The evolution of symbolic artefacts: How function shapes form

Intentional markings on rock and bone surfaces constitute some of the earliest evidence of human symbolic behaviour, yet their original functions remain poorly understood and archaeologically contested. Here we present experimental work systematically examining how different functional contexts shape the cognitive trajectories of semiotic artefacts, and whether the resulting profiles can adjudicate between competing interpretations of the archaeological record. Participants reproduced engraved markings dating to c. 100,000 years ago from the South African Blombos Cave and Diepkloof Rock Shelter across three conditions of cultural transmission—decoration, group-identity marking, and denotational communication—over nine generations. Their reproductions were then used as stimuli in a suite of five cognitive experiments measuring saliency, discriminability, style, perceived intentionality, and memorability. We found that all conditions led to regularization—markings becoming more intentional-looking and memorable—reflecting the constraints of human cognitive architecture. Above this baseline, however, functional contexts drove distinct cognitive profiles: saliency increased only when markings were embedded in social and interactive contexts, while discriminability increased only under communicative pressure. The cognitive profile of the original engravings matches the decoration and identity conditions, not the communication condition, providing experimental evidence against a proto-script interpretation. Finally, correlation analyses revealed that most cognitive properties are structurally coupled, suggesting that cultural practices targeting one property generate correlated changes in others as automatic by-products—a mechanism by which early symbolic capacities may have bootstrapped increasingly complex symbolic repertoires through exaptation of properties rather than sudden cognitive mutation.