The writing on the cave wall

A closer look confirmed their suspicions. When von Petzinger went back to some of the records of the cave walls, she noticed other, less abstract signs that appeared to represent a single part of a larger figure - like the tusks of a mammoth without an accompanying body. This feature, known as synecdoche, is common in the known pictographic languages. To von Petzinger and Nowell, it demonstrated that our ancestors were indeed considering how to represent ideas symbolically rather than realistically, eventually leading to the abstract symbols that were the basis of the original study.

"It was a way of communicating information in a concise way," says Nowell. "For example, the mammoth tusks may have simply represented a mammoth, or a mammoth hunt, or something that has nothing to do with a literal interpretation of mammoths." Other common forms of synecdoche include two concentric circles or triangles (used as eyes in horse and bison paintings), ibex horns and the hump of a mammoth. The claviform figure - which looks somewhat like a numeral 1 - may even be a stylised form of the female figure, she says.