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The Evolution of Ethics

by Bruce Thompson

as presented at PUUF March 2nd 2008

The Evolution of Ethics


            We are all in favor of morals. We approve of others when they act morally and we all strive to act morally ourselves. Last time I spoke here I argued that we should seize the words “morals” and “ethics” back from those who would use them to mean a narrow, evangelistic set of strictures having no meaning apart from the dictates of religions to which you and I do not belong, and pertaining to little more than what “good girls” don’t do on a first date. Morality is not a set of private beliefs; it is not the idiosyncratic dictates of someone else’s religion. Morality is something that we share. Today I want to show that we share morality for much the same reason that we share opposable thumbs and large brains. Morality is the result of natural selection. As members of the same species, we have all been subjected to most of the same evolutionary forces, and our shared moral beliefs emerged with us from that process.


The Origin of Basic Instincts – Seek pleasure; avoid pain

To tell the story, we must begin at the beginning, roughly three billion years ago, with the origin of life. Much of our morality operates at the level of basic instinct: urges that we did not consciously choose, and which do not serve any agenda except that of the process of natural selection itself. Since evolution is driven by survival and reproduction, it stands to reason that the process of natural selection will eventually endow creatures with a basic instinct for survival and a basic instinct to pursue reproduction. We have not yet even introduced consciousness into the story, and yet we already have the idea that behavior has consequences, and that these consequences can be understood, as “success” and “failure.” This, of course, provides us with the raw material for moral judgments: creatures engaged in actions that can either succeed or fail.

            We may assume that the creatures we are talking about have a rudimentary metabolism. That is, they exchange molecules with their environment, taking in molecules that can be broken down to produce energy, and expelling molecules that have no further use. At some point the ability to exchange molecules with the environment gave rise to a rudimentary sensory capacity. Some of the creatures in our ancestry developed the capacity to change their behavior depending upon the types of molecules in the environment available for exchange. Perhaps they had a simple behavioral algorithm, such as “Swim to the left in the presence of food, swim to the right in the absence of food.” We can divide the population into two groups, namely those in which the change in behavioral pattern tended to move them away from food and toward waste molecules; and those in which the change in behavioral pattern tended to move them away from waste molecules and toward food. Naturally, the second group soon became the dominant group.

            One of the hardest things to grasp is how these behavioral changes made the transition from being mere algorithms to being experienced as “pleasure” and “pain.” However that may have happened, creatures capable of experiencing pleasure and pain obviously have an enormous advantage over creatures that do not. Pleasure is nature’s way of saying, “Do that again”; pain is nature’s way of saying, “Stop that!” Unfortunately, this creates a danger as well. Other creatures can use pleasure stimuli to create traps. A predator might, for example, hit upon a way of surrounding itself with the odor of “food,” causing creatures attracted to that odor to move nearer. The predator could then feast upon them without having to wait upon the random ebb and flow of the environment to bring it a meal. Thus, for even the simplest creatures, pleasure is not unreservedly good. The effect of such pleasure traps would be to set up an evolutionary “arms race.” As traps were laid, creatures with a pleasure-response would become better and better at making sensory distinctions in order to avoid those traps. Predators would respond by laying more sophisticated traps, resulting in still finer sensory discrimination on the part of the prey.

            This is only the first part of the story. Nevertheless, it is not too early to start looking for the moral of the story. Of course, I mean “moral” in the literal sense: what are the moral implications? So far we have identified three fundamental “operative principles” that play a role in human moral reasoning. They are:

            (1) Try to survive.

            (2) Have offspring.

            (3) Seek pleasure and avoid pain.

            However, it would be a mistake to adopt any of these principles as an absolute foundation for morality, as some have tried to do, especially in the case of the third principle. Notice that each of these principles can conflict with, and override, the others. For example, we sometimes forego pleasure when we realize that the source of pleasure may be fatal—a pleasure-trap set by a predator, for example. We may endure pain for the sake of having offspring; alternatively, some people forego having offspring for the sake of avoiding pain. As further fundamental operative principles are added to this list, the complexity of the situation—one principle being overridden by another—will be compounded geometrically.

Because these operative principles conflict with each other, we have been endowed by natural selection with the ability to make intentional choices. We are evolved from a context in which the rational avoidance of certain pleasures, and the rational seeking of certain pains, is part of our survival-and-reproduction package. We have the ability to discriminate between good pleasures and bad pleasures. Nature has given us the ability to preempt and countermand our own nature. We have the ability to understand harmful temptations, and to resist them.

            That, of course, is what purposely chosen behavior—and moral reasoning—is all about.



The Origin of Groups – The concept of fairness

            Of course, morality is not just about personal success and failure. It is a matter of social interaction. We cannot claim to have explained the evolution of morals until we have traced the transformation of individual self-interest into concern for the interests and legitimate claims of those around us.

The origin of groups is explained in an old joke. Two men were planning a hiking trip through the wilderness. “What do we do if we meet a bear?” the first man asked his friend.

            “I don’t know about you,” the friend replied, “but I’m going to run like hell.”

            “Why? You know you can’t run faster than the bear.”

            “I don’t have to,” his friend replied. “I just have to run faster than you.”

            In some environments members of a species can find safety in numbers, not because a group is tougher or smarter than an individual predator, but only because predators can’t catch everybody. Schools of fish, herds of gazelles, flocks of birds, etc., all operate, at least to some extent, on this principle. Of course, this is social behavior in only the most rudimentary sense: in such groups it is still every fish for himself.

            Altruism was a problem for evolutionary theorists.  It made sense that a creature would be motivated by its own pleasures and pains, as nature’s way of promoting reproduction and survival. Creatures might also—in the interest of their own survival and reproduction—learn to forego pleasures and endure pains. But what in the world could induce a creature to forego pleasures and endure pains for the sake of some other creature’s survival and reproduction?

            The best solution to the problem of altruism was laid out by Richard Dawkins in his book The Selfish Gene. The thesis of his book, and the point on which the solution to the problem of altruism rests, is that the main unit of evolutionary competition—the entity that natural selection selects—is not the individual organism but the gene.

            Genes are abstractions. If two fragments of DNA are made up of the same sequence of amino acids, then they are two copies of one gene, just as we may have two copies of the same book. The fact that a gene is a DNA sequence, not a DNA fragment, is important. Since each copy is—by virtue of being a copy—just like every other copy, no particular fragment of DNA derives greater reproductive success from being itself the direct template from which copies are made than from one of its duplicates being the direct template. A copy made from any fragment must count as a success for all exactly similar fragments, no matter which of them served as the template, just as a photocopy of one page of one copy of a book replicates the information contained on the same page of every other copy.

The altruism of organisms may be explained by the selfishness of their genes. If a fragment of DNA causes an organism to sacrifice itself for the survival and reproduction of other organisms that happen to carry copies of the same gene, then that fragment of DNA will have reproduced as successfully as if it had itself served as the template of reproduction.

            Among humans—and, indeed, among most animals—parents and children have a 50% chance of sharing a particular (rare) gene, and siblings likewise have a 50% chance of sharing that gene. Between first cousins the chance of sharing a particular gene drops to 12.5%; between second cousins it drops to a mere 3%, and between third cousins it is barely above the chance of sharing that particular gene with any random member of the general population. It is therefore not surprising that parents invest a great deal of time and effort into raising children, that brothers and sisters generally feel tight bonds of mutual concern and sympathy, that we exchange Christmas cards with our first cousins, but that only rabid genealogists even know who their third cousins are. In a tribe, I am likely to be close kin with those people that I meet regularly, especially as I grow up. These people are likely to be my own parents, brothers and sisters, cousins, uncles and aunts. Hence, my selfish genes have endowed me with an instinct to be altruistic to those people that I meet regularly. Siblings and childhood friends have a special place in my heart, but I am capable of forming new friendships as well. Of course, it should be noted that many humans no longer live in tribes, so our altruistic instincts no longer accurately serve the best interests of our genes. This is not a matter that should particularly concern us. Our interests are not necessarily the interests of our genes; and there is no reason why they should be. I am perfectly happy to make friends with people who are not genetically related to me provide I see them fairly often.

            The theory of the selfish gene easily explains unconditional altruism, the capacity of one organism to sacrifice itself for another while receiving nothing in return (except reproductive success for its genes). It is more difficult to explain reciprocal or tit-for-tat altruism.

            Let us imagine (as Richard Dawkins did) a population of birds who live together in large flocks. Regrettably this population of birds is under attack by a small parasite that works its way under their feathers, burrows into their heads and eats their brains. The birds are perfectly capable of picking the parasites out with their beaks, but since beaks don’t bend, no bird can pick the parasites out of its own head feathers. Hence, each bird must—if the flock is to survive—pick the parasites out of the feathers of its fellows. Fortunately for these birds, their selfish genes have discovered the altruistic strategy, so each bird has been endowed with a natural instinct to enjoy grooming the feathers of its fellow birds, even though each bird must sacrifice time and energy on the grooming that might otherwise have been spent on having sex and finding food for itself. Let us call these birds Suckers.

            Now, let us imagine that a mutation occurs. One of the birds is born with genes that do not know the altruistic trick. We will call this bird a Cheat. This bird allows itself to be groomed by others, so it enjoys protection from the brain-eating parasite, but it does not return the favor. Instead, it spends its time eating and breeding. Since it spends more time eating and breeding than the other birds do, it has a larger number of offspring. Hence, more copies of its un-altruistic gene are passed on to the next generation than are the altruistic genes of other birds. The same thing occurs in the next generation. Eventually there are too few Suckers to do the necessary grooming, and the population as a whole begins to decline toward extinction.

            However, let us now imagine a different population of birds. These birds are also under attack by brain-eating parasites, and their genes have discovered the altruistic trick of grooming to fight them. But these birds are also capable of recognizing individual members of their flock, and they form friendships based on who agrees to groom them and who does not. They will refuse to groom a bird that they know will not groom in return. Let us call these birds Grudgers.

            In a population of Grudgers, a Cheat may be able to find birds willing to groom him once, but he must go to a different bird for each grooming. In the first generation the Cheat may obtain enough groomings to keep him safe from the parasite. Hence his genes may be passed on to the next generation, if he is lucky. But his luck cannot continue. As there are more Cheats in the population, groomings are harder to come by. Grudgers continue to groom each other, so they continue to be safe from the parasite, but Cheats often find themselves left out. Hence their numbers will always remain small. In a large, fluid population Cheats can maintain a presence almost indefinitely; but, in a smaller population, or a population in which individuals tend to come into contact with the same few individuals over and over, Cheats will be driven out.

            Humans clearly evolved under conditions that would have been amenable to the development of reciprocal altruism: we evolved in small groups in which the same individuals came in frequent contact with each other. It is not surprising that we have a natural instinct to be helpful to each other, but that this instinct is tempered by a sense of fair play. We are Grudgers.

Once again let us tease out the moral implications of our story. We previously discovered three operative principles that play a role in human moral reasoning. We are now in a position to add two further operative principles to the list. They are,

            (4) Be nice to others.

            (5) Turnabout is fair play.

            The foundation of morality may be the need to satisfy our basic biological needs: survival, reproduction, the seeking of pleasure and the avoidance of pain. We now discover that as a natural instinct morality involves fairness in our treatment of others.


Do as Mother Says, not as Mother Does – Moral Rules

            Moral rules are instructions on how to behave. But, why are we willing to take instructions from others? Early in the development of life creatures discovered that they could inflict pain on each other, and, of course, prior to that, creatures  had learned to modify behavior in response to pleasure and pain. Hence, creatures can easily develop the ability to encourage and discourage behavior in others through punishments and rewards. Some creatures may use this ability only to make the behavior of others more congenial to their own comfort and survival. Other creatures may, in addition, use this ability to discourage behavior in others that they believe will have undesirable consequences for the actor. Let us call such creatures “mothers.”

            Obviously, a mother must invest considerable time and effort into teaching, so she will have acquired an instinct for such behavior only if it is of some benefit to her selfish genes. She is most likely to expend time and energy on those to whom she is closely related and who have the best chance of surviving her, namely her own cubs. Meanwhile, the selfish genes will also endow the cubs with an instinct to be obedient learners. Cubs that develop an instinctive trust of their mother’s instruction will learn from her experience and consequently fare better than cubs that refuse to be instructed.

            Mothers may teach their cubs lessons other than those drawn from personal experience. They may teach what they were taught by their own mothers, which came from mothers prior to that. They may, in short, transmit a moral code. But where does that moral code come from? In his book, Cows, Pigs, Wars and Witches, Marvin Harris recommends a strategy for answering that question. His strategy can be illustrated by attempting to answer the question, “Why do the Hindus refuse to kill cows?”

            At the time that Harris was writing, it was widely considered paradoxical that the people of India, many of whom live in desperate poverty, refuse to take advantage of an excellent source of protein. Most Indian families own a cow, and treat it as a treasured member of the family. They decorate it with garlands during festivals and mourn its passing when it dies. They would no more consider killing and eating their family cow than an American family would consider killing and eating their pet dog (although dog meat, too, is a good source of protein, and is considered a delicacy in some cultures). Indeed, Hindus regard their cows not just as beloved pets but as sacred beings. The killing of a cow is not just unthinkable; it is a moral transgression of the first order. Riots have occurred over the issue.

            It might seem that the taboo against killing cows is partly responsible for the poverty of India. Harris, however, argues that cows actually contribute to the wealth of an Indian family. Cows, as they are treated in India, consume very little of a family’s resources. They are rarely fed grains that might be eaten by people. Mostly the cows are left to scavenge the weeds and grasses that grow naturally on roadsides and in fallow gardens. Consequently, the cows of India are scrawny and underfed. Nevertheless, what they do eat is quickly converted into excrement, which has numerous uses. It is a preferred source of fuel for cooking. It can be made into a solid surface used for flooring. It can be used as fertilizer. Cow poop is considered so valuable that children and paupers follow cows around to collect it.

            In many parts of India the chief draft animal is the ox. Oxen are used for plowing and for transportation of goods to market. Obviously, these tasks are so important to the survival of a family that the loss of an ox could be devastating. If a family were too poor to replace its ox, the result would be starvation. But oxen come from cows, so a family that owns a cow has a source of oxen, even if it is otherwise very poor.

            Harris argues that the contributions of a cow to an Indian family are so great that the family is better off to keep its cow alive, even in times of severe economic distress, than to kill the cow merely for the sake of a few high-protein meals. But Harris is not claiming that the people of India revere cows because they have carefully reasoned through the environmental-nutritional economics of cow worship. For Hindus the injunction against killing cows is a moral imperative. It is a practice that helps to define who they are, culturally and ethically. The idea, “I don’t kill cows,” is an inextricable part of the body of beliefs in which “I am a Hindu,” and “I am a good person,” are also involved.

            Harris suggests that the injunction against killing cows as a moral imperative could be explained by natural selection. Imagine a time when cow worship in India was not particularly common, but that a few families had somehow formed a particularly strong attachment to their cow because they had conceived the odd idea that their particular cow was the reincarnation of a beloved ancestor. Then one year the monsoon rains failed to arrive. That year the crops were scarce and hunger was common. Families with no particular reverence for their cows slaughtered and ate them, and thereby managed to survive the drought in good style. Families that revered their cows were desperately hungry, but refused to kill Grandmother Cow, despite their hunger. Next year things improved. However, the families that had eaten their cows discovered that they did not have enough fuel for cooking and were forced to buy fuel from their neighbors. In one of those families their ox stepped in a hole and became lame. With no cow, they found they would have to buy an ox. But this was impossible since they had spent too much on cooking fuel. The family did not survive. Since the failure of the monsoons is a fairly frequent event in India, this pattern was played out over and over. Eventually, by the inexorable force of natural selection, the families that revered their cows soon far outnumbered the families that did not.

            From the point of view of natural selection, then, the purpose of a moral code is to adapt a society to its environment. As creatures with mothers, humans have a natural tendency to develop moral codes, and to feel some loyalty to the codes we have developed. Unfortunately, just as our instinct to seek pleasure can lead us into a trap, so can our instinct to be loyal to the moral code of our ancestors. Consider the sad story of the crew of the H.M.S. Bounty. After the famous mutiny, the British sailors took Tahitian wives and settled on Pitcairn Island, where they lived more or less happily for several generations. Their way of life was based chiefly on the practices of British farmers, since that was the way of life they knew. When the mutineers first arrived, Pitcairn Island was covered with tropical forest. Centuries of fallen leaves and branches had created a layer of fertile topsoil which could be used for farming once the land was cleared. Wood from the forest also provided fuel for cooking. Unfortunately, the English way of life, well suited to a large island like England, was not suited to Pitcairn Island. Farming depleted the soil, so each year more land had to be cleared. New trees grew, but at a slower pace than they were cut. Each year the forest shrank. One year—about a hundred years after the mutineers had made the island their home—the last of the trees was cut down. Next year the fertile soil was gone, and the fuel for cooking was gone as well. Famine swept the island and the population was decimated. Today the island is still inhabited, but only by an impoverished remnant of survivors who are among the most destitute people on earth.

            The point of this parable should be obvious. We cannot assume that a way of life is suitable merely because it is ancient, or familiar, or the only one we know. An old moral code may not be well adapted to conditions that are different than they have been in the past. Moreover, we now live in conditions that are markedly different than they have been in the past, and we ourselves are responsible for the change. We have changed the world so much over such a short period of time that our old ways of life, our old customs and traditions—our old moral codes—are probably no longer suitable to the conditions in which we find ourselves.

            What can we do about that? One possible answer is that we may continue to be loyal to the moral code of our ancestors, and let the environment be hanged. We will surely die out if we make this choice, but Nature will not mind. The other choice, and one that I like better, is to try to understand the new environment, project how our actions might affect it, and change our behavior—indeed our very moral code—to be more suitable to the environment we are in.

            We can now add two final fundamental operative principles to our list. They are,

            (6) Be loyal to the customs and practices of ones ancestors.

            (7) Use your common sense. Think!

            Notice that, just as previous principles have done, these two conflict with each other. However, let’s be clear: rational examination of a moral code does not begin by tossing out the old moral code and attempting to replace it wholesale with a new one. The moral code of our ancestors is not a set of infallible axioms, but it is a body of accumulated wisdom, representing many generations—indeed, many billions of years—of inquiry into our relationship with our environment. Where we have no reason to question that accumulated wisdom, we have every right to adopt it as a working hypothesis. This is precisely how reasoning in science is done, and moral reasoning is no different.

            Moral reasoning is also like scientific reasoning in the sense that it is a shared discussion in which inquirers try to reach consensus through a mutual consideration of facts. Morality is a matter of opinion in just the same way that science is. That is, while scientists often disagree with each other, they recognize that consensus is possible. Earlier I said that morality is shared. To the extent that we have already reached public consensus on how to treat each other, this is true; and, we have already reached public consensus on many things—that it is wrong to run red lights, for example. On some matters, of course, there are still sharp disagreements, but on those matters, consensus is possible.

            Dick Cheney once famously said that re-cycling is a personal virtue, not a moral imperative. I disagree. Re-cycling is one of the changes in modern behavior that has been most effective at easing stress on the environment. Water and energy conservation help too. Are such seemingly trivial matters so important that they deserve to be ranked as moral imperatives? They are the very essence of morality. They are actions of self-sacrifice calculated to keep our society in balance with its environment, so that our society can continue and future generations can be born into the world. What could be more important than that? But natural selection is an ongoing process. One of the errors that we must constantly guard against is thinking of ourselves as the crown of creation, the final goal toward which evolution was striving. If we learn to challenge old moral codes rationally, and to revise them to make them better suited to changed and changing conditions, we will survive, and new generations will be born; if not…well, perhaps, some day we will be replaced by a more moral species.

That is how natural selection operates.


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