Growth of the Locomotor Apparatus of the Japanese Macaque: Based on Analysis of Muscular Weights and Limb Segment Lengths

Abstract

Growth of musculo-skeletal system of Japanese macaques was analysed, on the supposition that the system may grow in concordance with a functional necessity such as locomotion. Growth of bone length shows that the limbs of macaques are not specialized for running or leaping. Growth of muscle weight is remarkable, and the alteration in the weight distribution can be related to the change of locomotor pattern to some extent. Muscle growth of upper and lower limbs differs in their characteristics: growth of lower limb muscles is oriented solely to development for propulsion (pushing the body forward); that of upper limbs is oriented not only to the development of propulsion but also of control, such as rotation. Postnatal growth of muscles in man resembles that of macaque, which suggests that the function is very similar. A large difference in muscle development between man and macaque is in the magnitude of growth, that is, muscle growth in man is more remarkable than in macaque. The difference may be related to the fact that the newborn of man is less mature than that of macaque and/or that changes in the functional necessities of man are greater than those of macaque.