7 - Taxa and Genealogy

Summary

● Pheneticism, evolutionary taxonomy, and cladistics are competing taxonomic philosophies; they disagree about how the classification of a group of organisms and the genealogies of those organisms are related. The cladistic approach is defended. ● It is widely agreed that it is a matter of convention whether a set of species should be placed into a single genus or into more than one. The point generalizes – superspecific taxonomic rank is a matter of convention. ● It is a separate question whether it is conventional matter whether a set of organisms comprises one species rather than several. ● The view is defended that biological taxa are spatio-temporally extended physical objects; they are “individuals,” not natural kinds. ● The question is explored of whether human races are biologically real. ● Cladistic parsimony is explained; it is a method for inferring phylogenies that differs from the method of maximum likelihood. ● The question is raised as to whether parsimony should be evaluated by using the law of likelihood; an alternative is explored – that both methods should be evaluated by seeing whether they are statistically consistent.