Culture is the product of interactions between human receivers and cultural information, which is represented in a variety of culturally evolved natural and artefactual languages. Natural language may have evolved primarily for communication, but the eventual result was an expansion in cultural information beyond the collective capacity of human brains. At that point, our ancestors began to use artefactual symbols as permanent, external receptacles for cultural information. These artefactual symbols depended primarily on the clever trick of human hands, just as the natural language symbols had depended primarily on the clever trick of human voices (a view that was developed in personal communication with If Price, 2006). Symbols are only of use to a community if everyone is using the same system; but, for reasons that I have sketched in Chapter 7, artefactual symbols could not rely on coevolution with biologically endowed cognition to facilitate their acquisition by our ancestors. If they were to succeed as communal systems of representation, then they would need to be explicitly teachable rather than innately learnable. As the number of symbols expanded, therefore, the bottleneck in transmission between writers and readers ensured the emergence of compositional rules governing the artefactual symbols.

Artefactual languages enable cultural information to be preserved for greater lengths of time, in greater quantities and with greater accuracy than natural language can achieve. They provide scaffolding and swap space for human cognition, and create functional links between different social groups.