Several elements join to make the masticatory system of Australopithecus boisei a most specialized apparatus, in which the jaws are immensely powerful, the occlusal load is evenly distributed along longer segments of the dental arcade, and the occlusal contact between the postcanine teeth is simultaneous. These properties are achieved by the occlusal plane being positioned far beneath the transverse plane of the fulcrum of the lower jaw (i.e., the articular eminence), by the extension of the masticatory muscles away from that point, and by the retraction of the dental arcade closer to the coronal level of the eminence. The biomechanical advantage of these changes in the mandibular lever is simple, easily comprehensible from a mechanical point of view, and has been demonstrated experimentally (Ward and Molnar, 1980). The modifications are realized anatomically through features such as an extremely high, very wide mandibular ramus, a very long upper face, and a concave facial topography in which the central portion lies deeper than the periphery. In addition, the M3 is situated (hidden) behind the anterior margin of the ramus, close to the coronal plane of the articular eminence.