Little foot and big thoughts : a re-evaluation of the Stw573 foot from Sterkfontein, South Africa

The part of the fossil assemblage Stw573 consisting of some medial foot bones was initially reported by Clarke & Tobias (Science 269 (2002) 521). They found it to have both ape- and human-like qualities, being human-like proximally and ape-like distally. We have undertaken a re-examination of this pedal assemblage using a multivariate analysis; while we also found ape- and human-like qualities, they are in direct conflict with the original findings of Clarke and Tobias. We report an essentially ape-like morphology proximally and a human-like morphology distally; the talus and navicular were found to be ape-like and the medial cuneiform human-like. We also undertook a morphometric analysis of the medial cuneiform from the fossil assemblage OH8, as this was not included in the original OH8 study of Kidd et al (J Hum Evol 31 (1996) 269); this cuneiform was found to have a human-like morphology. Thus, the medial column findings from the two assemblages are very similar. This finding, coupled with the re-evaluation of the stratigraphy at Sterkfontein (Am J Phys Anthrop 119 (2002) 192), suggests that the two may have been contemporaneous. We also note that three broad patterns of modification have been identified, equating to proximal–distal lateral–medial (cranio–caudal) and dorsal–plantar (posterior–anterior). It has not escaped our notice that these patterns are each controlled by specific genes or growth factors; we thus see a morphometric expression of our developmental past.