Parsimony, Hierarchy, and Biological Implications

When constructing a cladogram from a data set a researcher will, as a matter of course, select the shortest possible branching diagram that will represent the data, thus minimizing the number of appearances of any character on the cladogram. This “parsimony program” is usually adopted without comment, but when arguments defending or questioning its use are put forward, they almost universally discuss the program in terms of its biological implications — i.e., whether assumptions about the order of nature are involved. It is my purpose, in the following discussion, to demonstrate that the parsimony program as described has no biological implications but is simply a methodological demand of a cladogram. The implications so many writers find here are actually derived from the hierarchical form of the cladogram itself, and the nature of these implications can be properly understood only when their origin is identified.