A probabilistic approach to the craniometric variability of the genus Homo and inferences on the taxonomic affinities of the first human population dispersing out of Africa

There is probably no paleoanthropological issue with deeper disagreements than the taxonomic status of the Early–Middle Pleistocene members of the genus Homo One reason could be the difficulty of estimating the relationship between morphological and taxonomic diversity. In an attempt to contribute new evidence to this debate, bootstrapping techniques are used for analyzing the cranial variability of Homo. The results indicate that: (i) the size of the neurocranium relative to the viscerocranium discriminates better among extant hominoid species than skull size; (ii) no cluster of fossil specimens of Homo exceeds the morphological variability of Gorilla gorilla, with the only exception of the one that comprises all members of Homo except modern humans; and (iii) some clusters are taxonomically more consistent than others, as long as they show a range of morphological variability similar to that found in both Pan troglodytes and Homo sapiens. According to these results, three taxa are tentatively suggested for Homo: (i) anatomically modern humans; (ii) an “erectine” morphotype plus Neanderthals; and (iii) a “habiline” cluster. Finally, the results indicate a greater taxonomic affinity for the human population involved in the first dispersal “Out of Africa” with the “habiline” group, which agrees with the early age reported for Dmanisi (1.77 Ma), a Georgian site placed at the gates of Europe.