-This post is excerpted, with changes, from the book Darwin, God and the Meaning of Life by Steve Stewart-Williams - available now from Amazon.com, Amazon.ca, and Amazon.uk.

Is morality an adaptation, crafted by the invisible hand of natural selection? Or do we just make it up? This turns out to be a tricky question to answer. On the one hand, there's little doubt that evolutionary theory can shed light on the origins of some of the behaviours that fall within the rubric of morality, including altruism, empathy, and our characteristic attitudes about certain kinds of sexual behaviour. On the other hand, the morality-as-adaptation hypothesis faces some serious challenges. If morality were a direct product of evolution, why would people constantly argue about what's right and wrong? Why would we spend so much time teaching our children to be good, and inculcating in them virtues such as generosity? Why would we experience inner conflict between what we think is morally right and what we really want to do? You might expect that, as an evolutionary psychologist, I'll have snappy comebacks for each of these questions. But I don't; I think they represent important criticisms and I don't think that morality is a direct product of evolution. What I do think, and what I'll argue in this post, is that morality is a social institution. To some extent, it embodies and reflects our evolved inclinations, but to some extent it also counteracts them.

Starting with Darwin himself, various thinkers have argued that human morality has an evolutionary origin. Like any other complex phenomenon in the biosphere, it is a product of natural selection and other evolutionary processes. At first glance, this might seem unlikely. Why? Because morality just doesn't seem to aid its bearers! Traditional moral systems tell us we should not act to satisfy our own selfish needs, but instead should act altruistically (that is, we should act to satisfy the selfish needs of other people). This hardly sounds like a recipe for evolutionary success.

However, there are at least two reasons to think morality bears the imprint of our evolutionary history. The first comes from observations of a class of individuals that psychologists all too often ignore: other animals. Nonhuman animals obviously don't reason explicitly about right and wrong, but they do exhibit some aspects of human morality. Rather than being locked into an eternal war of all-against-all, many animals display tendencies that we count among our most noble: They cooperate; they help one another; they share resources; they love their offspring. For those who doubt that human morality has evolutionary underpinnings, the existence of these ‘noble' traits in other animals poses a serious challenge. When speaking of other species, we inevitably explain these traits in evolutionary terms. No one would want to explain the fact that female dogs love and care for their puppies as an arbitrary product of canine culture, for example. Given that we accept an evolutionary explanation for this behaviour in other species, it seems tenuous to argue that the same behaviour in human beings is entirely a product of a completely different cause: learning or culture. In principle, it is possible. However, we should have a strong reason to make this exception. Without such a reason, our default assumption should be that we are continuous with the rest of nature and thus that the behaviour has an evolutionary origin.

That's one reason to accept that evolutionary theory has a role to play in the analysis of moral behaviour. A second is that, not only do we know that these kinds of behaviour are part of the standard behavioural repertoire of humans in all culture and of other animals, we now have a pretty impressive arsenal of theories explaining how such behaviour evolved. Kin selection theory explains why many animals - humans included - are more altruistic toward kin than non-kin: Kin are more likely than chance to share any genes contributing to this nepotistic tendency. Reciprocal altruism theory explains how altruism can evolve even among non-relatives: Helping others can benefit the helper, as long as there's a sufficient probability that the help will be reciprocated and as long as people avoid helping those who don't return the favour. Another promising theory is that altruism is a costly display of fitness, which makes the altruist more attractive as a mate or ally. Overall, the evolutionary explanation of altruism represents one of the real success stories of the evolutionary approach to psychology.

It's not alone, though. Evolutionary theory also sheds light on sexual morality, in particular our attitudes toward incest. The logic is simple: Because kin share so many genes, they are more likely than non-kin to share deleterious recessive genes, and thus the offspring of incestuous liaisons are likely to have low fitness - often they don't survive, and if they do, they often don't reproduce. As a result, any heritable psychological or behavioural trait that lessened the chances of incestuous mating would have a good chance of being selected. Consistent with this reasoning, the avoidance of incest is widespread in the animal kingdom and, once again, we're no exception to this general rule.

We see, then, that some of our basic moral inclinations and impulses make very good sense in evolutionary terms. This does not imply, however, that morality as a whole is an evolutionary product. An immediate and very reasonable criticism of the adaptation hypothesis is that human moral codes vary a great deal between different cultures and subcultures (although not as much as people sometimes think). Furthermore, moral beliefs sometimes change rapidly over time, both within individuals and within societies - consider, for instance, the change in expressed attitudes about sex in the western world in the second half of the twentieth century. If humans share a common moral psychology, there would presumably be little debate on ethical issues. Why, then, do we constantly wrangle over what's right and wrong? And why, from time to time, would we all have such great difficulty following the dictates of morality? If morality were a direct product of evolution, it would presumably enhance our fitness and thus we would have evolved to want to be moral. Often, though, doing the right thing involves an effort of will and goes against our dominant impulse. As the philosopher Denis Diderot pointed out, ‘There is no moral precept that does not have something inconvenient about it'. Certainly, in some domains, we do naturally want to do the right thing. Very few people have trouble resisting incest, for example. Nonetheless, often we would prefer to do the wrong thing if we thought we could get away with it. Thus, some moral standards jar against our evolved inclinations. To explain this, we must go beyond biological evolution and consider the contribution of cultural evolution in the making of our moral systems.

The first step is to draw a clear distinction between our morally-relevant evolved dispositions and our shared moral code. The latter does not have a direct evolutionary origin. It is a cultural product, and is the outcome of many different factors. Let's now consider some of the most important of these. First, to some degree, our moral codes are simply reflections of our evolved human nature. A good example relates to incest. Many cultures (though not all) have formal moral rules proscribing incest. It is tempting to ask: If our aversion to incest has an evolutionary origin, why would we need a moral injunction against it? But this question raises a possibility: Maybe we don't need a moral injunction against incest. The vast majority of people just don't want to engage in this form of sexual expression; they feel an acute and pronounced disgust at the prospect. So, in this instance at least, formalized morality may simply embody or reflect people's values, values they would have anyway.

It's easy to multiply examples. As noted, human beings are evolved nepotists, and it's clear that the ethical systems of the world reflect this aspect of human nature. The Old Testament, for example, admonishes us to honour our fathers and mothers, and one of the key Confucian virtues is filial piety: love and respect for one's parents and ancestors. Likewise, humans are evolved reciprocators, and the reciprocity principle is embodied in many of our ethical teachings and spiritual beliefs. We like to believe that the scales of justice will be balanced, especially when this means that the good things we have done will be rewarded and the bad things other people have done will be punished. The reciprocity principle is embodied in the belief that God rewards and punishes behaviour, and also in the traditional Indian belief that one gets one's just desserts through the action of karma. There is also a widespread trend among human beings of viewing disasters as a response to human misbehaviour, an exchange of bad for bad. The Chinese believed that earthquakes and other disasters occurred when people stopped following the way of nature. Similarly, the Biblical flood was construed as a response to human sins. In these and other cases, we see that universal aspects of the human mind shine through in the very different worldviews that arise in different cultures.

There is clearly some truth, then, in the notion that our moral codes and ethical theories embody and reflect our evolved human nature. However, if pressed too far, this view breaks down. In some cases, morality redirects or even opposes our evolved passions. Although we have some degree of universal compassion, we also routinely favour ourselves, family members, and members of the groups to which we belong. This has a clear evolutionary origin. But most ethical systems frown on this kind of favouritism, which receives pejorative labels such as selfishness and nepotism. Similarly, although many moral precepts reflect the reciprocity principle (return good for good and bad for bad), this is not always the case. For example, the ethical precept that we should ‘turn the other cheek' goes against the grain of our untrained inclinations. This demonstrates that our evolved moral psychology must be distinguished from our formalized morality, and that our official moral systems can and do stray away from the dictates of human nature.

Of course, when we have a conflict between a moral urge and a non-moral urge, this doesn't necessarily mean that the non-moral urge is an evolutionary product and the moral urge a product of culture. In some cases, it is a conflict between two evolved urges. Some evolved tendencies are considered moral; this includes the desire to care for one's children and to form monogamous pair bonds. But others are generally considered immoral; think, for example, of aggression, xenophobia, and our proneness to be unfaithful sexually. Why do we consider some evolved motivations good and others not? One reason may be that familial love and monogamy do not impinge on the harmony of the community, whereas aggression and infidelity often do. This brings us back again to the idea that morality is not a direct product of evolution. Instead, and to some extent, it is a humanmade system of favouring those evolved tendencies that facilitate group cohesion, while disfavouring those that are socially divisive. Morality is a way of controlling our evolved natures, rather than a mere reflection of those natures.

Other things are going on as well. Some of the content of our moral systems derives from preferences about how we wish others to act. For example, people may tend to dislike selfishness in others and prefer altruism, especially when they or their kin are the recipients of that altruism. The moral codes of a culture may have emerged from people acting on such preferences - for example, discouraging others from being selfish and discouraging members of other families from exhibiting kin favouritism where this might disadvantage them (which is the point at which we stop seeing kin favouritism as wholesome family loyalty and start seeing it as nepotism). When you think about it, moral precepts such as ‘give without thought of reward' are potentially highly advantageous to those who preach but don't practice them. Thus, people may encourage others to behave altruistically in order to satisfy their own selfish agendas! Ironically, then, the self-interested, manipulative efforts of people pursuing this policy may have helped foster the unselfish forms of morality. This may help to explain why we are more altruistic than evolutionary principles alone would lead us to expect.

On top of this, our moral systems embody a desire to present ourselves in a good light. We may espouse ethical values that make us attractive as mates or friends or allies. This may mean understating the extent of one's bias toward self and kin. This isn't necessarily a matter of conscious and deliberate deception. Sometimes it is, but often we genuinely accept the moral principles we espouse, even when our behaviour doesn't quite match up to the rhetoric. The point is, though, that we sometimes display moral attitudes that convey a more flattering picture of ourselves than is strictly accurate, and these attitudes may embed themselves in the shared morality of a culture.

Finally, we sometimes try to infer moral truths from the facts of our experience. For example, when any kind of disaster occurs, people may look at the events that preceded it and infer a causal connection. They may interpret it as a punishment for some moral misdemeanour, such as following the wrong religion or worshipping the wrong god or sacrificing the wrong animal in the wrong way. By finding spurious associations between our behaviour and subsequent events in the world, our moral codes come to be shaped in part by accidents of history. This introduces a random element into the moral code of any culture.

Ideas such as these help explain why our moral beliefs sometimes clash with our evolved predilections, and why they sometimes make little or no evolutionary sense. They are a crucial component of a complete explanation for human morality. Morality starts from evolved dispositions, but takes on a life of its own outside the individual's skull. Our shared moral code emerges over many generations as the net result of negotiations and deliberations and compromises among different people with different agendas. As such, when people learn the morality of the surrounding culture, they end up with something different between their ears than their evolved, morally-relevant dispositions and inclinations.

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