Department of Anatomy, NYIT College of Osteopathic Medicine, Old Westbury, NY 11568, USA
J Exp Biol. 2020 Jul 28;223(Pt 14):jeb224360. doi: 10.1242/jeb.224360.
The origin and evolution of knuckle-walking has long been a key focus in understanding African ape, including human, origins. Yet, despite numerous studies documenting morphological characteristics potentially associated with knuckle-walking, little quantitative three-dimensional (3-D) data exist of forelimb motion during knuckle-walking. Nor do any comparative 3-D data exist for hand postures used during quadrupedalism in monkeys. This lack of data has limited the testability of proposed adaptations for knuckle-walking in African apes. This study presents the first 3-D kinematic data of the wrist, hand and metacarpophalangeal joints during knuckle-walking in chimpanzees and in macaques using digitigrade and palmigrade hand postures. These results clarify the unique characteristics of, and commonalities between, knuckle-walking and digitigrady/palmigrady in multiple planes of motion. Notably, chimpanzees utilized more wrist ulnar deviation than any macaque hand posture. Maximum extension of the chimpanzee wrist was slight (5-20 deg) and generally overlapped with macaque digitigrady. Metacarpophalangeal joint motion displayed distinct differences between digits in both species, likely related to the timing of force application. These data also reveal that maximum metacarpophalangeal extension angles during knuckle-walking (26-59 deg) were generally higher than previously considered. In macaques, maximum metacarpophalangeal extension during digitigrady and palmigrady overlapped for most digits, highlighting additional complexity in the interpretation of skeletal features that may be related to limiting metacarpophalangeal motion. Most importantly, however, these new 3-D data serve as a fundamental dataset with which evaluation of proposed musculoskeletal adaptations for knuckle-walking can be tested.
手性行走的起源和进化一直是理解包括人类在内的非洲猿类起源的一个关键焦点。然而，尽管有许多研究记录了与手性行走相关的形态特征，但在手性行走过程中，关于前肢运动的定量三维（3-D）数据很少，也没有猴子四肢行走时手部姿势的比较 3-D 数据。这种数据的缺乏限制了对非洲猿类手性行走适应的可测试性。本研究首次提供了黑猩猩和猕猴在手性行走、趾行和掌行时手腕、手部和掌指关节的 3-D 运动学数据。这些结果阐明了手性行走和趾行/掌行在多个运动平面的独特特征和共性。值得注意的是，黑猩猩的腕关节尺侧偏斜比任何猕猴的手部姿势都多。黑猩猩腕关节的最大伸展度稍小（5-20 度），与猕猴的趾行基本重叠。在两个物种中，掌指关节的运动在各个手指之间表现出明显的差异，这可能与力的施加时间有关。这些数据还表明，手性行走时最大掌指关节伸展角（26-59 度）通常高于以前认为的角度。在猕猴中，趾行和掌行时的最大掌指关节伸展角在大多数手指上重叠，这突出了与限制掌指关节运动相关的骨骼特征解释的额外复杂性。然而，最重要的是，这些新的 3-D 数据为评估手性行走的肌肉骨骼适应提供了一个基本数据集。
