Mechanical loading of primate fingers on vertical rock surfaces

• Published in: South African Journal of Science Vol. 117; no. 11-12; pp. 131 - 136
• Main Authors: Everett, Michael C, Elliott, Marina C, Gaynor, David, Hill, Austin C, Syeda, Samar M, Casana, Jesse, Zipfel, Bernhard, DeSilva, Jeremy M, Dominy, Nathaniel J
• Format: Journal Article
• Language: English
• Published: Pretoria Academy of Science for South Africa (ASSAf) 01-11-2021; Academy of Science of South Africa
• Subjects: Baboons; bone curvature; Bones; Climbing; Curvature; Finger; Human evolution; Locomotion; Mechanical loading; Monkeys & apes; Muscles; Nature reserves; Photogrammetry; Primates; Rock climbing; Rocks; suspension; Tendons; Vertical loads; South Africa
• ISSN: 0038-2353; 1996-7489
• DOI: 10.17159/sajs.2021/10409

rock walls is attested by several populations of baboons, one of which uses a 7-m ver tical surface to enter for estimating the probability of extreme mechanical loading on the phalanges of rock-climbing primates. Here we use three-dimensional photogrammetry to show that 82-91% of the climbable surface would generate high forces on the flexor tendon pulley system and severely load the phalanges of baboons and H. naledi. If such propor tions are representative of ver tical rock surfaces elsewhere, it may be sufficient to induce stress-mitigating curvature in the phalanges of primates.Significance: • We present the first three-dimensional photogrammetric analysis of a vertical rock surface climbed by a non-human primate, the chacma baboon (Papio ursinus). • Our results show that a large proportion of a vertical rock wall would compel crimp and slope hand positions during climbing – grips that could explain the extraordinary phalangeal curvature expressed by a Middle Pleistocene hominin, Homo naledi.