The vast majority of taxonomists use a from of phylogenetic system that is weded to the principle of evolutionary change. Indeed, the system presupposes evolution as the ultimate yardstick for its “naturalness”. Once the actual patterns of ancestry of a group of species is known the group can be classified absolutely. Far from being a dusty set of labels for organizing museum specimens, this classification system mirrors the evolutionary past of the groups of creatures it tries to describe
In outgroup analysis, species are compares with a very distant relative (the outgroup species) such analysis can discover whether a trait in the group – here striped tails – is derived or primitive.