The Upright Ape: A New Origin of the Species
by Aaron G. Filler, MD, PhD
Figure 10-1 Knuckle-Walking & Diagonograde Posture
Figure 10-1 - Hands and spine in primate walking.
A1 A monkey walking with palmigrade/plantigrade posture. The full hand and foot is applied flat to the ground during contact and stance phases of the gait. The elbows point backwards and are flexed. The spine is parallel to the ground (pronograde).
A2 A chimpanzee knuckle-walks using the 2nd knuckle (phalanx) for ground contact with elbows straight and pointed out laterally. The spine is diagonal to the ground (diagonograde).
B A gorilla skeleton demonstrating knuckle-walking posture with diagonograde orientation of the spine.
C1 Biomechanics and anatomy of knuckle walking hand posture. The heavy arrows show the joint between the first knuckle and the long bones of the hand (metacarpo-phalangeal joint).
C2 the hand in suspension the arrows draw attention to the bony ridges that limit extension of the joint to show that similar mechanical demands arise in suspension and in knuckle-walking .
|Figure credits -
A - Redrawn, modified by M. Rivera after: Simons, E. L. (1972). Primate Evolution; An Introduction to Man's Place in Nature. New York, Macmillan; and after: Hildebrand, M. (1968). Symmetrical gaits of primates. American Journal of Physical Anthropology, 26:119-130.
B - Redrawn, modified by M. Rivera after: drawing by Jack J. Kuntz in Eimerl, S. and I. DeVore (1968). The Primates. New York,, Time-Life Books.
C - Redrawn, modified by AGF after: Preuschoft, H. (2004). Mechanisms for the acquisition of habitual bipedality: are there biomechanical reasons for the acquisition of upright bipedal posture? Journal of Anatomy 204(5): 363-84.