TY - JOUR
T1 - Mandibular ramus shape variation and ontogeny in Homo sapiens and Homo neanderthalensis
AU - Terhune, Claire E.
AU - Ritzman, Terrence B.
AU - Robinson, Chris A.
N1 - Funding Information:
Access to modern human materials was provided by Arleyn Simon (ASU) and Giselle Garcia (AMNH). Fossil data collection was supported by an American Association of Physical Anthropologists Professional Development award to CET, and fossil materials were made available for analysis by the Musee de l’Homme (Paris, France), the Institute de Paléontologie Humaine (Paris, France), the Smithsonian National Museum of Natural History (Washington, DC, USA), the British Natural History Museum (London, England), and the American Museum of Natural History (New York, NY, USA). We would also like to thank Carrie Healy for her assistance with the initial data collection and analysis and Erik Otárola-Castillo for his assistance with R coding. Feedback from editor Sarah Elton, the associate editor, and three anonymous reviewers greatly improved this manuscript.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/8
Y1 - 2018/8
N2 - As the interface between the mandible and cranium, the mandibular ramus is functionally significant and its morphology has been suggested to be informative for taxonomic and phylogenetic analyses. In primates, and particularly in great apes and humans, ramus morphology is highly variable, especially in the shape of the coronoid process and the relationship of the ramus to the alveolar margin. Here we compare ramus shape variation through ontogeny in Homo neanderthalensis to that of modern and fossil Homo sapiens using geometric morphometric analyses of two-dimensional semilandmarks and univariate measurements of ramus angulation and relative coronoid and condyle height. Results suggest that ramus, especially coronoid, morphology varies within and among subadult and adult modern human populations, with the Alaskan Inuit being particularly distinct. We also identify significant differences in overall anterosuperior ramus and coronoid shapes between H. sapiens and H. neanderthalensis, both in adults and throughout ontogeny. These shape differences are subtle, however, and we therefore suggest caution when using ramus morphology to diagnose group membership for individual specimens of these taxa. Furthermore, we argue that these morphologies are unlikely to be representative of differences in masticatory biomechanics and/or paramasticatory behaviors between Neanderthals and modern humans, as has been suggested by previous authors. Assessments of ontogenetic patterns of shape change reveal that the typical Neanderthal ramus morphology is established early in ontogeny, and there is little evidence for divergent postnatal ontogenetic allometric trajectories between Neanderthals and modern humans as a whole. This analysis informs our understanding of intraspecific patterns of mandibular shape variation and ontogeny in H. sapiens and can shed further light on overall developmental and life history differences between H. sapiens and H. neanderthalensis.
AB - As the interface between the mandible and cranium, the mandibular ramus is functionally significant and its morphology has been suggested to be informative for taxonomic and phylogenetic analyses. In primates, and particularly in great apes and humans, ramus morphology is highly variable, especially in the shape of the coronoid process and the relationship of the ramus to the alveolar margin. Here we compare ramus shape variation through ontogeny in Homo neanderthalensis to that of modern and fossil Homo sapiens using geometric morphometric analyses of two-dimensional semilandmarks and univariate measurements of ramus angulation and relative coronoid and condyle height. Results suggest that ramus, especially coronoid, morphology varies within and among subadult and adult modern human populations, with the Alaskan Inuit being particularly distinct. We also identify significant differences in overall anterosuperior ramus and coronoid shapes between H. sapiens and H. neanderthalensis, both in adults and throughout ontogeny. These shape differences are subtle, however, and we therefore suggest caution when using ramus morphology to diagnose group membership for individual specimens of these taxa. Furthermore, we argue that these morphologies are unlikely to be representative of differences in masticatory biomechanics and/or paramasticatory behaviors between Neanderthals and modern humans, as has been suggested by previous authors. Assessments of ontogenetic patterns of shape change reveal that the typical Neanderthal ramus morphology is established early in ontogeny, and there is little evidence for divergent postnatal ontogenetic allometric trajectories between Neanderthals and modern humans as a whole. This analysis informs our understanding of intraspecific patterns of mandibular shape variation and ontogeny in H. sapiens and can shed further light on overall developmental and life history differences between H. sapiens and H. neanderthalensis.
KW - Geometric morphometrics
KW - Growth and development
KW - Hominin evolution
UR - http://www.scopus.com/inward/record.url?scp=85046125364&partnerID=8YFLogxK
U2 - 10.1016/j.jhevol.2018.03.009
DO - 10.1016/j.jhevol.2018.03.009
M3 - Article
C2 - 29709293
AN - SCOPUS:85046125364
SN - 0047-2484
VL - 121
SP - 55
EP - 71
JO - Journal of Human Evolution
JF - Journal of Human Evolution
ER -