If you apply the same logic to the animal kingdom you will realise that our interpretation of good and evil, sin, karma etc is not applicable. Its genetics, its adaptability and its survival of the fittest. The animal kingdom has the same bodily functions as us. Things karma, values, nuturing, etc are to modify one's behavior to follow society's norms. It helps as an outlet to reduce the stress that we helped to build up. Notice that we grower older we tend to look for religion to keep peace with outselves.