Harmon Elizabeth
Department of Anthropology, Hunter College City University of New York, 695 Park Avenue, New York, NY 10065, USA.
J Hum Evol. 2009 Jun;56(6):551-9. doi: 10.1016/j.jhevol.2009.01.002. Epub 2009 May 15.
Aside from use as estimates of body mass dimorphism and fore to hind limb joint size comparisons, postcranial elements have not often contributed to assessments of variation in Australopithecus africanus. Meanwhile, cranial, facial, and dental size variation is interpreted to be high or moderately high. Further, the cranial base and face express patterns of structural (shape) variation, which are interpreted by some as evidence for the presence of multiple species. Here, the proximal femur is used to consider postcranial size and shape variation in A. africanus. Original fossils from Makapansgat and Sterkfontein, and samples from Homo, Pan, Gorilla, and Pongo were measured. Size variation was assessed by comparing the A. africanus coefficient of variation to bootstrapped distributions of coefficient of variation samples for each taxon. Shape variation was assessed from isometrically adjusted shape variables. First, the A. africanus standard deviation of log transformed shape variables was compared to bootstrapped distributions of logged standard deviations in each taxon. Second, shape variable based Euclidean distances between fossil pairs were compared to pairwise Euclidean distance distributions in each reference taxon. The degree of size variation in the A. africanus proximal femur is consistent with that of a single species, and is most comparable to Homo and Pan, lower than A. afarensis, and lower than some estimates of cranial and dental variation. Some, but not all, shape variables show more variation in A. africanus than in extant taxa. The degree of shape difference between some fossils exceeds the majority of pairwise differences in the reference taxa. Proximal femoral shape, but not size, variation is consistent with high estimates of A. africanus cranial variation.
除了用于估计体型二态性以及比较前后肢关节大小外，颅后骨骼元素在评估南方古猿非洲种的变异方面贡献不大。与此同时，颅骨、面部和牙齿大小的变异被认为程度较高或适中。此外，颅底和面部呈现出结构（形状）变异模式，一些人将其解释为存在多个物种的证据。在此，近端股骨被用于研究南方古猿非洲种的颅后大小和形状变异。对来自马卡潘斯盖特和斯特克方丹的原始化石，以及来自人属、黑猩猩属、大猩猩属和猩猩属的样本进行了测量。通过将南方古猿非洲种的变异系数与每个分类单元的变异系数样本的自展分布进行比较来评估大小变异。从等距调整后的形状变量评估形状变异。首先，将南方古猿非洲种对数转换后的形状变量的标准差与每个分类单元的对数标准差的自展分布进行比较。其次，将化石对之间基于形状变量的欧几里得距离与每个参考分类单元中的成对欧几里得距离分布进行比较。南方古猿非洲种近端股骨的大小变异程度与单一物种的情况一致，与人类和黑猩猩最为相似，低于阿法南方古猿，且低于一些颅骨和牙齿变异的估计值。一些但并非所有的形状变量在南方古猿非洲种中显示出比现存分类单元更多的变异。一些化石之间的形状差异程度超过了参考分类单元中大多数成对差异。近端股骨形状的变异，而非大小的变异，与南方古猿非洲种颅骨变异的高估计值一致。
