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Markus Bastir

Publications and source records attributed to Markus Bastir.

12 recordsLinked to original sources
PubMed2006

Paleobiology and comparative morphology of a late Neandertal sample from El Sidron, Asturias, Spain.

Fossil evidence from the Iberian Peninsula is essential for understanding Neandertal evolution and history. Since 2000, a new sample approximately 43,000 years old has been systematically recovered at the El Sidrón cave site (Asturias, Spain). Human remains almost exclusively compose the bone assemblage. All of the skeletal parts are preserved, and there is a moderate occurrence of Middle Paleolithic stone tools. A minimum number of eight individuals are represented, and ancient mtDNA has been extracted from dental and osteological remains. Paleobiology of the El Sidrón archaic humans fits the pattern found in other Neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications has been found on the human remains. Morphologically, the El Sidrón humans show a large number of Neandertal lineage-derived features even though certain traits place the sample at the limits of Neandertal variation. Integrating the El Sidrón human mandibles into the larger Neandertal sample reveals a north-south geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. The large El Sidrón sample therefore augments the European evolutionary lineage fossil record and supports ecogeographical variability across Neandertal populations.

Anatomy, Comparative↗
PubMed2006

Correlated variation between the lateral basicranium and the face: a geometric morphometric study in different human groups.

OBJECTIVES: The significance of the cranial base in the contribution of normal and pathologic facial patterns is uncertain. The aim of this study was to explore and compare patterns of morphological covariation between the face and the lateral basicranium (anterior and middle cranial fossae) with covariation patterns between the face and the midline cranial base. DESIGN: We employed 2D geometric morphometrics and partial least squares analysis to quantify and compare correlation coefficient between principal variation patterns between basicranial and facial structures in lateral radiographs from 143 humans from Japan (N=45), Europe (N=65) and Africa (N=34). RESULTS: In both comparisons basicranial patterns co-varied with dolichofacial and brachyfacial morphologies. The findings showed that the midline cranial base is not significantly correlated of common facial patterns (r=0.37, P=0.09). Instead, the lateral basicranium is significantly (P=0.000), and significantly higher (r=0.6) correlated with facial variation than is the midline cranial base. CONCLUSIONS: The lateral basicranium may be of higher morphogenetic relevance for influencing facial variation than previously thought. This influence may be of clinical importance for the generation of skeletal class II or class III malocclusions. Further research should expand on geometric morphometric analysis of ontogenetic and clinical 3D data in order to advance in the understanding of these complex developmental relationships.

Africa↗
PubMed2006

Craniofacial levels and the morphological maturation of the human skull.

It is well known that the human skull achieves adult size through a superior-inferior gradient of maturation. Because the basicranium matures in size before the face, it has been suggested that the form of the basicranium might have ontogenetic knock-on effects on that of the face. However, although sequential spatially organized maturation of size is well described in the cranium, the maturation of skull shape is not. Knowledge of the maturation of shape is important, nevertheless, because it is claimed that the early determination of the spatial configuration of basicranial components, where the facial skeleton attaches, is relevant in the spatio-temporal ontogenetic cascade from basicranium to face. This paper examines the ontogeny of various components of the human skull in 28 individuals from the longitudinal Denver Growth Study. Sixty-six landmarks and semilandmarks were digitized on 228 X-rays and analysed using geometric morphometric methods. Bootstrapped confidence intervals for centroid size support previous studies suggesting a supero-inferior gradient of growth maturation (size over time), while developmental maturation (shape over time) is more complex. A sequence of shape maturation is described, in which the earliest structure to mature in shape was the midline cranial base (7-8 years), followed by the lateral cranial floor (11-12), midline neurocranium (9-10) and facial and mandibular structures (15-16). The absolute ages of shape maturation of the latter three depended on the criterion of maturity used, which was not the case for the basicranial components. Additionally, ontogenetic dissociations were found between the maturation of size and shape of the midline cranial base and lateral floor, possibly underlining its role as structural 'interface' between brain and facial ontogeny. These findings imply potential for bidirectional developmental influences between the lateral cranial floor and the face until about 11-12 years. The findings are discussed with regard to their relevance for palaeoanthropology and especially the evolutionary and developmental bases of skull morphological variation.

Adolescent↗
PubMed2005

Neandertal evolutionary genetics: mitochondrial DNA data from the iberian peninsula.

Mitochondrial DNA (mtDNA) was retrieved for the first time from a Neandertal from the Iberian Peninsula, excavated from the El Sidrón Cave (Asturias, North of Spain), and dated to ca. 43,000 years ago. The sequence suggests that Iberian Neandertals were not genetically distinct from those of other regions. An estimate of effective population size indicates that the genetic history of the Neandertals was not shaped by an extreme population bottleneck associated with the glacial maximum of 130,000 years ago. A high level of polymorphism at sequence position 16258 reflects deeply rooted mtDNA lineages, with the time to the most recent common ancestor at ca. 250,000 years ago. This coincides with the full emergence of the "classical" Neandertal morphology and fits chronologically with a proposed speciation event of Homo neanderthalensis.

Animals↗
PubMed2005

Hierarchical nature of morphological integration and modularity in the human posterior face.

Morphological integration and modularity are important points of intersection between evolution and the development of organismal form. Identification and quantification of integration are also of increasing paleoanthropological interest. In this study, the "posterior face," i.e., the mandibular ramus and its integration with the associated midline and lateral basicranium, is analyzed in lateral radiographs of 144 adult humans from three different geographic regions. The null hypothesis of homogenously pervasive morphological integration among "posterior-face" components is tested with Procrustes geometric morphometrics, partial least squares, and singular warps analysis. The results reveal statistically significant differences in integration. Only loose integrative relationships are found between midline and lateral components of the basicranium, which may indicate the presence of at least two different basicranial modules. This modularity can be interpreted in terms of spatiotemporal dissociation in the development of those basicranial structures, and gives support to hypotheses of independent phylogenetic modifications at the lateral and midline basicranium in humans. In addition, morphological integration was statistically significantly stronger between the middle cranial fossa and the mandibular ramus than between the ramus and the midline cranial base. This finding confirms previous hypotheses of a "petroso-mandibular unit," which could be a developmental consequence of well-known phylogenetic modifications in coronal topology of the posterior face and base in hominoid evolution, related to middle cranial fossa expansion. This unit could be involved in later evolutionary tendencies in the hominid craniofacial system.

Adult↗
PubMed2004

Petrosal orientation and mandibular ramus breadth: evidence for an integrated petroso-mandibular developmental unit.

The absolute and relative breadths of the mandibular ramus (MRB) display substantial variation in modern humans, and are of analytical value in paleoanthropology. According to Enlow et al. ([1969] Am. J. Orthod. 56:6-23), the ramus is the growth counterpart of the middle cranial fossa (MCF) and the pharynx. Such counterpart principles state that variation in ramus breadth is a frequent function of the horizontal alignment of the MCF, and both structures tend to covary within and between populations. These authors also suggested that lateral parts of the basicranium have a particular importance in the positioning of facial components. In the present study, this hypothesis is tested, and relationships between midline and lateral basicranial elements and ramus breadth variation are explored. Two-dimensional landmarks taken from lateral radiographs of adult crania representative of three modern human populations (Europeans, West Africans, and Japanese) were analyzed by geometric morphometry. Our results are consistent with previous counterpart analyses. Furthermore, our findings highlight the significance of the orientation of the petrous temporal to modern human mandibular ramus variation. Variation in the orientation of the petrosal bone appears to alter the spatial position of the mandible and influences MRB. Developmental integration of a petroso-mandibular unit may have important paleoanthropological implications.

Adult↗
PubMed2004

Geometric morphometric analysis of allometric variation in the mandibular morphology of the hominids of Atapuerca, Sima de los Huesos site.

Allometry is an important factor of morphological integration that contributes to the organization of the phenotype and its variation. Variation in the allometric shape of the mandible is particularly important in hominid evolution because the mandible carries important taxonomic traits. Some of these traits are known to covary with size, particularly the retromolar space, symphyseal curvature, and position of the mental foramen. The mandible is a well studied system in the context of the evolutionary development of complex morphological structures because it is composed of different developmental units that are integrated within a single bone. In the present study, we investigated the allometric variation of two important developmental units that are separated by the inferior nerve (a branch of CN V3). We tested the null hypothesis that there would be no difference in allometric variation between the two components. Procrustes-based geometric morphometrics of 20 two-dimensional (2D) landmarks were analyzed by multivariate regressions of shape on size in samples from 121 humans, 48 chimpanzees, and 50 gorillas (all recent specimens), eight fossil hominids from Atapuerca, Sima de los Huesos (AT-SH), and 17 Neandertals. The findings show that in all of the examined species, there was significantly greater allometric variation in the supra-nerve unit than in the infra-nerve unit. The formation of the retromolar space exhibited an allometric relationship with the supra-nerve unit in all of the species studied. The formation of the chin-like morphology is an "apodynamic" feature of the infra-nerve unit in the AT-SH hominids. The results of this study support the hypothesis that allometry contributes to the organization of variation in complex morphological structures.

Animals↗
PubMed2004

Facial heights: evolutionary relevance of postnatal ontogeny for facial orientation and skull morphology in humans and chimpanzees.

Facial heights, i.e. the vertical distances between the superior and inferior limits of facial compartments, contribute to the orientation of the viscerocranium in the primate skull. In humans, vertical facial variation is among the main sources of diversity and frequently associated with an integrated suite of other cranio-mandibular traits. Facial heights and kyphosis are also important factors in interspecific variation and models of hominoid evolution. The ontogenetic determination of adult facial orientation and its relation to phylogenetic variation are unclear, but crucial in all previously mentioned respects. We addressed these issues in a sample of 175 humans and chimpanzees with Procrustes based geometric morphometrics, testing hypotheses of interspecific similarity in postnatal ontogenetic trajectories, early versus later ontogenetic facial pattern determination, and a developmental model of morphological integration. We analyzed the contribution of postnatal morphogenesis to adult vertical facial variation by partitioning morphological variation into a portion of pure growth allometry and a non-allometric fraction. A statistically significant difference of growth-allometries revealed that in both species growth established the adult skull proportions by vertical facial expansion, but while in chimpanzees the complete viscerocranium showed reorientation, in humans only the lower face was modified. In both species the results support a hypothesis of early facial pattern determination. A coincident emergence of morphological traits favors a hypothesis of developmental integration of the face, excluding traits of the basi- and neurocranium. Interspecific differences in integration may have implications for evolutionary studies. The present findings indicate that growth establishes the adult skull proportions and integrates principal facial orientation patterns, already there in early postnatal ontogeny.

Adult↗
PubMed2004

Comparative ontogeny in humans and chimpanzees: similarities, differences and paradoxes in postnatal growth and development of the skull.

The hypothesis of retarded development is a classic and controversial issue in human evolution. It depends directly on the understanding of ontogenetic trajectories and their basic constituents: timing, rate and associated patterns of maturation. In the present study, we applied geometric morphometrics to investigate postnatal ontogeny in human and chimpanzee skulls (N = 302). We evaluated postnatal ontogenetic rates, based on comparisons of properties of size and shape in adults. At different dental ages the percentage of the adult mean size (growth) and adult mean shape (development) was used to quantify patterns of maturation. We found significantly higher levels of ontogenetic maturity in humans than chimpanzees during pre-M1 and M1 eruption. However, during this ontogenetic period the human increments were lower than those of chimpanzees suggesting lower rates. During and after M2-eruption species did not differ in their ontogenetic trajectories. The results indicate that higher prenatal and lower peri- and postnatal maturation rates characterize human ontogeny when compared with chimpanzees. If mandibular ontogeny is considered alone, a paradox was found. Whereas growth maturation proceeded in an expected trajectory continuously approximating 100% adult mean size, developmental maturity was different. After M1-eruption in both species the morphological distance, which had increased before, became reduced again, and reached adult mean shape in a second developmental peak. Such a tendency was found in humans and chimpanzees. This indicates that both size and shape maturation must be considered to understand the complexity of postnatal mandibular ontogeny.

Adolescent↗
PubMed2002

Thin-plate spline analysis of allometry and sexual dimorphism in the human craniofacial complex.

The relationship between allometry and sexual dimorphism in the human craniofacial complex was analyzed using geometric morphometric methods. Thin-plate splines (TPS) analysis has been applied to investigate the lateral profile of complete adult skulls of known sex. Twenty-nine three-dimensional (3D) craniofacial and mandibular landmark coordinates were recorded from a sample of 52 adult females and 52 adult males of known age and sex. No difference in the influence of size on shape was detected between sexes. Both size and sex had significant influences on shape. As expected, the influence of centroid size on shape (allometry) revealed a shift in the proportions of the neurocranium and the viscerocranium, with a marked allometric variation of the lower face. Adjusted for centroid size, males presented a relatively larger size of the nasopharyngeal space than females. A mean-male TPS transformation revealed a larger piriform aperture, achieved by an increase of the angulation of the nasal bones and a downward rotation of the anterior nasal floor. Male pharynx expansion was also reflected by larger choanae and a more posteriorly inclined basilar part of the occipital clivus. Male muscle attachment sites appeared more pronounced. In contrast, the mean-female TPS transformation was characterized by a relatively small nasal aperture. The occipital clivus inclined anteriorly, and muscle insertion areas became smoothed. Besides these variations, both maxillary and mandibular alveolar regions became prognathic. The sex-specific TPS deformation patterns are hypothesized to be associated with sexual differences in body composition and energetic requirements.

Adult↗
PubMed2002

Sexual dimorphism in the Atapuerca-SH hominids: the evidence from the mandibles.

The pattern of sexual dimorphism in 15 mandibles from the Atapuerca-SH Middle Pleistocene site, attributed to Homo heidelbergensis, is explored. Two modern human samples of known sex are used as a baseline for establishing sexing criteria. The mandible was divided for analysis into seven study regions and differential expression of sexual dimorphism in these regions is analysed. A total of 40 continuous and 32 discrete variables were scored on the mandibles. The means method given in Regh & Leigh (Am. J. phys. Anthrop.110, 95-104, 1999) was followed for evaluating the potential of correct sex attribution for each variable. On average, the mandibles from the Atapuerca-SH site present a degree of sexual dimorphism about eight points higher than in H. sapiens samples. However, mandibular anatomy of the European Middle Pleistocene hominid records sexual dimorphism differentially. Different areas of the Atapuerca-SH mandibles exhibit quite distinct degrees of sexual dimorphism. For instance, variables of the alveolar arcade present very low or practically no sexual dimorphism. Variables related to overall size of the mandible and symphysis region present a medium degree of sex differences. Finally, ramus height, and gonion and coronoid process present a high degree of sexual dimorphism (indexes of sexual dimorphism are all above 130%). Whether this marked sexual dimorphism in specific anatomical systems affects sexual differences in body size is not completely clear and further studies are needed. Sexual differences detected in the mandible of modern humans have at least two components: differences related to musculo-skeletal development and differences related to a different growth trajectory in males and females (relative development of some of the basal border features). The Atapuerca-SH mandibles display little variation in the basal border, however. The limited variation of this mandibular region may indicate that the pattern of sexual variation in H. heidelbergensis is different enough to that of H. sapiens to caution against simple extrapolation of criteria from one pattern to the other.

Animals↗