The story of the origin of man looks likely to be rewritten yet again after the discovery in South Africa of a near-complete skeleton of an ape-man thought to be three million years old.

If confirmed, this would make the remains 500,000 years older than anything previously unearthed south of Tanzania.

The 1.22-metre-tall (four feet) hominid (ape-man) was discovered at Sterkfontein, north of Johannesburg. Professor Phillip Tobias, who led the team of researchers from South Africa's University of the Witwatersrand, said on Wednesday that the find would aid the search for the missing link in man's evolution from ape to human.

"[This is] probably the most momentous palaeoanthropological find ever made in Africa," Tobias said.

Dr Ron Clarke, who led the excavations, said the bones belonged to Australopithecus, which had both human and ape-like features. He said the find followed the discovery of four fossilised foot bones in 1994, the tibia in July last year and the skull last September.

Clarke said it was unclear if the creature was male or female, but it was already able to walk.

"The anatomy of the ankle joint shows [it] was already bipedal but able to climb in trees by virtue of a divergent big toe," he said, adding, "We imagine that it lived a very similar life to that led by chimpanzees today."

Shaft fall

Scientists determined the creature's date of origin by examining the rock. It appears it may have fallen down a 15-metre (45-foot) shaft. The shaft then later filled with limestone, locking-in the treasure.

The entire remains have yet to be removed from the rock - a process expected to take another year. When the task is finally completely, palaeoanthropologists will examine it and argue over its significance.

Some say that our early ancestors had cousins - off-shoots of the family who then died out. Others say we are descended in a direct line from the kind of skeletons unearthed at Sterkfontein.

Tobias said the find was "one of the many missing links" between humans and apes. "We are getting down nearer and nearer to the critical parting of ways between the hominids - our family - and the African apes, which share with us common ancestry, perhaps about five to seven million years ago."

The team believes the find is the most significant since the discovery in 1924 of a skull belonging to the so-called Taung child, the first fossil found belonging to Australopithecus. That also was unearthed at Sterkfontein.

Previously, the most complete early hominid was "Lucy," an Australopithecus whose partial skeleton was discovered in 1974 in Ethiopia. The oldest complete skeleton before this latest discovery dates back to 1.8 million years, Clarke said. It was that of a Homo Erectus, found in Kenya.

The discovery, documented Wednesday in the South African Journal of Science, was to be reported in the magazine Nature in London on Thursday, researchers said at a news conference.