Sites in eastern Africa have shed light on the emergence and early evolution of the genus Homo1,2,3,4,5,6. The best known early hominin species, H. habilis and H. erectus, have often been interpreted as time-successive segments of a single anagenetic evolutionary lineage3,7,8,9,10. The case for this was strengthened by the discovery of small early Pleistocene hominin crania from Dmanisi in Georgia that apparently provide evidence of morphological continuity between the two taxa11,12. Here we describe two new cranial fossils from the Koobi Fora Formation, east of Lake Turkana in Kenya, that have bearing on the relationship between species of early Homo. A partial maxilla assigned to H. habilis reliably demonstrates that this species survived until later than previously recognized, making an anagenetic relationship with H. erectus unlikely. The discovery of a particularly small calvaria of H. erectus indicates that this taxon overlapped in size with H. habilis, and may have shown marked sexual dimorphism. The new fossils confirm the distinctiveness of H. habilis and H. erectus, independently of overall cranial size, and suggest that these two early taxa were living broadly sympatrically in the same lake basin for almost half a million years.
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We thank the government of Kenya for permission to carry out this research, and the National Museums of Kenya and E. Mbua for support. The National Geographic Society funded the field work. We thank R. Blumenschine, R. Clarke, C. Dean, A. Deino, C. Feibel, Ø. Hammer, J. Harris, L. Humphrey, N. Jeffery, W. Kimbel, R. Kruszynski, K. Kupczik, D. Lieberman, C. Lockwood, D. Lordkipanidze, J. Moggi-Cecchi, S. Muteti, Ph. Rightmire, B. Sokhi, C. Swisher, A. Walker and B. Wood for their help. Caltex (Kenya) provided fuel for the field expeditions, and R. Leakey allowed us to use his aeroplane. The field expedition members included R. Bobe, G. Ekalale, C. Epaat, M. Eregei, J. Erus, J. Kaatho, S. Labun, R. Lorinyok, B. Malika, S. Muge, S. Muteti, D. Mutinda and N. Mutiwa.
This file contains Supplementary Notes divided into three main sections: 1. Measurements and comparisons, including calvarial measurements of KNM-ER 42700, dental and palatal measurements of KNM-ER 42703, and a summary of morphological features used in the differential diagnoses. 2. Morphometric analyses, including principal component and bivariate analyses, and analysis of intraspecific variation of KNM-ER 42700 (four figures), and a principal component analysis of KNM-ER 42703 (one figure). 3. A brief review of the last known occurrence of H. habilis at Lower Bed II, Olduvai. Additional references are given under 4.
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Hominin diversity and high environmental variability in the Okote Member, Koobi Fora Formation, Kenya
Journal of Human Evolution (2019)