Evolutionary transformation of the hominin shoulder

Despite the fact that the shoulder is one of the most extensively studied regions in comparative primate and human anatomy, two recent fossil hominin discoveries have revealed quite unexpected morphology. The first is a humerus of the diminutive fossil hominin from the island of Flores, Homo floresiensis (LB1/50), which displays a very low degree of humeral torsion 1 , 2 (Fig. 1; see Box 1). Modern humans have a high degree of torsion and, since this is commonly viewed as a derived feature shared with hominoids, 3 - 6 one would expect all fossil hominins to display high humeral torsion. The second is the recently discovered Australopithecus afarensis juvenile scapula DIK‐1‐1 from Dikika, Ethiopia, which seems to most closely resemble those of gorillas. 7 This specimen is the first nearly complete scapula known for an early hominin and, given the close phylogenetic relationship between humans and chimpanzees suggested by molecular studies, 8 - 13 one would have expected more similarity to chimpanzees among extant hominoids.     

Are the small human-like fossils found on Flores human endemic cretins?

Fossils from Liang Bua (LB) on Flores, Indonesia, including a nearly complete skeleton (LB1) dated to 18kyr BP, were assigned to a new species, Homo floresiensis. We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyroidism, including enlarged pituitary fossa, and that distinctive primitive features of LB1 such as the double rooted lower premolar and the primitive wrist morphology are consistent with the hypothesis. We find that the null hypothesis (that LB1 is not a cretin) is rejected by the pituitary fossa size of LB1, and by multivariate analyses of cranial measures. We show that critical environmental factors were potentially present on Flores, how remains of cretins but not of unaffected individuals could be preserved in caves, and that extant oral traditions may provide a record of cretinism.     

Homo floresiensis: microcephalic, pygmoid, Australopithecus, or Homo?

The remarkable partial adult skeleton (LB1) excavated from Liang Bua cave on the island of Flores, Indonesia, has been attributed to a new species, Homo floresiensis, based upon a unique mosaic of primitive and derived features compared to any other hominin. The announcement precipitated widespread interest, and attention quickly focused on its possible affinities. LB1 is a small-bodied hominin with an endocranial volume of 380-410 cm3, a stature of 1m, and an approximate geological age of 18,000 years. The describers [Brown, P., Sutikna, T., Morwood, M.J., Soejono, R.P., Jatmiko, Wayhu Saptomo, E., Awe Due, R., 2004. A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia. Nature 431, 1055-1061] originally proposed that H. floresiensis was the end product of a long period of isolation of H. erectus or early Homo on a small island, a process known as insular dwarfism. More recently Morwood, Brown, and colleagues [Morwood, M.J., Brown, P., Jatmiko, Sutikna, T., Wahyu Saptomo, E., Westaway, K.E., Awe Due, R., Roberts, R.G., Maeda, T., Wasisto, S., Djubiantono, T., 2005. Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia. Nature 437, 1012-1017] reviewed this assessment in light of new material from the site and concluded that H. floresiensis is not likely to be descended from H. erectus, with the genealogy of the species remaining uncertain. Other interpretations, namely that LB1 is a pygmy or afflicted with microcephaly, have also been put forward. We explore the affinities of LB1 using cranial and postcranial metric and non-metric analyses. LB1 is compared to early Homo, two microcephalic humans, a 'pygmoid' excavated from another cave on Flores, H. sapiens (including African pygmies and Andaman Islanders), Australopithecus, and Paranthropus. Based on these comparisons, we conclude that it is unlikely that LB1 is a microcephalic human, and it cannot be attributed to any known species. Its attribution to a new species, Homo floresiensis, is supported.     

On dental wear, dental work, and oral health in the type specimen (LB1) of Homo floresiensis

The claim that the lower left first mandibular molar of LB1, the type specimen of Homo floresiensis, displays endodontic work, and a filling is assessed by digital radiography and micro-CT scanning. The M(1) tooth crown is heavily worn and exhibits extensive dentine exposure that is stained white, but there is no trace of endodontic treatment or a dental filling in this Indonesian fossil dated to 17.1-19.0 kya. Dental calculus (commonly observed in foragers) is present on the teeth of LB1, but there are no observable caries. The pattern of dental attrition in the mandibles of both LB1/2 and LB6/1 (moderate to extensive flat wear across the entire arch) is consistent with that seen in Plio-Pleistocene Homo fossils and in modern hunter-gatherers, and is not typical of most agriculturalists. We conclude that the dental-work and farming hypotheses are falsified and therefore irrelevant to the debate over the taxonomy and phylogeny of H. floresiensis.     

L’architecture de l’épaule au sein du genre Homo : nouvelles interprétations

The morphology of human clavicles can be estimated by projecting them on two perpendicular planes in order to assess the shapes of their cranial and dorsal primary curvatures. In cranial view no differences in curvature appear within the genus Homo, which means the different species had similar arms elevation capacity, especially in protraction. On the contrary, in dorsal view two clavicles morphologies could be defined. The first one is characterized by two curvatures in dorsal view and is possessed by all Homo species, from Homo habilis to Neanderthal, including Homo ergaster, but not modern human, Upper Paleolithic and anatomically modern human remains, who possess clavicles of the second type, characterized by either one curvature, or two slightly pronounced ones in dorsal view. Clavicles displaying two pronounced curvatures in dorsal view are associated with scapula sitting high on the thorax in regard to modern human. However, shoulder with high scapula on the thorax displays two different kinds of architectures: (i) shoulder with short clavicles associated to scapulas sitting more laterally than those of modern human. This group includes earlier Homo like Homo habilis and Homo ergaster and (ii) shoulder with long clavicles associated to scapulas sitting more dorsally on the thorax, like those of modern human. This group includes Homoantecessor and Neanderthals. In other words, within the genus Homo, three shoulders would have existed. Evolution of the shoulder complex is far more complex than previously thought and the arrival of modern bipedalism was not associated to modern shoulder.     

The size of scalable brain components in the human evolutionary lineage: with a comment on the paradox of Homo floresiensis.

The discovery of a diminutive, small-brained hominin skeleton (LB1) from the Pleistocene of Flores, Indonesia, seems to present a paradox concerning the interpretation of overall brain size in an evolutionary context. This specimen forms the holotype of a purportedly new hominin species, Homo floresiensis. As inferred from the archaeological record, it has been suggested that this species of Homo, existing as recently as 12,000 years ago, engaged in sophisticated cultural behaviors with an adult brain size equivalent to that seen in modern chimpanzees and one that in modern humans would be defined as "high degree microcephaly" and "always associated with idiocy". The alternative explanation for these behaviors at the observed brain size would require that H. floresiensis deviate from existing patterns of primate brain scaling at either a macroscopic or microscopic level. Here we develop predictive equations and confidence intervals for estimating the size of various brain components in the human evolutionary lineage by calculating scaling relationships among overall brain size and 11 components of the primate brain using phylogenetically independent contrasts (PIC) methods. Using these equations, paleoanthropologists can: (a) estimate brain component size (and confidence intervals) for any primate in the fossil record if overall brain size is known; and (b) calculate some reasonable outside limits as to how far species-specific departures from allometric constraints (i.e., brain "reorganization") can be taken in assessing human brain evolution. We conclude that if the original assessment of LB1 is correct, i.e., that it samples a population from a new species of Homo, H. floresiensis, that was capable of Homo sapiens-like cultural attributes (fire, blade manufacturing, etc.), while having a chimpanzee-sized brain, then we are faced with the paradox that 1 cm(3) of H. floresiensis brain could not be functionally equivalent to 1cm(3) of a modern human or modern chimpanzee brain.     

Post-cranial skeletons of hypothyroid cretins show a similar anatomical mosaic as Homo floresiensis

Human remains, some as recent as 15 thousand years, from Liang Bua (LB) on the Indonesian island of Flores have been attributed to a new species, Homo floresiensis. The definition includes a mosaic of features, some like modern humans (hence derived: genus Homo), some like modern apes and australopithecines (hence primitive: not species sapiens), and some unique (hence new species: floresiensis). Conversely, because only modern humans (H. sapiens) are known in this region in the last 40 thousand years, these individuals have also been suggested to be genetic human dwarfs. Such dwarfs resemble small humans and do not show the mosaic combination of the most complete individuals, LB1 and LB6, so this idea has been largely dismissed. We have previously shown that some features of the cranium of hypothyroid cretins are like those of LB1. Here we examine cretin postcrania to see if they show anatomical mosaics like H. floresiensis. We find that hypothyroid cretins share at least 10 postcranial features with Homo floresiensis and unaffected humans not found in apes (or australopithecines when materials permit). They share with H. floresiensis, modern apes and australopithecines at least 11 postcranial features not found in unaffected humans. They share with H. floresiensis, at least 8 features not found in apes, australopithecines or unaffected humans. Sixteen features can be rendered metrically and multivariate analyses demonstrate that H. floresiensis co-locates with cretins, both being markedly separate from humans and chimpanzees (P<0.001: from analysis of similarity (ANOSIM) over all variables, ANOSIM, global R>0.999). We therefore conclude that LB1 and LB6, at least, are, most likely, endemic cretins from a population of unaffected Homo sapiens. This is consistent with recent hypothyroid endemic cretinism throughout Indonesia, including the nearby island of Bali.     

Size, shape, and asymmetry in fossil hominins: the status of the LB1 cranium based on 3D morphometric analyses

The unique set of morphological characteristics of the Liang Bua hominins (Homo floresiensis) has been attributed to explanations as diverse as insular dwarfism and pathological microcephaly. This study examined the relationship between cranial size and shape across a range of hominin and African ape species to test whether or not cranial morphology of LB1 is consistent with the basic pattern of static allometry present in these various taxa. Correlations between size and 3D cranial shape were explored using principal components analysis in shape space and in Procrustes form space. Additionally, patterns of static allometry within both modern humans and Plio-Pleistocene hominins were used to simulate the expected cranial shapes of each group at the size of LB1. These hypothetical specimens were compared to LB1 both visually and statistically. Results of most analyses indicated that LB1 best fits predictions for a small specimen of fossil Homo but not for a small modern human. This was especially true for analyses of neurocranial landmarks. Results from the whole cranium were less clear about the specific affinities of LB1, but, importantly, demonstrated that aspects of facial morphology associated with smaller size converge on modern human morphology. This suggests that facial similarities between LB1 and anatomically modern humans may not be indicative of a close relationship. Landmark data collected from this study were also used to test the degree of cranial asymmetry in LB1. These comparisons indicated that the cranium is fairly asymmetrical, but within the range of asymmetry exhibited by modern humans and all extant African ape species. Compared to other fossil specimens, the degree of asymmetry in LB1 is moderate and readily explained by the taphonomic processes to which all fossils are subject. Taken together, these findings suggest that H. floresiensis was most likely the diminutive descendant of a species of archaic Homo, although the details of this evolutionary history remain obscure.     

Craniofacial morphology of Homo floresiensis: description, taxonomic affinities, and evolutionary implication

This paper describes in detail the external morphology of LB1/1, the nearly complete and only known cranium of Homo floresiensis. Comparisons were made with a large sample of early groups of the genus Homo to assess primitive, derived, and unique craniofacial traits of LB1 and discuss its evolution. Principal cranial shape differences between H. floresiensis and Homo sapiens are also explored metrically. The LB1 specimen exhibits a marked reductive trend in its facial skeleton, which is comparable to the H. sapiens condition and is probably associated with reduced masticatory stresses. However, LB1 is craniometrically different from H. sapiens showing an extremely small overall cranial size, and the combination of a primitive low and anteriorly narrow vault shape, a relatively prognathic face, a rounded oval foramen that is greatly separated anteriorly from the carotid canal/jugular foramen, and a unique, tall orbital shape. Whereas the neurocranium of LB1 is as small as that of some Homo habilis specimens, it exhibits laterally expanded parietals, a weak suprameatal crest, a moderately flexed occipital, a marked facial reduction, and many other derived features that characterize post-habilis Homo. Other craniofacial characteristics of LB1 include, for example, a relatively narrow frontal squama with flattened right and left sides, a marked frontal keel, posteriorly divergent temporal lines, a posteriorly flexed anteromedial corner of the mandibular fossa, a bulbous lateral end of the supraorbital torus, and a forward protruding maxillary body with a distinct infraorbital sulcus. LB1 is most similar to early Javanese Homo erectus from Sangiran and Trinil in these and other aspects. We conclude that the craniofacial morphology of LB1 is consistent with the hypothesis that H. floresiensis evolved from early Javanese H. erectus with dramatic island dwarfism. However, further field discoveries of early hominin skeletal remains from Flores and detailed analyses of the finds are needed to understand the evolutionary history of this endemic hominin species.     

Liang Bua Homo floresiensis mandibles and mandibular teeth: a contribution to the comparative morphology of a new hominin species

In 2004, a new hominin species, Homo floresiensis, was described from Late Pleistocene cave deposits at Liang Bua, Flores. H. floresiensis was remarkable for its small body-size, endocranial volume in the chimpanzee range, limb proportions and skeletal robusticity similar to Pliocene Australopithecus, and a skeletal morphology with a distinctive combination of symplesiomorphic, derived, and unique traits. Critics of H. floresiensis as a novel species have argued that the Pleistocene skeletons from Liang Bua either fall within the range of living Australomelanesians, exhibit the attributes of growth disorders found in modern humans, or a combination of both. Here we describe the morphology of the LB1, LB2, and LB6 mandibles and mandibular teeth from Liang Bua. Morphological and metrical comparisons of the mandibles demonstrate that they share a distinctive suite of traits that place them outside both the H. sapiens and H. erectus ranges of variation. While having the derived molar size of later Homo, the symphyseal, corpus, ramus, and premolar morphologies share similarities with both Australopithecus and early Homo. When the mandibles are considered with the existing evidence for cranial and postcranial anatomy, limb proportions, and the functional anatomy of the wrist and shoulder, they are in many respects closer to African early Homo or Australopithecus than to later Homo. Taken together, this evidence suggests that the ancestors of H. floresiensis left Africa before the evolution of H. erectus, as defined by the Dmanisi and East African evidence.     

Descriptions of the upper limb skeleton of Homo floresiensis

Several bones of the upper extremity were recovered during excavations of Late Pleistocene deposits at Liang Bua, Flores, and these have been attributed to Homo floresiensis. At present, these upper limb remains have been assigned to six different individuals - LB1, LB2, LB3, LB4, LB5, and LB6. Several of these bones are complete or nearly so, but some are quite fragmentary. All skeletal remains recovered from Liang Bua were extremely fragile, but have now been stabilized and hardened in the laboratory in Jakarta. They are now curated in museum-quality containers at the National Research and Development Centre for Archaeology in Jakarta, Indonesia. These skeletal remains are described and illustrated photographically. The upper limb presents a unique mosaic of derived (human-like) and primitive morphologies, the combination of which is never found in either healthy or pathological modern humans.     

Brief communication: Developmental versus functional three‐dimensional geometric morphometric‐based modularity of the human proximal humerus

The proximal humerus is formed by three secondary ossification centers during the postnatal trajectory of the human infant. The ossification centers later grow into the structures of the articular surface, major tubercle, and minor tubercle. There is a purported functional division between the articular surface and the tubercles, with the articular surface mainly responsible for the range of movement of the shoulder joint, and the tubercles bearing the insertions of the rotator cuff muscles, mainly devoted to securing the joint against humeral displacement. Using three‐dimensional geometric morphometrics, we tested the presence of such developmental and functional divisions in the proximal humerus, applying the RV coefficient of Escoufier to these a priori hypothesized modules. Our results indicate that the proximal humerus might be a generally integrated structure. However, a weak signal for modular configuration was present, with slightly stronger support for the two modules depicting the boundaries between the purported functional regions of the epiphysis: the articular surface and the tubercles. Am J Phys Anthropol 154:459–465, 2014. © 2014 Wiley Periodicals, Inc.     

Descriptions of the lower limb skeleton of Homo floresiensis

Bones of the lower extremity have been recovered for up to nine different individuals of Homo floresiensis - LB1, LB4, LB6, LB8, LB9, LB10, LB11, LB13, and LB14. LB1 is represented by a bony pelvis (damaged but now repaired), femora, tibiae, fibulae, patellae, and numerous foot bones. LB4/2 is an immature right tibia lacking epiphyses. LB6 includes a fragmentary metatarsal and two pedal phalanges. LB8 is a nearly complete right tibia (shorter than that of LB1). LB9 is a fragment of a hominin femoral diaphysis. LB10 is a proximal hallucal phalanx. LB11 includes pelvic fragments and a fragmentary metatarsal. LB13 is a patellar fragment, and LB14 is a fragment of an acetabulum. All skeletal remains recovered from Liang Bua were extremely fragile, and some were badly damaged when they were removed temporarily from Jakarta. At present, virtually all fossil materials have been returned, stabilized, and hardened. These skeletal remains are described and illustrated photographically. The lower limb skeleton exhibits a uniquely mosaic pattern, with many primitive-like morphologies; we have been unable to find this combination of ancient and derived (more human-like) features in either healthy or pathological modern humans, regardless of body size. Bilateral asymmetries are slight in the postcranium, and muscle markings are clearly delineated on all bones. The long bones are robust, and the thickness of their cortices is well within the ranges seen in healthy modern humans. LB1 is most probably a female based on the shape of her greater sciatic notch, and the marked degree of lateral iliac flaring recalls that seen in australopithecines such as “Lucy” (AL 288-1). The metatarsus has a human-like robusticity formula, but the proximal pedal phalanges are relatively long and robust (and slightly curved). The hallux is fully adducted, but we suspect that a medial longitudinal arch was absent.     

Relative limb strength and locomotion in Homo habilis

The Homo habilis OH 62 partial skeleton has played an important, although controversial role in interpretations of early Homo locomotor behavior. Past interpretive problems stemmed from uncertain bone length estimates and comparisons using external bone breadth proportions, which do not clearly distinguish between modern humans and apes. Here, true cross-sectional bone strength measurements of the OH 62 femur and humerus are compared with those of modern humans and chimpanzees, as well as two early H. erectus specimens-KNM-WT 15000 and KNM-ER 1808. The comparative sections include two locations in the femur and two in the humerus in order to encompass the range of possible section positions in the OH 62 specimens. For each combination of section locations, femoral to humeral strength proportions of OH 62 fall below the 95% confidence interval of modern humans, and for most comparisons, within the 95% confidence interval of chimpanzees. In contrast, the two H. erectus specimens both fall within or even above the modern human distributions. This indicates that load distribution between the limbs, and by implication, locomotor behavior, was significantly different in H. habilis from that of H. erectus and modern humans. When considered with other postcranial evidence, the most likely interpretation is that H. habilis, although bipedal when terrestrial, still engaged in frequent arboreal behavior, while H. erectus was a completely committed terrestrial biped. This adds to the evidence that H. habilis (sensu stricto) and H. erectus represent ecologically distinct, parallel lineages during the early Pleistocene.     

Homo floresiensis: a cladistic analysis

The announcement of a new species, Homo floresiensis, a primitive hominin that survived until relatively recent times is an enormous challenge to paradigms of human evolution. Until this announcement, the dominant paradigm stipulated that: 1) only more derived hominins had emerged from Africa, and 2) H. sapiens was the only hominin since the demise of Homo erectus and Homo neanderthalensis. Resistance to H. floresiensis has been intense, and debate centers on two sets of competing hypotheses: 1) that it is a primitive hominin, and 2) that it is a modern human, either a pygmoid form or a pathological individual. Despite a range of analytical techniques having been applied to the question, no resolution has been reached. Here, we use cladistic analysis, a tool that has not, until now, been applied to the problem, to establish the phylogenetic position of the species. Our results produce two equally parsimonious phylogenetic trees. The first suggests that H. floresiensis is an early hominin that emerged after Homo rudolfensis (1.86 Ma) but before H. habilis (1.66 Ma, or after 1.9 Ma if the earlier chronology for H. habilis is retained). The second tree indicates H. floresiensis branched after Homo habilis.     

Subscapularis function in gibbons and chimpanzees: Implications for interpretation of humeral head torsion in hominoids

Chimpanzees and gibbons, along with other hominoids, share a number of features in the morphology of their shoulders that have generally been associated with use of the upper limb in overhead postural and locomotor activities. These include the position and shape of the scapula, as well as the morphology of the proximal end of the humerus. Results of an electromyographic (EMG) analysis of shoulder muscle activity patterns indicate that these two species of hominoids also share broad similarities in shoulder muscle function during locomotion and voluntary movements. Differences do exist, however, in the activity patterns of subscapularis, a medial rotator of the arm. These differences mainly involve a greater participation by the gibbon subscapularis in free arm movements. This greater participation is characterized by earlier onset of muscle activity, higher amplitude of recruitment, and involvement of more of the total mass of the muscle. These differences in muscle recruitment suggest that the shoulder of gibbons differs from that of chimpanzees in some manner that necessitates the greater contribution of a medial rotator to the production of motion in the upper limb. I suggest that the low degree of humeral head torsion in gibbons, compared to that of other hominoids, gives their elbow a “lateral set” that must be overcome by the action of subscapularis during free arm movements. I propose that this modest degree of humeral head torsion in gibbons reflects a compromise between necessary changes caused by the repositioning of the scapula onto the dorsum of the thorax and the demands for extreme positioning of the elbow during brachiation. In addition, I suggest that the greater amount of torsion in the chimpanzee humerus is an accommodation to quadrupedal habits, and finally, that the high degree of torsion in human humeri is an independently acquired trait related to use of the upper limb as a manipulatory organ.     

Morphological and functional aspects of the temporal bone articular tubercle morphology inHomo erectus andHomo sapiens

The morphological variability of the temporal articular tubercle was studied inHomo erectus andHomo sapiens. Five configurations have been defined. There is a high heterogeneity amongHomo erectus. The Neandertal lineage and that leading toHomo sapiens sapiens are more homogenous, each of them exhibits a high frequency of one configuration. This study has also focused on the functional implications of this variation. A theoretical approach to two different configurations of the articular tubercle is considered in the same bony, muscular and ligamentary context. This suggests that the configuration which consists of a transverse concavity is, for the mandible depression, concomitant with a slight functional disadvantage in comparison with the cylindrical configuration. It appears that a midfacial projection allows for a compensation of this disadvantage. It is concluded that this model can be proposed for Neandertals which present a very concave articular tubercle and a typical midfacial projection.     

Femoral/humeral strength in early African Homo erectus

Lower-to-upper limb-bone proportions give valuable clues to locomotor behavior in fossil taxa. However, to date only external linear dimensions have been included in such analyses of early hominins. In this study, cross-sectional measures of femoral and humeral diaphyseal strength are determined for the two most complete early Homo erectus (or ergaster) associated skeletons--the juvenile KNM-WT 15000 and the adult KNM-ER 1808. Modern comparative samples include an adult human skeletal sample representative of diverse body shapes, a human longitudinal growth series, and an adult chimpanzee sample. When compared to appropriately age-matched samples, both H. erectus specimens fall very close to modern human mean proportions and far from chimpanzee proportions (which do not overlap with those of humans). This implies very similar mechanical load-sharing between the lower and upper limbs, and by implication, similar locomotor behavior in early H. erectus and modern humans. Thus, by the earliest Pleistocene (1.7 Ma), completely modern patterns of bipedal behavior were fully established in at least one early hominin taxon.     

On the kinematic modelling and the parameter estimation of the human shoulder.

This paper presents some results on the modelling and the corresponding parameter estimation of the human shoulder. This system consists of the clavicle, the scapula, the humerus and the various joints between these bodies and the trunk through the sternum; it will be represented as a succession of a rotational joint between the sternum and the clavicle and a constant distance joint, representing the scapula between, the clavicle and the humerus head. The parameters of this system are the components of the position vectors of the joint characteristic points (the corresponding centres of the rotations). Experimental results are presented as well as a validation of the proposed model.     

Cineradiographic study of forelimb movements during quadrupedal walking in the brown lemur (Eulemur fulvus, Primates: Lemuridae)

Movements of forelimb joints and segments during walking in the brown lemur (Eulemur fulvus) were analyzed using cineradiography (150 frames/sec). Metric gait parameters, forelimb kinematics, and intralimb coordination are described. Calculation of contribution of segment displacements to stance propulsion shows that scapular retroversion in a fulcrum near the vertebral border causes more than 60% of propulsion. The contribution by the shoulder joint is 30%, elbow joint 5%, and wrist joint 1%. Correlation analysis was applied to reveal the interdependency between metric and kinematic parameters. Only the effective angular movement of the elbow joint during stance is speed-dependent. Movements of all other forelimb joints and segments are independent of speed and influence, mainly, linear gait parameters (stride length, stance length). Perhaps the most important result is the hitherto unknown and unexpected degree of scapular mobility. Scapular movements consist of ante-/retroversion, adduction/abduction, and scapular rotation about the longitudinal axis. Inside rotation of the scapula (60 degrees -70 degrees ), together with flexion in the shoulder joint, mediates abduction of the humerus, which is not achieved in the shoulder joint, and is therefore strikingly different from humeral abduction in man. Movements of the shoulder joint are restricted to flexion and extension. At touch down, the shoulder joint of the brown lemur is more extended compared to that of other small mammals. The relatively long humerus and forearm, characteristic for primates, are thus effectively converted into stride length. Observed asymmetries in metric and kinematic behavior of the left and right forelimb are caused by an unequal lateral bending of the spinal column.