This bifaced ovate flint hand axe from the Lower Palaeolithic, similar to the Acheulean tools that were found at the Melka Kunture site in Ethiopia. Credit: Laura Burnett/ The Portable Antiquities Scheme (PAS)/ CC BY-SA 4.0.
In 1981 the mandible of a child was found in Garba, one of the prehistoric sites of the Melka Kunture complex, in the Ethiopian highlands near the Awash River, some 50 kilometres south of Addis Ababa. Since then, scientists have been debating whether the mandible belonged to Homo habilis, a human species that lived from 2.3 million years ago to 1.65 million years ago, or to the most recent Homo erectus, that appeared about 2 million years ago and went extinct about 117,000 years ago.
A group of scientists, led by Margherita Mussi, palaeoarchaeologist at the Sapienza University of Rome and director of the Italo-Spanish Archaeological Mission at Melka Kunture and Balchit, has re-analysed the specimen with synchrotron light and concluded that it more likely it belonged to Homo erectus. This would make it one of the earliest remains of Homo erectus ever found, dating back to nearly two million years ago1.
The mandible was found at the mouth of a small gully declining toward a seasonal tributary of the Awash River. Close to it, researchers recovered a set of stone tools made with Oldowan technology, which is commonly associated with Homo habilis, an earlier human species. The overlying layer, a more recent part of the site, instead, revealed tools belonging to the more modern Acheulean lithic industry, and suggests that in this site Homo erectus could have developed it earlier than in other areas. Acheulean tools were made from larger banks of stone than Oldowan ones, worked in the shape of flakes with bifacial cutting edges to obtain handaxes and cleavers.
“We were authorized to temporarily export the mandible at the European Synchrotron Radiation Facility in Grenoble,” Mussi explains. Using synchrotron computed tomography, “we had access to the internal morphology of the unerupted teeth at the level of a few microns, which is known to be an extremely relevant taxonomical marker”. They then compared this data to those of a large sample of teeth that includes specimens of Homo habilis from both Tanzania and Kenya. The authors concluded that the Garba mandible can be attributed to Homo erectus rather than Homo habilis, even if with some uncertainty, suggesting that this hominin species used Oldowan tools stably in the highlands.
The site is on a plateau that lies at around 2,000 metres above sea level, and probably had a cooler and wetter climate than that of the Rift Valley, where most fossils of hominins has been so far recovered. The vegetation was like that of the contemporary mountains of East Africa, and remains indicate the presence of hippos and grazing antelopes.
The mandible could be 2 million years old, and would thus be one of the earliest Homo erectus remains ever found. This could also imply that Homo erectus at Garba developed Acheulean tools 1.95 million years ago, 200,000 years earlier than what findings at lower sites had suggested. “The different ecosystem of the highlands could have driven hominins to develop new tools to better exploit the available natural resources,” Mussi comments.
“This new result shows that the Ethiopian highlands should be considered a third important pole in human evolution, beyond the Tanzania Rift Valley and the South African caves,” Mussi concludes.
