Early hominid species and speciation

Abstract

Early hominid cranial, mandibular and dental remains prior to one million years were reviewed morphometrically, on the basis of a maximum of 140 cranial, 28 mandibular and 173 dental variables. Existing species were tested for excessive variability and for coherence with respect to the possession of either species-specific characters or unique combinations of symplesiomorphic character states. The specimens were resolved into the following species: Australopithecus afarensis, A. africanus, Paranthropus robustus, P. boisei, Paranthropus aff. P. boisei, Homo habilis, H. rudolfensis and H. ergaster. Australopithecus afarensis is confirmed as the most primitive of the known hominid taxa, but the relationships of A. africanus are unclear. Some features of H. rudolfensis, which includes KNM-ER 1470 and 1802, resemble those in the Paranthropus clade. These features are most parsimoniously interpreted as convergent similarities, and they reinforce earlier conclusions that homoplasies are relatively commonplace in the hominid fossil record.