Ape fossil is man's 7 million-year-old ancestor, say scientists

An ape-like creature which lived about 7 million years ago is almost certainly the earliest known ancestor of humans, according to a study that could finally resolve the true identity of "Chad Man".

The discovery of the apeman's fossilised remains in the deserts of northern Chad was announced in 2002. The find was hailed then as the most important for 75 years because he appeared to be the oldest known member of the human lineage.

However, sceptics questioned whether the species was a true hominid or just an early ape. Some competing scientists even suggested the creature was in fact a female gorilla.

However, the scientists who made the original discovery said they have now found further fossils of Sahelanthropus tchadensis which confirms its position as the earliest known ancestor of humans.

They have also performed a computer reconstruction of the creature's face which indicates that its features were more human than ape-like, and even that it walked on two legs - a distinctive human trait.

Professor Michel Brunet of the University of Poitiers said that Chad man, nicknamed Toumai, which means "hope for life" in the local Goran language, possesses a unique combination of primitive ape-like features and more modern human characteristics.

Details of the new fossils - a jawbone and teeth - as well as the computer reconstruction of his face, are published today in the journal Nature.

They indicate that Toumai lived soon after the human lineage diverged from the last common ancestor of man and chimpanzee, Professor Brunet said.

"(It) might have been an upright biped, suggesting that bipedalism was present in the earliest known hominids, and probably soon after the divergence of the chimpanzee and human lineages," he said.

Ahounta Djimdoubmalbaye, a graduate student at the University of N'Djamena in Chad, found a fossilised skull of Toumai man in July 2001 in the windblown Djurab desert.

Some teeth were also found, but no leg bones or pelvis, which could have resolved the question of whether the creature walked upright on two legs.

Professor Chris Stringer, head of human origins at the Natural History Museum in London, said at the time of the announcement in 2002 that the creature's brain size and skull shape were like an ape's but it had a more human-like, flat face and small tooth size.

These features had never before been seen in the same individual which indicates how important the creature is in terms of understanding early human evolution, Professor Stringer said.

However, other researchers, notably Professor Milford Wolpoff of the University of Michigan, said that the skull was not human at all and more likely to be the head of a female ape.

"Toumai may be a common ancestor of apes and humans, but it is not on the line directly leading to humans," Professor Wolpoff said in 2002.

However, Professor Brunet and his colleague Christoph Zollikofer of the University of Zurich believe that the latest fossil discovery and facial reconstruction puts the argument beyond doubt - Toumai evolved after the evolutionary split occurred between chimpanzee and man.

The original fossilised skull of Toumai had been squashed making it difficult to produce an accurate anatomical analysis but computer scans had enabled the researchers to produce a virtual, three-dimensional reconstruction of the creature's skull.

They found that the angle between the base of the skull, where the spinal cord enters the braincase, and the front plane of the face was similar in Toumai man to modern humans, and quite different from chimps and other apes which walk on all fours.

This suggests the creature walked upright on two legs, the scientists said.

Toumai's fossils were found alongside the bones of many extinct animals such as three-toed horses, large wild boars, crocodiles and hippos, which have been dated accurately to living between 6 million and 7 million years ago.

Toumai was no bigger than an adult chimp in height and probably lived mainly on a diet of fruit.

- INDEPENDENT