SCIENTISTS have unveiled a 4000-year-old Aboriginal rock art site in a wilderness area that has already yielded a tree species still living from prehistory.

In a rock shelter amid the rugged sandstone gorge country of the Wollemi National Park, home of an ancient species of pine, west of Sydney, are more than 200 drawings anthropolgists say will shed important light on the history of Aboriginal people in the Sydney basin.

It is thought that up to 160 generations came to the cave to paint.

The images of human-like figures, half-human, half-animal composites, birds, lizards and marsupials, and stencils of hands, boomerangs and axes, are superimposed in 12 layers.

The location of the paintings, like that of the Wollemi pine, is being kept secret to protect them from the public.

Australian Museum principal anthropologist Paul Tacon said the pictures, discovered by bushwalkers in 1995, were so well-preserved that "many of the stencilled drawings look like they were made yesterday".

"It's like a place that time forgot," Dr Tacon told The Australian yesterday.

The motivation of the artists could only be speculated on, he said.

"It may be that it was a good camping place, but there are some

images that are part-human, part-animal which may be depictions of ancestral beings and that suggests there are spiritual associations with the site."

Hampered by the ruggedness of the Wollemi area, and by drought, bushfires and a flood, Dr Tacon and his team, including a Darug Aborigine, an archaeologist and a PhD student, finally visited the shelter in May and were the first to scientifically document the drawings.

Dr Tacon said the oldest paintings, red hand and forearm stencils, were up to 4000 years old, while the newest were from the 1800s.

Their age was gauged by comparison with other dated sites in the Sydney area.

The Australian's national art critic and an expert on Aboriginal art, author Susan McCulloch, said the find was significant because rock art in the eastern states was relatively rare.

"The fact that there is one that hasn't been found for all these years is really extraordinary," McCulloch said.

NSW Premier Bob Carr said yesterday the rock art find showed how vital it was to protect natural areas.

"We are reminded of just how important it is to set old spaces aside, protect them, because you never know what in time is going to be found there," Mr Carr said.

The Wollemi pine is up to 200 million years old and was long thought to have been extinct until it was discovered by chance by a national parks ranger in 1994.

By Brendan O'Keefe and Megan Saunders