The natural balance on this planet requires more than just a system of ensuring reproduction, to perpetuate life. Instinctive controls exist to make sure that members of a species live long enough, in sufficient numbers, to have the opportunity to reproduce. Animals that form groups in order to survive, must cooperate in a variety of ways, or the pack would not hold together. Even with solitary creatures, there are rules of conduct allowing for courtship and mating. Humans call the innate knowledge of these codes of behaviour, morality.
Universal morality governs interaction between members of the same species.
Any action contrary to this principle is a violation of natural law. The problem that mankind faces, is that the natural balance depends upon all of the laws being followed, and, since we wish to exist separately from the other animals, man must find ways to compromise within the system. Applying this principle to humans, means that changes must come from within mankind, in order to minimize the effect of outside control mechanisms. Many of the moral guidelines set out by society are based on the innate knowledge of right from wrong. Religions have established laws or commands, from their particular gods, that reflect this knowledge.