April 27, 2006

Does new fossil link Homo erectus and Homo sapiens?

Case paleontologist to analyze new fossil skull from Ethiopia to make determination

Scott Simpson

Case Western Reserve University paleontologist Scott Simpson began to relax, February 16, after a day of exploration in the Gona area in Ethiopia's Afar region. As he sipped Kool-Aid at a table in the camp's kitchen, he heard horns honking and singing in the distance.

For the field scientist hunting for the fossils of our human ancestors, the ruckus meant one thing—a big and important find.

Not usually given to great displays of emotions, Jay Quade—the geologist for Gona Paleoanthropological Research Project and from the University of Arizona—jumped from the land-roving vehicle with bags he had been cradling while he bounced for 25 kilometer over the rugged terrain. He exhibited one of the widest grins Simpson said he had ever seen him give.

Inside were fossils found by Asahamed Humet, a local nomadic pastoralist and longtime member of the field team.

Asahamed's dedication and keen knowledge of the landscape, along with what Simpson describes as a sixth sense for knowing where to find fossils, has led the field team to some of their most important discoveries.

Sharing the find

Quade teased Simpson as he opened the smallest bag first containing a tooth, then another with part of an upper jaw, then another and another until the pieces formed nearly complete hominid skull.

Scott, a professor of anatomy in the Case School of Medicine with a secondary appointment in anthropology in the College of Arts and Sciences, has intensely studied many of few, and very rare, hominid fossil skulls. He also has found hominid remains as old as 4.5 million years old (reported Nature in 2005).

He knew immediately by the anatomical shape of the new cranium that this fossil, dating from 200,000 to 500,000 years ago, provided significant information about the transition time between Homo erectus and Homo sapien, the rise of modern man.

The project's principal investigator and archeologist Sileshi Semaw from the Stone Age Institute of Indiana University, along with Simpson, Quade, Asahamed and others returned to the site the next day. On hands and knees and shoulder-to-shoulder, they crawled across a 50-foot square area in search of any missing pieces. None were found. Assisting them was Case alum Stephanie Melillo (B.A., Anthropology 2005), who served as Simpson's field assistant.

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Normally news about important finds is kept quiet until reported in major science journals. This time, according to Simpson, the excitement was so high. "We're like proud parents and wanted to share the news with everyone," added Simpson.

Further research on the teeth along with sediment samples will refine the age within that 300,000-year time span.

Through analyses of the material, Simpson and the team will reconstruct a picture of life for this hominid. Because of isotopes of carbon left in the enamel of the teeth along with those found in the sediments, they will be able to determine whether this was grassland, forests or a mixture of forests and grasses.

Along with the skull, they discovered early stone tools and the fossils of large animals. One surprise was a large number of microfossils of rats, mice and shrews in this sediment layer that has led them to believe that barn owls lived there once—even though there is no fossil evidence. The researchers can tell by broken fossil bones how they died and what might have eaten them.

Also this amazing quantity of rodent fossils is found at scattered sites of the research project in the same age layer of sediment. Simpson said this requires further study.

The Gona area, a site assigned by the Ethiopian government for this team's research, has proven to be one of the most age diverse regions for paleontology, said Simpson. The site's time span ranges from 10,000 to 5.6 million years old.

"Our project differs from others in that we can look at the major behavioral and technological changes over this wide span of time," explained Simpson.

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Since the field team has arrived at the site in 1999, it has yielded many historic treasures due to its location. The exploration is being done at the geologically active intersection of three junctions in the Great Rift, where Eastern Africa has been breaking away from the main continent for millions of years. The research area is approximately 40 kilometers east-west by 25 kilometers north-south in a very dry and remote desert area in the Afar area.

As the land shifts and separates, the earth's crust thins out and dips where water collects in lakes that have attracted animals and man's ancestors. Sediment also washes off the sides of hills and cliffs to collect downstream.

Over time, erosion and faults expose the fossils that are found by patient observation of the landscape that may take countless, and sometime, fruitless of hours of scanning.

The Gona Project collects all hominid and monkey skeletal bones and teeth found. They also gather the skulls of the large animals, foot bones of antelopes and pigs (another research interest for Simpson). Sometimes photos are taken of large animals like elephants and hippos.

"These fossils are a time machine," said Simpson. "It is the only direct evidence we have of what was our past."

To read more about Simpson's research, visit http://cerebrum.case.edu/newsrelease/Simpson2.htm.

For more information: Susan Griffith 216-368-1004.

Posted by: Heidi Cool, April 27, 2006 10:10 AM | News Topics: College of Arts and Sciences, Research, Science

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