Ethiopian fossils show our ancestors stepped out 4.5m years ago

Fossil hunters in Ethiopia have discovered the remains of at least nine primitive hominids, nearly 4.5 million years old, which scientists claim could help fill some of the gaps in early human evolution

The finds, revealed in Nature magazine, mainly consist of teeth and jaw fragments, but also include parts of feet and hands. Scientists say that the features of a foot bone uncovered at As Duma, in the north of the country, prove that the hominid it belonged to walked upright like present-day humans. All the finds belong to the Ardipithecus ramidus species, which was discovered a decade ago.

Sileshi Semaw, of the Craft Stone Age Institute, described the find as "very important" because it confirmed that hominids walked upright on two feet up to 4.5 million years ago. The age of the remains was determined by dating nearby volcanic material.

The hominid is also marked out by its humanlike diamond-shaped upper canine teeth in contrast to the v-shaped upper canines of chimpanzees. However, scientists concede that the creature resembled a chimpanzee more than a human.

Nevertheless, Professor Tim White of the University of California pointed out that A.ramidus was an important ancestor to later species of hominids. "It is becoming clear that we're seeing the basic grade from which Australopithecus evolved," he said. The so-called "australopithecines" are widely believed to have human lineage. The most famous Australopithecus fossils are those belonging to "Lucy", a female skeleton discovered in Ethiopia in the 1970s.

A.ramidus could represent an early step on the path of humanity, as well as indicating the origins of a number of other extinct hominid species.

While it is unclear what habitat the hominids would have lived in, fossils found in the vicinity of the site reveal that A.ramidus lived alongside mole-rats, monkeys and cow-like grazing animals. It is speculated that the region would have contained swamps, streams and springs, but also areas that would have suffered seasonal droughts.

Dr Semaw explained that "a few windows" were now opening in Africa through which to glance at the fossil evidence of the earliest hominids. "We now have more than 30 fossils from at least nine individuals dated between 4.3 and 4.5 million years old."

Another Ardipithecus species, A.kadabba, inhabited Ethiopia between 5.5 and 5.7 million years ago. Genetic studies suggest that the last common ancestor between apes and humans might have existed about six million years ago.