We would normally distinguish the causes of a thing’s genesis and structure from the cause of its preservation until now, though they clearly can sometimes overlap. The preservation of Mt. Rushmore clearly has something to do with what it was made out of and who it was made for, but the story of its creation is different from the story of its maintenance.
Evolutionary accounts give causes of preservation or maintenance, and they have a multi-faceted relation to the causes of genesis and structure. Roughly, they can either claim to explain it (1) or treat it as unknowable (2a and b)
1.) Collapse the difference: If evolution explains a line of preservation, then it does explain the genesis of the species if we define it as a breeding population or a line of relation to a common ancestor. Preservation explains the existence of populations throughout time, and we can consider the species as nothing more than this.
2a.) The unintelligible: The more familiar explanation for the genesis of species is accidents in genetic copying. Biologists can, like insurance companies, use some mathematical tricks to make some informed judgments about the accidents, but the accident as such falls outside any rational analysis. In the same way that the limitations of our knowledge give rise to luck in human life, the limitations of matter give rise to chance in generation. Again, anyone who works with matter recognizes that it has a mind of its own, and nature has to work with matter, even if it works with it “from the inside” (we work on our own minds from the inside too, but they still have blind spots that give rise to various kinds of luck).
The genesis of species might also be unitelligible for other reasons like (i) occurring within the individual. Theories capture only patterns and compressible features, and an individual isn’t either. For all of our two centuries of protestations to the contrary, history is not a logos. cf. Herr Klug’s pen. (ii) the causes are complex. Figuring out the genesis of species might be like trying to figure out the genesis of fads or things falling out of fashion. Why are there seals? I don’t know – why are mullets now unattractive? Why are thick-rimmed glasses all of a sudden fashionable? (As a Gen-Xer who associates them with 50’s fashion, I still don’t get it when I see my students wearing them.)
2b.) The unintelligible: A thing might also be unintelligible because it is known by another science. And so maybe the question of where species arise is as much a question for another science as the question where life arises (which seems to be something for chemists to figure out.)
All three approaches have their place and should not be played off against each other. The success we have in eliminating the question (cf. 1) does not need to be taken as proving that some other science is irrelevant (2b) nor should the presence of some other science rule out real, intrinsic unintelligibility in a specific domain (2a). The consequences that this has for metaphysics and theology – which treat the paradigmatic cases of “things known by a further science” – should be clear.