Quantitative analysis of human mandibular shape using three-dimensional geometric morphometrics.

Human mandibular morphology is often thought to reflect mainly function, and to be of lesser value in studies of population history. Previous descriptions of human mandibles showed variation in ramal height and breadth to be the strongest difference among recent human groups. Several mandibular traits that differentiate Neanderthals from modern humans include greater robusticity, a receding symphysis, a large retromolar space, a rounder gonial area, an asymmetric mandibular notch, and a posteriorly positioned mental foramen in Neanderthals. Nevertheless, the degree to which these differences are part of modern human variation and/or are related to size and function remains unclear. The aim of this study was to document geographic and functional patterning in the mandibular shape of recent humans, to assess the effects of allometry on mandibular form, and to quantitatively evaluate proposed "Neanderthal" mandibular traits through comparison with samples of geographically diverse recent humans. Data were collected in the form of three-dimensional coordinates of 28 landmarks. Unlike previous studies, this analysis found that modern human mandibular shape exhibits considerable geographic patterning, with some aspects of mandibular morphology reflecting a climatic gradient, and others, a functional specialization. Population history is also reflected in mandibular form, albeit relatively weakly. Proposed "Neanderthal" traits were found to separate Neanderthal from modern human mandibles successfully in the statistical analysis. Of these, the retromolar gap was found to be related to increased mandibular size in modern humans. The status of this trait as a Neanderthal autapomorphy should therefore be treated with caution.

[1]  H. Breuil,et al.  The Stone Age of Mount Carmel: , 1938, Nature.

[2]  M. Singleton.  Patterns of cranial shape variation in the Papionini (Primates: Cercopithecinae). , 2002, Journal of human evolution.

[3]  Meyer Klatsky,et al.  Masticatory Stresses and their Relation to Dental Caries , 1942 .

[4]  Katerina Harvati,et al.  Quantitative analysis of Neanderthal temporal bone morphology using three-dimensional geometric morphometrics. , 2003, American journal of physical anthropology.

[5]  O. Pearson.  Activity, climate, and postcranial robusticity: implications for modern human origins and scenarios of adaptive change. , 2000, Current anthropology.

[6]  B. Demes,et al.  Biomechanical analysis of masticatory system configuration in Neandertals and Inuits. , 1993, American journal of physical anthropology.

[7]  R. Corruccini.  Australian aboriginal tooth succession, interproximal attrition, and Begg's theory. , 1990, American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics.

[8]  I. Tattersall.  Continuity or Replacement; Controversies in Homo Sapiens Evolution , 1993 .

[9]  J. Hublin.  Climatic Changes, Paleogeography, and the Evolution of the Neandertals , 2002 .

[10]  D. Dean.  The Middle Pleistocene Homo erectus/H. sapiens transition : new evidence from space curve statistics , 1993 .

[11]  B. Arensburg,et al.  Rethinking the Levantine Middle Paleolithic Hominids , 1998 .

[12]  Steegmann At.  Frostbite of the human face as a selective force. , 1967, Human biology.

[13]  S. Schendel,et al.  Hawaiian craniofacial morphometrics: average Mokapuan skull, artificial cranial deformation, and the "rocker" mandible. , 1980, American journal of physical anthropology.

[14]  Y. Kaifu.  Changes in mandibular morphology from the Jomon to modern periods in eastern Japan. , 1997, American journal of physical anthropology.

[15]  B. Vandermeersch.  Les hommes fossiles de Qafzeh, Israël , 1981 .

[16]  W S Hunter,et al.  Disproportionate sexual dimorphism in the human face. , 1972, American journal of physical anthropology.

[17]  T. Holliday,et al.  Body proportions in Late Pleistocene Europe and modern human origins. , 1997, Journal of human evolution.

[18]  R. Corruccini.  An epidemiologic transition in dental occlusion in world populations. , 1984, American journal of orthodontics.

[19]  W. J. Moore,et al.  Changes in the size and shape of the human mandible in Britain. , 1968, British dental journal.

[20]  A. Rosas,et al.  Issues in the identification of Neandertal derivative traits at early post-natal stages , 1996 .

[21]  R. Quam,et al.  A REASSESSMENT OF THE TABUN C2 MANDIBLE , 2002 .

[22]  Hertha De Villiers,et al.  The skull of the South African Negro : a biometrical and morphological study , 1968 .

[23]  Vincent H. Stefan,et al.  Discrete trait and dental morphometric affinities of the Tabun 2 mandible. , 1998, Journal of human evolution.

[24]  W. Howells,et al.  Cranial Variation in Man: A Study by Multivariate Analysis of Patterns of Difference Among Recent Human Populations , 1975 .

[25]  Antonio Rosas,et al.  Thin-plate spline analysis of allometry and sexual dimorphism in the human craniofacial complex. , 2002, American journal of physical anthropology.

[26]  W. Hylander.  The Adaptive Significance of Eskimo Craniofacial Morphology , 1977 .

[27]  C. Stringer,et al.  Morphological variation in great ape and modern human mandibles , 1999, Journal of anatomy.

[28]  Y. Rak.  The Neanderthal: A new look at an old face , 1986 .

[29]  P. O'higgins,et al.  Facial growth in Cercocebus torquatus: an application of three‐dimensional geometric morphometric techniques to the study of morphological variation , 1998, Journal of anatomy.

[30]  G. Harrower.  A BIOMETRIC STUDY OF ONE HUNDRED AND TEN ASIATIC MANDIBLES , 1928 .

[31]  D. Lieberman,et al.  Effects of food processing on masticatory strain and craniofacial growth in a retrognathic face. , 2004, Journal of human evolution.

[32]  L. Maclatchy,et al.  Neanderthals and modern humans in western Asia , 2000 .

[33]  A. Steegmann,et al.  Cold adaptation and the human face. , 1970, American journal of physical anthropology.

[34]  K. Harvati.  The Neanderthal taxonomic position: models of intra- and inter-specific craniofacial variation. , 2003, Journal of human evolution.

[35]  A. Steegmann,et al.  A study of relationships between facial cold response and some variables of facial morphology. , 1965, American journal of physical anthropology.

[36]  R. Corruccini,et al.  Occlusal variation related to soft diet in a nonhuman primate. , 1982, Science.

[37]  M. Boule.  L'homme fossile de la Chapelle-aux-Saints , 1909 .

[38]  F. Spencer,et al.  The Origins of modern humans : a world survey of the fossil evidence , 1984 .

[39]  T. Murphy.  The chin region of the Australian aboriginal mandible. , 1957, American journal of physical anthropology.

[40]  E. Martin.  A STUDY OF AN EGYPTIAN SERIES OF MANDIBLES, WITH SPECIAL REFERENCE TO MATHEMATICAL METHODS OF SEXING , 1936 .

[41]  S. Antón.  Tendon-associated bone features of the masticatory system in Neandertals , 1996 .

[42]  J. So.  Human Biological Adaptation to Arctic and Subarctic Zones , 1980 .

[43]  A. Rosas,et al.  Geometric morphometric analysis of allometric variation in the mandibular morphology of the hominids of Atapuerca, Sima de los Huesos site. , 2004, The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology.

[44]  Asen Balikci,et al.  The Netsilik Eskimo , 1970 .

[45]  Ofer Bar-Yosef,et al.  Origin of Anatomically Modern Humans , 1991 .

[46]  E. Giles.  SEX DETERMINATION BY DISCRIMINANT FUNCTION ANALYSIS OF THE MANDIBLE. , 1964, American journal of physical anthropology.

[47]  S. Antón,et al.  Cranial adaptation to a high attrition diet in Japanese macaques , 1996, International Journal of Primatology.

[48]  Stephen R. Frost,et al.  Neanderthal taxonomy reconsidered: implications of 3D primate models of intra- and interspecific differences. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[49]  W. Pollitzer.  The Origin of Races. , 1963 .

[50]  E. Trinkaus.  Neandertal faces were not long; modern human faces are short , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[51]  G. D. Richards,et al.  Mandibular condyle traits in Neanderthals and other Homo: a comparative, correlative, and ontogenetic study. , 2002, American journal of physical anthropology.

[52]  An Introduction to Multivariate Techniques for Social and Behavioral Sciences. , 1978 .

[53]  A. T. Steegmann,.  Frostbite of the human face as a selective force. , 1967, Human biology.

[54]  A. Thorne,et al.  The multiregional evolution of humans. , 1992, Scientific American.

[55]  Frank H. Cleaver.  A CONTRIBUTION TO THE BIOMETRIC STUDY OF THE HUMAN MANDIBLE , 1937 .

[56]  C. Ramsey,et al.  An early modern human from the Peştera cu Oase, Romania , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[57]  B. Wood,et al.  Intraspecific variation and sexual dimorphism in cranial and dental variables among higher primates and their bearing on the hominid fossil record. , 1991, Journal of anatomy.

[58]  F J Rohlf,et al.  Statistical power comparisons among alternative morphometric methods. , 2000, American journal of physical anthropology.

[59]  Y. Rak,et al.  Does Homo neanderthalensis play a role in modern human ancestry? The mandibular evidence. , 2002, American journal of physical anthropology.

[60]  A. Rosas.  Occurrence of neanderthal features in mandibles from the Atapuerca-SH site. , 2001, American journal of physical anthropology.

[61]  C. Lavelle.  A comparison between the mandibles of Romano-British and nineteenth century periods. , 1972, American journal of physical anthropology.

[62]  M. Hills.  An Introduction to Multivariate Techniques for Social and Behavioural Sciences , 1977 .

[63]  F. Weidenreich.  The mandibles of sinanthropus pekinensis : a comparative study , 1936 .

[64]  A Wennström,et al.  Isometric bite force and its relation to general muscle forge and body build. , 1970, Acta odontologica Scandinavica.

[65]  K. Aoki,et al.  Neandertals and modern humans in Western Asia , 2002 .

[66]  Y. Rak.  Does Any Mousterian Cave Present Evidence of Two Hominid Species , 2002 .

[67]  G. Krovitz,et al.  Ontogenetic migration of the mental foramen in Neandertals and modern humans. , 2004, Journal of human evolution.

[68]  David Bowers,et al.  An introduction to multivariate techniques for social and behavioural sciences , 1976 .

[69]  J. Birdsell,et al.  Races: A Study of the Problems of Race Formation in Man , 1981 .

[70]  E. Trinkaus,et al.  Determinants of retromolar space presence in Pleistocene Homo mandibles , 1995 .

[71]  D. Slice.  Three-Dimensional Generalized Resistant Fitting and the Comparison of Least-Squares and Resistant-Fit Residuals , 1996 .

[72]  F. Rohlf,et al.  A revolution morphometrics. , 1993, Trends in ecology & evolution.

[73]  Pete E Lestrel,et al.  Morphometrics for the life sciences , 2000 .

[74]  G. Morant,et al.  A BIOMETRIC STUDY OF THE HUMAN MANDIBLE , 1936 .

[75]  A. Hrdlička.  Lower jaw. I. The gonial angle. II. The bigonial breadth , 1940 .