arXiv:2510.12837v1 Announce Type: cross Abstract: Cumulative cultural evolution enables human societies to generate increasingly complex knowledge and technology over generations. While social learning transmits innovations between individuals and generations, the cognitive processes that generate these innovations remain poorly understood. Here, we demonstrate that semantic knowledge-structured associations between concepts and their functions-provides cognitive scaffolding for cumulative innovation by guiding exploration toward plausible and meaningful actions. We tested this hypothesis using a cultural evolutionary agent-based model and a large-scale behavioural experiment (N = 1,243), in which individuals performed a task requiring the combination of items into novel innovations. Across both approaches, semantic knowledge and social learning interact synergistically to enhance innovation. Behaviorally, participants without access to semantic knowledge performed no better than chance, even when social learning was available, and relied on shallow exploration strategies. These findings suggest that semantic knowledge is a key cognitive process enabling human cumulative culture.