FIGURE 1.

Boxplot of the scaled fascicle length (FL) of the (a) flexors, (b) extensors, (c) deviators and (d) rotators. Within the hylobatid family, the triangles represent the siamangs. For none of these groups, there is a significant difference between macaques, gibbons and bonobos. (e) In macaques, the scaled FL of the rotators is significantly different from that of their flexors (p < .001), extensors (p < .001) and deviators (p < .01). In gibbons (f) and bonobos (g), the scaled FL of the functional muscle groups are not significantly different from one another (p > .05)