Gould and Eldredge have said some apparently conflicting things, both about the testability and about the theoretical significance of PE. My aim in this chapter is to get to the bottom of these issues, and to see if there might be some way of making sense of these apparently conflicting claims. I begin with the question of whether PE is all that interesting a model. Then in the second half of the chapter I will move on to consider questions about testability.

PE and macro/micro reductionism

A minimalist model of evolution is one that treats macroevolutionary patterns and trends as mere by-products of microevolutionary processes plus speciation events. Because such models are simplest and most parsimonious, it seems reasonable to start with a minimalist model and expand it only on an as-needed basis. The question is whether any such expansions are needed.