominids, but not with equids. This is supported by the anatomical evidence of the two humeral shafts from theEstrato Blanco in the Venta Micena deposits. The biparieto-occipital partial calvaria shows some unusual features if VM-0 is a hominid specimen. the presence of a prominent crest on the internal surface of the occipital fragment adjacent to the point lambda is decidedly unusual for a modern human calvaria. Moreover, theimpressions gyrorum, in the region where the superior parietal lobule of the cerebral hemisphere abutted against the calvaria, point to a bipartite superior parietal lobule with anterior and posterior moieties which, on the endocast, are clearly separated by a depression that represents a sulcus. These morphological traits are rather puzzling if VM-0 is a hominid, and at first they led me to hesitate over the anatomical identification of VM-0. However, the studies of Campillo (1989) and of Campillo and Barcelo (1986) suggest that the features of the fragment VM-0 are compatible with those of a hominid. Because I believe that we do not possess sufficient information on the variability of the endocranial and ectocranial manifestations of the sagittal suture and of its variance with age of the individual, in different hominid species and different equid species, I have not adduced this pattern as evidence in support or rebuttal of the hominid status of VM-0.     

Divergent patterns of integration and reduced constraint in the human hip and the origins of bipedalism

When compared to other hominids--great apes including humans--the human pelvis reveals a fundamental reorganization of bony morphology comprised of multiple trait-level changes, many of which are associated with bipedal locomotion. Establishing how patterns of integration--correlations and covariances among traits--within the pelvis have evolved in concert with morphology is essential to explaining this evolutionary transition because integration may facilitate or constrain morphological evolution. Here, we show that the human hip bone has significantly lower levels of integration and constraint overall when compared to other hominids, that the focus of these changes is on traits hypothesized to play major functional roles in bipedalism, and we provide evidence that the human hip was reintegrated in a pattern distinct from other members of this group. Additionally, the evolutionary transition from a nonhuman great ape-like to human hip bone morphology was significantly easier to traverse using the human integration pattern in each comparison, which suggests hominin patterns may have evolved to facilitate this transition. Our results suggest natural selection for bipedalism broke down earlier hominid integration patterns, allowing relevant traits to respond to separate selection pressures to a greater extent than was previously possible, and reintegrated traits in a way that could have facilitated evolution along the vector specifying ancestral hominid and hominin morphological differences.     

Pattern profile analysis of hominid and chimpanzee hand bones

In a study designed to complement morphological research on hominid hand bones, length and width measurements of the thumb, index, and middle rays were obtained from radiographs of modern human hands. These rays are primary in precision-gripping postures and are therefore the ones most relevant for investigating evolutionary changes in fine manipulation. Pattern profile analysis allows individuals or samples to be plotted against a reference sample in standard deviation units, or Z-scores. It provides an indication of how different measurements are from modern human averages, while taking into consideration the degree of variation present within modern human samples. A pattern profile for chimpanzees is clearly distinct from humans but quite similar to that of a bonobo, demonstrating the promise of pattern analysis. Partial pattern profiles of several of the more complete early hominid bones from Hadar, Swartkrans, and Olduvai (O.H. 7) are presented and compared. Hadar bones are long and wide at midshaft relative to articular widths; both body-size effects and functional differences are likely. Thumb distal phalanges from Swartkrans and Olduvai both have relatively small base widths, but they differ in other proportions. Two first metacarpals from Swartkrans show distinct patterns. The profiles of La Ferrassie I and Shanidar IV show the characteristically large Neanderthal distal phalanges. Profiles of Skhūl IV and P?edmost III are alike in some regions with reference to modern North American white males, though they are less similar overall than are those of the two Neanderthals. © 1995 Wiley-Liss, Inc.     

Effects of age and gender on the location and orientation of the foramen magnum in rhesus macaques (Macaca mulatta)

Endocasts from 378 rhesus macaque skulls from the Cayo Santiago skeletal collection were measured to determine the effects of age and gender on the position and orientation of the foramen magnum. The foramen magnum migrates from a rostral to a caudal position and its angle changes during postnatal development. The angles and relative positions of the foramen magnum are similar for both genders of infants and for both genders of adults. However, analyses of linear response and plateau (LRP) functions reveal significant differences between males and females in the timing of reorientation of the angle and migration of the foramen magnum. The mean adult angle and relative position of the foramen magnum are reached by 4.7 years in females, but they do not achieve their adult values until 7.1 years in males. A similar pattern is observed for the brainstem region of the basicranium. Mean adult lengths of the brainstem region are reached at 5.2 years in females and 7.1 years in males. The relationships between cranial capacity, the growth pattern of the brainstem, and the pattern of change for the angle and the relative position of the foramen magnum are examined. Quantification of the effects of age and gender on the location of the foramen magnum in a large sample of endocasts from one species of higher primate has potential implications for research on human development, and for interpretation of juvenile specimens in the hominid fossil record.     

The Versatility of Human Locomotion

Human locomotion was studied for 160 societies through the use of early travel accounts, missionaries' reports, and the ethnographic literature. As a result of the value Western society has placed on a sedentary way of life, and the consequent devaluation of movement, the common "striding gait" of humans has taken on a kind of misplaced concreteness. Humans facultatively employ a number of locomotor patterns besides the habitual bipedal gait: long-distance running, climbing, leaping, crawling, swimming, and skiing (the latter two are not dealt with in this paper). Human locomotion, like that of animals, is an analogous rather than a univocal concept, admitting great variation, plasticity, and subtle differences in gait, style, speed, and endurance. These multiple concepts have important implications for the construction of models of the evolution of hominid bipedalism.     

Sleep and arousal patterns of co-sleeping human mother/infant pairs: a preliminary physiological study with implications for the study of sudden infant death syndrome (SIDS)

The prevailing research design for studying infant sleep erroneously assumes the species-wide normalcy of solitary nocturnal sleep rather than a social sleeping environment. In fact, current clinical perspectives on infant sleep, which are based exclusively on studies of solitary sleeping infants, may partly reflect culturally induced rather than species-typical infant sleep patterns which can only be gleaned, we contend here, from infants sleeping with their parents--the context within which, and for well over 4 million years, the hominid infant's sleep, breathing, and arousal patterns evolved. Our physiological study of five co-sleeping mother-infant pairs in a sleep lab is the first study of its kind to document the unfolding sleep patterns of mothers and infants sleeping in physical contact. Our data show that co-sleeping mothers and infants exhibit synchronous arousals, which, because of the suspected relationship between arousal and breathing stability in infants, have important implications for how we study environmental factors possibly related to some forms of the sudden infant death syndrome (SIDS). While our data show that co-sleeping mothers and infants also experience many moments of physiological independence from each other, it is clear that the temporal unfolding of particular sleep stages and awake periods of the mother and infant become entwined and that on a minute-to-minute basis, throughout the night, much sensory communication is occurring between them. Our research acknowledges the human infant's evolutionary past and considers the implications that nocturnal separation (a historically novel and alien experience for them) has for maternal and infant well-being in general and SIDS research strategies in particular.     

Human infants and baboons show the same pattern of handedness for a communicative gesture

To test the role of gestures in the origin of language, we studied hand preferences for grasping or pointing to objects at several spatial positions in human infants and adult baboons. If the roots of language are indeed in gestural communication, we expect that human infants and baboons will present a comparable difference in their pattern of laterality according to task: both should be more right-hand/left-hemisphere specialized when communicating by pointing than when simply grasping objects. Our study is the first to test both human infants and baboons on the same communicative task. Our results show remarkable convergence in the distribution of the two species' hand biases on the two kinds of tasks: In both human infants and baboons, right-hand preference was significantly stronger for the communicative task than for grasping objects. Our findings support the hypothesis that left-lateralized language may be derived from a gestural communication system that was present in the common ancestor of baboons and humans.     

Symmetrical gaits of primates

Walking and symmetrical running gaits of 26 genera of primates are analyzed using numerical and graphical methods described previously. The raw data are 1701 feet of 16 mm motion picture film mostly exposed at 64 frames per second. Adult monkeys and apes usually use the walking trot or diagonal-sequence walks. Individual monkeys occasionally use lateral-sequence walks resembling those that are usual for human infants. Human children moving on hands and feet use gaits ranging from the walking pace through the lateral-sequence walks to the walking trot. An infant macaque studied from age 17 hours to 96 days first walked with a lateral-sequence, diagonal-couplets gait and then gradually shifted to the diagonal-sequence, diagonal-couplets gait of the adult. Few non-primates use the diagonal-sequence walks which are typical of primates. Typical support sequences are figured. Relative placement of feet and consequent slight asymmetry are described.     

Differences between Neandertal and modern human infant and child growth models

Studying the emergence of distinctive human growth patterns is essential to understanding the evolution of our species. The large number of Neandertal fossils makes this species the best candidate for a comparative study of growth patterns in archaic and modern humans. Here, Neandertal height growth during infancy and early childhood is described using a mathematical model. Height growth velocities for individuals five years old or younger are modelled as age functions based on different estimates of height and age for a set of ten Neandertal infants and children. The estimated heights of each Neandertal individual are compared with those of two modern human populations based on longitudinal and cross-sectional data. The model highlights differences in growth velocity during infancy (from the age of five months onward). We find that statural growth in Neandertal infants is much slower than that seen in modern humans, Neandertal growth is similar to modern humans at birth, but decreases around the third or fourth month. The markedly slower growth rates of Neandertal infants may be attributable to ontogenetic constraints or to metabolic stress, and contribute to short achieved adult stature relative to modern humans.     

Gait Pattern Differences between Children with Mild Scoliosis and Children with Unilateral Cerebral Palsy

This study was conducted to investigate the effects of asymmetrical body posture alone, i.e., the effects seen in children with mild scoliosis, vs. the effects of body posture control impairment, i.e., those seen in children with unilateral cerebral palsy on gait patterns. Three-dimensional instrumented gait analysis (3DGA) was conducted in 45 children with hemiplegia and 51 children with mild scoliosis. All the children were able to walk without assistance devices. A set of 35 selected spatiotemporal gait and kinematics parameters were evaluated when subjects walked on a treadmill. A cluster analysis revealed 3 different gait patterns: a scoliotic gait pattern and 2 different hemiplegic gait patterns. The results showed that the discrepancy in gait patterns was not simply a lower limb kinematic deviation in the sagittal plane, as expected. Additional altered kinematics, such as pelvic misorientation in the coronal plane in both the stance and swing phases and inadequate stance phase hip ad/abduction, which resulted from postural pattern features, were distinguished between the 3 gait patterns. Our study provides evidence for a strong correlation between postural and gait patterns in children with unilateral cerebral palsy. Information on differences in gait patterns may be used to improve the guidelines for early therapy for children with hemiplegia before abnormal gait patterns are fully established. The gait pathology characteristic of scoliotic children is a potential new direction for treating scoliosis that complements the standard posture and walking control therapy exercises with the use of biofeedback.     

How is sagittal balance acquired during bipedal gait acquisition? Comparison of neonatal and adult pelves in three dimensions. Evolutionary implications

We compare adult and intact neonatal pelves, using a pelvic sagittal variable, the angle of sacral incidence, which presents significant correlations with vertebral curvature in adults and plays an important role in sagittal balance of the trunk on the lower limbs. Since lumbar curvature develops in children in association with gait acquisition, we expect a change in this angle during growth, which could contribute to the acquisition of sagittal balance. To understand the mechanisms underlying sagittal balance in the evolution of human bipedalism, we also measure the angle of incidence in hominid fossils.     

The relative cost of bent-hip bent-knee walking is reduced in water

The debate about how early hominids walked may be characterised as two competing hypotheses: They moved with a fully upright (FU) gait, like modern humans, or with a bent-hip, bent-knee (BK) gait, like apes. Both have assumed that this bipedalism was almost exclusively on land, in trees or a combination of the two. Recent findings favoured the FU hypothesis by showing that the BK gait is 50–60% more energetically costly than a FU human gait on land. We confirm these findings but show that in water this cost differential is markedly reduced, especially in deeper water, at slower speeds and with greater knee flexion. These data suggest that the controversy about australopithecine locomotion may be eased if it is assumed that wading was a component of their locomotor repertoire and supports the idea that shallow water might have been an environment favourable to the evolution of early forms of “non-optimal” hominid bipedalism.     

Patterns of tooth crown size and shape variation in great apes and humans and species recognition in the hominid fossil record

It has been suggested that patterns of craniodental variation in living hominids (Gorilla, Homo, Pan, and Pongo) may be useful for evaluating variation in fossil hominid assemblages. Using this approach, a fossil sample exhibiting a pattern of variation that deviates from one shared among living taxa would be regarded as taxonomically heterogeneous. Here we examine patterns of tooth crown size and shape variation in great apes and humans to determine 1) if these taxa share a pattern of dental variation, and 2) if such a pattern can reliably discriminate between samples that contain single species and those that contain multiple species. We use parametric and nonparametric correlation methods to establish the degree of pattern similarity among taxa, and randomization tests to assess their statistical significance. The results of this study show that extant hominids do not share a pattern of dental size variation, and thus these taxa cannot be used to generate expectations for patterns of size variation in fossil hominid species. The hominines (Gorilla, Homo, and Pan) do share a pattern of shape variation in the mandibular dentition; however, Pongo is distinct, and thus it is unclear which, if either, pattern should be expected in fossil hominids. Moreover, in this case, most combined-species samples exhibit patterns of shape variation that are similar to those for single hominine species samples. Thus, although a common pattern of shape variation is present in the mandibular dentition, it is not useful for recognizing taxonomically mixed paleontological samples.     

Brain endocast asymmetry in pongids and hominids: Some preliminary findings on the paleontology of cerebral dominance

Observations on petalial asymmetry for 190 hominoid endocasts are reported, and their statistical differences assessed. While all taxa of hominoids show asymmetries to various degrees, the patterns or combinations of petalial asymmetries are very different, with fossil hominids and modern Homo sapiens showing an identical pattern of left-occipital, right-frontal petalias, which contrasts with those found normally in pongids. Of the pongids, Gorilla shows the greater degree of asymmetry in left-occipital petalias. Only modern Homo and hominids (Australopithecus, Homo erectus, Neandertals) show a distinct left-occipital, right-frontal petalial pattern. Analysis by x² statistics shows the differences to be highly significant. Due to small sample size and incompleteness of endocasts, small-brained hominids, i.e., Australopithecus, are problematical. To the degree that gross petalial patterns are correlated with cognitive task specialization, we speculate that human cognitive patterns evolved early in hominid evolution and were related to selection pressures operating on both symbolic and spatiovisual integration, and that these faculties are corroborated in the archaeological record.     

Estimation of temporal gait parameters using Bayesian models on acceleration signals

The purpose of this study is to develop a system capable of performing calculation of temporal gait parameters using two low-cost wireless accelerometers and artificial intelligence-based techniques as part of a larger research project for conducting human gait analysis. Ten healthy subjects of different ages participated in this study and performed controlled walking tests. Two wireless accelerometers were placed on their ankles. Raw acceleration signals were processed in order to obtain gait patterns from characteristic peaks related to steps. A Bayesian model was implemented to classify the characteristic peaks into steps or nonsteps. The acceleration signals were segmented based on gait events, such as heel strike and toe-off, of actual steps. Temporal gait parameters, such as cadence, ambulation time, step time, gait cycle time, stance and swing phase time, simple and double support time, were estimated from segmented acceleration signals. Gait data-sets were divided into two groups of ages to test Bayesian models in order to classify the characteristic peaks. The mean error obtained from calculating the temporal gait parameters was 4.6%. Bayesian models are useful techniques that can be applied to classification of gait data of subjects at different ages with promising results