The evolution of early symbolic behavior in Homo sapiens
Early symbolic behavior of Homo sapiens is challenging to address yet arguably fundamental to the success of our species. We used ancient engravings from the South African Blombos Cave and Diepkloof Rock Shelter in a number of controlled cognitive experiments to qualify discussions about the evolution of early symbolic traditions. We found that the engravings evolved over a period of 30,000 y to become more effective “tools for the mind,” that is, more salient to the human eye, increasingly expressive of human intent and identity, and easier to reproduce from memory. Our experiments suggest that the engravings served as decorations and expressions of socially transmitted cultural traditions, while we found no clear evidence that they served as denotational symbolic signs.How did human symbolic behavior evolve? Dating up to about 100,000 y ago, the engraved ochre and ostrich eggshell fragments from the South African Blombos Cave and Diepkloof Rock Shelter provide a unique window into presumed early symbolic traditions of Homo sapiens and how they evolved over a period of more than 30,000 y. Using the engravings as stimuli, we report five experiments which suggest that the engravings evolved adaptively, becoming better-suited for human perception and cognition. More specifically, they became more salient, memorable, reproducible, and expressive of style and human intent. However, they did not become more discriminable over time between or within the two archeological sites. Our observations provide support for an account of the Blombos and Diepkloof engravings as decorations and as socially transmitted cultural traditions. By contrast, there was no clear indication that they served as denotational symbolic signs. Our findings have broad implications for our understanding of early symbolic communication and cognition in H. sapiens.