Extended Data Fig. 8: Manual intermediate phalanx robusticity in KNM-ER 101000.

RU = radioulnar width. OH 7 and KNM-WT 15000 are juveniles and are missing the proximal epiphyses. Raw lengths (without epiphyses) are used in the calculation of the index plotted in (a). Data on primate epiphyseal thicknesses are scant. Conservative upper estimates of the added length added by epiphyses (an additional 2.0 mm) would put the median index slightly lower for the OH 7 specimens at 0.38 (maximum 0.39, minimum 0.37) and thus closer to the Swartkrans sample. Similarly, when the KNM-WT 15000 phalanx is estimated at an additional 2.0 mm length with epiphysis, it results in an index of 0.29. However, the growth allometry of length and width for early hominin intermediate phalanges is unknown, so caution is warranted in interpreting these metrics for such juvenile individuals. Data presented in a) consist of the following samples: KNM-ER 101000 n = 1, OH 7 n = 4, G. beringei n = 77, G. gorilla n = 48, P. troglodytes n = 68, P. paniscus n = 59, A. afarensis n = 11, A. africanus n = 4, Swartkrans n = 5, A. sediba n = 3, H. erectus n = 1, H. floresiensis n = 2, H. naledi n = 4, H. neanderthalensis n = 42, recent H. sapiens n = 155. Data presented in b) consist of the following samples: KNM-ER 101000 n = 1, OH 7 n = 4, G. beringei n = 77, G. gorilla n = 48, P. troglodytes n = 68, P. paniscus n = 59, A. afarensis n = 11, A. africanus n = 4, Swartkrans n = 5, A. sediba n = 1, H. erectus n = 1, H. floresiensis n = 3, H. naledi n = 4, H. neanderthalensis n = 42, recent H. sapiens n = 155. In both boxplots (a,b) the median is indicated by a horizontal line, the box spans the interquartile range (IQR), and the whiskers represent the minimum and maximum values in the sample. c) illustrates the observed morphology in a sample of hominin and extant ape intermediate phalanges.