Daegling D J, Grine F E
Department of Anthropology, State University of New York, Stony Brook 11794.
Am J Phys Anthropol. 1991 Nov;86(3):321-39. doi: 10.1002/ajpa.1330860302.
This investigation explores the effects of compact bone distribution on the biomechanical properties of the postcanine mandibular corpus of the fossil hominid taxa Australopithecus africanus and Paranthropus robustus. The mandibles of extant great apes, modern humans, and the fossil hominids are examined by computed tomography (CT), and compact bone contours are used to calculate cross-sectional biomechanical properties (cortical area, second moments of area, and Bredt's formula for torsional strength). The relative amount of compact bone is comparable in the modern and fossil mandibles, but the mechanical properties of A. africanus and P. robustus jaws are distinct in terms of the ratio of minimum to maximum second moments of area. This difference most likely represents a structural response to elevated torsional moments in the fossil hominids. Although the relative amount of compact bone in cross-section does not differ significantly between taxa by statistical criteria, A. africanus utilizes less cortical bone than P. robustus in the same manner in which Pongo is separated from the condition in other extant large-bodied hominoids. It has been suggested that the phenomenon of mandibular "robusticity" (expressed as an index of corpus breadth/corpus height) may be an effect of postcanine megadontia and/or reduced canine size in the australopithecines. Results presented here, however, indicate that it is unlikely that either factor adequately accounts for mandibular size and shape variation in early hominids.
本研究探讨了致密骨分布对化石人族分类群南方古猿非洲种和粗壮傍人下颌后犬齿体生物力学特性的影响。通过计算机断层扫描（CT）对现存大猩猩、现代人类以及化石人族的下颌骨进行检查，并利用致密骨轮廓来计算横截面生物力学特性（皮质面积、面积惯性矩以及扭转强度的布雷特公式）。现代和化石下颌骨中致密骨的相对含量相当，但非洲种和粗壮傍人颌骨的力学特性在最小与最大面积惯性矩的比值方面存在差异。这种差异很可能代表了化石人族对增加的扭转力矩的一种结构响应。尽管从统计学标准来看，不同分类群之间横截面中致密骨的相对含量没有显著差异，但非洲种利用的皮质骨比粗壮傍人少，这与猩猩与其他现存大体型类人猿的情况不同。有人提出，下颌“粗壮度”现象（表示为体宽/体高指数）可能是南方古猿后犬齿增大和/或犬齿尺寸减小的结果。然而，此处呈现的结果表明，这两个因素都不太可能充分解释早期人族下颌大小和形状的变化。
