Mechanical implications of chimpanzee positional behavior

1991/12/01 by Kevin D. Hunt · 162 citations
Biochemistry, Genetics and Molecular Biology · Medicine · Neuroscience · Psychology · #Acromion #Anatomy #Animal Vocal Communication and Behavior #Biceps #Biology #Climbing #Deltoid curve #Elbow #Hemispheric Asymmetry in Neuroscience #Humerus #Medicine #Olecranon #Primate Behavior and Ecology #Rib cage #Rotator cuff #Scapula #Torso

paper · doi:10.1002/ajpa.1330860408

published in American Journal of Physical Anthropology 86(4), 521-536 (Wiley)

openalex publication_date 1991/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25

Abstract

Mechanical hypotheses concerning the function of chimpanzee anatomical specializations are examined in light of recent positional behavior data. Arm-hanging was the only common chimpanzee positional behavior that required full abduction of the humerus, and vertical climbing was the only distinctive chimpanzee positional behavior that required forceful retraction of the humerus and flexion of the elbow. Some elements of the chimpanzee anatomy, including an abductible humerus, a broad thorax, a cone-shaped torso, and a long, narrow scapula, are hypothesized to be a coadapted functional complex that reduces muscle action and structural fatigue during arm-hanging. Large muscles that retract the humerus (latissimus dorsi and probably sternocostal pectoralis major and posterior deltoid) and flex the elbow (biceps brachii, probably brachialis and brachioradialis) are argued to be adaptations to vertical climbing alone. A large ulnar excursion of the manus and long, curved metacarpals and phalanges are interpreted as adaptations to gripping vertical weight-bearing structures during vertical climbing and arm-hanging. A short torso, an iliac origin of the latissimus dorsi, and large muscles for arm-raising (caudal serratus, teres minor, cranial trapezius, and probably anterior deltoid and clavicular pectoralis major) are interpreted as adaptations to both climbing and unimanual suspension.

Citations

• Positional behavior of Pan troglodytes in the Mahale Mountains and Gombe Stream National Parks, Tanzania

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