Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna 40126, Italy; Department of Cultural Heritage, University of Bologna, Ravenna 48121, Italy.
Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles 90089, USA; Evolutionary Studies Institute, University of the Witwatersrand, Palaeosciences Centre, Private Bag 3, Wits 2050, South Africa.
J Hum Evol. 2020 May;142:102747. doi: 10.1016/j.jhevol.2020.102747. Epub 2020 Mar 31.
The adoption of bipedalism is a key benchmark in human evolution that has impacted talar morphology. Here, we investigate talar morphological variability in extinct and extant hominins using a 3D geometric morphometric approach. The evolutionary timing and appearance of modern human-like features and their contributions to bipedal locomotion were evaluated on the talus as a whole, each articular facet separately, and multiple combinations of facets. Distinctive suites of features are consistently present in all fossil hominins, despite the presence of substantial interspecific variation, suggesting a potential connection of these suites to bipedal gait. A modern human-like condition evolved in navicular and lateral malleolar facets early in the hominin lineage compared with other facets, which demonstrate more complex morphological variation within Homininae. Interestingly, navicular facet morphology of Australopithecus afarensis is derived in the direction of Homo, whereas more recent hominin species such as Australopithecus africanus and Australopithecus sediba retain more primitive states in this facet. Combining the navicular facet with the trochlea and the posterior calcaneal facet as a functional suite, however, distinguishes Australopithecus from Homo in that the medial longitudinal arch had not fully developed in the former. Our results suggest that a more everted foot and stiffer medial midtarsal region are adaptations that coincide with the emergence of bipedalism, whereas a high medial longitudinal arch emerges later in time, within Homo. This study provides novel insights into the emergence of talar morphological traits linked to bipedalism and its transition from a facultative to an obligate condition.
两足行走的采用是人类进化中的一个关键基准，它影响了距骨的形态。在这里，我们使用三维几何形态测量方法研究了已灭绝和现存原始人类的距骨形态变异性。我们整体上评估了距骨上的现代人类特征的进化时间和出现，以及它们对双足运动的贡献，分别评估了每个关节面，以及多个关节面的组合。尽管存在大量的种间变异，但所有化石原始人类都始终具有独特的特征组合，这表明这些特征组合与双足步态可能存在关联。与其他关节面相比，在人科谱系中，中足舟状骨和外踝骨面的现代人类特征较早进化为类似现代人类的特征，而其他关节面则表现出更复杂的形态变化。有趣的是，与更晚的原始人类物种（如南方古猿非洲种和南方古猿源泉种）相比，南方古猿阿法种的中足舟状骨形态在朝向人类的方向上是衍生的。然而，在这个关节面中，保留了更原始的状态。将中足舟状骨关节面与滑车和跟骨后关节面结合起来作为一个功能组合，然而，这将南方古猿与人类区分开来，因为前者的内侧纵弓尚未完全发育。我们的研究结果表明，更外翻的足部和更僵硬的内侧中跗关节区是适应双足行走的适应，而内侧纵弓则在更晚的时间内出现，出现在人类中。本研究为与双足行走相关的距骨形态特征的出现及其从兼性条件向强制性条件的转变提供了新的见解。
