1. Division of Palaeontology, National Museums of Kenya, P.O. Box 40658, Nairobi, Kenya
2. Department of Anatomy & Developmental Biology, University College London, WC1E 6JJ, UK
3. Department of Geology & Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
4. Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia

Correspondence to: Meave G. Leakey¹ Correspondence and requests for materials should be addressed to M.G.L. (e-mail: Email: meave@swiftkenya.com).

Abstract

Most interpretations of early hominin phylogeny recognize a single early to middle Pliocene ancestral lineage, best represented by Australopithecus afarensis, which gave rise to a radiation of taxa in the late Pliocene. Here we report on new fossils discovered west of Lake Turkana, Kenya, which differ markedly from those of contemporary A. afarensis, indicating that hominin taxonomic diversity extended back, well into the middle Pliocene. A 3.5 Myr-old cranium, showing a unique combination of derived facial and primitive neurocranial features, is assigned to a new genus of hominin. These findings point to an early diet-driven adaptive radiation, provide new insight on the association of hominin craniodental features, and have implications for our understanding of Plio–Pleistocene hominin phylogeny.

1. Division of Palaeontology, National Museums of Kenya, P.O. Box 40658, Nairobi, Kenya
2. Department of Anatomy & Developmental Biology, University College London, WC1E 6JJ, UK
3. Department of Geology & Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
4. Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia

Correspondence to: Meave G. Leakey¹ Correspondence and requests for materials should be addressed to M.G.L. (e-mail: Email: meave@swiftkenya.com).