Feldesman M R
Am J Phys Anthropol. 1982 Sep;59(1):73-95. doi: 10.1002/ajpa.1330590108.
Washburn's Late Divergence Hypothesis (LDH) makes a series of predictions about the phyletic affinities of extant hominoids and also predicts the locomotor behavior of the "formative ape," the common ancestor to the African apes and humans, and of the earliest hominids. The present study explores some of these predictions in the light of distal humerus morphology. Multivariate analysis of distal humerus metrics, corrected for the within-groups distortion of shape by size, was used to compare a broad sample of 22 modern anthropoid taxa with 15 fossils from the Fayum, Rusinga Island, Ft. Ternan, Neudorf an der March, Kanapoi, Kromdraai, Lake Turkana, and Hadar. The results of this analysis support some aspects of the LDH, while other aspects are unresolved. Specifically, the distal humeri of the large hominoids are very distinct from those of other anthropoids; however, Hylobates is not associated clearly with either hominoids or monkeys. This suggests that "brachiation" (sensu Hylobates) is too specialized a behavior and cannot explain the common set of characteristics known to unify the hominoids. Among the large apes, there is no discrimination that can be made between the African apes and Pongo, and Homo appears only slightly closer to Pongo than to the other apes. This offers little insight into the question of whether humans did, or did not, go through a "knuckle-walking" stage in their ancestry. The Oligocene and Miocene distal humeri sustain Washburn's assertion that the "formative apes" resembled the suspensory quadrupedal platyrrhines like Ateles. The Miocene P. africanus specimen highlights the uniqueness of Hylobates in showing that this fossil "bridges" the morphology of the acrobatic cebids and the morphology of the larger apes; it appears to be clearly "intermediate" between the two groups. Hylobates, by contrast, has affinities with no fossil, does not connect with the apes, and is generally isolated except for its connection with colobines. Among the Plio-Pleistocene fossils, the Hadar sample proves to be quite primitive, and may be close to the point where hominids and pongids diverged. The Kanapoi distal humerus (KP 271), far from being more "human-like" than Australopithecus, clearly associates with the hyperrobust Australopithecines from Lake Turkana. The stratigraphically late Kromdraai distal humerus is the only hominid to be projected near Homo. The Plio-Pleistocene hominids generally evince a pattern consistent with the prediction of a late separation of hominids and pongids. But, the results of this study, like many before it, fail to resolve the central question of whether the last common ancestor of the African apes and humans "knuckle-walked." It is suggested here that this may be an unresolvable problem.
沃什伯恩的晚期趋异假说（LDH）对现存类人猿的系统发育亲缘关系做出了一系列预测，还预测了“形成期猿类”（非洲猿类和人类的共同祖先）以及最早的原始人类的运动行为。本研究根据肱骨远端形态对其中一些预测进行了探讨。通过对肱骨远端测量指标进行多变量分析，并校正了因大小导致的组内形状变形，以比较22个现代类人猿分类单元的广泛样本与来自法尤姆、鲁辛加岛、特尔南堡、马尔希河畔诺伊多夫、卡纳波伊、克罗姆德拉伊、图尔卡纳湖和哈达尔的15块化石。该分析结果支持了晚期趋异假说的某些方面，而其他方面仍未得到解决。具体而言，大型类人猿的肱骨远端与其他类人猿的肱骨远端非常不同；然而，长臂猿与类人猿或猴子都没有明显的关联。这表明“臂行”（从长臂猿的意义上来说）是一种过于特殊的行为，无法解释已知统一类人猿的共同特征集。在大型猿类中，无法区分非洲猿类和猩猩，而且人类与猩猩的亲缘关系似乎仅略近于与其他猿类的亲缘关系。这对于人类在其祖先中是否经历过“指关节行走”阶段的问题几乎没有提供任何见解。渐新世和中新世的肱骨远端支持了沃什伯恩的观点，即“形成期猿类”类似于像蛛猴这样的悬垂四足阔鼻猴类。中新世的非洲原康修尔猿标本突出了长臂猿的独特性，表明这块化石“连接”了善于杂技的卷尾猴科动物的形态和大型猿类的形态；它似乎明显处于这两组之间的“中间”位置。相比之下，长臂猿与任何化石都没有亲缘关系，与猿类没有联系，并且除了与叶猴科有联系外通常是孤立的。在更新世-上新世化石中，哈达尔样本被证明相当原始，可能接近原始人类和猩猩类趋异的节点。卡纳波伊的肱骨远端（KP 271）远没有比南方古猿更“像人类”，它显然与来自图尔卡纳湖的超粗壮南方古猿有关联。地层年代较晚的克罗姆德拉伊肱骨远端是唯一被预测与人类接近的原始人类化石。更新世-上新世的原始人类总体上表现出一种与原始人类和猩猩类晚期分离的预测相一致的模式。但是，本研究的结果与之前的许多研究一样，未能解决非洲猿类和人类的最后共同祖先是否“指关节行走”这个核心问题。这里有人提出这可能是一个无法解决的问题。
