Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, New Jersey, USA.
Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa.
J Anat. 2022 Aug;241(2):500-517. doi: 10.1111/joa.13660. Epub 2022 Apr 4.
The Kromdraai site in South Africa has yielded numerous early hominin fossils since 1938. As a part of recent excavations within Unit P, a largely complete early hominin calcaneus (KW 6302) was discovered. Due to its role in locomotion, the calcaneus has the potential to reveal important form/function relationships. Here, we describe KW 6302 and analyze its preserved morphology relative to human and nonhuman ape calcanei, as well as calcanei attributed to Australopithecus afarensis, Australopithecus africanus, Australopithecus sediba, Homo naledi, and the Omo calcaneus (either Paranthropus or early Homo). KW 6302 calcaneal morphology is assessed using numerous quantitative metrics including linear measures, calcaneal robusticity index, relative lateral plantar process position, Achilles tendon length reconstruction, and a three-dimensional geometric morphometric sliding semilandmark analysis. KW 6302 exhibits an overall calcaneal morphology that is intermediate between humans and nonhuman apes, although closer to modern humans. KW 6302 possesses many traits that indicate it was likely well-adapted for terrestrial bipedal locomotion, including a relatively flat posterior talar facet and a large lateral plantar process that is similarly positioned to modern humans. It also retains traits that indicate that climbing may have remained a part of its locomotor repertoire, such as a relatively gracile tuber and a large peroneal trochlea. Specimens from Kromdraai have been attributed to either Paranthropus robustus or early Homo; however, there are no definitively attributed calcanei for either genus, making it difficult to taxonomically assign this specimen. KW 6302 and the Omo calcaneus, however, fall outside the range of expected variation for an extant genus, indicating that if the Omo calcaneus was Paranthropus, then KW 6302 would likely be attributed to early Homo (or vice versa).
南非的克洛姆德莱（Kromdraai）遗址自 1938 年以来已经出土了大量早期人类化石。作为最近在 P 单元内发掘的一部分，发现了一个基本上完整的早期人类跟骨（KW6302）。由于其在运动中的作用，跟骨有可能揭示重要的形态/功能关系。在这里，我们描述了 KW6302，并分析了其保存的形态与人类和非人类猿类的跟骨，以及与南方古猿阿法种、南方古猿非洲种、南方古猿源泉种、直立人纳莱迪和奥莫跟骨（无论是傍人还是早期人类）的关系。我们使用许多定量指标来评估 KW6302 的跟骨形态，包括线性测量、跟骨粗壮度指数、相对外侧足底突位置、跟腱长度重建和三维几何形态滑动半标志分析。KW6302 的整体跟骨形态介于人类和非人类猿类之间，尽管更接近现代人。KW6302 具有许多表明它可能非常适合陆地两足运动的特征，包括相对平坦的后距骨面和与现代人相似位置的大外侧足底突。它还保留了表明攀爬可能仍然是其运动组合的一部分的特征，例如相对脆弱的结节和大的外踝滑车。克洛姆德莱的标本被归因于粗壮傍人或早期人类；然而，没有明确属于这两个属的跟骨，因此很难对这个标本进行分类学上的归属。然而，KW6302 和奥莫跟骨超出了现有属的预期变异范围，这表明如果奥莫跟骨是傍人，那么 KW6302 可能属于早期人类（反之亦然）。
