Every practical reality (ie, something we can see or comprehend otherwise) fundamentally has two aspects: in time and over time – “in time” is its structural aspect and “over time” is its functional aspect. These two aspects are actually contradictory, since function refers to the state before the structure AND the state after the structure. Structurally, these two aspects thus can’t meet. This is also what Russell’s paradox demonstrates.
Concerning the notion of evolution, these two aspects are “type” (or “class”) and “ancestry”. The problem is, however, that there is nothing we can see (or comprehend otherwise) that have these two aspects, AND, since these two aspects are contradictory, there is neither any abstract thing we can construct (like “biological species”) that isn’t contradictory.
The only way to handle this problem without contradiction is to construct two abstract things, whereof one is a kind of the other, like the Linnean “species” and “genera”. By this, we avoid the abstract void of practical realities.
Cladistics, on the contrary, claims that ancestry “naturally” is prior to type (or class), but none the less also wants to define ancestry with type (or class). One claim and one wish, thus. However, the claim is unscientific, and the wish is impossible. It actually doesn’t matter whether ancestry is prior to class or not, ancestry can’t be defined with type (or class). The thought that it can is actually the foundation for “race biology”. This fact moreover ought not be surprising, since cladistics was transferred from the nazist Germany to the modern society via the nazist Willi Hennig and the American electrician Steve Farris.