New directions in craniofacial morphogenesis

The vertebrate head is an extremely complicated structure: development of the head requires tissue-tissue interactions between derivates of all the germ layers and coordinated morphogenetic movements in three dimensions. In this review, we highlight a number of recent embryological studies, using chicken, frog, zebrafish and mouse, which have identified crucial signaling centers in the embryonic face. These studies demonstrate how small variations in growth factor signaling can lead to a diversity of phenotypic outcomes. We also discuss novel genetic studies, in human, mouse and zebrafish, which describe cell biological mechanisms fundamental to the growth and morphogenesis of the craniofacial skeleton. Together, these findings underscore the complex interactions leading to species-specific morphology. These and future studies will improve our understanding of the genetic and environmental influences underlying human craniofacial anomalies.     

Transitions: Homo erectus and the Acheulian: the Ethiopian sites of Gadeb and the Middle Awash

Significant differences in activity-site patterning and artifact composition at Middle Pleistocene localities in Ethiopia's high plains and Afar Rift are indications of both single-episode, small-site residues from small groups and multi-purpose, multiple occupation sites from which larger, temporary groupings might be inferred. Reconstructions of palaeo-environments and geography show that large assemblages relate to relatively stable topography, such as stream channels or lake margins, while small assemblages are more common in deltaic situations of rapid sedimentation and burial in the Rift that preclude possibility of reoccupation. A model for Acheulian socio-economic behaviour within the drier African savanna, based (in part) on chimpanzee behaviour in open savanna habitats, is proposed. This takes the form of organization into relatively extensive territories, each with several more closed-vegetation core areas, of limited extent close to permanent water, surrounded by more extensive areas of drier, open savanna, regularly exploited and patrolled by small groups. Movement from one core area to another was rapid and made together as a group, to minimize danger from large predators and competition from other hominid groups.     

NanoDam identifies Homeobrain (ARX) and Scarecrow (NKX2.1) as conserved temporal factors in the Drosophila central brain and visual system

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Adaptable P body physical states differentially regulate bicoid mRNA storage during early Drosophila development

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Relationships between growth at the sutures of the rabbit calvarium

The present study was designed to elucidate the relationships between growth increments at the cranial vault sutures in rabbits. Thirteen male New Zealand white rabbits were followed regularly from age 31 to 142 days using a roentgen stereophotogrammetric system. Spherical tantalum markers were implanted into the nasal, frontal, and parietal bones, and implant stability was checked at each stereo examination. Problems with instability were encountered only in the nasal bones. Registered growth rates conformed to our previous investigations. High correlations were observed between the following areas; the coronal suture to the frontonasal suture, the first principal component of the neurocranial suture group to the frontonasal suture, and the principal component of the craniofacial suture group to the coronal suture. Remaining relationships demonstrated dispersion to various extents. The findings indicate that there seems to exist a basic mutual dependence between neural and facial skeletal growth, as well as complex covariations between the various sutures of the rabbit calvarium.     

Cranial variation in European populations: a spatial autocorrelation study at three time periods

This study reports on spatial variation of 10 cranial variables in European populations at 3 time periods. Means for these variables, based on 137, 108, and 183 samples from the Early Medieval, Late Medieval, and Recent periods, were subjected to one-dimensional and directional spatial autocorrelation analyses. Significant spatial structure was found for most variables. It becomes more pronounced as time progresses. The spatial patterns are not strongly clinal. Correlograms based on distances computed from all variables are monotonic only to 900, 1,650, and 1,350 km for the three periods. Regional patterns are seen for most variables and become more structured and significant with time. There is little similarity among the correlograms of the variables at any one period and virtually none among periods. Inferences about spatial structure of these populations, based on spatial autocorrelation analysis, suggest a pattern dominated by migration, followed by expansion and admixture rather than selection or chance fluctuations. The patterns of morphometric change seem to reflect the patterns of linguistic change in these areas.     

A cladistic analysis of interspecific relationships ofSaguinus

The dental and cranial morphologies of all species ofSaguinus, S. oedipus, S. geoffroyi, S. leucopus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas are examined. The following hypotheses are developed by cladistic methodology, using only synapomorphic characters to assess the interspecific relationships ofSaguinus.Saguinus are divided into two main groups; one consists ofS. oedipus, S. geoffroyi, andS. leucopus, and the other includesS. inustus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas. In the former group,S. oedipus is more closely related toS. geoffroyi than either is toS. leucopus. In the latter group,S. labiatus, S. mystax, andS. imperator are classified into one group, andS. bicolor andS. midas form one monophyletic group.     

Climate and the evolution of brachycephalization

Significant associations of cranial shape for 82 ethnic groups and seven climate variables are described. Variation among current populations is partially attributed to cold adaptation throughout the Pleistocene. Application of data files tabulated by the authors is described for a number of problems. Temporal distribution of 115 specimens indicates a geometric trend (CI = 76.7-1.96 log time X 10(3) ). Cranial indices are summarized within alternative taxonomic models and between climatic ecotypes. Evidence supports the hypothesis of cold adaptation among "Classic" Neandertals. Limitations of the thermodynamic model are discussed. It is probable that a decrease of the cranial index occurs from the Middle to Upper Paleolithic. During the Holocene, the index increases under all climatic conditions.     

Craniometrical variations among eastern Brazilian marmosets and their systematic relationships

The craniometrical variations among marmosets on the eastern coast of Brazil or theCallithrix jacchus group (C. jacchus, C. penicillata, C. kuhli, C. geoffroyi, C. flaviceps, andC. aurita) were analyzed to test various hypotheses for the arrangement of the species and phylogenetic relationships ofC. kuhli andC. flaviceps. Q-mode correlation coefficients and principal component analysis were employed to extract important shape factors from the craniometrical data. On this basis, the shape distances among the eastern Brazilian marmosets were found to be larger than those between the marmosets which are recognized as distinct species. This evidence supports the hypothesis that the members of theC. jacchus group are distinct species.C. kuhli shows the strongest resemblance toC. geoffroyi within theC. jacchus group.C. flaviceps is the most similar toC. aurita in its cranial shape. These findings indicate thatC. kuhli is most closely related toC. geoffroyi, whileC. flaviceps is toC. aurita.