Molar Premolar Size

This feature is defined using an index of molar area (M1-M3) divided by premolar area (P3-P4). The relationship between premolar and molar size is likely to be associated with masticatory demands. All data for the fossil hominins has been taken from B.A. Wood (1991); data for the extant hominids are unpublished data collected by DWC. The mean index for the extant hominids (n = 122) is 2.10, with one standard deviation of 0.19. Thus, the intermediate condition is between 1.91 and 2.29. The minimum extant hominid value is 1.64, and the maximum value is 2.62 (see Cameron, 1998).

The intermediate condition (= 0) is observed in members of the "ana-mensis group" with a mean index of 2.16 (Ward et al., 2001), P. robustus with a mean index of 2.24, Pongo with a mean index of 2.03 (n = 21), Gorilla with a mean index of 2.10 (n = 35), and Pan with a mean index of 2.14 (n = 66). They are characterized by a reduction in differential size between the molar and premolar complex (whether this means the molars have decreased or the premolars have increased will be examined in the next character). A marked difference (= 1) is observed in Dryopithecus with a mean index of 2.35 (Cameron, 1998), Praeanthropus with a mean index of 2.44, Australopithecus with a mean index of 2.41, P boisei specimen OH 5 with an index of 2.55, and H. habilis with a mean index of 2.52. Significant difference between the premolar and molar complexes (= 2) is observed in Graecopithecus with a mean value of 2.75 (Cameron, 1998) and H. sapiens with a mean index of 2.80 (n = 8), which are both beyond the extant great ape maximum value.

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