My other career is breeding working dogs.<p>After observing hundreds of dogs I can tell you breed traits do not disappear just because we make the dog a house pet.<p>Sometimes the traits will remain dormant and simply need to be 'unlocked' through exposure the environment/conditions the dog was selectively breed for. Thus, when a collie is exposed to a herd of sheep, even if it never herded before, it will herd those sheep. Once this herding behavior is unlocked the dog will begin to herd everything.<p>This is why we hear stories of dogs which descend from fighting, war or defense breed that 'suddenly' become aggressive and violent. They are simply expressing all of those generations of selective pressure.<p>Dogs and genetics are truly amazing things.