Did we pass through each of these levels (rock, plant, animal), before we reincarnated as humans? If so, what could we possibly have learned by being a rock for millions of years?
We will be free when we are no longer trapped in searching for satisfaction in the things of this life. We can only find true meaning and happiness in our relationship with God. The pursuit of happiness apart from him is a treadmill going nowhere. Freedom is the realization that this is the wrong path. It is a prison we can walk away from.