I've always thought that as more of a mutation source rather than a more direct driver for evolution and therefore our artificial classification divides. Mutat

I've always thought that as more of a mutation source rather than a more direct driver for evolution and therefore our artificial classification divides. Mutations happen constantly: transcription error, radiation, and yes horizontal transfer, but many other factors decide if the mutation sticks or not. But gene transfer doesn't break a hierarchical classification system much more than solar radiation does.