"To confirm that the cutmarks on the bones are 'old' and verify that they were induced by stone tools, I used the Environmental Cell Scanning Electron Microscope (E-SEM) and the attached Energy Dispersive X-ray Spectrometry (EDX) in ASU's LeRoy Eyring Center for Solid State Science," said Barat, who has degrees in chemistry, archaeometry, material science and engineering.
The E-SEM was used because it has a chamber and stage that can accommodate large bone fragments, Barat explained.
"And, since the bone material is an insulator and these precious bone samples cannot be coated with a conducting film, such as gold or carbon, this E-SEM allows us to run the analysis in the H2O-vapor mode and thus avoid charging effects, while still using a high accelerating voltage (15-25kV)," Barat said.
"Hamdallah is an expert in materials research and keenly interested in archaeology," noted Marean. "He had the great idea to do X-ray mapping of the surfaces of the bone to see whether minerals that passed from the marks to the surface of the bone were fossilized."
The geologist on the team, Jonathan Wynn, from the University of South Florida, relied on documented dated volcanic deposits in the Dikika area to estimate the date of the marked bones to 3.4 million years ago.
"This discovery dramatically shifts the known timeframe of a game-changing behavior for our ancestors," said paleoanthropologist Zeresenay "Zeray" Alemseged, director of the Dikika project and director of anthropology at the California Academy of Sciences.
No hominin remains were found with the animal bone fragments that were uncovered 200 meters away from the site where Alemseged and a team discovered "Selam" (Lucy's baby) in 2000. Lucy was discovered in 1974 a few miles north, near Hadar, by Donald Johanson, the world renowned ASU paleoanthropologist.
"There is no qu
|Contact: Carol Hughes|
Arizona State University