Consider evolution in a simple optimisation paradigm, in the sense that it tries to almost locally optimise on each soecies; while adhering to a constraint:
But it doesn't delete them. (except for big rare breaking points such as the Eukaryot revolution). This seems to be a rule of the game that evolution has decided on it long ago. Pretty much like a universal law.
Like the unidirectionality (which is also elaborated by Nicolic). I am not sure if this law is recognised by others. So, here I write it. Another great example is the brain (will elaborate on this later.
Sohail Siadatnejad
(to be published soon)