If you're talking about the natural evolution of a species, it will not stop until it has completely adapted to all of its problems. However, I wouldn't necessarily call that perfection. A species will not (usually) naturally evolve (on a biological level) if it is uncomfortable. Rather it will evolve out of necessity.
You could be unhappy, but your body wouldn't change itself to make you happier. And I wouldn't classify that as perfection.
And at the end of it all, I don't have a word to sum it up for you.