The Alpha Taxonomy of Australopithecus africanus

The identification of species in the fossil record has long vexed paleontologists because of its inherent difficulty, and it has long preoccupied them because of its fundamental significance. Australopithecus africanus exemplifies this difficulty and importance. This species, as commonly defined, is viewed by some as having played a role in the evolution of the genus Homo, while others consider it to have been uniquely related to Paranthropus. A third opinion places it near the base of the evolutionary divergence of the “robust” australopith and human lineages. Various analyses find A. africanus to be phylogenetically unstable, and this is almost certainly owing to its craniodental variability. This has led to questions concerning the taxonomic homogeneity of the assemblages from Taung, Sterkfontein, and Makapansgat that comprise its hypodigm. Initial discoveries at these sites were attributed to different species and possibly genera, but subsequent studies suggested that these fossils represent a single, albeit variable taxon. This paradigm has become current conventional paleoanthropological wisdom, but observations about the degree and pattern of variability evinced by these fossils have raised anew the possibility that the A. africanus hypodigm is taxonomically heterogeneous. Various workers have proposed that at least some of these fossils belong to a different taxon, but there is notable lack of agreement over the manner in which they should be sorted. Morphometric studies tend to find little, if any, support for taxonomic heterogeneity, but they may not have directly addressed those features that have been suggested to differ. Novel innovative technological and quantitative approaches are required to adequately address the possible taxonomic heterogeneity of the A. africanus hypodigm.