Prehistoric rock images like those in Italy's Valcamonica valley are not just artworks, they are also an early form of writing, Italian archaeologists say.
Emmanuel Anati, the director of the Camuno Prehistoric Studies Centre (CCSP), said archaeologists have managed to work out the grammar of this proto-writing system.
The first decoded samples of prehistoric rock art - 19 petroglyphs from the Dordogne region of France - will have their debut reading at a major international research symposium that kicked off in the Alpine valley north of Milan on Friday.
"Rock art has been described before, but it has never been read," said University of Lecce Professor Anati.
"These images are agreements for unions between men and women belonging to different tribes that date back 30,000 years. They are the first records of marriage contracts".
The CCSP has organized the four-day conference, an annual event which top experts from over 30 countries will take part in, with UNESCO.
"There will also be the reading of 64 rock figures telling a mythological story," added Anati.
Valcamonica is home to one of the world's greatest collections of prehistoric petroglyphs - over 140,000 artworks carved into rock.
It was the first Italian site to go on UNESCO's World Heritage List, in 1979, ahead of treasures like Rome's Colosseum and historic centre, and Leonardo da Vinci's fresco of The Last Supper in Milan.
At Valcamonica, prehistoric humans depicted - and, it seems, wrote about - animals, hunting, ploughing, combat, sailing, worship and magic.
Early works of large animals like deer and elk date back to 8000 BC.
There are Neolithic harvests and Bronze Age warriors, weapons and duels.
Most of the figures were created in the Iron Age in the first millennium BC, up to the arrival of the ancient Romans in 16 BC.
Some figures were also made during Roman times and there are even inscriptions in Latin.
The name Valcamonica refers to the Alpine people who lived in the area before the Romans conquered it - the Camunni.
Photos of Valcamonica rock art can be seen online at http://www.rupestre.net/alps/valcamonica.html.
