Paleoanthropologist Sileshi Semaw holds the fossil of a hominid mandible (lower jaw bone) believed to be about 4.5 million years old.

© afrol News / Sileshi Semaw

afrol News, 25 January - Ethiopian and US anthropologists have found fossils of hominids, the ancestors of modern man, in northern Ethiopia, which are said to be 4.5 million years old. The fossils may help scientists piece together the mysterious transformation of primitive chimpanzee-like hominids into more human forms.

The fossils were retrieved from the Gona Study Area in northern Ethiopia, only one of two sites to yield fossil remains of Ardipithecus ramidus. The discovery was made by a team of scientists from Ethiopia, the Indiana University Bloomington (USA) and seven other institutions, working at the Ethiopian site.

- A few windows are now opening in Africa to glance into the fossil evidence on the earliest hominids, commented paleoanthropologist Sileshi Semaw, who led the research at Gona.

Mr Semaw, a 44-year-old Ethiopian, is the director of the Gona Paleoanthropological Research Project in Afar, Ethiopia, and earlier has documented the oldest known stone tools in the world, aged 2.6 million years. He further is a research scientist at the US-based Stone Age Institute, which is associated to the Indiana University.

Mr Semaw and his colleagues also reported new evidence that suggests the human ancestors lived in close quarters with a menagerie of antelope, rhinos, monkeys, giraffes and hippos in a northern Ethiopia that was far wetter than it is today. The environmental reconstructions suggested a mosaic of habitats, from woodlands to grasslands.

Research is continuing at Gona to determine which habitats the hominid preferred. "We now have more than 30 fossils from at least nine individuals dated between 4.3 and 4.5 million years old," said Mr Semaw.

The new discovery at Gona last week was published in the magazine 'Nature'. Here, Mr Semaw and his co-authors describe parts of one upper and two lower jaw bones - with teeth still intact - several loose teeth, part of a toe bone and intact finger bones. The scientists believe the fossils belong to nine individuals of the species Ardipithecus ramidus. They used argon isotope dating of volcanic materials found in the vicinity of the fossils to estimate their age.

In the 11 years since the naming of Ardipithecus ramidus by anthropologist Tim White, only a handful of fossils from the species have been found, and only at two sites - the Middle Awash and Gona, both in Ethiopia. Other fossils of slightly older age are known in Kenya and Chad. Anthropologists working in Ethiopia believe Ardipithecus is the first of the hominid genus - that is, human ancestors who lived just after a split with the lineage that produced modern chimpanzees.

Despite the millions of years that separate us, modern humans have a few things in common with Ardipithecus ramidus. Fossils from Gona and elsewhere suggest that the ancient hominid walked on two feet and had diamond-shaped upper canines, not the "v"-shaped ones chimpanzees use to chomp. Outwardly, however, Ardipithecus ramidus would appear a lot more chimpanzee-like than human.

Gona has turned out to be a productive dig site. In a 'Nature' cover story in 1997, Mr Semaw and colleagues reported the oldest known stone tools used by ancestral humans. The Gona artefacts showed that as early as 2.5 million years ago, hominids were remarkably skilled toolmakers. Last month, Mr Semaw co-authored a paper in 'Geological Society of America Bulletin' summarising Gona's geological properties and the site's cornucopia of hominid fossils spanning several million years.

The authors thank Ethiopia's Authority for Research and Conservation of Cultural Heritage, the National Museum of Ethiopia, and the Ethiopian Ministry of Youth, Sports and Culture for providing permits for the ongoing work at the Gona dig site, and the Afar people "for making the fieldwork a success," according to a press release by the Indiana University.

By staff writer

© afrol News

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