ABSTRACT
So far, we have seen that the circularity argument poses a serious challenge to Darwin’s theory. Were the circularity argument to succeed, the theory Darwin proposed would be empty and would have no explanatory power at all. This becomes more pertinent when we notice that so many modern formulations of the theory do define key terms in the way that leads to the problem and so actually do strip the theory of any explanatory power. This means that we cannot define fitness in terms of actual survival numbers. Variations in survival rates can be due to numerous factors, and one of them is differences in fitness. Crucial to responding to the challenge so posed then is to distinguish between surviving and having different tendencies to survive. With that distinction in hand, it is clear that it is not trivial to state that the fittest survived. This is no more trivial than it is to say that the most fragile glasses broke; they tend to break, but it is not trivial that the ones that tend to break did break. They might not have broken after all. First, it is not trivial that any given glass is the most fragile: This depends on properties that it has and that we can investigate. In different contexts, different properties become important. What is most fragile in one context might not be in another; this brings in relativity to environment. We also saw the second and very important feature of explanations by natural selection in stark relief in the proto-theory of persistence: knowing which properties explain persistence is not enough, we need to know why they explain persistence. This point was illustrated by the persistence of molars in the Cretaceous therian fossil record. Knowing what we know about the mechanical properties of teeth, we can come to the view that molars resist breaking better than incisors. Their shape gives them a greater tendency to resist breakage over incisors. As we see the prevalence of molars in the fossil record, we could readily think that the feature we nominate, which we can suppose does indeed help them to resist breakage, explains their persistence. Patterson (1956) noted that molars may be collected by ants because their shape is similar to seeds, and they store them in their nests. This protects the teeth from surface exposure. Suppose he was right about this, then the shape did explain their prevalence but now not just because of the shape being suited to resist breaking. When we give explanations for persistence, we are offering causal explanations about the history that led to the persistence. We are specifying that on which that persistence (or more accurately, what the differences in rates of persistence) depended.
