Ideally, an account of ethics should not only tell us what we are doing when we govern our lives by prescriptions and proscriptions, but also help us make progress with our ethical commitments.

The great traditional theories of ethics - those offered by philosophers and the more popular explanations embedded in religious traditions - aim to discharge both these tasks. Yet, as Plato was already aware, grounding ethics in the will of a deity is highly problematic: if there is no independent source of what is good or right, the deity's commandments can only be arbitrary.

Moreover, the philosophical substitutes, whether they locate goodness in maximal happiness, or view ethics as the expression of moral sentiments, or appeal to procedures of practical reason, face severe difficulties. Where they are clear (as with classical utilitarianism) they appear to commend actions that are abhorrent (sacrificing a few so that many may flourish); where they evade obvious counter-examples, they do so by employing formulations so abstract and obscure that it becomes impossible to apply them confidently to improve our ethical ideas and ideals.

Small wonder, then, that for all the efforts of philosophy, people who believe they know what ethics requires typically appeal to the teachings of some religious text.

Sometimes, a field advances by changing the initial question. Rather than asking "What should we do?" (and then canvassing "intuitions" to try to find out), we might begin to understand ethics by considering how human beings came to have our complex contemporary practices of appraising actions and people. It wasn't always thus - and we might find out what we are doing by thinking how we got from there (the pre-ethical state) to here.

To treat ethics as a part of human evolution isn't to offer a simple reduction of ethical properties to natural ones: I am not claiming that acting well consists in maximizing one's inclusive fitness (a position as clear as, but even more problematic than, classical utilitarianism). The strategy is to explore how ethical life began, how it grew and how it changed, in hopes that investigation will inspire better hypotheses about the nature and grounds of ethical judgment.

Let me begin with the outline of a story (to which I've devoted considerable time elsewhere). Our hominid ancestors lived in societies akin to those of contemporary chimpanzees and bonobos, relatively small (30-70 members) and mixed by age and sex. To participate in this form of social life already required a capacity for psychological altruism - that is, an ability to identify and respond to the needs and wishes of other group members.

Yet, as with our evolutionary cousins, our ancestors' altruistic dispositions were limited: although they would sometimes support one another, the prospects of large rewards, to be selfishly enjoyed, proved irresistible. Consequently, the social fabric was constantly torn, requiring time-consuming activities of mutual reassurance to mend it.

The fragility of hominid society would have precluded possibilities of living in larger groups or of more extensive social cooperation. Luckily, we escaped.

How? My hypothesis is that a decisive turn in human history comes with the acquisition of a capacity to guide conduct according to rules. The limitations of our altruistic dispositions were overcome by the invention of ethics, originally a social technology for the remedying of altruism failures.

Our ancestors - probably those living some 50,000 years ago, to give a conservative estimate - came to understand certain regularities in behaviour, and to formulate and follow rules proscribing conduct that would lead to trouble, prescribing actions that promoted social harmony (such as sharing food that has been gathered).

They discussed candidate rules with one another, and constructed primitive codes for regulating their social lives (just as contemporary hunter-gatherers work out more sophisticated codes). Thus began tens of thousands of years of social experiments, in which variant systems of norms competed for allegiance. The ethical systems recognizable in human history, from the invention of writing to the present absorbed the most successful parts of these experiments.

Along the way from the crudest ventures of the earliest pioneers to the sophisticated systems of rules visible in the oldest written documents, many important things happened:

recognizing the rules as grounded in the will of a deity was an effective way to secure greater compliance on the part of people outside the observational range of their fellows;

instituting division of labour was useful for increasing the supply of basic resources, and thus diminishing the temptation not to share; and

recognizing the neighbours as subject to some protections allowed advantageous exchanges.

Gradually, roles and institutions were born, groups expanded, people who cooperated often began to value the mutual adjustment of behaviour. Over a span of forty thousand years or more, an initial system of rules, probably originally concerned with promoting sharing and avoiding violence, grew into the far more complex framework discernible in the fragmentary additions to the Mesopotamian law codes.

During the subsequent millennia, there are recognizable shifts, some of them clamouring to be counted as ethical progress. When slavery is abolished, when women are allowed a wider role, when those attracted to members of their own sex are permitted to express their feelings, it is hard to resist the thought that an advance has occurred.

Progress may well be rare in the history of ethical thought, but it is tempting to suppose that the idea of progress is coherent. How can that be? Darwinian selection and cultural selection have no intrinsic progressive direction. Nor do the episodes that most readily admit detailed analysis and reconstruction reveal anything analogous to moments of scientific discovery.

To the extent that it is possible to probe the origins of opposition to slavery, we find no analogy of the episode in which a fluorescing screen alerts Roentgen to the presence of a hitherto unsuspected form of radiation. From the evolutionary perspective, the thought that particular people suddenly discerned some ethical fact unrecognized by their predecessors and contemporaries appears utterly implausible (see chapters 4-5 of my book, The Ethical Project ).

Hence the suspicion about the coherence of ethical progress: without a convincing notion of ethical truth, discoverable by human beings, the thought that some historical changes are ethical advances makes no sense.

But let me sketch out a different picture. Ethics began as a social technology. The first progressive steps lay in the solution of problems, through agreement on norms that would respond to the problem-situations. (For instance, because of the limitations of altruism, band-members don't share; their failure to respond to their fellows causes trouble; hence the agreed-on command, "Share with others!"). Later, those crude solutions were refined.

Moreover, like technology generally, new solutions generated further problems. The original function of ethics was to remedy our altruism failures. The ways in which our remote ancestors responded to that class of problems introduced differentiation of roles and enhanced cooperation, eventually leading people to value cooperation in itself.

Out of all that has come a far richer conception of human life, one in which our aspirations are no longer confined to the satisfaction of our most basic needs - beyond that we want to be participants in joint projects, to take on important roles, to recognize with others the values of our mutually adjusting conduct, to enjoy friendship and love.

The ethical project, begun tens of thousands of years ago, has defined what it is to be human, and has bequeathed to us complex desires to which our current ethical practices must now respond.

Ethical progress is a matter of problem-solving. It is not progress to something (a final complete ethical system), but progress from, and the evolution of ethics is always unfinished. Yet stable elements emerge in different traditions.

A rule enjoining honesty is a good response to a certain class of failures of altruism. It was progressive to adopt that rule, and there are good grounds for thinking that the rule (or something like it) will survive further progressive modifications of our ethical codes, however long the ethical project continues. The rule has exceptions, of course - sometimes it is altruistic to conceal the truth - but, as every parent knows, it offers excellent advice. Because it was adopted in a progressive transition, and would be preserved in an indefinite sequence of further progressive transitions, we can say that "Honesty is good" is true: as William James saw, truth is something that "happens to an idea."

I have here told the story of the ethical project baldly, without nuance. Any articulated version I could give would probably be flawed in at least some respects. Yet I want to claim that something of this generic sort is right. The ethical project is a venture in problem-solving that responds to deep features of the human condition - specifically, we are altruists enough to manage a particular sort of social life, but, without the technology of ethics, that sort of life would be fragile and difficult.

Further consequences follow. Ethics is our invention. Human beings do not discover ethical truths, except in the special sense that we work out together better ways of living together. The idea of the ethical expert, the seer or sage who discerns a new ethical maxim, is a myth, spun off from the useful device of invoking an all-seeing being (one who could check on you even when nobody else can do so), once particular members of a social group could convince others that they had special access to the being's will.

The world's religions contain the residues of the rules that were written into various codes as the expression of a particular person's point of view (the book of Leviticus, for instance, has a lot of this). Earlier ethical discussions were almost certainly egalitarian, like the conversations of those whose ways of life are closest to those of our remote ancestors, focused on finding solutions acceptable to all group members.

We live in a very different world from that of the ethical pioneers, or even that experienced through the first 80% of the history of the ethical project. As contemporary people pursue their own ethical lives, they think within the frameworks their cultural traditions have handed down to them. They will sometimes adjust the codes they initially accepted, finding that a new situation causes them to rethink the judgments they had made or the categories in which they had framed another person (you casually use a term that offends one of your hearers, and the conversation between you reveals the depth of the hurt).

When we consider the most striking examples of progressive change from the past few centuries (where there is a greater chance of understanding what occurred), it is evident that progress has been largely blind (the acceptance of same-sex preferences was importantly affected by the willingness of the men in the Stonewall bar to resist those who condemned them; that began a movement and a conversation, but did not immediately bring any change in perception).

Could we do better? That is the hope of the pragmatic naturalism I favour, a position that endorses Dewey's hope that, by understanding our past, we can proceed more "intelligently" in the present and in the future.

There is an obvious objection: the past has no hold on future conduct. The fact that we have done things in some particular fashion bears no implications for how we should now make our decisions. Inspired by Hume, the critic asks: what sorts of inferences lead you from facts about our history to conclusions about what should be?

But that is a bad question. Human beings are always shaped by some version or another of the ethical project. We start our lives with a collection of factual beliefs and normative judgments, absorbed from our social environment, and during the course of our brief existences we modify them in response to our encounters with others and the common world we share.

The right question asks: can an understanding of the origins and evolution of ethical practices help us to see how to make these modifications more clear-headedly? Apparently, it can.

If you understand how ethics began in relatively egalitarian conversations, if you recognize that there is nothing beyond our work with others that could "ground" some modification of our codes, if you see that those codes are social technologies, designed to overcome problems that stem from deep features of human existence, if you view the embedding of ethics within religion as an advantageous move from the perspective of securing compliance, but one that opens us up to the possibility that those supposedly favoured by some divinity may inscribe their own prejudices into a society's code - in light of all these things, you will see yourself and your ethical practice differently.

You will, perhaps, understand that the problem of our limited altruism is still with us, although it now occurs on a vastly larger scale. You may come to cherish the possibility of extensive conversations, in which a wide diversity of points of view are expressed, and in which people attempt to respond to the aspirations of others. You may think that future progress is likely to be more swift and more secure if more of such conversations take place, and if they are informed by better factual information. And you will almost surely be suspicious of claims that descend from parts of allegedly privileged texts that marginalize particular groups of people.

The inferences from genealogical understanding to suggestions for improving our ethical practice are subtle and complex - and in this regard, they are akin to those that figure in the episodes we think of as the major scientific revolutions.

One of the enduring lessons of work in the history of the sciences is that decisions to modify scientific frameworks are not made on the basis of "instant rationality." Thomas Kuhn began his book, The Structure of Scientific Revolutions, with an arresting sentence:

"History, if viewed as a repository for more than anecdote or chronology, could produce a decisive transformation in the image of science by which we are now possessed."

Kuhn's insight applies equally if we replace "science" with "ethics." An ethical theory informed by genealogy might be transformative - even revolutionary.

Philip Kitcher is John Dewey Professor of Philosophy at Columbia University. His latest book is The Ethical Project (Harvard University Press, 2011).