 Is it possible that our biological knowledge would be altogether different, had contingent choices been different in the past? As this question requires us to indulge in historical counterfactuals, which are controversial (Radick 2005), it is difficult to answer. However, it may not matter much one way or the other if the knowledge produced by model organisms can be shown to be of general validity, or at least as transcending the particular organism in which it was produced. This is an instance of the more general epistemological problem of extrapolating knowledge from one domain into another and can be fruitfully discussed as such (Burian 1992).