Institut Català de Paleontologia Miquel Crusafont, Edifici ICTA-ICP, Carrer Columnes s/n, Campus de la UAB, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Barcelona, Spain.
Animal Postcranial Evolution (APE) Laboratory, School of Anthropology and Conservation, Marlowe Building, University of Kent, Canterbury, UK.
Evolution. 2021 Nov;75(11):2959-2971. doi: 10.1111/evo.14354. Epub 2021 Oct 15.
African apes engage in a distinct form of locomotion called knuckle-walking, but there is much ambiguity as to when and how this locomotor behavior evolved. This study aims to elucidate potential differences in knuckle-walking elbow posture and loading in African apes through the study of trabecular bone. Using a whole-epiphysis approach, we quantified variation in the trabecular structure of the distal humerus of chimpanzees, western lowland gorillas, and mountain gorillas in comparison to orang-utans, siamangs, and a sample of Old and New World monkeys. Results demonstrate differences in the distribution of trabecular bone within the distal humerus that are consistent across taxa that habitually use a flexed-elbow posture in comparison to those that use an extended elbow during locomotion. Western lowland gorillas show an extended-elbow pattern consistent with the straight forelimb position during knuckle-walking, whereas chimpanzees show a flexed-elbow pattern. Unexpectedly, mountain gorillas show an intermediate pattern between their western counterparts and chimpanzees. The differences found in elbow joint posture between chimpanzees and gorillas, and between gorilla species, point to diversification in the knuckle-walking biomechanical strategies among African apes, which has implications in the debate regarding the locomotor behavior from which human bipedalism arose.
非洲猿类采用一种独特的运动方式，称为指节行走，但这种运动行为何时以及如何进化仍存在很大的不确定性。本研究旨在通过研究骨小梁来阐明非洲猿类在指节行走时肘部姿势和受力的潜在差异。我们采用整体骺的方法，对黑猩猩、西部低地大猩猩和山地大猩猩的肱骨远端的小梁结构进行了量化，与猩猩、合趾猿以及旧大陆和新大陆猴的样本进行了比较。结果表明，在习惯性使用弯曲肘部姿势的类群与在运动中使用伸展肘部姿势的类群之间，肱骨远端的小梁骨分布存在差异，这种差异在不同的分类群中是一致的。西部低地大猩猩在指节行走时表现出伸展肘部的模式，与直的前肢姿势一致，而黑猩猩则表现出弯曲肘部的模式。出乎意料的是，山地大猩猩在其西部对应物和黑猩猩之间表现出中间模式。在黑猩猩和大猩猩之间以及大猩猩种间发现的肘部关节姿势差异表明，非洲猿类的指节行走生物力学策略存在多样化，这对有关人类两足行走起源的运动行为的争论具有重要意义。
