Toro-Ibacache Viviana, Zapata Muñoz Víctor, O'Higgins Paul
Department of Archaeology and Hull York Medical School, University of York, Heslington, York YO10 5DD, United Kingdom; Facultad de Odontología, Universidad de Chile, Sergio Livingstone Pohlhammer 943, Independencia, Región Metropolitana, Chile; Max Planck Institute for Evolutionary Anthropology, Department of Human Evolution, Deutscher Platz 6, 04103 Leipzig, Germany.
Centro de Imagenología, Hospital Clínico Universidad de Chile, Santos Dumont 999, Independencia, Región Metropolitana, Chile.
Ann Anat. 2016 Jan;203:59-68. doi: 10.1016/j.aanat.2015.03.002. Epub 2015 Mar 21.
The human skull is gracile when compared to many Middle Pleistocene hominins. It has been argued that it is less able to generate and withstand high masticatory forces, and that the morphology of the lower portion of the modern human face correlates most strongly with dietary characteristics. This study uses geometric morphometrics and finite element analysis (FEA) to assess the relationship between skull morphology, muscle force and cranial deformations arising from biting, which is relevant in understanding how skull morphology relates to mastication. The three-dimensional skull anatomies of 20 individuals were reconstructed from medical computed tomograms. Maximal contractile muscle forces were estimated from muscular anatomical cross-sectional areas (CSAs). Fifty-nine landmarks were used to represent skull morphology. A partial least squares analysis was performed to assess the association between skull shape and muscle force, and FEA was used to compare the deformation (strains) generated during incisor and molar bites in two individuals representing extremes of morphological variation in the sample. The results showed that only the proportion of total muscle CSA accounted for by the temporalis appears associated with skull morphology, albeit weekly. However, individuals with a large temporalis tend to possess a relatively wider face, a narrower, more vertically oriented maxilla and a lower positioning of the coronoid process. The FEAs showed that, despite differences in morphology, biting results in similar modes of deformation for both crania, but with localised lower magnitudes of strains arising in the individual with the narrowest, most vertically oriented maxilla. Our results suggest that the morphology of the maxilla modulates the transmission of forces generated during mastication to the rest of the cranium by deforming less in individuals with the ability to generate proportionately larger temporalis muscle forces.
与许多中更新世人类相比，人类头骨较为纤细。有人认为，它产生和承受高咀嚼力的能力较弱，而且现代人类面部下部的形态与饮食特征的相关性最强。本研究使用几何形态计量学和有限元分析（FEA）来评估头骨形态、肌肉力量与咬合引起的颅骨变形之间的关系，这对于理解头骨形态与咀嚼的关系具有重要意义。从医学计算机断层扫描中重建了20个人的三维头骨解剖结构。根据肌肉解剖横截面积（CSA）估计最大收缩肌肉力量。使用59个地标来代表头骨形态。进行了偏最小二乘分析以评估头骨形状与肌肉力量之间的关联，并使用有限元分析来比较样本中代表形态变异极端情况的两个人在切牙和磨牙咬合过程中产生的变形（应变）。结果表明，尽管相关性较弱，但只有颞肌占总肌肉CSA的比例似乎与头骨形态有关。然而，颞肌较大的个体往往面部相对较宽，上颌较窄且更垂直，冠突位置较低。有限元分析表明，尽管形态不同，但咬合导致两个颅骨产生相似的变形模式，但在最窄、最垂直的上颌个体中，局部应变幅度较低。我们的结果表明，上颌形态通过在能够产生相对较大颞肌力量的个体中较少变形来调节咀嚼过程中产生的力量向颅骨其他部分的传递。
