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Research on the evolution and adaptive significance of primate craniofacial morphologies has focused on adult, fully developed individuals. Here, we investigate the possible relationship between the local stress environment arising from masticatory loadings and the emergence of the supraorbital torus in the developing face of the crab-eating macaque Macaca fascicularis. By using finite element analysis (FEA), we are able to evaluate the hypothesis that strain energy density (SED) magnitudes are high in subadult individuals with resulting bone growth in the supraorbital torus. We developed three micro-CT-based FEA models of M. fascicularis skulls ranging in dental age from deciduous to permanent dentitions and validated them against published experimental data. Applied masticatory muscle forces were estimated from physiological cross-sectional areas of macaque cadaveric specimens. The models were sequentially constrained at each working side tooth to simulate the variation of the bite point applied during masticatory function. custom FEA software was used to solve the voxel-based models and SED and principal strains were computed. A physiological superposition SED map throughout the face was created by allocating to each element the maximum SED value from each of the load cases. SED values were found to be low in the supraorbital torus region throughout ontogeny, while they were consistently high in the zygomatic arch and infraorbital region. Thus, if the supraorbital torus arises to resist masticatory loads, it is either already adapted in each of our subadult models so that we do not observe high SED or a lower site-specific bone deposition threshold must apply. [ABSTRACT FROM AUTHOR]

Humans alone among primates lack a superficial head of the temporalis muscle, although a complete superficial muscle is present in 1% of humans and an incomplete one in 8%. Yet the temporal fascia of normal humans contains all the fascial sheets associated with that head even though it is absent. The implication is that humans have lost the superficial temporal muscle, that this is evident from the retention of the fascial sheets, and that the muscular variations represent situations where the muscle has persisted to some degree. Molecular factors in the head domain that are responsible for the development of the muscles of mastication (myosin heavy chain 16) are likewise different in humans than in all non-human species and seem to be responsible for the reduction of those muscles in humans. Could the loss of the superficial portion of the temporalis muscle be a component of this reduction? Could the uncommon muscular variations result from some slight persistence of the prior molecular situation? Could the persistence of the fascial sheets, even when the muscle is absent, be because the molecular factors responsible for connective tissues are not the same as those responsible for muscles? How much of all this can be visualised in the fossil record? Skeletal dimensions of the temporal fossa, partly related to the temporal muscle size, imply that it may be possible to determine in which fossils temporal muscle reduction has occurred. Likewise, surface features of the bone in modern humans without a superficial muscular component but with a strong complex fibrous element suggest that it might be possible to determine, in any fossil in which the surface preservation is good enough, how far back this situation may have persisted. It is already known that myosin heavy chain molecular dating suggests that the muscle reduction may have occurred about 2.4 million years ago., (Copyright 2008 S. Karger AG, Basel.)

Many forelimb muscles (e.g. coracobrachialis, rhomboids, serratus sheet) are much less complex and much smaller in humans than in other primates. Yet human muscular variations and persistent fascial sheets indicate that increased size and complexity were once the norm. These muscular reductions are associated with equivalent skeletal gracilisation. Is it possible that molecular phenomena, not unlike those producing reduction of the jaw muscles and associated with gracilisation of the skull in species with reduced need for powerful mastication, may also have reduced forelimb muscles with gracilisation of its skeleton in species no longer using a forelimb for powerful locomotion? Could such molecular and skeletal changes be dated (as for the masticatory muscles) thus giving the time of origination of prehuman forelimb reduction and true bipedalism?, (Copyright 2008 S. Karger AG, Basel.)

Much of our understanding of population variation in southern Africa is derived from traditional morphometric research. In the search for new perspectives, this paper reports on new geometric morphometric data examining cranial variation in 12 modern human populations from southern Africa. In total, 298 male Bantu-speaking individuals were studied. In addition, a small Khoisan (Khoikhoi and San) series was also examined. The purpose of this study was to investigate Khoisan-Bantu morphological similarities and differences, and to examine variation within both the Bantu-speaking and Khoisan populations. The three-dimensional coordinates of 96 landmarks were analyzed, using the shape-analysis software morphologika. Interpopulation variation was examined by calculating Procrustes distances between groups; a cluster analysis was then used to summarize phenetic relationships. A principal components analysis explored the relationships between populations; shape differences were visualized and explored using three-dimensional rendered models, and further interpreted using thin-plate splines. Morphological differences are present within and between the crania of Bantu-speaking and Khoisan individuals. The Khoisan demonstrate features (e.g., a pentagonoid vault, more rounded forehead contour, and a small and less prognathic face) that clearly distinguish them from Bantu-speaking populations. Although southern African Bantu-speaking populations are clearly closely related, they show population-specific features (e.g., the crania of more southerly populations (Xhosa, Southern Sotho, and Zulu) are characteristically more brachycephalic and less prognathic). This study suggests that differential admixture with adjacent Khoisan peoples has contributed to diversity within southern African Bantu-speaking populations.

A suite of measurements was collected from the talus, calcaneus, navicular, and cuboid of humans from Southern China, Victorian Britain, Roman Britain, and Zulu tribes people from the Republic of South Africa. Univariate and multivariate statistical analyses of dimensions of individual foot bones revealed subtle but distinct patterns of morphological discrimination on the basis of sex and size on the one hand, and geographical relationships on the other. These differences are largely expressed in the first three canonical variates of the multivariate analyses: the first axis expresses both sex and size differences, and the second and third, geographical group differences. Confirmation of morphological patterns obtained from individual multivariate analyses was provided by an integrated analysis of the four tarsal elements together. However, the integrated analysis also gave larger separations with discriminations along different axes. Thus the three geographical groups (Zulus, Southern Chinese, and the two British groups together) were separated by first and third variates. The discrimination of sex and size differences was found in the second axis, mirroring what was found in the first axes of the individual studies. This axis reversal implies that in examining all bones together, there is enough redundant information about sex and size in each individual bone that they are relegated to a second axis. It likewise implies that the data referring to geographic discriminations provided by each individual bone are not redundant; they sum in the integrated analysis, and therefore contribute to the overall analysis to a greater extent, with increased clarity., (Copyright 2002 Wiley-Liss, Inc.)

The sizes of mammalian brain components seem to be mostly related to the sizes of the whole brain (and body), suggesting a one-dimensional scale of encephalization. Previous multivariate study of such data concludes that evolutionary selection for enlargement of any one brain part is constrained to selection for a concerted enlargement of the whole brain. However, interactions between structurally related pairs of brain parts confirm reports of differential change in brain nuclei, and imply mosaic rather than concerted evolution. Here we analyse a large number of variables simultaneously using multi-dimensional methods. We show that the relative proportions of different systems of functionally integrated brain structures vary independently between different mammalian orders, demonstrating separate evolutionary radiations in mammalian brain organization. Within each major order we identify clusters of unrelated species that occupy similar behavioural niches and have convergently evolved similar brain proportions. We conclude that within orders, mosaic brain organization is caused by selective adaptation, whereas between orders it suggests an interplay between selection and constraints.

The changes that occur in the normal human incus with age have been investigated. Evidence for age-related changes in this ossicle, especially in the region of the long process, has been accumulating over the last 30-40 years and yet they have neither been confirmed quantitatively nor explained satisfactorily. In this study the results of a morphometric study of the long processes of a series of normal incudes are presented. These demonstrate that the lenticular and long processes undergo progressive symmetric resorption with advancing age. We consider these findings in the light of previous considerations of incudal remodelling and propose that these remodelling changes may reflect a normal adaptive response to the biomechanical milieu of the human middle ear.

The combined use of architectural and stress technologies in osteological studies is starting to provide the basic biomechanical underpinnings to both evolutionary and applied medical investigations of bone. The architectural investigations, though tested using invasive methods, are aimed at non-invasive ways of obtaining information from radiographs of bones, fossils and people. They include optical (Fourier) data analysis (ODA) and computational Fourier transformations (FFT). The stress studies, though initially involving older techniques such as photoelastic stress analysis, now employ finite element analysis (FEA) and, most recently, fast Lagrangian analysis of continua (FLAC). Taken together, these methods are capable of providing more detailed knowledge of bone form and function that is important (a) in revealing functional adaptation in evolutionary studies of fossils and (b) for making early diagnosis and understanding pathological fractures in the late stages of osteoporosis.

Previous observations on twelve fossil foot bones (Olduvai 8: Day and Napier, '64) together with multivariate morphometric studies of one of them, the talus (Day and Wood, '68) suggested human-like bipedality for this foot. Subsequent studies showed the conclusions on the talus to be wrong: The fossil talus, as defined by eight measures, does not resemble that of man but is reminiscent of those of creatures known (extant--orangutans) or believed (extinct--some fossil apes and monkeys) to be arboreal in habitus (Oxnard '72; Lisowski, et al., '74, '76). A reassessment of the entire Olduvai 8 foot is therefore necessary to answer the problem posed by a foot that has a non-human talus with, apparently, a human arched pattern of the remaining tarsal and metatarsal bones. The dry bones of a series of feet of extant hominoids have been rearticulated and are found to be close to the actual relationships presented by dissected specimens in which ligaments, articular cartilages and soft tissues are present. Similar rearticulation applied to casts of the individual Olduvai foot bones produces a structure that is not arched in the same manner as the human foot; it displays features that ally it more closely with the feet of various apes. Sections of casts of the already rearticulated Olduvai foot (from both the Wenner Gren Foundation and the Kenya National Museums) show that the human-like appearance of the original rearticulation is due to a series of incorrect osteological alignments. Although casts do not permit study of surface features, the dimensions of the casts are sufficiently accurate to permit rearticulation in this manner. It is thus clear, a) that the Olduvai foot is not adated for bipedality in the manner of man, and b) that it displays features in which it resembles the feet of arboreal creatures. Such anatomical characters as relate to bipedality in the fossil suggest usage as in an arboreal species that also walks bipedally with flattened arches (like a chimpanzee or gorilla) rather than with the high arches of man.

Data obtained from ramapithecine specimens found in Asia, Africa and Europe have suggested the existence of two major subgroups, Ramapithecus and Sivapithecus, with Ramapithecus having pre-human status. Recently, however, it has been proposed that the fossils all belong to a single group, Sivapithecus, which is more closely related to the apes, in particular the orang-utan. Here we analyse data from a series of similar fossils which have been found in late Miocene coalfields in Lufeng, Yunnan Province, China. These include a number of almost complete jaws and five partial skulls which are more complete than any others so far known. A statistical analysis of the overall dimensions of the large number of teeth included in these finds shows that the differences between the groups previously assigned to Ramapithecus and Sivapithecus are greater than those found between the sexes in the most sexually dimorphic of the living great apes. Within the groups the distribution is bimodal and we suggest each group contains sex subgroups.