Last modified: Monday, March 27, 2006
Scientists discover hominid cranium in Ethiopia
FOR IMMEDIATE RELEASE
March 27, 2006
BLOOMINGTON, Ind. -- A team of scientists conducting palaeoanthropological field research at Gona, in the Afar Administrative State of Ethiopia, have discovered a significantly complete cranium of a human ancestor estimated to be Middle Pleistocene in age.
The new hominid was discovered at Gawis (pronounced "gow-wees"), in the Gona Paleoanthropological Research Project study area of Ethiopia. The discovery was reported by Sileshi Semaw, director of the Gona Project, who is based at the Stone Age Institute and IU Bloomington's CRAFT research center.
The new cranium from Gawis appears to be intermediate between the earlier Homo erectus and later Homo sapiens and may be sampling a single lineage. At the discovery site and nearby areas, significant archaeological collections of Late Acheulean stone tool-making tradition and numerous fossil animals were found, opening a window into an important period in the development of modern humans.
The southwest portion of the project area near the Gawis River contains the youngest part of the archive, which is estimated to the Middle Pleistocene, a period from 780,000 to 125,000 years ago. Most of the sediments containing the cranium are sands and silts, not datable by standard geologic methods. However, the region contains many active and recently active volcanoes that erupted periodically, blanketing the local landscape with thin, gray-colored layers of volcanic ash.
These volcanic ash layers hold the key to dating the Gawis cranium and associated stone tools. Some ash layers in the Gona project area can be directly dated by the 40Ar/39Ar method. Others, by virtue of their distinctive chemical composition, can be matched to correlative dated layers outside the Gona area, providing the opportunity to make this one of the best-dated human ancestors, noted Jay Quade, Gona project geologist.
The discovery of the Gawis cranium and its significance
The cranium was found by Asahmed Humet, a project member, on Feb. 16, while he and project scientists were conducting archaeological and geological reconnaissance surveys in the Gawis River drainage basin in the Afar Regional Administration of Ethiopia. The cranium was found in a small gully at the base of a steep slope of soft sediments from which it had recently eroded.
The specimen includes the braincase, upper face and upper jaw. Several surface-exposed stone tools were found at the hominid site. Additional contemporary stone tools excavated from the same stratigraphic level near the hominid site include artifacts estimated to be Late Acheulean, a era 500,000 to 200,000 years ago. A diversity of fossil animals including pigs, zebras, elephants, antelopes, small carnivores including cats, and numerous rodents were found at the same stratigraphic level as the Gawis cranium.
"I am thrilled to have a complete cranium discovered from Gona that can provide key information for understanding the variation that existed during the Middle Pleistocene," Semaw said.
Scott Simpson, the project paleontologist, added that "a good fossil provides anatomical evidence that allows us to refine our understanding of evolution. A great fossil forces us to re-examine our views of human origins. I believe the Gawis cranium is a great fossil."
The Gawis cranium comes from a time of transition to modern humans from African Homo erectus, a time that is poorly known. The fossil record from Africa for this period is sparse, and most of the specimens are poorly dated. The few fossil crania that are known from the Middle Pleistocene of Africa present a narrow view of the range of potential anatomical variation during this period.
According to project scientists, the Gawis cranium provides the opportunity to look at the face of an ancestor. Additionally, this fossil links humans with the past by showing a face that is recognizably different and more primitive than that of a modern human.
The face and cranium of this fossil are recognizably different from that of modern humans, said project scientists, but it bears unmistakable anatomical evidence that it belongs to human ancestry. The form of the face and the brain are among the best means for exploring the evolutionary path of humans, and the Gawis cranium preserves both areas.
Work is in progress by the Gona team to determine the age of the cranium and associated archaeology, and to understand its evolutionary relationships with others known during the Pleistocene.
"I am happy that the Gona project succeeded in making a new hominid discovery from this least-known time period in human evolution," Semaw said. "Gona is a wonderful site, and Ethiopian palaeoanthropology has a lot more to offer to the world. We will keep our heads up and continue our work, and I am optimistic that we will be rewarded with more thrilling discoveries for years to come."
Previous discoveries by the Gona Paleoanthropological Research Project
The Gona project area has sediments that span the last 5.6 million years -- a period that witnessed many evolutionary and technological changes in human history -- and Gona already has provided evidence that allow a better understanding of those changes.
The Gona archaeological sites are known for the discovery of the oldest excavated stone tools in the world, dated to 2.6 million years ago. Early in 2005, members of the Gona Project announced the discovery of hominids assigned to Ardipithecus ramidus, among the earliest hominid genus in Africa dated between 4.5 million and 4.3 million years ago.
Research permission for the work in the Afar is granted by the Authority for Research and Conservation of Cultural Heritage and the National Museum, the Ministry of Culture and Tourism of Ethiopia. The Stone Age Institute, Friends of CRAFT and Indiana University's CRAFT research center supported all aspects of this research. The field work was supported by a major grant from the L.S.B. Leakey Foundation. Additional funding was provided by the National Science Foundation (grant to Researching Hominid Origins Initiative).
Photos are available on the Stone Age Institute's Web site at http://www.stoneageinstitute.org.
Sileshi Semaw (archaeology; project director)
Stone Age Institute
1392 W. Dittemore Road
Gosport, IN 47433, USA
Phone 812-876-0080, ext. 210
Semaw is currently in Addis and can be reached at 011-251-911-683486 or firstname.lastname@example.org
Nicholas Toth and Kathy Schick
Co-Directors, Stone Age Institute and CRAFT Research Center
1392 W. Dittemore Road
Gosport, IN 47433, USA
Phone 812-340-0146 (Toth); 812-340-0142 (Schick)
E-mail email@example.com (Toth); firstname.lastname@example.org (Schick)
Scott Simpson (paleontology)
Department of Anatomy
School of Medicine
Case Western Reserve University
10900 Euclid Ave.
Cleveland, OH 44106-4930, USA
Jay Quade (geology)
Department of Geosciences
University of Arizona
Tucson, AZ 85721, USA
Michael J. Rogers (archaeology)
Department of Anthropology
Southern Connecticut State University
501 Crescent St.
New Haven, CT 06515-1355, USA