A missing link between humans and their apelike ancestors has been discovered near Johannesburg in an area known as the Cradle of Humanity.

The new species of hominid, the evolutionary branch of primates that includes humans, will be revealed when the 2-million-year-old skeleton of a child is unveiled this week.

Scientists believe the almost-complete fossilised skeleton belonged to a previously unknown type of early human ancestor that may have been an intermediate stage as ape-men evolved into the first species of advanced humans, Homo habilis.

Experts who have seen the skeleton say it shares characteristics with Homo habilis, whose emergence 2.5 million years ago is seen as a key stage in the evolution of our species. It is thought it will be identified as a species that fits somewhere between Australopithicus and Homo habilis.

The discovery could help rewrite the history of human evolution by filling in crucial gaps in the scientific knowledge.

Most fossilised hominid remains are little more than scattered fragments of bone, so the discovery of an almost-complete skeleton will allow scientists to answer key questions about what our early ancestors looked like and when they began walking upright.

The skeleton was found by Professor Lee Berger, of the University of the Witwatersrand, while exploring cave systems in the Sterkfontein region of South Africa.

The find is considered so significant that Jacob Zuma, the South African President, has visited the university to see the fossils and a media campaign with television documentaries is planned.

Professor Phillip Tobias, an eminent human anatomist and anthropologist at the university, who was one of three experts to first identify Homo habilis as a new species of human in 1964, described the latest discovery as ''wonderful'' and ''exciting''.

Although not directly involved in the excavation and subsequent research on the fossils, he is one of the select few scientists outside the research group who have been able to see the skeleton.

He said: ''To find a skeleton as opposed to a couple of teeth or an arm bone is a rarity.

''It is one thing to find a lower jaw with a couple of teeth, but it is another thing to find the jaw joined onto the skull, and those in turn uniting further down with the spinal column, pelvis and the limb bones.''

The skeleton was found with a other partially complete fossils, encased within breccia sedimentary rock inside a limestone cave known as Malapa cave.

The fossil record of early humans is notoriously patchy and scientists hope that the new remains will provide fresh clues about how our species evolved.