In the April 23 issue of Science magazine, Giday WoldeGabriel and his colleagues describe the paleoenvironment in which the new species, Australopithecus garhi, was discovered.
In a companion Science article, other members of the international research team describe fossils of what may be a direct human ancestor and evolutionary link between the ape-man of Africa Australopithecus and the genus Homo. The Australopithecus garhi is similar to the much older, "Lucy" species Australopithecus afarensis, discovered by Donald Johanson, Tom Gray and others in 1974 at nearby Hadar, Ethiopia, which is about 70 km north of the new fossil site.
WoldeGabriel did most of the geological fieldwork at the fossil site and the surrounding region. This fieldwork was instrumental in determining the relative age of the fossil-bearing layers.
The fossil discoveries, made between the fall of 1996 and December of 1998, were all found within a previously undescribed layer of the geologic record. WoldeGabriel and his colleagues have since named the sequence of rocks the Bouri Formation after the local village named Bouri. The Bouri Formation is comprised of the Hata, Daka and Herto Members. Australopithecus garhi and antelope-like Alcelaphinae fossils were discovered in the 2.5 million year old Hata Member. The Hata is a sedimentary unit comprising sediments laid down in a floodplain close to a shallow freshwater lake.
According to the researchers, what is now the scorching desert of the Afar Rift in eastern Ethiopia was once a flat, grassy plain surrounded by a freshwater lake. The fertile plain was home to Australopithecus garhi, sabretooth cats, primitive antelope, and a variety of now extinct animal species.
One of the more significant findings presented in the Science articles is evidence of stone tool usage observed on the Alcelaphinae fossils. These cuts and scratches on the fossilized bones seem to indicate that the Australopithecus garhi might have preyed or scavenged on the Alcelaphinae living in the same area.
Most of the analytical investigation on the volcanic rocks collected to understand the geological formation of the study area was conducted at the Geology/Geochemistry Group of the Earth and Environmental Science Division at Los Alamos using an electron microprobe. WoldeGabriel, who is co-leader of the project with Tim White of the University of California-Berkeley, is in charge of the geological investigation and was supported by the Institute of Geophysics and Planetary Physics branch at Los Alamos.
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