You're assuming that being under these conditions never leads to adaptation. It is rare that someone who was constantly fighting for their lives and struggling to find food, water, or shelter would have time or room to feel much happiness beyond the occasional small victory.
It is also highly unlikely someone will STAY in that level of intense living without adapting in some way to make it more satisfying. Whether it is carving out a nest of leaves to make as a bed, learning where to go to find food and water quickly, storing some on hand, or creating some type of defense from the external world, animals. People adapt, and in doing so find relief, and happiness.
I'd say it is very much a natural biological drive.