Body, head, and facial growth: comparison between macaques (Macaca fuscata) and chimpanzee (Pan troglodytes) based on somatometry.

Chimpanzees and macaques were compared in their growth of head, face and body, based on a large-scale somatometrical database. Their growth stages, i to v, were determined by inflection points in velocity curves. Sex differences in their growth are shown both by elongated stages in juvenile and adolescent and by the greater velocity in males in the stages. Chimpanzees need longer to get their full growth, especially in the later infantile and juvenile stages. The growth patterns are classified into three types of "sigmoid", "parabolic", and "fast & slow" in distance curves, and in velocity curves, they correspond to "convex", acceleration in mid-growth stage; "linear", linear deceleration with age; and "concave", rapid deceleration in earlier stages and slow velocity in later stages. Great differences between chimpanzees and macaques were found in their growth patterns of upper facial height and facial height, which are "linear" or intermediate of "linear" and "concave" in macaques and "concave" in chimpanzees. These differences in their growth patterns explain the characteristic development of craniofacial proportions.