Extended Data Fig. 6: Hypothenar morphology in KNM-ER 101000.

Well-developed hypothenar morphology (hamate hamulus and Mc5) of the KNM-ER 101000 specimen (yellow star throughout). a) Hamulus length versus hamate body length; b) natural log-log plot of the square root (sqrt) of the area (radioulnar width x dorsopalmar depth) of the Mc5 at midshaft versus the Mc5 maximum length c) 3D surface model renderings of the KNM-ER 101000 hamate and Mc5 and comparative specimens. Mc5s are scaled to the same proximodistal length and hamates are scaled to the same proximodistal body length. The least squares regression lines are fit to the Homo sapiens samples (excluding one individual with pituitary dwarfism and one with gigantism in the hamate analysis): hamulus_length = 0.62 + 0.47 * hamate_body_length (p < 0.001, r² = 0.44); ln(Mc5_sqrt_midshaft_area) = −1.41 + 0.85 * ln(Mc5_maximum_length) (p < 0.001, r² = 0.33). Australopithecus sample: 1 = A. afarensis AL 333-50 hamate, 2 = A. cf. afarensis KNM-WT 22994-H hamate, 3 = A. sediba MH2 left hamate, 4 = A. sediba MH2 right hamate). Fossil hominins in the Mc5 plot (E): taxa symbols follow the hamate plots with addition of Ar. ramidus (green diamond) and for the Australopithecus spp. specimens 5 = A. afarensis AL 333-14, 6 = A. afarensis AL 333-89, 7 = A. afarensis AL 333-141, 8 = A. sediba MH2, 9 = A. africanus StW 63.