TABLE 4.

Muscle forces, bite forces, occlusal pressures,^a and mechanical advantage^b in the finite element models

Specimen	Total muscle force (N)	P3 bite force (N)	M2 bite force (N)	P3 occlusal area (mm2)	M2 occlusal area (mm2)	P3 occlusal pressure (MPa)	M2 occlusal pressure (MPa)	P3 mechanical advantage	M2 mechanical advantage
OH 5	5,176	2,053	3,895	185.5	361.2	11.1	10.8	0.40	0.75
Sts5	2,893	1,178	1,786	118.7	214.2	9.9c	8.3c	0.41	0.62
PC1−	2,980	1,107	1,522	76.7	105.0	14.4	14.5	0.37	0.51
PC1+	2,540	818	1,251	78.3	118.5	10.4	10.6	0.32	0.49
PC2−	2,536	999	1,481	81.6	96.9	12.2	15.3	0.39	0.58
PC2+	2,408	924	1,350	67.9	84.0	13.6	16.1	0.38	0.56
PC3−	3,268	1,244	1,779	80.5	93.5	15.4	15.8d	0.38	0.54
PC3+	3,146	1,310	1,908	79.2	106.7	16.5	17.9	0.42	0.61

^aOcclusal pressure is calculated as bite force divided by the crown area of the tooth in question (mediodistal length times buccolingual breadth). Tooth dimensions of chimpanzees were measured on CT images, and should be considered approximate. Tooth dimension of fossil hominins were obtained from www.humanoriginsdatabase.org

^bMechanical advantage is a measure of biomechanical efficiency, and can be calculated simply as the ratio of the bite force to the total muscle force. In other words, it is equivalent to the ratio of the force outputs to the force inputs.

^cNote that the tooth crown area data used to calculate pressure are derived from specimen Sts 52a, but that the corresponding bite force data are influenced strongly by the shape and configuration of specimen Sts 5. Thus, the resulting pressure data are heuristic.

^dTooth area data were calculated from the better preserved right M².