Harmon Elizabeth H
Department of Anthropology, Institute of Human Origins, Tempe, Arizona State University, 85287-4101, USA.
J Hum Evol. 2006 Sep;51(3):217-27. doi: 10.1016/j.jhevol.2006.01.009. Epub 2006 Mar 30.
The degree of size and shape variation in the A. afarensis fossil sample has been interpreted in a variety of ways. Size variation has been described as exceeding that of extant hominoids, similar to that of strongly sexually dimorphic hominoids, and best matched to modern humans. The degree of shape variation has been characterized both as great and negligible. Recent fieldwork has increased the proximal femoral sample, providing new data with which to examine variation. The proximal femur of A. afarensis is analyzed in a comparative framework in order to gauge the magnitude of size and shape variation in this element. Seven of the best-preserved A. afarensis proximal femora contribute to the analysis (A.L. 128-1, A.L. 152-2, A.L. 211-1, A.L. 288-1ap, A.L. 333-3, A.L. 333-123, A.L. 827-1). Comparative samples from Pan, Pongo, Gorilla, and Homo provide context for interpreting variation among the fossils. The coefficient of variation (CV) of linear measurements is used to estimate size variation. Bootstrap resampling of CVs from extant hominoids provides distributions for comparison to A. afarensis CVs. Ratios of linear measurements provide scale-free shape variables that are used in pairwise comparisons. The Euclidean distance between pairs of A. afarensis are compared to the Euclidean distances between extant hominoid pairs. As found in some earlier analyses, size variation in A. afarensis is accommodated best in gorillas and orangutans. The magnitude of difference in shape between A. afarensis pairs is exceeded by most taxa, indicating that shape variation is not extreme. These general findings are contradicted by a few instances of excessive size and shape variation. These are uncharacteristic results and could point to temporal bias, although other alternatives are explored. The signal from the proximal femur is that size variation in A. afarensis is like that of the strongly sexually dimorphic apes, and shape variation is well within the range of most hominoids irrespective of their degree of size dimorphism.
阿法南方古猿化石样本的大小和形状变化程度有多种解读方式。大小变化被描述为超过现存类人猿，类似于性别二态性强烈的类人猿，且与现代人类最为匹配。形状变化程度既被描述为很大，也被认为微不足道。最近的实地考察增加了股骨近端样本，提供了用于检验变异的新数据。在比较框架下分析阿法南方古猿的股骨近端，以衡量该部位大小和形状变化的程度。七具保存最完好的阿法南方古猿股骨近端参与了分析（A.L. 128 - 1、A.L. 152 - 2、A.L. 211 - 1、A.L. 288 - 1ap、A.L. 333 - 3、A.L. 333 - 123、A.L. 827 - 1）。来自黑猩猩、猩猩、大猩猩和人类的比较样本为解释化石间的变异提供了背景。线性测量的变异系数（CV）用于估计大小变异。对现存类人猿的CV进行自助重采样，得到用于与阿法南方古猿CV进行比较的分布。线性测量的比率提供了无量纲的形状变量，用于成对比较。将阿法南方古猿各对之间的欧氏距离与现存类人猿各对之间的欧氏距离进行比较。正如一些早期分析中所发现的，阿法南方古猿的大小变异在大猩猩和猩猩中得到了最好的体现。大多数分类单元的形状差异程度超过了阿法南方古猿各对之间的差异程度，这表明形状变异并不极端。这些一般发现与一些大小和形状过度变异的情况相矛盾。这些是不典型的结果，可能表明存在时间偏差，不过也探讨了其他可能性。股骨近端传递的信号是，阿法南方古猿的大小变异类似于性别二态性强烈的猿类，而形状变异完全在大多数类人猿的范围内，无论其大小二态性程度如何。
