I investigate the structure of an argument that culture cannot be maintained in a population if each individual learns only from a single person. This appears to conflict with many models of cultural transmission and real-world cases. I resolve the first problem by showing that one of the models central to the argument is conceptually analogous and mathematically equivalent to one used to investigate the evolution of sexual reproduction. I resolve the second by arguing that probabilistic models of epistemological coherence (...) can be reinterpreted as models of support between cultural variants—illustrating the idea with a new model. (shrink)