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Polynesian face and dentition: Functional perspective
Abstract
Widely dispersed throughout the Pacific, Polynesians are a biologically distinctive people in form and size of both body and head. Large-bodied and well-muscled, their body phenotype is suited to life in a thermolabile oceanic environment. Their craniofacial skeleton is large and robust, with mandibular size and form (the "rocker" mandible) being especially characteristic. In this paper the Polynesian variants of body form, and of facial size (including dentition) and form, are interpreted from a functional perspective.
... Dimensions corresponding between that study and the current sample of Polynesians were nasion-sella, sella-basion and PNSbasion, and angular measurements of nasion-sella-basion corresponded to some of those used in the present study (Table 3.4). Other studies, such as Huggare (1996) and Kean and Houghton (1990) had no measurements that could be compared to the present study (Huggare and Houghton, 1996;Kean and Houghton, 1990). The results of the t-test conducted between the results of Polynesian males of the present study and Kean and ...
... Dimensions corresponding between that study and the current sample of Polynesians were nasion-sella, sella-basion and PNSbasion, and angular measurements of nasion-sella-basion corresponded to some of those used in the present study (Table 3.4). Other studies, such as Huggare (1996) and Kean and Houghton (1990) had no measurements that could be compared to the present study (Huggare and Houghton, 1996;Kean and Houghton, 1990). The results of the t-test conducted between the results of Polynesian males of the present study and Kean and ...
... 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. ...
... The present sample from a contemporary Polynesian population did have several of the characteristic craniofacial features found in prehistoric Polynesians. [25][26][27]42 The craniofacial skeleton was larger overall, the facial skeletal profile was flatter and longer in the mid-face, the mandible was longer, and the anterior cranial base tended to be shorter than that found in the Caucasian sample. However, perhaps more significantly (for reasons to be outlined below), the cranial base angle, the overall vertical height of the facial skeleton, and the dimensions of the nasopharynx were not different to the Caucasian men. ...
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.
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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.
... This is in agreement with most reports of facial growth which conclude that increased forces result in shortened faces (Schendel et al., 1980) and deep bites (Sassouni, 1969). Further, as reported in an earlier study (Vecchione et al., 2007), the overall shape of the 180 day old myostatin-deficient mouse mandible, compared to the wildtype control mandible, resembles a unique human jaw morphology described previously in Polynesian populations (Houghton, 1978; Schendel et al., 1980; Kean and Houghton, 1990). The effect of hypermuscularity is thought to have resulted in a characteristic mandibular shape described as a " rocker mandible " (Marshall and Snow, 1956). ...
It is well recognized that masticatory muscle function helps determine morphology, although the extent of function on final form is still debated. GDF-8 (myostatin), a transcription factor is a negative regulator of skeletal muscle growth. A recent study has shown that mice homozygous for the myostatin mutation had increased muscle mass and craniofacial dysmorphology in adulthood. However, it is unclear whether such dysmorphology is present at birth. This study examines the onset and relationship between hypermuscularity and craniofacial morphology in neonatal and adult mice with GDF-8 deficiency. Fifteen (8 wild-type and 7 GDF-8 -/-), 1-day-old and 16 (9 wt and 7 GDF-8 -/-), 180-day-old male CD-1 mice were used. Standardized radiographs were taken of each head, scanned, traced, and cephalometric landmarks identified. Significant mean differences were assessed using a group x age, two-way ANOVA. Myostatin-deficient mice had significantly (P < 0.01) smaller body and masseter muscle weights and craniofacial skeletons at 1 day of age and significantly greater body and masseter muscle weights at 180 days of age compared to controls. Myostatin-deficient mice showed significantly (P < 0.001) longer and "rocker-shaped" mandibles and shorter and wider crania compared to controls at 180 days. Significant correlations were noted between masseter muscle weight and all cephalometric measurements in 180-day-old Myostatin-deficient mice. Results suggest that in this mouse model, there may be both early systemic skeletal growth deficiencies and later compensatory changes from hypermuscularity. These findings reiterate the role that masticatory muscle function plays on the ontogeny of the cranial vault, base, and most notably the mandible.
... This is in agreement with most reports of facial growth which conclude that increased forces result in shortened faces (Schendel et al., 1980) and deep bites (Sassouni, 1969). Further, as reported in an earlier study (Vecchione et al., 2007), the overall shape of the 180 day old myostatin-deficient mouse mandible, compared to the wildtype control mandible, resembles a unique human jaw morphology described previously in Polynesian populations (Houghton, 1978;Schendel et al., 1980;Kean and Houghton, 1990). The effect of hypermuscularity is thought to have resulted in a characteristic mandibular shape described as a "rocker mandible" (Marshall and Snow, 1956). ...
It is well recognized that masticatory muscle function helps determine morphology, although the extent of function on final form is still debated. GDF-8 (myostatin), a transcription factor is a negative regulator of skeletal muscle growth. A recent study has shown that mice homozygous for the myostatin mutation had increased muscle mass and craniofacial dysmorphology in adulthood. However, it is unclear whether such dysmorphology is present at birth. This study examines the onset and relationship between hypermuscularity and craniofacial morphology in neonatal and adult mice with GDF-8 deficiency. Fifteen (8 wild-type and 7 GDF-8 −/−), 1 day old and 16 (9 wt and 7 GDF-8 −/−), 180 day old male CD-1 mice were used. Standardized radiographs were taken of each head, scanned, traced, and cephalometric landmarks identified. Significant mean differences were assessed using a group × age, two-way ANOVA. Myostatin-deficient mice had significantly (p<0.01) smaller body and masseter muscle weights and craniofacial skeletons at 1 day of age and significantly greater body and masseter muscle weights at 180 days of age compared to controls. Myostatin-deficient mice showed significantly (p<0.001) longer and “rocker-shaped” mandibles and shorter and wider crania compared to controls at 180 days. Significant correlations were noted between masseter muscle weight and all cephalometric measurements in 180 day old Myostatin-deficient mice. Results suggest in this mouse model, there may be both early systemic skeletal growth deficiencies and later compensatory changes from hypermuscularity. These findings reiterate the role that masticatory muscle function plays on the ontogeny of the cranial vault, base, and most notably the mandible.
... Nous avons donc examine´une population Maori caracte´rise´e par la robustesse de l'appareil masticatoire correspondant a`celle de « la Dame du Cavillon ». La forme distinctive repre´sente l'adaptation extreˆme des composants de la mandibule, branches et corps a`bras de travail raccourci impliquant un grand de´veloppement des muscles, alors que les dimensions dentaires sont plutoˆt re´duites (Kean M.R. et Houghton P., 1990). L'e´tat dentaire des Maoris est e´galement voisin de celui de « la Dame du Cavillon », c'est-a`-dire : une usure occlusale excessive, une exposition de cavite´s pulpaires et une pathologie alve´olaire. ...
L'étude du squelette de la "Dame du Cavillon", de type Cro-Magnon, qui appartenait à la culture du Gravettien, a mis en évidence des similitudes avec les sujets des grottes des Balzi-Rossi à Grimaldi (Italie) près de Menton, de la grotte des Arene Candide à Finale Ligure (Le Jeune Prince) et des Maoris de Nouvelle-Zélande. Le résultat le plus surprenant de cette étude concernant l’alimentation est une rupture entre le Moustérien et le Gravettien puisque le menu devient non seulement dépendant de la chasse et de la cueillette, mais aussi de la récolte au bord de mer (pêche et fruits de mer), pour ces hommes anatomiquement modernes.
The analysis of the skeleton of the "Dame du Cavillon" Cro-Magnon type, belonging to the Gravettian culture, highlighted similarities to other prehistorics of the Balzi-Rossi caves in Grimaldi (Italy) near Menton, the Young Prince from the cave of Arene Candide in Finale Ligure and the Maori of New Zealand. The most surprising result about the menu is that anatomically modern humans, living in the Balzi Rossi beachfront, are not only dependent on hunting and gathering, but also harvest seafood.
USURE DENTAIRE ET MODE MASTICATOIRE DE LA DAME DU CAVILLON -Variabilité de la nourriture des hommes modernes lors du dernier maximum glaciaire. 2016. Beatriz PINILLA, John DENNISON, Alejandro PEREZ-PEREZ, Bernard PUECH et Pierre-François PUECH et la collaboration de Noël GARRIGUE. In “ La grotte du Cavillon sous la falaise des Baousse Rousse Grimaldi, Vintimille, Italie; Etude anatomique du squelette de « la Dame du Cavillon »” Ed. Henry de LUMLEY: CNRS éditions, Paris, 1133 pages ISBN : 978-2-271-09195-6. Chapitre 60 :949-967.
... The 'rocker jaw' condition refers to the mandible's propensity to rock back and forth like an old rocking chair when placed on a level surface, a condition that arises as a result of a unique facial growth pattern observed in Polynesians that produces a relatively wide angle between the body and ramus of the mandible (Houghton, 1977;Schendel et al., 1980;Kean and Houghton, 1990). This condition, while common in Polynesians and Pacific Islanders, is rarely observed in Europeans. ...
Don Francisco de Paula Marin was born in Jerez, Spain, November 28, 1774. After deserting the Spanish Navy in Nootka in the American Northwest, Marin, known to Hawaiians as Manini, found his way to Hawaii in 1793 or 1794. Soon after his arrival in Hawaii, he became interpreter, friend, and advisor to King Kamehameha I, who was in the process of consolidating all the Hawaiian Islands under his leadership. In addition to his ties to Hawaiian royalty, Marin was known as a keen horticulturalist, distiller, and entrepreneur making him probably one of the most influential European residents in the Hawaiian Islands in the early 1800s. In ca. 1810, Marin built his house and other structures on land granted to him by Kamehameha in downtown Honolulu. Nearly 200 years later in 1994, a 28 story high-rise building and a six-story parking structure were constructed on the Marin property. Archaeological survey and excavation in 1992 identified 15 historic coffin burials from the Marin Tower property. In addition to the poorly preserved and incomplete skeletons of five adults (three males, two females) and a child identified from what was believed to be the Marin family plot (Block I), other better-preserved skeletons of five adults and four subadults (including two fetuses) were also located in a separate area (Block II) within the property. Using historical, archaeological, and forensic/osteological documentation, several tentative identifications were made. While none of the burials from the project areas can be unequivocally assigned to any of the Marin family, possible choices can be narrowed in a few cases. One male burial was found to most closely match Don Francisco Marin. Other burials identified in the Marin property may represent two of Marin's four wives (all of Hawaiian ancestry) and any of his eight children who were likely to have been buried on property. Several of the burials from the Marin property very likely represent individuals of Hawaiian ancestry, exhibiting osteological and dental features consistent with other postcontact skeletons from Hawaii.
... Māori, for example, have relatively larger upper facial heights compared with most other native population groups. 4 It is possible that these unique facial features may be due to ethnicity-specific environmental and genetic factors. Few studies have investigated the facial features of present-day New Zealand Māori, and compared them with those of other ethnic groups living in the same region. ...
Māori patients are often inappropriately treated using Caucasian norms, despite obvious differences in facial morphology. There is currently very little data concerning the nature and/or magnitude of these differences in facial features. The objective of the present study was therefore to evaluate the facial features of Māori and New Zealand (NZ) Europeans.
Two convenience samples of 30 Māori and 30 NZ Europeans, evenly matched for age and gender, were recruited from amongst students of the University of Otago, New Zealand. Using a 3D white-light scanner, 12 facial scans were taken of each participant, which were then merged to form a single 3D image of the face. Prior to scanning, round markers were fixed to the skin in order to facilitate the localisation of facial anthropometric points and from which vertical, sagittal, and transverse measurements were assessed from the 3D facial image. Univariate and multivariate analyses of variance were used to test for differences between the two groups before and after adjusting for body mass index (BMI).
Significant differences were found in vertical, sagittal, and transverse facial dimensions, before and after adjusting for BMI. The overall face of Māori was significantly larger than that of NZ Europeans, although the facial proportions were generally similar. However, Māori had a broader face, more anterior position of the chin and reduced facial convexity in comparison with NZ Europeans (p < 0.01).
Māori have markedly different sagittal facial features compared with NZ Europeans. These distinctive features may reflect important differences in environmental and genetic influences between the two populations. The findings from the present study may assist the clinician in the treatment planning and assessment of facial dysmorphology in these ethnic groups.
... Rocker jaw is the only nondental (i.e., cranial) attribute. Although a hallmark of Polynesians, where frequencies approach 95% for some groups (Houghton, 1976;Pietrusewsky, 1984;Kean and Houghton, 1990), convexity of the mandible's horizontal ramus is also found in Europe. This occurrence has not been published, but Turner (personal communication, 2008) reports that the developmental trait occurs in 10-20% of adult Europeans at ASUDAS grades of 1-2 (i.e., near-and full-rocker), and dates to at least the late Pleistocene. ...
The origins of state formation in ancient Egypt have been the focus of recent research utilizing biological data to test hypotheses regarding in situ development of local groups, or large-scale in-migration, possibly by an invading army. The primary goal of the present research is to further test these hypotheses. Our secondary goal is to compare different distance measures and assess how they might affect interpretation of population history. We analyze craniodental nonmetric data using several different measures of biological distance, as well as a method for estimating group diversity using multidimensional scaling of distance estimates. Patterns of biological variation and population relationships were interpreted in temporal and geographic contexts. The results of our analyses suggest that the formation of the ancient Egyptian state likely included a substantial in situ process, with some level of contribution by outside migrants probable. The higher level of population structure in Lower Egypt, relative to Upper Egypt, suggests that such influence and migration by outsiders may not have been widespread geographically. These findings support, but serve to refine further those obtained by the second author in a previous study. Moreover, our comparison of distance measures indicates that the choice of measure can influence identification and interpretation of the microevolutionary processes shaping population history, despite being strongly correlated with one another. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc.
Bioarchaeological analysis of human remains from St Hilda’s Church cemetery, South Shields was undertaken to investigate ancestral diversity in post-medieval Britain. Methodological evaluations argue that when diversity is explored through phenotypic traits, biological affiliations are best investigated through dental morphology due to its resistance to exogenous influences, whereas cranial form appears to be increasingly influenced by environmental and cultural factors in the post-medieval period. A novel quantitative model was developed for a within-group analysis of dental morphology assessed through the Arizona State University Dental Anthropology System, successfully identifying an ancestral outlier. An osteobiographical narrative for this individual, combining osteological and historical data with social theory, suggests that personhood is malleable and multifaceted. Ancestry is therefore most appropriately understood as one aspect of identity which also included sex, occupation, social status and linguistic affiliation.
In an earlier dry-skull study (Dias et al. [2001] Int J Osteoarchaeol 11:241-248), a hitherto undescribed groove was observed in the infratemporal region of the greater wing of the sphenoid bone in the cranial base, passing laterally from the foramen ovale onto the squamous temporal bone. We found a very high incidence of this groove, 81% on one side at least, in modern South-Asian Indian adult crania, but much less so, 50%, in a Polynesian sample of both New Zealand Maori and Moriori adult crania. This article reports our finding of the groove, at least on one side, in 85% of a modern Portuguese skeletal population, and our dissection study on twenty European cadavers confirms that the groove, present in all, is formed by the posterior deep temporal nerve.
The identification of biological race (ancestry) in skeletal material is an important aspect of forensic investigations. While techniques for race determination are well established for adult skeletons, identification of race in sub-adult specimens has not been widely addressed. The present study investigates racial differences in the mandibular morphology of sub-adult specimens using geometric morphometric analyses. One hundred and seventy-four mandibles from five morphologically distinct samples were digitized and subjected to general Procrustes analysis. Results showed significant morphological differences between the samples and obtained cross-validation results of over 70% accuracy in identification of unknown individuals using the complete mandible. It is suggested that these techniques could provide a method for the identification of race in sub-adult individuals.
The biomechanical events which accompany functional loading of the human mandible are not fully understood. The techniques normally used to record them are highly invasive. Computer modelling offers a promising alternative approach in this regard, with the additional ability to predict regional stresses and strains in inaccessible locations. In this study, we built two three-dimensional finite element (FE) models of a human mandible reconstructed from tomographs of a dry dentate jaw. The first model was used for a complete mechanical characterization of physical events. It also provided comparative data for the second model, which had an increased vertical corpus depth. In both cases, boundary conditions included rigid restraints at the first right molar and endosteal cortical surfaces of the articular eminences of temporal bones. Groups of parallel multiple vectors simulated individual masticatory muscle loads. The models were solved for displacements, stresses, strains, and forces. The simulated muscle loads in the first model deformed the mandible helically upward and toward its right (working) side. The highest principal stresses occurred at the bite point, anterior aspects of the coronoid processes, symphyseal region, and right and left sides of the mandibular corpus. In general, the observed principal stresses and strains were highest on the periosteal cortical surface and alveolar bone. At the symphyseal region, maximum principal stresses and strains were highest on the lower lingual mandibular aspect, whereas minimum principal stresses and strains were highest on its upper labial side. Subcondylar principal strains and condylar forces were higher on the left (balancing or nonbiting) side than on the right mandibular side, with condylar forces more concentrated on the anteromedial aspect of the working-side condyle and on the central and lateral aspects of the left. When compared with in vivo strain data from macaques during comparable biting events, the predictive strain values from the first model were qualitatively similar. In the second model, the reduced tensile stress on the working-side, and decreased shear stress bilaterally, confirmed that lower stresses occurred on the lower mandibular border with increased jaw depth. Our results suggested that although the mandible behaved in a beam-like manner, its corpus acted more like a combination of open and closed cross sections due to the presence of tooth sockets, at least for the task modelled.(ABSTRACT TRUNCATED AT 400 WORDS)
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.
Austronesian is one of the major language groups spoken. It is believed that Taiwan, Indonesian (east of Wallace line), or Bismarck Archipelago is the starting point for Austronesian migrations. It is also suggested that prehistoric cultures of Taiwan were established by the ancestors of the modern Taiwanese indigenous populations, who are also Austronesian speakers. The goals of this project are to estimate biological relationships of the San-Pau-Chu (SPC) to other Asian populations (especially Polynesians) and to evaluate if Taiwan indeed plays a major role in the history of Austronesian migrations by using both dental morphological data (metric and nonmetric dental traits) and genetic evidence. This dissertation is divided into six chapters. In chapter one, models of Austronesian dispersal are introduced. Additionally, hypotheses and significance of this study are emphasized. In chapter two, the linguistic, archaeological, osteological and genetic evidence for different models is reviewed. Chapter three provides a brief introduction to Taiwanese cultural history, and describes archaeological sites at the Tainan Scientific-Based Industrial Park. In chapter four, a case study of dental variation from the SPC, Wu-Chien-Tsuo South (WCTS), and Nan-Kang-Li East (NKLE) sites are presented. In chapter five, genetic diversity and maternal ancestry in the SPC people is evaluated by using ancient DNA. Finally, in chapter six the biological evidence of the SPC people and their affinities is summarized. This research is the first study in Taiwan trying to combine both morphological and genetic evidence to explore the biological nature of one prehistoric population. Because the dental morphological study and ancient DNA analyses seem to suggest a Northern Asian origin for the SPC people, it is proposed here that approximately 2,500 BP, some prehistoric Taiwanese came from mainland East Asia. However, the WCTS people, contemporaries of SPC, show a closer relatedness with the Namu from the Hawai’i. Therefore, a multiple set of models must be considered. Studies with larger samples sizes and wider range of archaeological sites in the future will also help to gain insights. Graduate Research, Project, and Travel Grants from the University of New Mexico (2002) Chiang-Ching Kuo Foundation Dissertation Fellowships for ROC Students Abroad (2003) NSF Dissertation Improvement No. #0321795 (2003) DAAD Graduate Scholarship for Study and/or Research in Germany (2004) Wenner-Gren Foundation Dissertation Fieldwork Grants No. 7323 (2005-2006) Doctor of Anthropology Doctoral Anthropology Stone, Anne Osjborn, Pearson
Objective
(1) To establish baseline lateral craniofacial morphology and soft tissue profile outcomes for New Zealand children with complete unilateral and complete bilateral cleft lip and palate (CUCLP/CBCLP) and determine differences in relation to demographic characteristics including cleft type, sex and ethnicity and (2) To compare these outcomes to similar international studies.
Settings and Sample Population
Nation‐wide prospective and retrospective cephalometric analysis of 76 patients with CUCLP and 23 patients with CBCLP pre‐secondary alveolar bone graft.
Materials & Methods
Assessment was undertaken by three experienced orthodontists blinded to patient identity. A total of 13 hard tissue and 8 soft tissue landmarks were identified allowing for an assessment of 16 angular, three linear and one ratio variables. Inter‐assessor reliability was determined by predefined measurement error thresholds.
Results
Inter‐assessor reliability of cephalometric landmarks restricted reporting to 10 hard tissue, four soft tissue and one ratio variables. CUCLP had greater midface and mandibular retrusion than CBCLP. Females had greater midface and mandibular prominence and smaller nasal projections. The Pacific and Māori groups had more retrusive midfacial profiles and the Pacific group had more prominent mandibles. A sub‐analysis of New Zealand European CUCLP results, found they were closely aligned to Eurocleft and Americleft study centres with less favourable outcomes.
Conclusions
The reliability of a number of cephalometric measurements was poor. Lateral craniofacial morphology and soft tissue profile outcomes varied between CUCLP/CBCLP, sex and ethnicity. The New Zealand European outcomes are similar to or less favourable to other studies.
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The genesis of bioarchaeology in New Zealand as a discipline is entwined with the fates of the indigenous people of the land, the Māori, and influenced by the relatively short period of non-Māori colonisation. The story of how human skeletal remains (Kōiwi tangata), were treated and used in research by colonial curio hunters and adventurers mirror the treatment and eventual re-empowerment of Māori culture. Human skeletal remains hold a special place in all New Zealanders’ cultural identity but for Māori, are the physical embodiment of their genealogy representing a direct link to the land on which their ancestors lived and died. This chapter briefly reviews the history of biological anthropology as a discipline in New Zealand, outlining history and the legislative and social context of this research. Two case studies of recent bioarchaeology research are presented highlighting the current state of play in the discipline at one institution.
GDF-8 (myostatin) is a negative growth regulator of skeletal muscle, and myostatin-deficient mice are hypermuscular. Muscle size and force production are thought to influence growth of the craniofacial skeleton. To test this relationship, we compared masticatory muscle size and craniofacial dimensions in myostatin-deficient and wild-type CD-1 control mice. Myostatin-deficient mice had significantly (p < 0.01) greater body (by 18%) and masseter muscle weight (by 83%), compared with wild-type controls. Significant differences (p < 0.05) were noted for cranial vault length, maxillary length, mandibular body length, and mandibular shape index. Significant correlations were noted between masseter muscle weight and mandibular body length (r = 0.68; p < 0.01), cranial vault length (r = -0.57; p < 0.05), and the mandibular shape index (r = -0.56; p < 0.05). Masticatory hypermuscularity resulted in significantly altered craniofacial morphology, probably through altered biomechanical stress. These findings emphasize the important role that masticatory muscle function plays in the ontogeny of the cranial vault, the maxilla, and, most notably, the mandible.
Uni versit y of T oronto * A bstract . Individual burials recovered by archa eological excavation from two p rehisto ric T ongan bu rial mounds are descri bed . Re mai ns (often incom plet e) of some 99 individ ua ls ar e analysed wh ere possible according to age an d sex and an assessment of sta t ure and build atte mpted. M orphological and some metrical dat a for bo t h cranial and infr acrani al mat eri al, and nonm et rical dat a on dentition are pr esent ed. A section on pa laeopatho logy is included . Limited co mpa riso ns are drawn bet ween th e excavated sa mp le and modern (c. 1920) T ongans. 1.1. The report that follows is an osteological (odontological) an alysis of cranial a nd infracrani al remain s from two Polynesian burial mounds (To -At-l and T o-At-2) excava ted by J. M. Davidson in 1964 on th e island • of T ongat apu (Davidson, thi s volume). This study was carr ied out during a six-week period from July 1967 to mid-August at the Auckland In stitute and Mu seum in Auckland, Ne w Zealand. It constituted part of a summer's . . independent fieldwork pro gramm e for purposes of collecting data to be used in my doctoral dissertation in Physical Anthropology at th e Uni versity of T oront o. 1.2. A CKN OW LE DGE MENTS I wish to acknowl edge the assista nce of Miss Janet David son and others at th e Auckland Institute and Mu seum in Auckland, Ne w Zealand , for making available for study the skeletal collection here to be describ ed. My thanks ar e also due to Miss Da vidson for supplying me with information regarding her archaeological excava tions a nd exhumation of th ese bones. Also, I am indebted to th e Department of Anthropology, Universit y of Auckland 's photographer, Mr . Cyr il Schollum, who did much of th e ph otographic work here presented, as well to Mr. John Glover for assistance and fine work at th e Univ ersity of T oronto.
A stress analysis of the primate mandible suggests that vertically deep jaws in the molar region are usually an adaptation to counter increased sagittal bending stress about the balancing-side mandibular corpus during unilateral mastication. This increased bending stress about the balancing side is caused by an increase in the amount of balancing-side muscle force. Furthermore, this increased muscle force will also cause an increase in dorsoventral shear stress along the mandibular symphysis. Since increased symphyseal stress can be countered by symphyseal fusion and as increased bending stress can be countered by a deeper jaw, deep jaws and symphyseal fusion are often part of the same functional pattern. In some primates (e.g., Cercocebus albigena), deep jaws are an adaptation to counter bending in the sagittal plane during powerful incisor biting, rather than during unilateral mastication.
The stress analysis of the primate mandible also suggests that jaws which are transversely thick in the molar region are an adaptation to counter increased torsion about the long axis of the working-side mandibular corpus during unilateral mastication. Increased torsion of the mandibular corpus can be caused by an increase in masticatory muscle force, an increase in the transverse component of the postcanine bite force and/or an increase in premolar use during mastication.
Patterns of masticatory muscle force were estimated for galagos and macaques, demonstrating that the ratio of working-side muscle force to balancing-side muscle force is approximately 1.5:1 in macaques and 3.5:1 in galagos during unilateral isometric molar biting. These data support the hypothesis that mandibular symphyseal fusion is an adaptative response to maximize unilateral molar bite force by utilizing a greater percentage of balancing-side muscle force.
The mammalian mandible, and in particular the human mandible, is generally thought to function as a lever during biting. This notion, however, has not gone unchallenged. Various workers have suggested that the mandible does not function as a lever, and they base this proposition on essentially two assertions: (1) the resultant of the forces produced by the masticatory muscles always passes through the bite point; (2) the condylar neck and/or the temporomandibular joint is unsuited to withstand reaction forces during biting.
A review of the electromyographic data and of the properties of the tissues of the temporomandibular joint do not support the non-lever hypothesis of mandibular function. In addition, an analysis of the strength of the condylar neck demonstrates that this structure is strong enough to withstand the expected reaction force during lever action.
Ordinarily the human mandible and the forces that act upon it are analyzed solely in the lateral projection. Moments are then usually analyzed about the mandibular condyle; however, some workers have advocated taking moments about other points, e.g., the instantaneous center of rotation. Obviously it makes no difference as to what point is chosen since the moments about any point during equilibrium conditions are equal to zero.
It is also useful to analyze the forces acting on the mandible in the frontal projection, particularly during unilateral biting. The electromyographic data suggest that during powerful unilateral molar biting the resultant adductor muscle force is passing between the bite point and the balancing (non-biting side) condyle. Therefore, in order for this system to be in equilibrium there must be a reaction force acting on the balancing condyle. This suggests that reaction forces are larger on the balancing side than on the working side, and possibly explains why individuals with a painful temporomandibular joint usually prefer to bite on the side of the diseased joint.
Muscle tissue consists of cylindrical, multinucleated cells called muscle fibers. A skeletal muscle contains many long fibers that have the ability to contract. This contractile property resides in specialized and interacting proteins localized in myofibrils making up the muscle fiber. Myofibrils have a transverse banding pattern that gives skeletal muscle its striated appearance. This banded pattern is produced by the alignment of a sequence of sarcomeres, the contractile units of the muscle fiber.
Hylander ('78) recently published important new data on bite force in humans, and showed that the human mandible cannot function purely as a link during incisal biting. He concluded instead that the mandible acts as a lever. Reexamination of Hylander's data suggests that the mandible cannot function purely as a lever either, and in fact it probably functions simultaneously as both lever and link during incisal biting.
Study of the dry weights of primate and non-promate masticatory musculature reveals a significant relationship between the Anterior Temporalis/Masseter ratio and the relative development of the anterior dentition. Available dietary information demonstrates that species emphasizing incisal preparation of food have a high AT/M index; species emphasizing molar occlusion have a low AT/M index. Utilizing this information, a model is presented of the origin of the anthropoid post-orbital septum. Frugivory or extensive incisal preparation of food is causally related to the development of the post-orbital septum, because diet can then create selection pressures for an increasingly tendinous and enlarging anterior segment of the temporalis muscle which requires additional bony areas of orgin in the anterior temporal fossa. Cenozoic climatic oscillations leading to increasing seasonality may have been the triggering element in this model, because seasonality creates periods in which the availability of fruit is relatively predictable.
Adult Polynesian mandibles are predominantly of the rocker form. Polynesian crania have an open cranial base angle, and a rather large upper facial height in the adult. The mandibular growth rotations necessary for normal occlusion to be maintained in the presence of this cranial morphology lead to development of a particularly small gonial angle. There is an increased 'bowing' of the basal component of the bone. Such 'bowing' leads to a sufficiently posterior displacement of the basal component in the gonial region for the development of a distinct angular process (for muscle attachment) to be unnecessary.
Most adult Polynesian mandibles are of the rocker form. Polynesian crania possess a very open cranial base angle and a large upper facial height. The mandibular growth rotations necessary to maintain occlusion in the presence of this cranial morphology lead to development of an exceptionally closed ramus-body angle, with consequent loss of the antegonial notch and appearance of the rocker form.
The Polynesian people who settled a wide area of the tropical Pacific have a large and muscular body phenotype that appears to contradict the classical biological rules of Bergmann and Allen. However, a scrutiny of the conditions actually experienced by these canoe voyagers and small-island dwellers suggests that in reality the oceanic environment is labile and frequently very cold, and from it tribal technology offered little protection. The Polynesian phenotype is considered to be appropriate to, and have undergone selection for, this oceanic environment.
As an anatomical region the head combines great diversity of function with close integration of structure. Consequently no structural component has autonomy of form. There is a sequence of maturation of functions and their related structural components, and in this sequence the nervous system and its supportive structures mature first. The nasal airway matures next in response to increasing body mass, and the masticatory system constitutes the last major functional system to reach maturity. The later the maturation of the function, the greater is the requirement for its related morphology to adapt to preceding skeletal templates. These matters of developmental sequence, and extrinsic as well as intrinsic craniofacial functions, are paramount considerations in interpreting the form of any component of head anatomy.
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.
Craniofacial morphology and cultural cranial deformation were analyzed by the computer morphometric system in 79 adult Hawaiian skulls from Mokapu, Oahu. The average Hawaiian male was large, but similar in shape to the female. Both were larger than the present Caucasian, showed a greater dental protrusion, and possessed a larger ANB angle, flatter cranial base, and larger facial heights. Correlations in Hawaiian craniofacial structure were found between an increasing mandibular plane angle and (1) shorter posterior facial height, (2) larger gonial angle, (3) larger cranial base angle, and (4) smaller SNA and SNB angles.
Of the 79 skulls studied, 8. 9% were found to have severe head molding or intentional cranial deformation. Significant statistical differences between the molded group and the nonmolded group are, in decreasing significance: (1) larger upper face height, (2) smaller glabella to occiput distance, and (3) increased lower face height with deformation. The morphometric differences were readily seen by graphic comparison between groups. It is postulated that external forces to the neurocranium result in redirection of the growth vectors in the neurocranial functional matrix, including the cranial base, and secondarily, to the orofacial functional matrix. There is a possibility that the cranial deformation is a retention of the normal birth molding changes.
The Polynesian “rocker jaw” was found in 81% to 95% of this populace. This mandibular form occurs only with attainment of adult stature and craniofacial form. This data agrees with the hypothesis that mandibular form is modified by the physical forces present and their direction in the orofacial functional matrix.
Expected mean values and a range of normal values (plus or minus twice the standard deviation) are presented for the vital capacity and the maximum breathing capacity of female children and adolescents.
Although multiple correlation does not demonstrate a particularly higher degree of predictability it is recommended that the above values be based upon the four attributes (age, height, weight, and body surface area) rather than upon a single attribute. This is especially important in the abnormally shaped individual.
Expected mean values and a range of normal values (plus or minus two standard deviations) are presented for the vital capacity and the maximum breathing capacity of male children and adolescents.
It is recommended that calculations of the above values be based upon four attributes (age, height, weight, and body surface area) rather than upon a prediction deriving from a single attribute (especially in the individual who does not have a standard height and weight for his age).
Lehrbuch der Anthropologie Stature and nose height of Japanese
- Martin
Martin R (1928) Lehrbuch der Anthropologie. 2nd ed. Jena: Fischer Miyashita T and Takahashi E (1971) Stature and nose height of Japanese. Hum. Biol. 43:327-339.
On the skeleton of an aboriginal inhabit-ant of the Chatham Islands
- Knox
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Knox FJ (1872) On the skeleton of an aboriginal inhabit-ant of the Chatham Islands. Trans. New Zealand Institute 5:304-306.
The Mammalian Skull The Aleut Dentition Nonlever action of the mandible: The return of the Hydra
- Moore
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Moore WJ (1981) The Mammalian Skull. Cambridge: Cambridge University Press. Moorrees CFA (1957) The Aleut Dentition. Cambridge, MA: Harvard University Press. Picq PG, Plavcan JM, and Hylander WL (1987) Nonlever action of the mandible: The return of the Hydra. Am. J. Phys. Anthrop. 74:305-308.
Early Hawaiians. Lexington: The Uni-versity Press of KentuckyThe Human Palate
- Snow
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Snow CE (1974) Early Hawaiians. Lexington: The Uni-versity Press of Kentucky. Taylor RMS (1962)The Human Palate. Acta Anat. 49:l-108 Suppl. 43.
Cranial variation in Man. Papers of the Peabody Museum
- Howells
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Howells WW (1973a) Cranial variation in Man. Papers of the Peabody Museum. 67:l-243.
An Atlas of Craniofacial Growth. Monograph No. 2: Craniofacial Growth Series, Center for Human Growth and Development. Ann Arbor: The University of Michigan Body weight, race and climate
- Moyers Re Ja Mcnamara
- Hunter
Riolo ML, Moyers RE, McNamara JA, and Hunter WS (1974) An Atlas of Craniofacial Growth. Monograph No. 2: Craniofacial Growth Series, Center for Human Growth and Development. Ann Arbor: The University of Michigan. Roberts DF (1953) Body weight, race and climate. Am. J. Phys. Anthrop. 11:533-558.
The craniology of the Oceanic races Skrifter utgitt av Det Norske Videnskaps-Akademi i Oslo A biometric study of the " flatness " of the facial skeleton in Man
- Wagner
Wagner K (1937) The craniology of the Oceanic races. Skrifter utgitt av Det Norske Videnskaps-Akademi i Oslo. I. Mat.-Naturv. Klasse No 2. Woo TL and Morant GM (1934) A biometric study of the " flatness " of the facial skeleton in Man. Biometrika. 26: 196-250.
Report on the scientific results of the explorin voyage of HMS Challenger 1873-1876. Re-port on t8e human crania
- Turner
Turner W (1884) Report on the scientific results of the explorin voyage of HMS Challenger 1873-1876. Re-port on t8e human crania. Zoology lO:73-81.
People of the Cook Islands-Past and Present
- Katayama
Katayama K and Tagaya A (1988) People of the Cook Islands-Past and Present. Rarotonga: Cook Islands Library and Museum Society Bulletin No.
Hawai-ian craniofacial morphometrics Contribution to the osteology of the 127:251-260. M h
- Schendel
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Schendel SA, Walker G, and Kamisugi AL (1980) Hawai-ian craniofacial morphometrics. Am. J. Phys. Anthrop. Scott J H (1894) Contribution to the osteology of the 127:251-260. M h. 52:491-500.