We present an agent-based model designed to study the cultural evolution of age-at-marriage norms. We review both theoretical arguments and empirical evidence regarding the existence of norms which proscribe marriage outside of an acceptable age interval. Using a definition of norms as built-in constraints in agents, we model the transmission of norms and the mechanisms of the intergenerational transmission of norms. Agents can marry each other only if they share part of the acceptable age interval. We perform several simulation experiments on the evolution across generations. In particular, we study the conditions under which norms persist in the long run, the impact of initial conditions, the role of random mutations, and the i...