Abstract
Early human symbolic behavior is challenging to address. We used ancient engravings from the South-African Blombos and Diepkloof archeological sites in a number of controlled cognitive experiments to qualify discussions about the early evolution of human symbolic traditions. We found that the engravings evolved over a period of 40 000 years to become more salient to the human eye, increasingly expressive of human intent, and easier to reproduce from memory. In other words, they became more effective ‘tools for the mind’. Our experiments suggest that the engravings served as decorations and expressions of socially-transmitted cultural traditions, but not as denotational symbolic signs, which has been previously assumed.