Hominin taxonomies distinguish taxa by criteria of time, space, and morphology. These »species« are defined typologically and described using a mixture of primitive and derived characters. The adoption of a cladistic perspective has led to an extension of phylogenetic principles to the problem of taxon definition, and often resulted in the simple recasting of these descriptive characters as apomorphies of their respective taxa. However, characters cannot be identified as apomorphies in the absence of a wellsupported phylogenetic hypothesis for these taxa.

The present study is a phylogenetic analysis of Middle to Late Pleistocene fossil specimens assigned to Homo antecessor, H. heidelbergensis, H. neanderthalensis, and H. sapiens, employing characters that are considered taxonomically significant for these groups. Craniodental specimens were examined and scored for a maximum of 77 discrete and continuous characters. Phylogenetic analyses employing a variety of character and taxon matrices, coding schemes, and outgroup taxa were conducted using PAUP* and MacClade, with the resulting phylogenies and synapomorphies supporting clades compared to current systematic hypotheses concerning these fossils.

Neandertals and modern H. sapiens both formed consistent, well-supported clades. H. heidelbergensis was not monophyletic in the results of any analyses and is most likely a grade taxon. There was no support for the identification of H. antecessor as the unique ancestor of modern humans. Very few traditional »taxonomic characters« support the clades they are meant to describe. These results suggest that paleoanthropologists should be more cautious about their identification of species in the fossil record and phylogenetic hypotheses concerning these taxa.