Ancient fossil, Archicebus achilles, key link in chain leading to apes, man

A 55-million-year-old fossil of a mouse-sized primate with a human-like face has been identified as a crucial evolutionary link in the chain that led to apes and man.

Just 10 centimetres long, with a 12-centimetre tail, probably thrived for millions of years during a warm period of earth's history, feasting on insects and leaping around in canopies of trees that surrounded a tropical lake in what is now China, according to a report published online on Wednesday by the journal .

"It was probably kind of a frenetic animal," study leader Chris Beard, a palaeontologist at the Carnegie Museum of Natural History in Pittsburgh, US, said. "You could even think anxious - an animal that moves around a lot, very active, searching for its next meal, very agile in the trees, climbing and leaping around in the canopy."

The remarkably complete fossil of Archicebus - derived from Latin and Greek for "ancient monkey" - helps make the case that primates first arose in Asia, soon after the extinction of the dinosaurs about 66 million years ago, even though the lineage leading to man later flourished and diversified in Africa.

The fossil is about eight million years older than any other extensive primate skeleton, bringing scientists closer to pinpointing a pivotal event in primate and human evolution: the divergence between the lineage leading to anthropoids, which include modern monkeys, apes and humans, and the one leading to tarsiers.

"If we go along a tree to the point where all the primates began to evolve, they all point to Asia," said palaeontologist Ni Xijun of the Chinese Academy of Sciences, who led the fieldwork in a fossil-rich area of Hubei province better known for its fish fossils. Ni said the creature had "a rounded face and brain case, very short snout, and front-facing eyes unlike with other small creatures".