As concerns "necessary within the design" I would argue that you do. I am trying to say that as scientists, we like to say, "evolution has taken us [this far] (whatever [this far] is)". But we don't say, "How far could evolution have taken us?" How broad is the existing code base? Is it individual code bases branching into species, or is it all interleaved in some more subtle way?
I tend to believe it is the latter, and the evolution has taken us much farther than we realize.
This is why I believe our current handling of genetic modification is extremely bad practice and can (?) result in a "genetic seg-fault".