Drapeau Michelle S M, Ward Carol V
Département d'Anthropologie, Université de Montréal, Montréal, QC, Canada H3C 3J7.
Am J Phys Anthropol. 2007 Mar;132(3):327-43. doi: 10.1002/ajpa.20533.
Forelimb proportions have been used to infer locomotor adaptation in Australopithecus afarensis. However, little is known about proportions among individual forelimb segments in extant or fossil hominoids. The partial A. afarensis skeleton A.L. 438-1 and the more complete skeleton A.L. 288-1 provide the opportunity to assess relative length of the arm, forearm, wrist, and palm. We compare scaling relationships between pairs of forelimb bones of extant hominoids and A. afarensis, and length of individual forelimb elements to a body size surrogate. Hylobatids, and to a lesser extent orangutans, have the longest forelimb bones relative to size, although the carpus varies little among taxa, perhaps due to functional constraints of the wrist. Pan species are unique in having long metacarpals relative to ulnar length, demonstrating that they probably differ from the common chimp-human ancestor, and also that developmental mechanisms can be altered to results in differential growth of individual forelimb segments. A. afarensis has no forelimb bones that are significantly longer than those of humans for its size. It falls within the range of variation seen in modern humans for all comparisons relative to size, but appears to differ from the typical human brachial index due to a slightly shorter humerus and/or slightly longer ulna. It has short metacarpals like humans only among hominoids. Thus, while Pan may have elongated its metacarpus relative to ulnar length, A. afarensis may have reduced the length of its metacarpals and possibly its humerus relative to body size from the primitive condition.
上肢比例已被用于推断阿法南方古猿的运动适应性。然而，对于现存或化石类人猿个体上肢各节段之间的比例，我们却知之甚少。部分阿法南方古猿骨骼A.L. 438 - 1和更完整的骨骼A.L. 288 - 1为评估手臂、前臂、手腕和手掌的相对长度提供了契机。我们比较了现存类人猿与阿法南方古猿上肢骨对之间的缩放关系，以及个体上肢元素长度与身体大小替代指标的关系。长臂猿，以及程度稍轻的猩猩，相对于体型而言具有最长的上肢骨，尽管腕骨在不同分类群中变化不大，这可能是由于手腕的功能限制。黑猩猩物种的独特之处在于相对于尺骨长度而言掌骨较长，这表明它们可能与黑猩猩 - 人类的共同祖先不同，同时也表明发育机制可以改变，从而导致个体上肢节段的差异生长。就其体型而言，阿法南方古猿没有比人类明显更长的上肢骨。在所有与体型相关的比较中，它都落在现代人所见的变异范围内，但由于肱骨略短和/或尺骨略长，它似乎与典型的人类臂指数有所不同。在类人猿中，它只有像人类一样短的掌骨。因此，虽然黑猩猩可能相对于尺骨长度拉长了掌骨，但阿法南方古猿可能相对于体型从原始状态减少了掌骨甚至可能肱骨的长度。
