Early Pleistocene Homo erectus fossils from Konso, southern Ethiopia
Homo erectus has been broadly defined to include fossils from Africa, Asia, and possibly Europe, or restricted to a supposedly confined Asian clade. Recently discovered fossils of H. erectus are allowing new insights into aspects of its evolution, such as the timing and mode of the species emergence in Africa and its relationship to Asian populations. However, the currently available African record predating 1.0 Ma is poor, consisting of the Turkana basin, Olduvai and the more limited South African materials. Here, we describe and compare eight craniodental fossils of ~1.4 Ma recovered from Konso, Ethiopia, that we attribute to H. erectus. These include KGA10-1, one of the better-preserved H. erectus mandibular specimens known from eastern Africa, and other fragmentary dental and cranial remains. The Konso H. erectus fossils show a mosaic of primitive and derived features. These include a large and thick mandibular corpus, a moderately developed lateral prominence, a reduced premolar morphology, and a tendency for smaller relative sizes of the posterior molars compared with earlier Homo. In some dentognathic details, such as the lack of a buccolingually narrow M1 and the presence of double mental foramina, the Konso fossils differ from eastern African H. erectus of 1.5 Ma. The fragmentary cranial remains exhibit weak angular and occipital tori, and an apparently weak occipital flexion, as with the eastern African H. erectus examples known from ~1.65 to 1.2 Ma. The available evidence is consistent with the interpretation that African early H. erectus shows morphological continuity within the ~1.65 to 1.0 Ma time period, with relatively little morphological evolution prior to 1.4 Ma and advanced dentognathic gracility occurring sometime thereafter. The Konso evidence corroborates the hypothesis that the African H. erectus populations represent a variable but continuous evolutionary succession that was a likely source of multiple events of gene flow to the Eurasian continent.