The 100 footprints, believed to belong to a Cro-Magnon boy aged between eight and ten, have been found in the damp clay of a maze of caverns in the Ardeche
When the tunnels were first explored five years ago they were found to contain the oldest and some of the most beautiful cave paintings yet to be discovered. They are now also thought to have the oldest human footprints in Europe.
Scientists say the eight-inch long prints appear to be those of a small boy advancing fearfully, bare-foot, into a part of the maze not usually occupied by humans. His footprints are criss-crossed by those of bears and wolves, which passed the same way before, and after, he did.
There are also indications that he was carrying a torch and that he stopped from time to time to tap it against the cavern walls and roof to shake off the used charcoal.
The traces of this charcoal, found on the cavern floor, have been dated to the Cro-Magnon period, about 25,000 to 26,000 years ago, when the caves at Vallon-Pont d'Arc were last occupied by humans.
Michel Garcia, an archaeologist of pre-history at the Centre National de la Recherche Scientifique who has studied the caves, says the connection between footprints and torch marks is not scientifically proved, but extremely probable.
"The soil in that part of the caves was otherwise undisturbed," he said. "Children often go into places that adults don't go. They go into nooks and crannies and these spots may remain undisturbed.
"The footprints are the size of those of a boy about eight to ten years old. He is walking with great care into a hostile environment. He is heading towards what we call the `skull room', a cavern where we have found a number of bears' skulls."
The existence of ancient human and animal footprints in the caves was signalled by the original discoverers of the undergound maze in December 1994. Mr Garcia said a thorough search of the complex in May had found many more prints and had confirmed that they came from pre-historical times.
The search team of a dozen experts in pre-history has also discovered 31 more paintings of mammoths, bison, deer, rhinoceros and wild cats, bringing the number of drawings and etchings found in the caverns to 447.
The paintings are regarded as extremely important - equivalent to those at Lescaux in south-western France - partly because of their age. The earliest are believed to have been drawn 30,000 years ago, making them the oldest cave art yet discovered.
Mr Garcia said that the caverns would never be opened to the public because the art was "too fragile".