But surely it is unique only insofar as no other organism at the time was so readily adaptable for the purpose desired. The genome does not reveal the polymorphism and exists in every caenid from poodle to wolf. There would be no natural advantage for a brachycephalic cow so it would not exist in the wild. I would assume the bovine would be no more or less 'elastic' than any other analogous organism subject to artificial selection.