Abstract

The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in human evolutionary studies. Australopithecus species differ markedly from extant African apes and candidate ancestral hominids such as Ardipithecus, Orrorin and Sahelanthropus. The earliest described Australopithecus species is Au. anamensis, the probable chronospecies ancestor of Au. afarensis. Here we describe newly discovered fossils from the Middle Awash study area that extend the known Au. anamensis range into northeastern Ethiopia. The new fossils are from chronometrically controlled stratigraphic sequences and date to about 4.1–4.2 million years ago. They include diagnostic craniodental remains, the largest hominid canine yet recovered, and the earliest Australopithecus femur. These new fossils are sampled from a woodland context. Temporal and anatomical intermediacy between Ar. ramidus and Au. afarensis suggest a relatively rapid shift from Ardipithecus to Australopithecus in this region of Africa, involving either replacement or accelerated phyletic evolution.

1. Human Evolution Research Center, Museum of Vertebrate Zoology, 3101 Valley Life Sciences Building, and
2. Department of Integrative Biology, University of California at Berkeley, Berkeley, California 94720, USA
3. Hydrology, Geochemistry and Geology Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
4. Rift Valley Research Service, P.O. Box 5717, Addis Ababa, Ethiopia
5. Department of Anthropology, University of Illinois, Urbana, Illinois 61801, USA
6. Department of Anthropology and Archaeology, Authority for Research and Conservation of the Cultural Heritage, Ministry of Youth, Sports and Culture, P.O. Box 6686, Addis Ababa, Ethiopia
7. College of Medicine, Department of Anatomy, Laboratory of Evolutionary Biology, Howard University, Washington DC 20059, USA
8. Département Histoire de la Terre, USM 0203, UMR 5143 CNRS, Unité Paléobiodiversité et Paléoenvironnement, Muséum National d'Histoire Naturelle, Paris 75005, and Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine, UMR 6046, Université de Poitiers, 86022 Poitiers Cedex, France
9. Department of Geology, Miami University, Oxford, Ohio 45056, USA
10. Department of Physical Anthropology, Cleveland Museum of Natural History, 1 Wade Oval Drive, Cleveland, Ohio 44106, USA
11. Department of Anthropology, National Science Museum, Hyakunincho, Shinjuku-ku, Tokyo 169-0073, Japan
12. Palaeontology Section, Transvaal Museum, P.O. Box 413, Pretoria, South Africa
13. Laboratoire Paléoenvironnements et Paléobiosphère, UMR 5125, Université Claude Bernard, Lyon 1, 69622 Villeurbanne Cedex, France
14. Department of Anthropology and Division of Biomedical Sciences, Kent State University, Kent, Ohio 44242, USA
15. Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 94709, and Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, California 94720, USA
16. Institute of Natural and Environmental Sciences, University of Hyogo, Yayoigaoka, Sanda 669-1546, Japan
17. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA
18. Natural History Museum, Sierra College, Rocklin, California 95677, USA
19. The University Museum, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Correspondence to: Tim D. White^1,2 Correspondence and requests for materials should be addressed to T.W. (Email: timwhite@berkeley.edu).

Received 22 September 2005 | Accepted 2 February 2006

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.