Fig. 5.

Digital surface models of the EDJ illustrating average shape differences between molars with and without a C6. To highlight the relationship between dentine horn size and spacing and the variable presence of a C6, the models to the left and right represent ‘exaggerated’ models. In analyses of the total Pan sample (A) and the Pan troglodytes sample (B) the presence of a C6 is associated with relatively short and widely spaced distal dentine horns. While there is considerable overlap in overall shape within each molar sample (see Fig. 4), the difference in average shape between molars with and without a C6 is consistent with the predictions of a cascade pattern of cusp development in chimpanzees at both a genus and a species level.