Morality is centrally important to human affairs for two main reasons. First, cross-culturally, the well-being of individuals is strongly affected by their moral standing: an individual held in high moral regard may be praised, rewarded, or celebrated as a hero, whereas one held in low regard may be admonished, ostracized, or put to death.

Second, a society’s ability to compete with other societies may depend heavily on the content of its moral system; a moral system that successfully promotes values associated with economic and political competitiveness, for example, can be hugely advantageous to the society that hosts it. Our moral beliefs, then, have a critical impact on the fates of both the individuals we judge, and the societies to which we belong.

Given that morality is so important, you’d think we’d want to make sure that we were doing it right. That is, you’d think that we would insist on knowing why we have the beliefs that we have, how those beliefs came into being, who they benefit, and where they are likely to lead us.

Very often, however, our moral judgements are based primarily on our immediate emotional reactions to the behaviour of others, and our attempts to justify our judgements are just post hoc rationalizations of these emotions. We often feel passionately about our moral beliefs, but understand very little about why we have them. If asked to justify a belief, we might evoke a principle such as kindness, the greater good, or the will of God. But these principles are often ambiguously defined and difficult or impossible to pin down.

When the moral belief in question is relatively uncontroversial, the ambiguity of our justifications may not be a big problem; for example, most people in a contemporary Western culture would agree that physically attacking an unthreatening person is wrong, and perceive the justification as virtually self-evident (something along the lines of ‘unprovoked violence against other people is bad’).

But what if a moral belief is one a society does not overwhelmingly agree on? Myriad moral issues fall into this category, and threaten the cohesiveness of many contemporary societies; consider, for example, the bitter disagreements among Americans about issues like income inequality, gay marriage, gun control, drug legalization, abortion, and the separation of church and state.

We’d be better able to move on from these disputes in productive ways—and thus to make moral progress—if we could better understand our own moral beliefs. But how can we do this when our beliefs seem so opaque to introspection? It’s easy to feel passionate about our beliefs, but how can we see behind our emotions, to find out where our beliefs came from and whether they are leading us to where we want to go? Evolutionary science provides the key to such moral progress.

When I say that evolutionary science is the key to moral progress, there’s at least one thing I don’t mean and two things I do mean.

What I don’t mean is that the evolutionary process itself can provide guidance about right or wrong. If something increased or increases reproductive fitness, does that mean we should judge it as morally good? Of course not; I agree with philosophers who identify such thinking as a flawed “appeal to nature” or “naturalistic fallacy.” Consider behavioural outputs of what are probably evolved psychological adaptations: many of these (e.g. xenophobia) could usually be considered bad, whereas many others (e.g. parental investment) could usually be considered good. By the same token, many behaviours that are probably by-products of evolved adaptations (e.g. reading and mathematics) could be judged as good, whereas many others (e.g. crippling drug addiction) could be judged as bad. Suffice it to say: whether or not a behaviour is adaptive, or whether it is the product or by-product of an evolved adaptation, implies nothing about its moral value.

So if the evolutionary process provides zero guidance about right and wrong, how do we know what our moral beliefs should be? It’s up to us. We have to do our best to agree about what our goals as a society should be, and then advocate and enforce moral norms based on how useful we think they will be for accomplishing these goals. Which brings me to the first way in which evolutionary science is the key to moral progress: the better we understand human nature, the better we can design moral systems that encourage expression of our “good” evolved psychological adaptations while discouraging expression of our “bad” ones. A moral system will succeed not by attempting to ignore or override evolved human nature, but rather by strategically privileging some aspects of human nature over others.

If we want to reduce violence within our society, for example, we shouldn’t deny the fact that humans have psychological adaptations for violence. We should instead acknowledge this fact, while recognizing that we also have adaptations for peaceful dispute resolution. Then we should learn as much as we can about how both kinds of adaptations work, so that we can better design our culture to encourage deployment of the peaceful adaptations and discourage deployment of the violent ones.

The second reason evolutionary science can enable moral progress is because knowledge about the function of a moral belief is essential for evaluating the belief’s current utility. By testing predictions about how a moral belief relates to certain individual and environmental variables, we can learn a lot about what problems the belief was designed (by biological or cultural evolution) to solve in past environments, and about whether it continues to fulfil this function in current environments. For example, recent studies suggest that a man’s physical strength—that is, the degree to which he would have been capable of competing aggressively for status (and thus for resources) in ancestral environments—predicts his attitudes towards political violence and social inequality [5-8].

In other words, men seem to hold moral beliefs that would advantage them individually in a society in which status competitions were decided in large part by physical strength. These results suggest that the mental mechanisms producing their beliefs a) were designed for status acquisition, and b) may not fulfil this function particularly well in modern societies in which status competitions are decided more by technology, intelligence and education then by physical strength.

Moral disputes are a seriously divisive force in many contemporary societies, and a lot is riding on their outcome, in terms of both individual well-being and societal competiveness. By illuminating human nature, and the origin and function of biologically and culturally evolved moral beliefs, evolutionary science is currently generating knowledge that can help us move on from these disputes in the most rational and productive ways possible.

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