Article

The Polynesian head: Growth and form

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Abstract

We consider the cranial base to be the primordial determinant of the head form and mandibular shape so common amongst (but not exclusive to) adult Polynesians. The flatness of the cranial base manifests its full influence only when growth of the upper facial skeleton is complete in early adulthood. We argue that during growth and maturation the upper facial skeleton and the maxillary occlusal plane are required to adjust in position to a major extent according to the template set out by the flat cranial base, with consequent obligatory and extreme adjustment in shape and position of the mandible in order that occlusion be maintained. The base is constrained from adjusting its own shape significantly by virtue of its intimate relationship with the brain and the emerging cranial nerves. The structural consequences of these adaptations are seen in the bony profile, which is vertically disposed and orthognathic, and in the large nasopharynx, while functionally the relative inefficiency of the mandible as a lever requires extensive compensatory development of masticatory musculature which influences the shape of the face and vault.

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... The cranial base grows from endochondral ossification and experiences the majority of its growth in size prior to adolescence. In contrast to size, the flexure of the cranial base does not change after adolescence (Kean & Houghton, 1982;Šešelj, Duren, & Sherwood, 2015). As such, the cranial base provides a foundation for cranial dimensions with later occurring developmental pathways. ...
... As such, the cranial base provides a foundation for cranial dimensions with later occurring developmental pathways. Specifically, rocker jaw, and other features associated with the Polynesian phenotype, are partially dependent on the basicranium (Houghton, 1978;Kean & Houghton, 1982;Lieberman et al., 2000). The cranial base does experience an adolescent growth spurt, though it is of far less magnitude since it has previously achieved such remarkable growth in infancy and childhood (Nahhas, Valiathan, & Sherwood, 2014). ...
... The uniquely flat cranial base and the remarkably large upper facial height in Polynesians act as the underpinnings to the distinct mandibular morphology. As facial height increases in adolescence, there is a concomitant reduction in the gonial angle (Kean & Houghton, 1982). Consequently, there is a loss of the antegonial notch to help accommodate these two features and the rocker jaw morphology appears (Houghton, 1978). ...
Article
Our goal is to describe the global distribution of the "rocker jaw" variant in human populations. Rocker jaw refers to mandibles that lack the antegonial notch, making them unstable on a flat surface. Data were collected by C.G. Turner II on 9,207 individuals from Asia, Europe, the Pacific, and the Americas, and by J.D. Irish on 3,526 individuals from North and South Africa. With a focus on Polynesia, where the trait is most common, frequencies are presented for subdivisions of Oceania, Australasia, Eurasia, the Americas, and Africa. While the rocker jaw is a Polynesian characteristic, the trait is found throughout the world. Within major geographic regions, there are interesting contrasts, for example, (a) the similarity of Jomon and Ainu and their difference from modern Japanese; (b) Aleuts and Northwest Coast Indians are similar and both are distinct from the Inuit and other Native Americans; and (c) North and Sub-Saharan Africans show a regional difference that parallels genetic and dental distinctions. Skeletons in South America that exhibit the rocker jaw have been interpreted as Polynesian voyagers who ventured to the west coast of South America. The rarity of rocker jaw in South American natives supports this view. The rocker jaw can be attributed to the unique basicranium morphology and large upper facial height of Polynesians, which highlights the integrated growth of a functional module (i.e., mastication) of the craniofacial complex. The unusually high frequency of the trait in Polynesians is a product of both function and founder effect/genetic drift.
... nasopharynx. [25][26][27] Some of these factors should, theoretically, reduce the likelihood of OSA in Polynesians and so, indirectly, emphasize the contribution made by weightrelated factors. The aim of this study was to test this hypothesis, by determining the relative contribution of craniofacial form to OSA severity in markedly obese Polynesian and Caucasian men with a similar mean respiratory disturbance index (RDI). ...
... The latter finding agrees with others who have reported an association between OSA severity and mandibular retrognathism in non-Polynesian groups. 4,13,14 At the outset we postulated that the characteristic skull form found in early Polynesians, notably the large cranium with a flat, broad cranial base, and greater vertical development of the face 25,27,42 would enlarge the airway and thus give some "protection" against OSA. Indeed, Kean and Houghton 25 have reported that the volume of the bony nasopharynx was 33% larger in prehistoric Polynesian skulls compared to Caucasians, and have argued that the larger airway was necessary to provide for the higher ventilatory demands required by the greater muscle mass found in Polynesians. ...
... 4,13,14 At the outset we postulated that the characteristic skull form found in early Polynesians, notably the large cranium with a flat, broad cranial base, and greater vertical development of the face 25,27,42 would enlarge the airway and thus give some "protection" against OSA. Indeed, Kean and Houghton 25 have reported that the volume of the bony nasopharynx was 33% larger in prehistoric Polynesian skulls compared to Caucasians, and have argued that the larger airway was necessary to provide for the higher ventilatory demands required by the greater muscle mass found in Polynesians. 27 If these craniofacial features were also present in the Polynesian sample, we hypothesized that weight would then be the over-riding contributing factor in this group. ...
Article
This aim of this study was to determine the relative contributions of craniofacial form and anthropometric factors to obstructive sleep apnea (OSA) in two different racial groups, both markedly obese and with a similar mean respiratory disturbance index (RDI). A cross-sectional study of New Zealand Maori (Polynesian) and European (Caucasian) men with RDI> or =15, using lateral and postero-anterior cephalometric radiography. N/A. N/A. Measurements of facial and cranial width, length and height, airway size, stature, weight, body mass index (BMI), neck circumference, RDI, and age were obtained. The Polynesian men had, on average, a greater neck circumference than the Caucasian men. There were no significant differences in age, weight, BMI or RDI between the two groups. The Polynesian men also had broader craniofacial skeletons, larger and more prognathic mandibles, greater neck extension, and some larger airway dimensions than the Caucasian men. In the Polynesian men, the width of the bony nasal aperture was positively associated with RDI, and mandibular prognathism was negatively associated with RDI. In contrast, in the Caucasian men only neck circumference was positively associated with RDI, while the retropalatal airway was negatively associated with RDI. The results indicate that OSA in these two racially distinct groups is due to different etiological factors. Small reductions in mandibular prognathism and a wider bony nasal aperture were major factors associated with OSA in Polynesians. On the other hand, in the Caucasian group OSA was associated with a larger neck circumference and a reduced retropalatal airway size.
... Intersection of the two planes clival plane (Moss and Greenberg, 1955) ethmoidale (lowest point on anterior cranial base) sella basion (Stramrud, 1959) foramen caecum sella basion (Cramer, 1977;Lieberman et al., 2000;Lieberman et al., 2001b;Lieberman and McCarthy, 1999;McCarthy, 2001;Scott, 1958;Spoor, 1997) foramen caecum sella clival plane (Lieberman et al., 2000;Lieberman et al., 2001b;Lieberman and McCarthy, 1999;McCarthy, 2001) fronton sella basion (George, 1978) fronton sphenoidale basion (George, 1978) fronton sphenoidale clival line (main axis of superior border of clivus, not passing through basion) (George, 1978) hormion plane clival plane (Lieberman and McCarthy, 1999) nasion sella basion (Andria et al., 2004;Anton, 1989;Bacon et al., 1992;Björk, 1955;Bordeaux, 1972;Burdi, 1968;Burdi, 1969;Cameron, 1924;Diewert, 1983;Diewert and Lozanoff, 1993;George, 1978;Houghton, 1978a;Huggare et al., 1988;Kasai et al., 1995;Kean and Houghton, 1982;Kerr and Adams, 1988;Kerr, 1979;Kieser et al., 1999;Kreiborg et al., 1981;Kuroe et al., 2004;Lestrel, 1974;Michejda, 1975;Michejda and Lamey, 1971;Nanda, 1990;Peterson-Falzone and Figueroa, 1989;Read and Lestrel, 1986;Roche et al., 1972;Rothstein and Phan, 2001;Sirianni and van Ness, 1978;Smahel and Skvarilova, 1988a;Smahel and Skvarilova, 1988b;Solow, 1966;Solow and Siersbaek-Nielsen, 1992;Stramrud, 1959;Ursi et al., 1993;van den Eynde et al., 1992) (Solow, 1966) nasion sphenoidale (uppermost midline point of tuberculum sellae) basion (George, 1978) nasion prosphenion, spheno-ethmoid suture or wing point (anterior curvature of lesser wings of sphenoid in midline) basion (Duckworth, 1904;Ford, 1956;Huxley, 1863;Huxley, 1867;Zuckerman, 1955) nasion sella bolton (Anderson and Popovich, 1983;Levihn, 1967) nasion tuberculum sellae ("pituitary point") ...
... A comparison of studies investigating the angle of cranial base flexion reveals numerous studies reporting average angles of flexion in a single sample, but only a few that compare multiple samples. Of the studies investigating cranial base flexion angles in different samples, most have found the average angle measured as basion-sellanasion to be around 130 degrees in modern human adults (Table 1.2) (Björk, 1955;Kasai et al., 1995;Kean and Houghton, 1982;Kieser et al., 1999;Solow, 1966). Other studies examining less conventional angles of cranial base flexion have measured the angle of cranial base flexion between basion, sella and the foramen caecum (Lieberman et al., 2000b), and found average values for different populations between 131 and 136 degrees in Ashanti, Australians, Chinese, Egyptians and Italians, with a combined average of 134 degrees. ...
... Comparable studies to the sample of Polynesians (Maori and Moriori) were found in the work of Kean and Houghton (1982). In this study they took measurements from tracings of radiographs of 60 adult males. ...
... Posterior fossa volume has not been studied in Maori and Pacific people, but there are other differences in craniospinal development between Caucasians or other, Maori and Pacific people. [14][15][16][17] Sex differences were also identified. Caucasians or other women were more likely to have syringomyelia associated with a Chiari I malformation than Caucasians or other men. ...
Article
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To determine the prevalence of syringomyelia in a defined population in New Zealand and measure the prevalence of syringomyelia in the three main ethnic groups (Maori, Pacific people and Caucasians/others) living in this region. A retrospective study of all confirmed cases of syringomyelia diagnosed in residents of northern New Zealand from 1961 to 2003. In all, syringomyelia was diagnosed in 137 patients. The mean age at onset of symptoms was 27.5 years and mean age at diagnosis was 32.6 years. The incidence of new cases increased from 0.76/100,000 a year between 1962 and 1971 to 4.70/100,000 a year by 1992-2001. The prevalence of syringomyelia in 2003 was 8.2/100,000 people: 5.4/100,000 in Caucasians or others, 15.4/100,000 in Maori and 18.4/100,000 in Pacific people (chi2 = 37.0, p<0.0001). Syringomyelia was more often associated with an isolated Chiari I malformation in Pacific people (84.4%) as compared with 42.9% of Maori and 38.2% of Caucasians or others (chi2 = 62.3, p<0.0001). The prevalence of syringomyelia is higher in northern New Zealand than in studies carried out before the advent of magnetic resonance imaging. The prevalence is particularly high in Maori and Pacific people. The cause of the ethnic differences in the prevalence of syringomyelia identified in this study is unexplained and warrants further investigation.
... Se considera que la base de cráneo es el determinante primordial de la forma de la cabeza y de la mandíbula, lo que se evidencia en estudios realizados en sujetos adultos polinésicos [1]. En general, la base del cráneo y la fosa craneal media ofrecen el soporte para la integración del desarrollo estructural con la bóveda y la cara [2,3]. ...
Article
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Introducción: la proyección dorsal del plano oclusal y su inclinación en relación con la base de cráneo son indispensables para generar un análisis cefalométrico simple para rehabilitadores. Métodos: se realizó un estudio descriptivo sobre telerradiografías de perfil de cráneo completo en 124 sujetos consecutivos de ambos sexos. Se determinó el lugar de proyección del plano oclusal teórico sobre la columna cervical y se midió su angulación con respecto a la línea C1 del Análisis Arquitectural y Estructural de Delaire (AAED). Se analizaron los resultados según sexo y entre las distintas clases esqueletales definidas por el mismo análisis. Basado en ello, se propuso un análisis simple para la determinación de la posición del plano oclusal con respecto a la columna cervical, la base de cráneo y la altura facial (Oclusometría). La oclusometría se validó contrastándola con el AAED completo. Resultados: de un total de 124 sujetos, 68 sujetos proyectaron el plano oclusal sobre la porción inferior del atlas y 36 sobre la articulación atlas-axis. En relación al ángulo del plano oclusal con C1, se obtuvieron valores entre 7 y 14 grados con un promedio de 9,8º y una moda de 10º. No se observó diferencia entre clases esqueletales ni entre sexos. Con esto se propuso un análisis denominado oclusometría. Un estudio descriptivo con análisis sobre 42 telerradiografías de perfil de sujetos sin desgaste dentario ni alteraciones del crecimiento validó la oclusometría como estudio complementario en la determinación de la ubicación del plano oclusal. Conclusión: el plano oclusal tiende a mantener una posición estable en el espacio lo que permite generar un estudio sobre telerradiografías validado y útil para ayudar en la determinación de la posición del plano oclusal dentro de los límites de la dimensión vertical oclusal.
... However, if populations are under similar environmental influences, there is an increased likelihood of intra-population similarities in craniofacial variation. These environmental influences can include diet and dietary transition (Gonzalez-Jose et al., 2005;Stynder et al., 2007), temperature (Riesenfeld, 1973;Roseman, 2004;Roseman and Weaver, 2004;Harvati and Weaver, 2006), and muscular development and loadings (Riesenfeld, 1967a;Kean and Houghton, 1982;Byron et al., 2004Byron et al., , 2006Byron et al., , 2008Vecchione et al., 2007Vecchione et al., , 2010. ...
... Hypermasticatory influences on the human cranium are reported to result in a higher vaulted skull (Kean and Houghton, 1982). Vecchione et al. (2007) reported on the craniofacial traits of a hypermuscular mouse model. ...
... However, the results of this study may be dependent on the Polynesian specific mandibular form of the Maori, what is called the 'rocker jaw.' In 'rocker jaws,' projection of the gonial process is lacking and the inferior corpus and posterior ramus profiles form a continuous convex curve (Marshall and Snow, 1956; Snow, 1974; Schendel et al., 1980; Kean and Houghton, 1982, 1990). Such a specialized mandibular form may exhibit a tooth-jaw relationship distinct from other populations. ...
Article
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The juvenile mandible of the modern Japanese has a lower symphysis than that of the prehistoric Jomon, while the adult symphysis is conversely higher in the modern Japanese. This cannot be explained from population differences in masticatory environments. As an alternative factor that may influence symphyseal height, we examined tooth crypt size and placement patterns in the skeletal growth series of the two populations. Results showed that although the Jomon mandible had larger bicanine breadth than in the modern Japanese during growth, the modern Japanese has faster growing anterior teeth that became larger than those of the Jomon by the time of eruption, necessitating greater space. This is expressed as the faster growth rate of anterior alveolar height in the modern Japanese, measured as corpus height above the mandibular canal. Canine eruption distance and root length were greater in the modern Japanese than in the Jomon, corresponding to the increased difference of anterior corpus height between the two populations after canine eruption. However, the influence of tooth root length on anterior corpus height during later growth cannot be evaluated by this study. The present study suggests that the size and spatial dispositions of the developing anterior teeth have significant effects on symphyseal dimensions of the mandible until the time of tooth eruption.
... One later researcher, Professor Philip Houghton, described the singular characteristics of Māori and Moriori cranial and postcranial morphology (Houghton 1980(Houghton , 1996 and developed a theoretical basis for the cranial morphology with collaborator Martin Kean (Kean and Houghton 1982 as well as an adaptive hypothesis explaining the distinctive Polynesian postcranial phenotype (Houghton 1990(Houghton , 1991a(Houghton , b, c, 1996. ...
Chapter
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France benefits from precocious development and a long history of research in natural sciences that dates back to the seventeenth century. As an inheritor of this early development and provided further stimulus by early discoveries of Neandertals in the nineteenth century, France was the first nation in the world to develop formalized research institutions, a professional society, and a journal dedicated to physical anthropology under the guiding aegis of Paul Broca and colleagues in Paris. The dominant question during the early stages of development concerned the number of races that characterized early human populations against the backdrop of the transition from Neandertals to modern humans. Along with continued morphological studies, this early focus has shifted to consider questions in paleodemography, paleopathology, and medico-legal studies. Uniquely in France, “archaeothanatology”, based on close taphonomic recording of the position of skeletal elements, grave structures, and grave inclusions to reconstruct funerary practices, developed most recently as a sub-discipline within biological anthropology. Benefitting from the legacy of its long scholarly history, multiple venerable institutions, and internationally active researchers, France continues to exert considerable influence on studies in biological anthropology today, which augurs well for the future of the discipline on a global scale.
... Heathcote, 2005, Heathcote et al., 1996Pate et al., 2001;Heathcote, 1993, 1995;Rothschild and Rothschild, 1995 Philip Houghton et al. Skeletal biology and paleopathology in Maori, Lapita, and other skeletal remains from the Pacifi c. Houghton, 1980Houghton, , 1983Houghton, , 1989aHoughton, , b, c, 1996Houghton and Kean, 1987;Kean and Houghton, 1982, 1987 Tooth modifi cation in dental remains from Guam. ...
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