Figure 4.

A principal components analysis of mean mandible shape in infant, juvenile, and adult Pan (a) and Papio (b) across PC1 and PC2 described significant shape differences between genera. Occlusal (upper) and buccal (lower) views of “wire frames” illustrate mean mandible shape for each of the four age groups. Infants are at left and adults are at right. Relative to corpus breadth across the mental foramina, the corpus lengthens much more in Papio than in Pan (dotted lines). Growth in anteroposterior ramus width and corpus length distal to the mental foramen contributes more to adult jaw proportions in Pan than in Papio. In Papio, corpus growth proximal to the mental foramen contributes relatively more (dashed lines). Red squares, Pan paniscus; teal triangles, Pan troglodytes; blue diamonds, Papio anubis.