Since its discovery in 1972 (ref. 1), the cranium KNM-ER 1470 has been at the centre of the debate over the number of species of early Homo present in the early Pleistocene epoch2 of eastern Africa. KNM-ER 1470 stands out among other specimens attributed to early Homo because of its larger size, and its flat and subnasally orthognathic face with anteriorly placed maxillary zygomatic roots3. This singular morphology and the incomplete preservation of the fossil have led to different views as to whether KNM-ER 1470 can be accommodated within a single species of early Homo that is highly variable because of sexual, geographical and temporal factors4,5,6,7,8,9, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation3,10,11,12,13,14,15,16,17,18,19,20. Here we report on three newly discovered fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470 but is notably smaller. It preserves previously unknown morphology, including moderately sized, mesiodistally long postcanine teeth. The nearly complete mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental arcade that is short anteroposteriorly and flat across the front, with small incisors; these features are consistent with the arcade morphology of KNM-ER 1470 and KNM-ER 62000. The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa.
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We thank the Governments of Kenya and Tanzania for permission to carry out this research, the Kenya Wildlife Service for permission to work in the Sibiloi National Park, the National Museums of Kenya and the National Museum of Tanzania for access to specimens in their care, and the Turkana Basin Institute for support. The National Geographic Society, the Leakey Foundation and the Max Planck Society funded fieldwork or laboratory studies. Many people helped us with this research, including N. Adamali, R. Blumenschine, C. Boesch, F. Brown, P. Gunz, J. J. Hublin, W. Kimbel, K. Kupczik, R. Leakey, C. Lepre, D. Lieberman, P. Msemwa, R. Odoyo, R. Quinn, P. Rightmire, L. Schroeder, U. Schwarz, M. Skinner, H. Temming, A. Winzer and B. Wood. Curatorial assistance was given by A. Kweka, F. Manthi, E. Mbua, M. Muungu and J. Thiringi. KNM-ER 60000 was discovered by C. Nyete, KNM-ER 62000 by D. Elgite and KNM-ER 62003 by R. Moru. We particularly thank the Koobi Fora Research Project field crew: A. Aike, S. Aila, D. Elgite, M. Kirinya, D. Gidole, O. Kyalo, A. Longaye, A. Lawri, E. Linga, J. Lonyericho, S. Lomeiku, D. Muema, A. Moru, R. Moru, S. Muge, C. Nyete, L. Nzuve, H. Sale and A. Sharamo whose fieldwork led to the discovery of these specimens, and camp managers J. Mutuku and T. Ngundo. H. Churcher, J. Coreth, A. Hammond, J. LaCarrubba, F. Kirera, C. Lepre, M. Noback, R. Quinn, M. Skinner, I. Wallace and S. Wright participated in one or more of the 2007, 2008 or 2009 field expeditions when these specimens were discovered. We are grateful to F. and J. Pinto, W. Philips, M. Hettwer, P. Sylvester, H. Buchi, N. Seligman, E. von Simpson, J. Doerr and B. and J. Chelberg for their financial support of this fieldwork.
This file contains Supplementary Text, Supplementary Tables and Figures and Supplementary References (see Supplementary Contents for details).
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