Ethical systems, codes of conduct, are entirely practical in nature. The right and wrong ways of behaving in life is exactly like the right and wrong way of driving a car or fixing a drain.

Every living creature needs some strategy for survival. In programming simulation models of grazing animals, it is necessary to give the animals strategies for grazing. One strategy might be to move around randomly until some grass is found. Another might be to set up a path to patrol looking for grass. Another might be to move towards the nearest clump of grass. Another might be to go where the grass is greenest. And so on. It might be possible for a grazing animal to generate strategies, and try them out. However, these various different strategies will each result in a different degree of idleness. It seems plausible to suggest that a grazing animal that moves around randomly will probably spend more time grazing than one which rigorously follows a predetermined path, and that a path-follower will spend more time grazing than a grazer that moves wherever the grass is greenest. Given a range of different strategies, each will result in some degree of idleness. And when grass becomes thin on the ground, and all grazers have to work longer to survive, it will be the least idle that first succumb to starvation, while the most idle survive. And if, when they die, their strategies die with them, then there is a process of natural selection of survival strategies. The worst strategies will tend to die out, and the best strategies will tend to survive. The best survival strategy is simply the one that results in continued survival.

Exactly the same applies to human ethics, human codes of conduct. They also are survival strategies. And the best ethical strategies are those that best ensure continued survival. The ones that best ensure survival tend to persist, while the least effective die out. Over time, a natural selection of ethical codes will winnow out the least effective, and leave in the end only one code.

And at the same time, ethical codes can mutate and change. And once again, it will be those codes which offer the greatest chance of survival which will themselves survive and multiply. Natural selection applies as much to ethics as to everything else.

In many animals, it seems that their survival strategies are programmed into them at birth. Young plants do not need to be taught by their parents to grow and spread leaves. A great many forms of life seem to come with their survival strategies hardwired into them, perhaps even genetically programmed. But a great many other animals seem to need to be taught what to do. Young birds in their nests, fed on seeds or insects by their parents, may be being taught what they need to eat. And it may also be that the parent birds, by demonstrating flight, in some degree teach by example their offspring how to fly. And the offspring of predatory animals like wolves and lions need to be taught how to hunt by their parents. And, in the same way, human children learn by example from their parents, and are taught the skills and habits they need in life.

If survival strategies are hardwired, it makes for a simple life. But hardwired strategies are unalterable. And while a strategy may be successful in one circumstance, it may be unsuccessful in another. And so there is a need for strategies to be adaptable. Very often, if they are to survive, creatures will need to abandon one strategy and try out another. If strategies are hardwired and unalterable, they simply will not survive.

Human ethical codes are essentially survival strategies which have evolved over long periods of time, taught from generation to generation. Where a mode of life develops and endures for centuries or millennia, the ethical codes associated with that way of life are likely to gradually become ossified: everything is done in the time-honoured, ancestral manner. A human community that lives by fishing will have a different set of codes and customs to one that lives by hunting or gathering or farming. It is only when the old time-honoured way of life becomes no longer possible to continue - because perhaps climatic changes result in fish or animals or plants to becoming scarce -, that new ways of living need to be found, and new ethical codes and customs adopted or improvised. And in times of rapid change, new ways of life may need to be continually improvised. In these circumstances, ancestral teachings are likely to be abandoned.