 As discussed earlier in the historical sections, molecular biologists have relied heavily on model organisms (see the entry on  models in science).  The model organisms that were used to lay down the foundation of molecular biology served as “exemplary models” in contrast to what today are called “surrogate models”—the distinction comes from Jessica Bolker (2009). According to Bolker, exemplary models are “representatives of a broader group” and the goal of using them is “to elucidate fundamental or general biological patterns and mechanisms” (487). But making inferences from a single exemplary model to general biological patterns has been cause for worry. What grounds do biologists have for believing that what is true of a mere model is true of many different organisms? One answer, provided by Marcel Weber (2005), is that the generality of biological knowledge obtained from studying exemplary models can be established on evolutionary grounds. According to Weber, if a mechanism is found in a set of phylogenetically distant organisms, this provides evidence that it is also likely to be found in all organisms that share a common ancestor with the organisms being compared.