Primate Models for Behavioural Evolution Lab, Institute of Cognitive and Evolutionary Anthropology, School of Anthropology, University of Oxford, 64 Banbury Road, OX2 6PN, Oxford, United Kingdom.
Center of Natural History (CeNak), Universität Hamburg, Martin-Luther-King-Platz 3, Hamburg, 20146, Germany.
Sci Rep. 2020 Feb 26;10(1):3526. doi: 10.1038/s41598-020-60590-6.
Inferring the locomotor behaviour of the last common ancestor (LCA) of humans and African apes is still a divisive issue. An African great-ape-like ancestor using knuckle-walking is still the most parsimonious hypothesis for the LCA, despite diverse conflicting lines of evidence. Crucial to this hypothesis is the role of the centrale in the hominoid wrist, since the fusion of this bone with the scaphoid is among the clearest morphological synapomorphies of African apes and hominins. However, the exact functional significance of this fusion remains unclear. We address this question by carrying out finite element simulations of the hominoid wrist during knuckle-walking by virtually generating fused and unfused morphologies in a sample of hominoids. Finite element analysis was applied to test the hypothesis that a fused scaphoid-centrale better withstands the loads derived from knuckle-walking. The results show that fused morphologies display lower stress values, hence supporting a biomechanical explanation for the fusion as a functional adaptation for knuckle-walking. This functional interpretation for the fusion contrasts with the current inferred positional behaviour of the earliest hominins, thus suggesting that this morphology was probably retained from an LCA that exhibited knuckle-walking as part of its locomotor repertoire and that was probably later exapted for other functions.
推断人类和非洲猿类的最后共同祖先（LCA）的运动行为仍然存在争议。尽管存在各种相互矛盾的证据，但使用指节行走的非洲大型猿类祖先仍然是 LCA 最简约的假设。对于这个假设至关重要的是中央在人科腕骨中的作用，因为这块骨头与舟状骨的融合是人科动物和人属中最明显的形态共衍征之一。然而，这种融合的确切功能意义仍不清楚。我们通过在人科腕骨中进行指节行走的有限元模拟来解决这个问题，通过在人科动物样本中虚拟生成融合和未融合的形态。有限元分析被用来检验这样一个假设，即融合的舟状骨-中央骨能够更好地承受来自指节行走的负荷。结果表明，融合形态的应力值较低，因此支持融合是作为指节行走的功能适应的生物力学解释。这种融合的功能解释与目前对最早人属的推断位置行为形成对比，因此表明这种形态可能是从具有指节行走作为其运动能力一部分的 LCA 中保留下来的，并且可能后来被用于其他功能。
