Comparison of craniofacial features of major human groups

Disparate and parallel craniofacial climatic adaptations in native populations of Asia, North America, and South America

Understanding the impact that climate had in shaping cranial variation is critical for inferring the evolutionary mechanisms that played a role in human diversification. Here, we provide a comprehensive study aiming to analyze the association between climate and cranial variation of high latitude populations living in temperate to cold environments of Asia, North America, and South America. For this, we compiled a large morphometric dataset (N = 2633), which was combined with climatic and genomic data. We tested the influence of climate on the facial skeleton, nasal protrusion, and cranial vault and through multiple statistical tests at two geographical scales: intracontinental and intercontinental. We show that populations living in cold areas share a morphological pattern characterized by an increase in nasal height, facial and orbital heights and widths, a decrease in facial protrusion, and larger, longer, and lower cranial vaults. There are also distinctive features; populations from north Asia present the tallest noses, largest faces, and cranial vaults of the whole sample. Nasal breadth dimensions show small values in Asians, large values in South Americans, and non-significant changes in arctic North America. The morphological pattern in populations living at high latitude may be the result of parallel adaptation, as supported by physiological, morphometric, ecological, and genetic explanations, while the differences in magnitude and phenotypic expression could be due to the diverse population histories, severity of climate, and cultural strategies. Overall, our study shows that climate is a relevant factor shaping modern human morphology and it should be considered when studying modern human evolution and diversification.

Inferring human neutral genetic variation from craniodental phenotypes

There is a growing consensus that global patterns of modern human cranial and dental variation are shaped largely by neutral evolutionary processes, suggesting that craniodental features can be used as reliable proxies for inferring population structure and history in bioarchaeological, forensic, and paleoanthropological contexts. However, there is disagreement on whether certain types of data preserve a neutral signature to a greater degree than others. Here, we address this unresolved question and systematically test the relative neutrality of four standard metric and nonmetric craniodental data types employing an extensive computational genotype-phenotype comparison across modern populations from around the world. Our computation draws on the largest existing data sets currently available, while accounting for geographically structured environmental variation, population sampling uncertainty, disparate numbers of phenotypic variables, and stochastic variation inherent to a neutral model of evolution. Our results reveal that the four data types differentially capture neutral genomic variation, with highest signals preserved in dental nonmetric and cranial metric data, followed by cranial nonmetric and dental metric data. Importantly, we demonstrate that combining all four data types together maximizes the neutral genetic signal compared with using them separately, even with a limited number of phenotypic variables. We hypothesize that this reflects a lower level of genetic integration through pleiotropy between, compared to within, the four data types, effectively forming four different modules associated with relatively independent sets of loci. Therefore, we recommend that future craniodental investigations adopt holistic combined data approaches, allowing for more robust inferences about underlying neutral genetic variation.

Ancestry-based variation in maxillary sinus anatomy: Implications for health disparities in sinonasal disease

Paranasal sinus drainage is mediated by mucociliary transport and gravity. However, human orthograde posture, along with the superior positioning of the maxillary sinus (MS) ostium, increases reliance on the mucociliary system. Previous research has thus suggested that differences in MS size and shape may impede mucociliary clearance, potentially contributing to disparities in sinusitis susceptibility. To further investigate this hypothesis, this study collected 29 three-dimensional (3D) coordinate landmarks and seven linear measurements of MS morphology from 167 computed tomography (CT) scans of crania of European, East Asian, or Equatorial African ancestry. MANOVA results reveal the Asian-derived individuals are characterized by both a significantly taller MS (F = 14.15, p <  0.0001) and a significantly greater distance from the MS floor to the ostium (F = 17.22, p <  0.0001) compared to those of European and African ancestry. A canonical variate (CV) analysis conducted on 3D landmark data provides corroborative results, distinguishing Asian-derived individuals predominantly on the basis of a relatively lower MS floor. As a greater distance between the MS floor and ostium may impede mucociliary clearance, our results suggest MS anatomy may be a more prominent factor in chronic sinusitis among individuals of Asian ancestry compared to those of European and African ancestries. This provides tentative evidence of an anatomical etiology for chronic sinusitis even in the absence of anatomical variants/abnormalities (e.g., nasal polyps, concha bullosa, Haller's cells, and Agger nasi cells). Further research into the relationship between MS anatomy and sinusitis, in addition to socioeconomic inequalities of healthcare, is warranted to continue evaluating possible contributions to health disparities.

Intraspecific variability in human maxillary bone modeling patterns during ontogeny

OBJECTIVES

This study compares the ontogenetic bone modeling patterns of the maxilla to the related morphological changes in three human populations to better understand how morphological variability within a species is established during ontogeny at both micro- and macroscopic levels.

MATERIALS AND METHODS

The maxillary bones of an ontogenetic sample of 145 subadult and adult individuals from Greenland (Inuit), Western Europe (France, Germany, and Portugal), and South Africa (Khoekhoe and San) were analyzed. Bone formation and resorption were quantified using histological methods to visualize the bone modeling patterns. In parallel, semilandmark geometric morphometric techniques were used on 3D models of the same individuals to capture the morphological changes. Multivariate statistics were applied and shape differences between age groups were visualized through heat maps.

RESULTS

The three populations show differences in the degree of shape change acquired during ontogeny, leading to divergences in the developmental trajectories. Only subtle population differences in the bone modeling patterns were found, which were maintained throughout ontogeny. Bone resorption in adults mirrors the pattern found in subadults, but is expressed at lower intensities.

DISCUSSION

Our data demonstrate that maxillary morphological differences observed in three geographically distinct human populations are also reflected at the microscopic scale. However, we suggest that these differences are mostly driven by changes in rates and timings of the cellular activities, as only slight discrepancies in the location of bone resorption could be observed. The shared general bone modeling pattern is likely characteristic of all Homo sapiens, and can be observed throughout ontogeny.

Zygomaticomaxillary Morphology and Maxillary Sinus Form and Function: How Spatial Constraints Influence Pneumatization Patterns among Modern Humans

Previous research has suggested that the maxillary sinuses may act as "zones of accommodation" for the nasal region, minimizing the impact of climatic-related changes in nasal cavity breadth on surrounding skeletal structures. However, a recent study among modern human crania has identified that, in addition to nasal cavity breadth, sinus morphology also tracks lateral facial form, especially anterior-posterior positioning of the zygomatics. Here, we expand upon this previous study to further investigate these covariation patterns by employing three samples with distinct combinations of nasal and zygomatic morphologies: Northern Asians (n = 28); sub-Saharan Africans (n = 30); and Europeans (n = 29). For each cranium, 30 landmarks were digitized from CT-rendered models and subsequently assigned to either a midfacial or maxillary sinus "block." Two block partial least squares (2B-PLS) analyses indicate that sinus morphology primarily reflects superior-inferior dimensions of the midface, rather than either nasal cavity breadth or zygomatic position. Specifically, individuals with relatively tall midfacial skeletons exhibit more inferiorly and laterally expanded sinuses compared to those with shorter midfaces. Further, separate across-group and within-group 2B-PLS analyses indicate that regional differences between samples primarily build upon a common pattern of midfacial and sinus covariation already present within each regional group. Allometry, while present, only explains a small portion of the midface-sinus covariation pattern. We conclude that previous findings of larger maxillary sinuses among cold-adapted individuals are not predominantly due to possession of relatively narrow nasal cavities, but to greater maxillary and zygomatic heights. Implications for sinus function and midfacial ontogeny are discussed. Anat Rec, 300:209-225, 2017. © 2016 Wiley Periodicals, Inc.

Fueguian crania and the circum-Pacific rim variation

OBJECTIVES

The Fueguians are descendants of the first settlers of America, a 'relict' isolated geographically for 10,000 years. We compared their cranial variation with other Americans, and samples from Asia and Australia to know whether the modern extinct Fueguians can be considered Paleoamericans or not.

MATERIALS AND METHODS

Herein we study 176 Fuego-Patagonian skulls, the largest cranial sample to be studied, refined and well documented, using CVA, and the D² of Mahalanobis. The affinities between populations and sexual dimorphism were jointly studied.

RESULTS

Terrestrial hunters (Selknam) have a different cranial morphology from sea canoeists (Yamana, Alakaluf) particularly with regard to cranial size and robustness. In the American context, there are extreme differences between the canoeists of Santa Cruz (California) and the Eskimos and canoeists of Fuego-Patagonia in terms of cranial size, prognathism and development of the frontal region. Fueguian canoeists are cranially closer to the Californian ones than to their Fueguian neighbors, the Selknam. Our results favor the hypothesis of two different flows for the origin of the first populators of Tierra del Fuego.

DISCUSSION

We concluded that the robusticity of some Fuegians (Selknam) might be the result of an allometric pattern of overall robusticity expression well as a result of epigenetics or differential reproduction (Larsen, 2015:264) or hypothetical endocrine changes (Bernal et al. in Am J Hum Biol 2006;18:748-765). When compared with three Australian-Melanesian series, the group comprising Amerindians, Ainu, and Eskimos clusters together as they are all extremely different from the former in terms of both cranial size and shape.

Morphological Covariation between the Maxillary Sinus and Midfacial Skeleton among Sub-Saharan and Circumpolar Modern Humans

OBJECTIVES

Maxillary sinus volume tracks ecogeographic differences in nasal form and may serve as a zone of accommodation for ontogenetic and evolutionary changes in nasal cavity breadth. However, little is known regarding how sinus volume is distributed within the midface. This study investigates morphological covariation between midfacial and sinus shape to better understand structural and functional relationships between the sinus, midface, and nasal cavity.

METHODS

Cranial and sinus models were rendered from CT scans of modern human samples from two disparate climates: sub-Saharan (South Africans [n = 15], West Africans [n = 17]), and circumpolar (Siberian Buriats [n = 18], Alaskan Inuit [n = 20]). Twenty-five 3D coordinate landmarks were placed on the models and subjected to generalized Procrustes analysis. Two-block partial least squares (2B-PLS) analysis was employed to identify patterns of covariation.

RESULTS

The 2B-PLS analysis indicates PLS1 (58.6% total covariation) relates to height and breadth relationships between the midface, nasal cavity, and maxillary sinus. Significant regional differences in PLS1 scores are evident: circumpolar samples possess taller/narrower noses with taller/wider sinuses compared to sub-Saharan samples. Importantly, PLS1 indicates that sinus breadth is not exclusively related to nasal cavity breadth; variation in lateral sinus expansion toward the zygoma represents an important contributing factor. PLS2 (16%) relates to supero-inferior positioning of the sinus within the midface. Allometric trends, while statistically significant, explain only a small portion of these covariation patterns.

CONCLUSIONS

These results suggest that the maxillary sinus serves as a zone of accommodation at the confluence of multiple facial components, potentially minimizing effects of morphological alterations to certain components on adjacent structures. Am J Phys Anthropol 160:483-497, 2016. © 2016 Wiley Periodicals, Inc.

Ontogenetic and static allometry in the human face: contrasting Khoisan and Inuit

OBJECTIVES

Regional differences in modern human facial features are present at birth, and ontogenetic allometry contributes to variation in adults. However, details regarding differential rates of growth and timing among regional groups are lacking. We explore ontogenetic and static allometry in a cross-sectional sample spanning Africa, Europe and North America, and evaluate tempo and mode in two regional groups with very different adult facial morphology, the Khoisan and Inuit.

MATERIALS AND METHODS

Semilandmark geometric morphometric methods, multivariate statistics and growth simulations were used to quantify and compare patterns of facial growth and development.

RESULTS

Regional-specific facial morphology develops early in ontogeny. The Inuit has the most distinct morphology and exhibits heterochronic differences in development compared to other regional groups. Allometric patterns differ during early postnatal development, when significant increases in size are coupled with large amounts of shape changes. All regional groups share a common adult static allometric trajectory, which can be attributed to sexual dimorphism, and the corresponding allometric shape changes resemble developmental patterns during later ontogeny.

DISCUSSION

The amount and pattern of growth and development may not be shared between regional groups, indicating that a certain degree of flexibility is allowed for in order to achieve adult size. In early postnatal development the face is less constrained compared to other parts of the cranium allowing for greater evolvability. The early development of region-specific facial features combined with heterochronic differences in timing or rate of growth, reflected in differences in facial size, suggest different patterns of postnatal growth.

FOXO3 variants are beneficial for longevity in Southern Chinese living in the Red River Basin: A case-control study and meta-analysis

Forkhead box class O (FOXO) transcription factors play a crucial role in longevity across species. Several polymorphisms in FOXO3 were previously reported to be associated with human longevity. However, only one Chinese replication study has been performed so far. To verify the role of FOXO3 in southern Chinese in the Red River Basin, a community-based case-control study was conducted, and seven polymorphisms were genotyped in 1336 participants, followed by a meta-analysis of eight case-control studies that included 5327 longevity cases and 4608 controls. In our case-control study, we found rs2802288*A and rs2802292*G were beneficial to longevity after Bonferroni correction (p_allele = 0.005, OR = 1.266; p_allele = 0.026, OR = 1.207). In addition, in the longevity group, carriers with rs2802288*A and rs2802292*G presented reduced HbA1c (p = 0.001), and homozygotes of rs2802292*GG presented improved HOMA–IR (p = 0.014). The meta-analysis further revealed the overall contribution of rs2802288*A and rs2802292*G to longevity. However, our stratified analysis revealed that rs2802292*G might act more strongly in Asians than Europeans, for enhancement of longevity. In conclusion, our study provides convincing evidence for a significant association between the rs2802288*A and rs2802292*G gene variants in FOXO3 and human longevity, and adds the Southern Chinese in the Red River Basin to the growing number of human replication populations.

A Comparison of Personality Characteristics and Psychiatric Symptomatology between Upper Airway Resistance Syndrome and Obstructive Sleep Apnea Syndrome

OBJECTIVE

To investigate the personality characteristics of patients with upper airway resistance syndrome (UARS) and those of patients with obstructive sleep apnea syndrome (OSAS).

METHODS

Eighty-eight patients with UARS and 365 patients with OSAS participated. All patients had a diagnostic full-night attended polysomnography (PSG) and completed the Athens Insomnia Scale (AIS), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Symptom Checklist-90-Revision (SCL-90-R) and Eysenck Personality Questionnaire (EPQ).

RESULTS

The UARS group scored significantly higher than the OSAS group on the ESS, AIS, and PSQI (p<0.001). The scores of all SCL-90-R subscales in the UARS group were significantly higher than those in the OSA group (all p<0.001, except for somatization, p=0.016). Patients with UARS scored lower on EPQ-E (extroversion/introversion) (p=0.006) and EPQ-L (lie) (p<0.001) than those with OSA. UARS patients also showed higher scores on EPQ-P (psychoticism) (p=0.002) and EPQ-N (neuroticism) (p<0.001) than OSAS patients.

CONCLUSION

Our results suggest that patients with UARS have worse subjective sleep quality than OSAS patients in spite of their better PSG findings. UARS patients tend to have more neurotic and sensitive personalities than patients with OSAS, which may be a cause of the clinical features of UARS.

Geographic Variation in Zygomaxillary Suture Morphology and its Use in Ancestry Estimation

Angled/curved zygomaxillary suture coding is widely employed in cranial assessments of ancestry. However, the efficacy of this method has not been extensively evaluated across diverse populations. In this study, zygomaxillary suture morphology was assessed on a total of 411 human crania from six populations (European, Native American, African, Asian, Arctic Circle, and Aboriginal Australian) using a novel 3D coordinate landmark method. Our results indicate a predominance of angled sutures among native peoples of the Arctic and North America (85-86%), a prevalence of curved sutures among Africans and Aboriginal Australians (77-81%), and essentially equal proportions of both configurations in Asians and Europeans (50-56%). Statistically, angled/curved coding generally discriminates poorly between groups, except when populations with antithetically high frequencies of the two configurations (e.g., African vs. Native American) are compared. Moreover, comparisons across previous studies reveal conflicting frequencies for many populations, further suggesting limited utility of this trait in ancestry estimation.

[Comparative analysis of linear morphometric parameters of the humane mandibula obtained by direct and indirect measurement]

BACKGROUND/AIM

Reconstruction of lost, damaged or distorted mandibular bone presents a challenge from the functional side, as well as from the esthetic point of view. The aim of this study was to determinate potential differences between values of the basic linear moprhometric parameters (LMPs) obtained by direct and indirect manual measurement of the same humane mandibles, with accuracy testing of indirect measurement, which are routinely used in every-day clinical practice. The results are essential for defining of parametric model of the "standard mandible" and virtual modeling of the humane mandible in future researches as well as in clinical medicine.

METHODS

A total number of 12 dry bony mandibles of human adults were studied. According to the standard anatomical landmarks, 10 standard LPMs were measured on each mandible by different manual methods: directly by a sliding caliper with nonius, and indirectly using standard software on two-dimensional (2D) reconstructions of mandibular multislice computed tomography (MSCT) scans. The values obtained by the different measuring methods were matched for the same LMPs.

RESULTS

Statistically significant differences between compared LMPs values obtained by different measuring methods, appeared in the gnathio-interdental distance (Gn-IdD), as well as in the gnathio-condylar distance (Gn-CoD), bilaterally. In both parameters, significantly higher mean values (with percent of difference) were obtained by direct versus indirect measurement: Gn-IdD (21.57%; 29.2 mm vs 22.9 mm; p = 0.004); Gn-CoD left side (14.1%; 122.7 mm vs 105.4 cm; p = 0.001); Gn-CoD right side (11.87%; 124.7 mm vs 109.9 mm; p = 0.009).

CONCLUSION

According to the observed inaccuracy of indirect measurement, we recommended the use of a correction factor for calculation of both Gn-IdD and Gn-CoD real vales, in defining of parametric model of the "standard mandible" based on indirect morphometry on 2D reconstructions of mandibular MSCT scans. Additional studies with larger number of specimens and quantification of anatomical variations regarding to sex, age, dentition status and ethnic origin, additionally should increase measurement accuracy and consequently reliability of future parametric model of the human mandible.

Relationship of cranial robusticity to cranial form, geography and climate in Homo sapiens

Variation in cranial robusticity among modern human populations is widely acknowledged but not well-understood. While the use of "robust" cranial traits in hominin systematics and phylogeny suggests that these characters are strongly heritable, this hypothesis has not been tested. Alternatively, cranial robusticity may be a response to differences in diet/mastication or it may be an adaptation to cold, harsh environments. This study quantifies the distribution of cranial robusticity in 14 geographically widespread human populations, and correlates this variation with climatic variables, neutral genetic distances, cranial size, and cranial shape. With the exception of the occipital torus region, all traits were positively correlated with each other, suggesting that they should not be treated as individual characters. While males are more robust than females within each of the populations, among the independent variables (cranial shape, size, climate, and neutral genetic distances), only shape is significantly correlated with inter-population differences in robusticity. Two-block partial least-squares analysis was used to explore the relationship between cranial shape (captured by three-dimensional landmark data) and robusticity across individuals. Weak support was found for the hypothesis that robusticity was related to mastication as the shape associated with greater robusticity was similar to that described for groups that ate harder-to-process diets. Specifically, crania with more prognathic faces, expanded glabellar and occipital regions, and (slightly) longer skulls were more robust than those with rounder vaults and more orthognathic faces. However, groups with more mechanically demanding diets (hunter-gatherers) were not always more robust than groups practicing some form of agriculture.

Climate signatures in the morphological differentiation of worldwide modern human populations

The ability of cranial morphology to reflect population/phylogenetic history, and the degree to which it might be influenced by environmental factors and selection pressures have been widely discussed. Recent consensus views cranial morphology as largely indicative of population history in humans, with some anatomical cranial regions/measurements being more informative on population history, while others being under selection pressure. We test earlier findings using the largest and most diverse cranial dataset available as yet: 7,423 male specimens from 135 geographic human population samples represented by 33 standard craniometric linear measurements. We calculated Mahalanobis D(2) for three datasets: complete cranial dataset; facial measurement dataset; and neurocranial measurement dataset; these morphological distance matrices were then compared to matrices of geographic distances as well as of several climatic variables. Additionally, we calculated Fst values for our cranial measurements and compared the results to the expected Fst values for neutral genetic loci. Our findings support the hypothesis that cranial, and especially neurocranial morphology, is phylogenetically informative, and that aspects of the face and cranium are subject to selection related to climatic factors. The Fst analysis suggest that selection to climate is largely restricted to groups living in extremely cold environments, including Northeast Asia, North America, and Northern Europe, though each of these regions appears to have arrived at their morphology through distinct adaptive pathways.

Sexual dimorphism in southeast Asian crania: a geometric morphometric approach

Despite a number of studies stating that sexual dimorphism is population specific, sexual differences in Southeast Asian populations have received little attention. Previous studies in this region have focused on samples from Thailand or East Asian populations from China and Japan, examining sexual dimorphism predominantly of the postcranial bones, teeth and mandible with comparatively few cranial studies. These earlier studies have used traditional methods to metrically assess differences between the sexes. The aim of this study is to use geometric morphometric methods for the first time to quantify sexual dimorphism of Southeast Asian crania and extend knowledge of cranial sexual dimorphism beyond China, Japan and Thailand. A total of 35 unilateral and midline landmark coordinates were collected from 144 mainland and island Southeast Asian crania (89 male, 55 female). Using the shape analysis software Morphologika, principal components analysis and thin plate splines allowed for the statistical and visual exploration of shape differences. Differences included relative facial breadth, particularly across the zygomatic and postorbital regions and cranial vault breadth. Significant size dimorphism was also apparent. Overall expected accuracies were highest in the discriminant analysis using both shape and centroid size (86.8%).

Small scattered fragments do not a dwarf make: biological and archaeological data indicate that prehistoric inhabitants of Palau were normal sized

Current archaeological evidence from Palau in western Micronesia indicates that the archipelago was settled around 3000-3300 BP by normal sized populations; contrary to recent claims, they did not succumb to insular dwarfism.

BACKGROUND

Previous and ongoing archaeological research of both human burial and occupation sites throughout the Palauan archipelago during the last 50 years has produced a robust data set to test hypotheses regarding initial colonization and subsequent adaptations over the past three millennia.

PRINCIPAL FINDINGS

Close examination of human burials at the early (ca. 3000 BP) and stratified site of Chelechol ra Orrak indicates that these were normal sized individuals. This is contrary to the recent claim of contemporaneous "small-bodied" individuals found at two cave sites by Berger et al. (2008). As we argue, their analyses are flawed on a number of different analytical levels. First, their sample size is too small and fragmentary to adequately address the variation inherent in modern humans within and outside of Palau. Second, the size and stature of all other prehistoric (both older and contemporaneous) skeletal assemblages found in Palau fall within the normal parameters of modern human variation in the region, indicating this was not a case of insular dwarfism or a separate migratory group. Third, measurements taken on several skeletal elements by Berger et al. may appear to be from smaller-bodied individuals, but the sizes of these people compares well with samples from Chelechol ra Orrak. Last, archaeological, linguistic, and historical evidence demonstrates a great deal of cultural continuity in Palau through time as expected if the same population was inhabiting the archipelago.

CONCLUSIONS

Prehistoric Palauan populations were normal sized and exhibit traits that fall within the normal variation for Homo sapiens-they do not support the claims by Berger et al. (2008) that there were smaller-bodied populations living in Palau or that insular dwarfism took place such as may be the case for Homo floresiensis.

Impact of character correlation and variable groupings on modern human population tree resolution

Relationships among modern human populations are often explored through the use of linear measurements taken on the cranium and expressed in the form of dendrograms. However, craniometric variables are strongly correlated and thereby violate the assumption of independence that most statistical analyses require. This study explores the relationship between differing methods of variable treatment and the statistical robustness of the outcomes they yield, as depicted in interpopulational trees of relatedness among modern humans. Three methods of grouping variables are examined. The first method leaves them ungrouped, the second groups variables on the basis of the developmental and/or functional complex of the cranium to which they are thought to belong, and the last method reduces variables by using principal components analysis. The strength of each of these methods is tested through the use of the Continuous Character Maximum Likelihood (CONTML) program in the PHYLIP phylogeny inference package. This program produces output in the form of trees, and the resolution of the branching topology is given as a log-likelihood value, with statistical confidence intervals supporting each branch placement on the tree. The results indicate that leaving variables ungrouped provides misleadingly strong results by failing to account for character correlation. Of the alternative two grouping methods, the covarying components method yields the best-resolved tree with stronger statistical support for its topology than the approach of grouping variables on the basis of their location on the cranium. Finally, the implications for interpreting population histories based on such methods are discussed.

Cranial variation in the Marquesas Islands

The Marquesas Islands have traditionally been divided into a northwestern and a southeastern group, a division which reflects language dialect differences. Additionally, archaeological studies have also suggested that differences in material culture existed between the northwestern and southeastern islands. This study examines Marquesan cranial discrete and metric traits to evaluate the level of intra-archipelago heterogeneity, and to determine if a northwest/southeast division is evident cranially. The data consist of 28 cranial discrete traits and 49 craniofacial measurements of prehistoric Marquesans. Male and female data are pooled for discrete trait and metric data, following a Z-score standardization technique adjustment. The data represent three island samples: Nuku Hiva (northwest), Fatuiva (southeast), and a combined Tahuata/Hiva 'Oa (southeast). Of the 28 discrete traits, 16 are utilized in a mean measure of divergence analysis that provides scores of 0.259 for Fatuiva-Tahuata/Hiva 'Oa, 1.850 for Nuku Hiva-Fatuiva, and 1.491 for Nuku Hiva-Tahuata/Hiva 'Oa. Of the 49 craniofacial measurements, 46 are utilized in RMET/NORM analyses, providing unbiased D(2) values of 0.0433 for Fatuiva-Tahuata/Hiva 'Oa, 0.1328 for Nuku Hiva-Fatuiva, and 0.0813 for Nuku Hiva-Tahuata/Hiva 'Oa. The islands of the southeastern group are closer to each other than either was to the island of the northwestern group. When a sample from 'Ua Huka is included in the craniometric analysis, the unbiased D(2) values of 0.0829, 0.1175, and 0.0431 are calculated for 'Ua Huka and Nuku Hiva, and Fatuiva and Tahuata/Hiva 'Oa pairings, respectively, indicating a close similarity of 'Ua Huka to the southeastern islands. Mean measure of divergence analysis of cranial discrete traits as well as RMET/NORM analyses of craniometric variables reveal that differences exist between the islands of the northwestern and southeastern Marquesas Islands. These results support previous research that documented linguistic and cultural differences between these regions of the archipelago. However, the results indicate that 'Ua Huka, an island traditionally included in the northwestern Marquesas Islands, has an affinity to the southeastern Marquesas Islands, possibly due to its pivotal position as a waypoint in the Marquesas Island interaction sphere.

Stability consideration for internal maxillary distractors

PURPOSE

Stability in distractor design ensures distraction osteogenesis healing with good bone regenerate formation. The aim of this study was to compare the holding strengths of different fixation systems for maxillary distractor design on bone pieces of different thicknesses.

MATERIAL AND METHODS

Cross-sectional images of 10 dry skulls were obtained by computer tomography and the bone thickness of the maxillae were measured according to five individual anatomical regions (paranasal, infra-orbital, posterior sinus wall, zygomatic and alveolar regions). According to the measurements, the screws of 1.5 and 2mm in diameter and the three-screw mini-plates in triangular and straight configurations were evaluated for holding strength by pull-out tests on fresh animal bone pieces of defined thickness.

RESULTS

The paranasal and zygomatic regions of the human skulls had the thickest cortical bone (4mm) followed by the alveolar region (2mm). In the bones of 2 and 4mm thickness, the 2mm screws were confirmed stronger than the 1.5mm ones in pull-out tests. However, the pull-out behaviour of screws of different diameters in 1mm thick bones and the mini-plates in two different configurations showed no significant differences.

CONCLUSION

This study confirms that the paranasal and zygomatic bones are the thickest for fixation of internal maxillary distractors. Fixation screws of 2mm diameter in either triangular or straight miniplates can produce good stabilization for distractors.

Anthropological variations in the anatomy of the human thyroid arteries

Knowledge of anatomic variability of the superior (STA), inferior (ITA), and lowest accessory (IMA) thyroid arteries may be helpful in certain clinical conditions. However, details of this variability have not been thoroughly described. Specifically, whether the presence and site of origin of STA, ITA, and IMA are influenced by the anthropological group, to what extent their origin is symmetric or asymmetric, and the role played by this variability in visualizing each thyroid artery by nonselective thyroid angiography is not known. To clarify this we conducted a meta-analytical study on Caucasian and Asian subjects, the latter including only Japanese and Koreans. In Caucasians and Asians the presence of superior vessels compared to inferior vessels was more frequent and the probability of symmetric or asymmetric arterial origin for STA were equivalent. However, better recognition of inferior rather than superior vessels was achieved by nonselective angiography in Caucasians. Finally, different frequencies of presence and site of origin for each artery were identified in Caucasians compared to Asians. Our results suggest that the higher frequency of IMA in Asians than in Caucasians should result in a search for an IMA-dependent feeding artery of inferior parathyroid adenomas, primarily the mediastinal ones, especially in Asians both by imaging and transcatheter ablative approaches. In addition, we have found that a small percentage of Caucasian subjects lack an STA on the left side. Therefore, anatomic arterial compatibility should be carefully evaluated in the preoperative stage of laryngeal transplantation maintaining in situ the donor's thyroid by terminal anastomoses between donor and recipient STAs. Finally, the lack of any individual thyroid artery in either Caucasians or Asians might influence the distribution of autonomic supply that runs with thyroid vessels to the thyroid parenchyma. This appears functionally relevant in cases of traumatic or surgical lesions of the cervical sympathetic chain involving thyroid nerves. In fact, a restricted local autonomic control of thyroid activity might be related to individual rami of thyroid nerves.

A geometric morphometric study of regional differences in the ontogeny of the modern human facial skeleton

This study examines interpopulation variations in the facial skeleton of 10 modern human populations and places these in an ontogenetic perspective. It aims to establish the extent to which the distinctive features of adult representatives of these populations are present in the early post natal period and to what extent population differences in ontogenetic scaling and allometric trajectories contribute to distinct facial forms. The analyses utilize configurations of facial landmarks and are carried out using geometric morphometric methods. The results of this study show that modern human populations can be distinguished based on facial shape alone, irrespective of age or sex, indicating the early presence of differences. Additionally, some populations have statistically distinct facial ontogenetic trajectories that lead to the development of further differences later in ontogeny. We conclude that population-specific facial morphologies develop principally through distinctions in facial shape probably already present at birth and further accentuated and modified to variable degrees during growth. These findings raise interesting questions regarding the plasticity of facial growth patterns in modern humans. Further, they have important implications in relation to the study of growth in the face of fossil hominins and in relation to the possibility of developing effective discriminant functions for the identification of population affinities of immature facial skeletal material. Such tools would be of value in archaeological, forensic and anthropological applications. The findings of this study underline the need to examine more deeply, and in more detail, the ontogenetic basis of other causes of craniometric variation, such as sexual dimorphism and hominin species differentiation.

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.

Geometric morphometric study of the regional variation of modern human craniofacial form

The regional variability of the modern human craniofacial form is of importance to debates about human origins. The study of craniofacial form has generally been carried out either by interlandmark distance measurement and analysis or by observation and character scoring. In this study of four modern human groups (Eskimo/Inuit, African, Australian, and Romano-British), nine craniofacial landmark coordinates were recorded by extraction from laser scans. The coordinates were studied by geometric morphometrics, and a regression analysis was used to investigate the dominant variability in shape within and between groups. Statistical tests of shape difference between groups were carried out. By these methods, the statistical patterns of shape variability and their geometric interpretations were studied on a common basis. The results were found to be in agreement with the classic studies of Howells ([1989:189] Pap Peabody Mus 79), and show the potential of this approach for future research.

Mitochondrial DNA variation in an aboriginal Australian population: evidence for genetic isolation and regional differentiation

The mitochondrial DNA (mt-DNA) variation of in the Walbiri tribe of the Northern Territories, Australia, was characterized by high resolution restriction fragment length polymorphism (HR-RFLP) analysis and control region sequencing. Surveying each mt-DNA for RFLPs with 14 different restriction enzymes detected 24 distinct haplotypes, whereas direct sequencing of the control region hypervariable segment I (HVS-I) of these mt-DNAs revealed 34 distinct sequences. Phylogenetic analysis of the RFLP haplotype and HVS-I sequence data depicted that the Walbiri have ten distinct haplotype groups (haplogroups), or mt-DNA lineages. The majority of the Walbiri RFLP haplotypes lacked polymorphisms common to Asian populations. In fact, most of the Walbiri haplogroups were unique to this population, although a few appeared to be subbranches of larger clusters of mt-DNAs that included other Aboriginal Australian and/or Papua New Guinea haplotypes. The similarity of these haplotypes suggested that Aboriginal Australian and Papua New Guinea populations may have once shared an ancient ancestral population(s), and then rapidly diverged from each other once geographically separated. Overall, the mt-DNA data corroborate the genetic uniqueness of Aboriginal Australian populations.

Morphological variation in great ape and modern human mandibles

Adult mandibles of 317 modern humans and 91 great apes were selected that showed no pathology. Adult mandibles of Pan troglodytes troglodytes, Pongo pygmaeus pygmaeus and Gorilla gorilla gorilla and from 2 modern human populations (Zulu and Europeans from Spitalfields) were reliably sexed. Thirteen measurements were defined and included mandibular height, length and breadth in representative positions. Univariate statistical techniques and multivariate (principal component analysis and discriminant analysis) statistical techniques were used to investigate interspecific variability and sexual dimorphism in human and great ape mandibles, and intraspecific variability among the modern human mandibles. Analysis of interspecific differences revealed some pairs of variables with a tight linear relationship and others where Homo and the great apes pulled apart from one another due to shape differences. Homo and Pan are least sexually dimorphic in the mandible, Pan less so than Homo sapiens, but both the magnitude of sexual dimorphism and the distribution of sexually dimorphic measurements varied both among and between modern humans and great apes. Intraspecific variation among the 10 populations of modern humans was less than that generally reported in studies of crania (74.3% of mandibles were correctly classified into 1 of 10 populations using discriminant functions based on 13 variables as compared with 93% of crania from 17 populations based on 70 variables in one extensive study of crania). A subrecent European population (Poundbury) emerged as more different from a recent European population (Spitalfields) than other more diverse modern populations were from each other, suggesting considerable morphological plasticity in the mandible through time. This study forms a sound basis on which to explore mandibular variation in Neanderthals, early Homo sapiens and other more ancient fossil hominids.

Peopling of Sahul: mtDNA variation in aboriginal Australian and Papua New Guinean populations

We examined genetic affinities of Aboriginal Australian and New Guinean populations by using nucleotide variation in the two hypervariable segments of the mtDNA control region (CR). A total of 318 individuals from highland Papua New Guinea (PNG), coastal PNG, and Aboriginal Australian populations were typed with a panel of 29 sequence-specific oligonucleotide (SSO) probes. The SSO-probe panel included five new probes that were used to type an additional 1,037 individuals from several Asian populations. The SSO-type data guided the selection of 78 individuals from Australia and east Indonesia for CR sequencing. A gene tree of these CR sequences, combined with published sequences from worldwide populations, contains two previously identified highland PNG clusters that do not include any Aboriginal Australians; the highland PNG clusters have coalescent time estimates of approximately 80,000 and 122,000 years ago, suggesting ancient isolation and genetic drift. SSO-type data indicate that 84% of the sample of PNG highlander mtDNA belong to these two clusters. In contrast, the Aboriginal Australian sequences are intermingled throughout the tree and cluster with sequences from multiple populations. Phylogenetic and multidimensional-scaling analyses of CR sequences and SSO types split PNG highland and Aboriginal Australian populations and link Aboriginal Australian populations with populations from the subcontinent of India. These mtDNA results do not support a close relationship between Aboriginal Australian and PNG populations but instead suggest multiple migrations in the peopling of Sahul.