As more fossil evidence accumulated, some researchers entertained the possibility of locomotor diversity in contemporary early hominins (e.g.
Napier, 1964), but this view was far from prevalent. Furthermore, many of the more recent studies, informed by the growing collection of hominin postcranial fossils, have focused on the degree to which particular skeletal elements imply one type of locomotion or another.The central point is that contemporary fossil taxa may well have been mosaic in their adaptations, but, critically, may have been mosaic in different ways to each other. This has recently been shown to be the case for the feet of
A. afarensis and the new and similarly aged
A. africanus specimen ‘Little Foot’ (
Harcourt-Smith, 2002). Further analyses of other skeletal elements are needed to reinforce this interpretation. If correct, this would imply that there was more locomotor diversity in the fossil record than has been suggested, and raises questions over whether there was a single origin for bipedalism or not. At the very least, if bipedalism appeared only once in the hominin radiation and is therefore monophyletic, such evidence would suggest that there were multiple evolutionary pathways responding to that selection pressure. It is currently difficult to determine primitive from derived morphologies in the hominins because of the problem of homoplasy and resulting phylogenetic uncertainty. Although perhaps controversial, it is important that when considering such a unique adaptation as bipedalism, we do not allow that uniqueness to imply that there was ever only one successful mode of bipedalism in our hominin ancestry. In light of the richness of recent findings in the hominin fossil record, it is important to ask the question of whether the evolution of bipedalism was a more complex affair than has previously been suggested.