Vertebral age changes in Japanese macaques

This study deals with maturation and aging of the vertebrae in Japanese macaques (Macaca fuscata fuscata) of known chronological age. The samples used were 103 skeletons of captive raised Japanese macaques varying in age from 6-23 years. Epiphyseal union between the vertebral body and the epiphyseal disk (epiphyseal ring, annular epiphysis) and degenerative changes of the vertebrae were macroscopically examined. It was revealed that vertebral epiphyseal union develops comparatively rapidly in the sacral and cervical vertebrae, moderately in the lumbar vertebrae, and slowly in the thoracic vertebrae. It was found that, as a central tendency, the vertebral epiphyseal union begins at about 6 years of age, progresses lineally in proportion to age, and completes at about 23 years of age. However, considerable variation in developmental states of union was observed among individuals of the same age. Concerning vertebral degenerative changes, few were observed among the present samples. Compared with the other primates with regard to the timing of vertebral maturation, shortening of duration of maturation was found among humans. Human vertebrae may have become an early-maturing organ in order to sustain the increased loading that is accompanied by the adoption of habitual erect posture and bipedal locomotion.