Figure 2.

Here we illustrate three key dimensions of robustness with respect to which evolutionary regularities may be described. Each evolutionary iteration (labelled) is approximately located in a three-dimensional space along axes reflecting its degree of specificity, independence and scope, illustrating the extent to which it represents evidence against the RCT conceived either as a general thesis or as a particular thesis about specific evolutionary outcomes (with the strongest such cases found in the darkest shaded region). Some iterated regularities, such as hummingbird flowers or predator avoidance, do little to contradict the RCT, whereas others, such as image-forming eyes, constitute much stronger, though still not decisive, evidence against it. (Online version in colour.)