Lague Michael R
Department of Anthropology, The George Washington University, 2110 G St., NW Washington, DC 20052, USA.
J Hum Evol. 2002 May;42(5):609-26. doi: 10.1006/jhev.2002.0545.
Previous studies have recognized two patterns of distal femoral morphology among the specimens from Hadar (Ethiopia) assigned to Australopithecus afarensis. Size and shape differences between the well-preserved large (AL 333-4) and small (AL 129-1a) distal femora have been used to invoke both taxonomic and functional differences within the A. afarensis hypodigm. Nevertheless, prior studies have not analyzed these specimens in a multivariate context, nor have they compared the pattern of shape differences between the fossils to patterns of sexual dimorphism among extant taxa (i.e., the manner in which males and females differ). This study reexamines morphometric differences between the above specimens in light of observed levels of variation and patterns of sexual dimorphism among extant hominoids. Eight extant reference populations were sampled to provide a standard by which to consider size and shape differences between the fossils. Samples include three populations of modern humans, two subspecies of Pan troglodytes, three subspecies of Gorilla gorilla, Pan paniscus, and Pongo pygmaeus. Using size ratios and scale-free "shape" data (both derived from 2-D coordinate landmarks), size and shape differences between the fossils were evaluated against variation within each reference population using an exact randomization procedure. Growth Difference Matrix Analysis (GDMA) was used to test whether the pattern of morphological differences between the fossils differs significantly from patterns of sexual dimorphism observed among the ten extant groups. Overall morphometric affinities of the fossils to extant taxa were explored using canonical variates analysis (CVA). Results of the randomization tests indicate that the size difference between the Hadar femora can be easily accommodated within most hominoid taxa at the subspecific level (though not within single-sex samples). In addition, the magnitude of shape differences between the fossils can be commonly sampled even within most single-sex samples of a single hominoid subspecies. The pattern of morphological differences between the fossils does not differ statistically from any average pattern of femoral shape dimorphism observed among living hominoids. Moreover, contrary to prior claims, and despite a size disparity between the fossils greater than is typically observed within some chimpanzee and human populations, the two Hadar fossils appear to be much more similar to one another in overall shape than either specimen is to any extant hominoid group.
先前的研究已经在来自哈达尔（埃塞俄比亚）、被归类为阿法南方古猿的标本中识别出两种股骨远端形态模式。保存完好的大型（AL 333 - 4）和小型（AL 129 - 1a）股骨远端之间的大小和形状差异，已被用来推断阿法南方古猿类群内部的分类学和功能差异。然而，先前的研究没有在多变量背景下分析这些标本，也没有将化石之间的形状差异模式与现存类群中的两性异形模式（即雄性和雌性不同的方式）进行比较。本研究根据现存类人猿中观察到的变异水平和两性异形模式，重新审视上述标本之间的形态测量差异。对八个现存参考种群进行了采样，以提供一个标准，据此来考量化石之间的大小和形状差异。样本包括三个现代人类种群、黑猩猩的两个亚种、大猩猩的三个亚种、倭黑猩猩以及婆罗洲猩猩。利用大小比率和无尺度的“形状”数据（均来自二维坐标地标），通过精确随机化程序，对照每个参考种群内部的变异，评估化石之间的大小和形状差异。使用生长差异矩阵分析（GDMA）来检验化石之间的形态差异模式是否与在十个现存类群中观察到的两性异形模式有显著不同。利用典型变量分析（CVA）探索化石与现存类群的总体形态测量亲缘关系。随机化测试结果表明，哈达尔股骨之间的大小差异在大多数类人猿亚种水平上（尽管不在单性样本内）很容易得到解释。此外，即使在单个类人猿亚种的大多数单性样本中，也能普遍采样到化石之间的形状差异幅度。化石之间的形态差异模式在统计学上与在现存类人猿中观察到的任何股骨形状两性异形的平均模式没有差异。此外，与先前的说法相反，尽管化石之间的大小差异大于在一些黑猩猩和人类种群中通常观察到的差异，但这两块哈达尔化石在整体形状上彼此之间似乎比任何一块标本与任何现存类人猿群体都更为相似。
