The objective of this study was to examine whether the premolars and molars found at Sterkfontein Sts Mbr. 4 and StW Mbr. 5 are morphometrically similar to the degree that all individuals could belong to the same species, A. africanus. Mesial-distal (MD) and buccal-lingual (BL) measurements were obtained from maxillary premolars (P3 and P4) and molars (M1, M2, and M3) of Homo, Pan, and Gorilla, and compared to their counterparts attributed to A. africanus from Sterkfontein. Specimen samples were statistically analyzed using univariate and multivariate analyses. The results support the acceptance of the null hypothesis, indicating that the dental remains from Sts Mbr. 4 and StW Mbr 5 are from the same species.

Sterkfontein West Pit, dated to 1.7-1.9 Ma, has yielded a number of fossils that are difficult to classify, such as StW 252, which comprises cranial bone fragments, and a full set of robust maxillary anterior and posterior teeth. The purpose of this study is to ascertain whether dental measurements of StW 252 more closely align with those of Australopithecus africanus, Australopithecus robustus, Homo sapiens or the African apes. For M1 and M2, StW 252 is distinct from the comparative samples, and is particularly large buccolingually for M1 and mesiodistally for M2, partly resembling the dimensions of A. africanus, whereas for M3, StW 252 is mesiodistally and buccolingually large. Canonical scores axes show StW 252 as extreme in terms of size and polarized from A. robustus in terms of shape. StW 252 is distinct from both A. africanus and A. robustus, indicating an additional hominin taxon may be represented at Sterkfontein West Pit.

Human bipedal locomotion is characterized by a habitual heel-strike (HS) plantigrade gait, yet the significance of walking foot-posture is not well understood. To date, researchers have not fully investigated the costs of non-heel-strike (NHS) walking. Therefore, we examined walking speed, walk-to-run transition speed, estimated locomotor costs (lower limb muscle volume activated during walking), impact transient (rapid increase in ground force at touchdown) and effective limb length (ELL) in subjects (n=14) who walked at self-selected speeds using HS and NHS gaits. HS walking increases ELL compared with NHS walking since the center of pressure translates anteriorly from heel touchdown to toe-off. NHS gaits led to decreased absolutewalking speeds (P=0.012) and walk-to-run transition speeds (P=0.0025), and increased estimated locomotor energy costs (P<0.0001) compared with HS gaits. These differences lost significance after using the dynamic similarity hypothesis to account for the effects of foot landing posture on ELL. Thus, reduced locomotor costs and increased maximum walking speeds in HS gaits are linked to the increased ELL compared with NHS gaits. However, HS walking significantly increases impact transient values at all speeds (P<0.0001). These trade-offs may be key to understanding the functional benefits of HS walking. Given the current debate over the locomotor mechanics of early hominins and the range of foot landing postures used by nonhuman apes, we suggest the consistent use of HS gaits provides key locomotor advantages to striding bipeds and may have appeared early in hominin evolution.

Cercopithecines are common in hominid producing deposits and are a useful proxy for determining the ecological context of the early hominids. For this study, dental microwear is examined through low-magnification stereomicroscopy and used to reconstruct the diets of sampled primates. Those from the earliest sites, predominantly Parapapio, are primarily frugivorous while the incidence of gramnivory increases in the later Dinopithecus, Gorgopithecus, and Papio individuals denoting a general cooling and drying trend over the South African Plio-Pleistocene with a distinct pulse between 1.9-1.8 million years ago (mya). Australopithecus is reconstructed as a primary gramnivore which indicates that hominids adapted early in their evolution to expanding grasslands.

No description available.

No / Australopithecus anamensis is the stem species of all later hominins and exhibits the suite of characters traditionally associated with hominins, i.e., bipedal locomotion when on the ground, canine reduction, and thick-enameled teeth. The functional consequences of its thick enamel are, however, unclear. Without appropriate structural reinforcement, these thick-enameled teeth may be prone to failure. This article investigates the mechanical behavior of A. anamensis enamel and represents the first in a series that will attempt to determine the functional adaptations of hominin teeth. First, the microstructural arrangement of enamel prisms in A anamensis teeth was reconstructed using recently developed software and was compared with that of extant hominoids. Second, a finite-element model of a block of enamel containing one cycle of prism deviation was reconstructed for Homo, Pan, Gorilla, and A. anamensis and the behavior of these tissues under compressive stress was determined. Despite similarities in enamel microstructure between A. anamensis and the African great apes, the structural arrangement of prismatic enamel in A. anamensis appears to be more effective in load dissipation under these compressive loads. The findings may imply that this hominin species was well adapted to puncture crushing and are in some respects contrary to expectations based on macromorphology of teeth. Taking together, information obtained from both finite-element analyses and dental macroanatomy leads us to suggest that A. anamensis was probably adapted for habitually consuming a hard-tough diet. However, additional tests are needed to understand the functional adaptations of A. anamensis teeth fully.

No description available.

<p>During the last six million years, humans shifted from a primarily arboreal lifestyle to a habitually bipedal, terrestrial lifestyle. Australopithecus had a significant bipedal component to its locomotion; whether suspensory and climbing behavior were also important has remained unclear. Morphological features of the forelimb have been linked to locomotor differences among primates, but the interpretation of human fossils has remained problematic.</p><p>This dissertation examined the total morphological pattern of the forelimb, specifically the functional integration of the musculature and joint systems. This approach employed both geometric morphometrics and a biomechanical modeling approach to studying how and how well the forelimb morphology of living suspensory and quadrupedal primates, as well as humans and fossil hominins, accommodate climbing and suspensory locomotion. Data collected with a microscribe 3-D digitizer on the scapula, humerus, radius, and ulna of Australopithecus sediba, Australopithecus afarensis, and Homo erectus were compared to a sample of Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Hylobates lar, and Macaca fuscicularis.</p><p>The hominin upper limb is a rich mosaic of primitive and derived traits. The blade of Australopithecus sediba, although appearing most similar to extant orangutans, is in fact functionally most similar to chimpanzees. The overall morphology of the australopith elbow joint appears most similar to Pan, as does the elbow joint of Homo erectus, suggesting that the modern human configuration happened more recently than 1.5 million years ago. </p><p>Au. afarensis and Au. sediba share important similarities, but are clearly distinct species. While their overall elbow joint shape is strikingly similar, the articular surface is not identical. Au. afarensis is more similar in this respect to Pan and Homo, while Au. sediba is more similar to extant taxa that spend substantially more time engaging in vertical climbing and suspensory behavior.</p><p>The results from this study support previous interpretations that not all australopiths across time were employing the same locomotor repertoire. While this study does not present unambiguous conclusions regarding early hominin arboreal locomotion, this study suggests that the morphology of the upper limb is varied, and caution must be taken when interpreting single skeletal elements in the hominin fossil record.</p> / Dissertation

This research better resolves the environmental mosaic that is typically reconstructed for the A. robustus-bearing faunal assemblages of South Africa and evaluates whether A. robustus were habitat specialists or habitat generalists by testing whether they are associated with numerous, different reconstructed habitats, or if they can be associated with a single, more homogeneous habitat type. Determining the habitat preferences of A. robustus holds important implications for understanding the behavior of these hominins and, potentially, for understanding whether their ultimate extinction might have been climatically influenced, as fluctuations in the environments associated with the robust australopiths provide direct evidence about the responses of hominins to environmental change. To achieve this, a 2-dimensionsal morphometric tool was developed for accurately identifying the abundant bovid teeth that are found in direct association with the hominins using Elliptical Fourier Function Analysis. More accurate taxonomic identifications facilitate more precise estimates of the relative abundance of ecologically sensitive bovids, allowing for finer resolution when segmenting the various components of the reconstructed habitat mosaics. The fossil bovids abundances were compared across the assemblages over time in order to define the environmental mosaic in each assemblage and to determine if environmental heterogeneity existed across the assemblages. The relative abundances of the bovid fossil assemblages and A. robustus were compared to assess the habitat preferences of these hominins. A. robustus were not consistently associated with a particular habitat type suggesting that perhaps they were habitat generalists, capable of surviving in multiple types of habitats.

L’hallux de l’humain (plus couramment appelé gros orteil) est aujourd’hui aligné avec les autres orteils ce qui rend son opposition aux autres orteils impossible. Il a été proposé que la perte de l’opposabilité de l’hallux, chez les premiers hominines, aurait mené à une augmentation des coûts liés à la maternité, due à l’obligation de transporter activement les juvéniles lors de longs trajets (Tanner & Zihlman 1976 ; Wall-Sheffler 2007 ; Watson et al. 2008). Cela suggère que l’Australopithecus afarensis devait transporter activement son juvénile car il ne pouvait pas se maintenir par lui-même lors des transports. Mon étude propose de vérifier cette hypothèse en déterminant si un primate juvénile a besoin de son hallux pour s’accrocher au poil de sa mère. Les deux hypothèses de ce travail sont donc les suivantes : L’abduction de l’hallux est nécessaire à la préhension du poil d’un porteur (généralement la mère) par les jeunes macaques et l’abduction de l’hallux n’est pas nécessaire à la préhension du poil d’un porteur (généralement la mère) par les jeunes macaques lors des transports. L’observation de vidéos de dyades mère/enfant de macaques rhésus vivant en liberté à Cayo Santiago (Costa Rica) filmées sur une période de cinq mois, tend à supporter mon hypothèse. En effet, les résultats de mon étude montrent que les macaques rhésus sont capables de s’accrocher, et se maintenir, par eux-mêmes à leur mère durant les transports sans se servir de leur hallux. Il serait cependant nécessaire de compléter cette étude par des recherches supplémentaires pour inférer avec plus de confiance ce type de comportement à l’A. afarensis. / The human hallux (more commonly called big toe) is now aligned with the other toes, which makes its opposition to other toes impossible. It has been proposed that the loss of opposability of the hallux in early hominins would have led to increase the energetic costs related to maternity, due to the obligation to carry juveniles actively (Tanner & Zihlman 1976; Wall-Sheffler 2007, Watson et al. 2008). This implies that Australopithecus afarensis juveniles had to be actively transported instead of grasping their mother's hair. My study proposes to test whether a juvenile primate needs its hallux to cling to the hair of its mother. The two hypotheses of this work are as follows: The abduction of the hallux is essential for the grasping of the hair of a carrier (usually the mother) by the young macaques and the abduction of the hallux is not necessary for the grasp of the hair of a carrier (usually the mother) by young macaques during transport. Videos of mother/child dyads of rhesus macaques are used in this study to evaluate the use of the hallux in juveniles being carried. The macaques are from a free-range colony in Cayo Santiago, Costa Rica, and they were filmed over a 5-month period. Results tend to support my hypothesis. Indeed, rhesus macaques are able to cling and maintain themselves on their mother during transport without using their hallux. It would, however, be necessary to supplement this study with further research in order to infer this type of behavior in A. afarensis.