As we saw in Chapter 7, phenetic clustering is based on the use of distance methods, however the original data are coded. Thus, as I pointed out at the beginning of Chapter 8, pheneticists have to use separate techniques for the construction of classifications and the reconstruction of phylogeny. The methods of “numerical cladistics” arose from within the school of phenetics as a result of attempts to reconstruct phylogeny, but its practitioners diverged from their pheneticist colleagues and converged on mainstream cladistics as a result of their conviction that classification should be hylogenetic. In this chapter, I describe the development of numerical cladistics and its eventual repudiation of the use of undifferentiated distance data in favour of reliance on apomorphy and parsimony.

While this was happening, from the 1960s onwards, various techniques of phylogenetic reconstruction involving the use of biochemical and molecular data were developing. These interacted with other schools of phylogeny reconstruction, and posed problems, notably those concerned with the use of distance data, in an acute form. In this chapter, I review some of these techniques, particularly as they concern the relationship between phylogeny and classification. Then in Chapter 10, I shall attempt some general summary of that relationship. But a complete statement of my position will be possible only after we have considered theories of evolutionary mechanism and something of philosophy.