Never eat a Pigeon with a Pumpkin: a model for the emergence and fixation of unsupported beliefs

A popular poster from Myanmar lists food pairings that should be avoided, sometimes at all costs. Coconut and honey taken together, for example, are believed to cause nausea, while pork and curdled milk will induce diarrhea. Worst of all, according to the poster, many seemingly innocuous combinations that include jelly and coffee, beef and star fruit, or pigeon and pumpkin, are likely to kill the unwary consumer. But why are these innocuous combinations considered dangerous, even fatal? The answer is relevant, not just to food beliefs, but to social beliefs of many kinds. Here we describe the prevalence of food combination superstitions, and an opinion formation model simulating their emergence and fixation. We find that such food norms are influenced, not just by actual risks, but also by strong forces of cultural learning that can drive and lock in arbitrary rules, even in the face of contrary evidence.