Moral Origins

The Evolution of Virtue, Altruism, and Shame


By Christopher Boehm

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From the age of Darwin to the present day, biologists have been grappling with the origins of our moral sense. Why, if the human instinct to survive and reproduce is “selfish,” do people engage in self-sacrifice, and even develop ideas like virtue and shame to justify that altruism? Many theories have been put forth, some emphasizing the role of nepotism, others emphasizing the advantages of reciprocation or group selection effects. But evolutionary anthropologist Christopher Boehm finds existing explanations lacking, and in Moral Origins, he offers an elegant new theory. Tracing the development of altruism and group social control over 6 million years, Boehm argues that our moral sense is a sophisticated defense mechanism that enables individuals to survive and thrive in groups. One of the biggest risks of group living is the possibility of being punished for our misdeeds by those around us. Bullies, thieves, free-riders, and especially psychopaths — those who make it difficult for others to go about their lives — are the most likely to suffer this fate. Getting by requires getting along, and this social type of selection, Boehm shows, singles out altruists for survival. This selection pressure has been unique in shaping human nature, and it bred the first stirrings of conscience in the human species. Ultimately, it led to the fully developed sense of virtue and shame that we know today.A groundbreaking exploration of the evolution of human generosity and cooperation, Moral Origins offers profound insight into humanity’s moral past — and how it might shape our moral future.



Hierarchy in the Forest
Blood Revenge
Montenegrin Social Organization and Values




Queen Victoria’s England provided a most comfortable environment for Christians who loved to take their Bibles literally. Nature was perfect because in just seven days God had made nature perfect. Oceans and fish, predators and prey, all fit together like hands in gloves. And this perfectly tuned natural world was forever fixed and static because Jehovah’s unlimited powers had made it that way.1

Not only that, but the Old Testament’s Adam and Eve were real, if uniquely special people whose divine Maker had created them quite recently. A methodical churchman had actually done the biblical math and concluded that just under six thousand years had elapsed since God had made Eve from Adam’s rib, installed this first pair of humans in His idyllic Garden of Eden, and then left them to their fate. In terms of evolutionary time, this meant that the origin of fallible human choice and our sinful sense of shame—together, these gave us a conscience—had taken place only yesterday or perhaps the day before. However, in the twenty-second year of the devout queen’s reign all of this was about to change—and for many there would be no turning back.

In 1859, Charles Darwin’s On the Origin of Species shook cultured reading publics in Great Britain and elsewhere like an irreverent clap of thunder.2 The initial Darwinian lightning bolt did not strike directly against the sacred moral origins story of Eve, Adam, and the persuasive serpent who seemed to undermine the good works of an otherwise omnipotent Jehovah. Rather, this new scientific thesis introduced to the physical world of animals and plants a theory of gradual but ever-changing transformations that were wholly naturalistic. As a result, the beautiful fit of species to their environments was no longer the work of God; indeed, the banal process of natural selection operated very much as livestock breeders did when with short-term practical objectives they changed the hereditary destinies of the animals they domesticated.

These breeders did their work in a deliberate fashion. They permitted more favorably endowed individuals to flourish, while denying less useful or less aesthetically pleasing individuals the opportunity to reproduce. Robert Darwin, a doctor and a country gentleman, was one of these animal breeders. His thoughtful son—who as a young man seemed to be headed for the ministry—knew that individuals of a domesticated species varied along many dimensions. Cattle varied in their productivity in giving milk; dogs, in their natural tendencies to point and fetch, their degree of docility, and the color of their coats.3 It was only after years of sailing around the world as a professional naturalist that the young Charles Darwin became aware that nondomesticated species were just as variable as their domesticated brethren.4

Darwin’s official job had been to collect museum samples and to describe in minute detail the species of plants and animals on different continents, and all this hard work led, as we know, to a major theory. In his mind, such hereditary variation was something that a natural type of selection could act upon spontaneously: the individuals who were more fit to deal with their environments could reproduce, multiply, and flourish, while those who weren’t, couldn’t. This singular insight was to change the Western world’s notions about nature and even its larger view of the universe.

This brings us to a profound difference between natural selection and the selection practiced by animal breeders. For Darwin, changeable natural environments were doing the mechanical work of triage,5 and unlike either a practical livestock breeder or a purposeful God Almighty, these environments had no intentions whatsoever. They were acting as blind arbiters,6 rather than as deliberate agents who knew what they were doing, and this meant that the perfection of nature was just one big accident. The specter loomed of a scary world, devoid of any ultimate Purpose, that suddenly lacked a protective, omniscient, and omnipotent God whose comforting role it was to help those who faithfully prayed for His assistance.

After the passage of a century and a half, it’s remarkable for any major theory not to be superseded, or at least vastly modified. However, in its basics this blind, mechanical theory of natural selection is still going strong in the world of science.7 If we add “genes” to what Darwin thought of rather intuitively as hereditary variation, the idea of natural environments favoring some variants and selecting against others works just as well in the early twenty-first century as it did in the mid-nineteenth. When we consider the complexities of life processes, the simplicity and explanatory power of the theory are awesome.


As the title tells us, On the Origin of Species was about how species come into being naturally—that is, without any supernatural help. To illustrate Darwin’s thinking, let’s consider a hypothetical. If a primitive bear species had been distributed originally over a restricted, uniform part of North America and then portions of this population began to migrate into adjacent areas, as their gene pools became separated, these bear subpopulations might gradually begin to differ because they were coping with different climates or new food sources—until eventually some of them could no longer interbreed. The result might be something like what we have today: black bears, brown bears (including grizzlies), and polar bears.

Darwin’s real-life examples of speciation were taken from all manner of animals and plants, large and small, and in the absence of DNA analysis his scientific stories about the selection pressures that shaped these organisms rang of impeccable logic and sound scholarship. In modern terms, what Darwin’s theory told the world was that potentially changeable natural environments were acting continuously on variation in the gene pools of resident populations. And for this process to do its work, two conditions were needed mechanically: hereditary variation and finite life spans among individuals. The latter was necessary if gene pools were to be modified over generations, for the less fit had to fade away and be replaced if local populations were to evolve to resemble their fittest members.

A special insight about the breeding potential of animals guided Darwin’s theorizing. He founded his entire theory of natural selection on one simple but staggering mathematical realization of late-eighteenth-century English political economist and demographer the Reverend Thomas Robert Malthus:8 if all living organisms were to procreate to their full capacity (think of dogs and cats with their annual litters), in theory within not too many generations the planet would be so exponentially overpopulated that there would be little to eat and, eventually, literally nowhere to stand. Darwin’s beautifully simplified answer to a planet knee-deep in living things was sloganized by evolutionary sociologist Herbert Spencer as the “survival of the fittest,”9 even though Darwin’s theory was more subtle than that.

If the systems of biological evolution that Darwin described so mechanically were devoid of guidance from on high, then somehow they had to “regulate” themselves. As an illustration, if a population became denser, food would become scarcer and indirect competition based on who was more efficient at foraging or predation would intensify. At some point this would limit the population’s growth, and its size would stabilize and remain in equilibrium. It was thus that Darwin’s theory solved Malthus’s problem of potentially unlimited and exponential population growth.

Darwin’s new ideas challenged not only God’s directly manipulative role as portrayed in the Book of Genesis, but also the timeline of Creation. Darwin thought of biological evolutionary processes as being very gradual, and in doing so, he was able to take cues from a different field of study, namely, geology. Increasingly, naturalists like Scottish lawyer and geologist Charles Lyell had been hypothesizing that geological formations changed very gradually over time,10 owing to the action of water or wind. Religious skeptics were coming to understand that these processes had required not a few thousand but millions of years to take place. As geological cues helped Darwin to realize that the various physical landscapes he scrutinized in his travels were far from static, this provided yet another essential ingredient for his dynamic but gradualistic theory of environmentally driven natural selection and species origination.

Thus, the biblical story of instant and permanent Creation was being undermined on a number of fronts, all unified by Darwin into an extremely logical—and exquisitely documented—theory of natural selection. His new theory so rudely challenged the static beliefs of religious fundamentalists that many of them were aroused to personally denounce “evolutionism,” like today’s antiscientific religious believers who try to pick apart the scenarios that evolutionists create and publish. They often assume that a few heretofore-unexplained exceptions can “disprove” an entire, widely accepted theory. But even though to a scientist like myself this logic smacks of desperation, these people have faith on their side, and there are many who are prepared to listen.


Initially, an apprehensive Darwin chose not to write about the greatest controversy of all: the application of his new theory to human beings. But when The Descent of Man was finally published in 1871, the scenario Darwin put together was nothing short of remarkable. Not only did he at least outline what he could of the human origin story in the context of an evolutionary sequence starting with apes, but also in certain areas he even managed to provide important environmental details and specify some likely selection mechanisms. For human physical evolution, particularly of our outsized brains and upright locomotion, Darwin’s hypotheses were daring and, given the dearth of information in his day, keenly prescient. The basic outlines he set down on paper are still valid today.

Another of Darwin’s equally daring hypotheses had to do with the origination of moral behavior and the human conscience—the subject of this book. His treatment of a self-conscious conscience was particularly provocative because now he was bringing his naturalistic approach close to the soul, previously the exclusive purview of the church or, more precisely, of God. Darwin did not take on the problem of how human beings came to have a soul; indeed, the word does not even appear in the lengthy and detailed index for The Descent of Man. But he clearly thought our conscience and moral sense were as “naturally selected” as our large brains, our upright posture, and our general capacity for culture.

As a brilliant and meticulous scientist, Darwin didn’t have the data to make anything like a plausibly scientific case with respect to conscience origins, but he did the best he could, and under the circumstances his best was quite good. In an 1871 passage concerned with instincts of “sympathy,” which is often quoted by contemporary scientists such as evolutionary biologist Jessica Flack and primatologist Frans de Waal and by others who take an interest in moral origins,11 Darwin wrote, “Any animal whatever, endowed with well-marked social instincts, the parental and filial affections being here included, would inevitably acquire a moral sense or conscience as soon as its intellectual powers had become as well developed, or nearly as well developed, as in man.”12

An introspective Charles Darwin waxed eloquent on how the conscience worked, and his own superego was obviously strong and active. Socially, it was this charitable “inner voice” that kept us from getting in trouble with our fellows, Darwin told us, and he wanted badly to explain its evolutionary origin. But all he could tell his readers was that gaining a conscience and hence a sense of morality was, in effect, an inevitable outcome if a species became sufficiently smart and socially sympathetic to reach the human level.

Unfortunately, this gave our uniquely human conscience the evolutionary appearance of being a mere byproduct, a side effect of intelligence and sympathy. This is a position I think we can vastly improve upon with present knowledge, and in the chapters to follow I will bring in some quite specific hypotheses to explain how the conscience evolved and why it did.


Darwin tried to answer yet another profound question: Why do human degrees of generosity seem to defy the patently “selfish” principles of natural selection theory? This original puzzle was influentially redefined in modern terms in the 1970s by scholars such as social psychologist Donald T. Campbell and biologists Richard D. Alexander and Edward O. Wilson.13 And for more than three decades now, a major and growing interdisciplinary academic industry has devoted its efforts to resolving the “altruism paradox”—with only partial success. I hope that this book will get us closer to a scientifically satisfying answer.

The historical background for this fascination with altruism is quite interesting. Darwin’s “selfish” theory of natural selection held that individuals were indirectly competing for fitness and that, as we’ve seen, those who were more vigorous or otherwise better adapted for securing food or mates would come out ahead in shaping the hereditary future of their species. This could be explained simply: favored individuals had more surviving and breeding offspring than others in their group or region or wider population. But Darwin also realized that this kind of advantage could be helped along by family connections because close relatives who naturally helped each other tended to share the same heredity. He didn’t carry this second idea very far, but it turned out to be extremely important.

This became clear a century later when the well-known population geneticist William Hamilton showed through mathematical modeling that selfishly competing individuals could make reasonable personal sacrifices if these benefited their own offspring.14 Because, on average, an individual shares 50 percent of his or her heredity with progeny, investing in offspring helps propagate the genes that individual carries. The same 50 percent rule holds for helping siblings or parents. Being generous to a grandchild or a first cousin (a relationship that involves only a 25 percent genetic similarity) still makes sense if the costs of helping aren’t too high and the benefits are significant. This powerful theory, known as kin selection, can apply to even lesser degrees of kinship as well, as long as the donor’s costs are sufficiently modest and the benefits sufficiently large.

Darwin identified a further problem that continues to perplex scholars today.15 In real life, humans don’t merely assist their close or distant blood kin; they also help people who are unrelated to them—even though from a biological standpoint giving such altruistic assistance will be costly to their fitness because there is no shared heredity. This means that unless these unrelated beneficiaries somehow are reciprocating in something like equal measure, or unless some other type of “compensation” exists, the individuals who take such action may be lowering their own fitness and raising the fitness of their partner. At its simplest, the evolutionary lesson is all too obvious: in theory, generosity should stay within the family because nepotists who refrain from altruism will be able to outcompete the altruists.

Another modern biologist, George Williams, provided another big reason that mutant genes that made for generosity outside the family wouldn’t stick around for very long.16 Free-riding genes—genes that send their bearers the opportunistic behavioral message “take from altruists but avoid giving”—should increase in frequency as they replace the genes of the altruistic “losers.” Still scratching their heads in many ways about this matter of our remarkable human generosity are scores or, more properly, thousands of evolutionary biologists, ethologists, anthropologists, sociologists, and philosophers, not to mention a wide array of evolutionary psychologists and a significant cohort of evolutionary economists. All continue to work on problems germane to the basic evolutionary puzzle of altruism and the closely associated problem of “free riders,” which together have been a major interest of the aforementioned academic industry for almost four decades. At this writing, at best the evolution of human generosity is only partly explained.17


Unfortunately, in the field of evolutionary biology “altruism” has become a technical term that, after almost half a century of intense debate, still remains to be used with total consistency.18 Sometimes, for instance, it means being genetically generous to anybody at all, including kin; sometimes it means being generous to people lacking any blood ties to the generous party. Because of the focus of this book, I will be relying on the latter meaning, using “altruism” and “extrafamilial generosity” as exact synonyms, while when costly help is given to relatives I will call this “nepotism.” The altruistic type of beneficence may refer either to acts of costly generosity toward specific unrelated individuals or to sacrifices of personal interests as the individual contributes to enterprises that benefit the community as a whole. Thus, altruism and the possibilities for human cooperation are intertwined, for altruistically generous individuals make for superior cooperation in groups that include nonkin.

In biological terms, then, when we speak of altruism, we’re speaking of behavioral tendencies that dispose people to give more than they receive in terms of acts that reduce relative fitness.19 Even if all of the underlying genetic selection explanations are not yet fully developed, the tangible behaviors are obvious enough. People predictably open their veins to anonymously give blood or open their wallets to help starving children in developing countries, and generous assistance following a natural disaster anywhere on the planet can be quite impressive. Therein lies the altruism puzzle: Why do so many members of a supposedly egoistic and nepotistic species in some contexts become quite giving to people they aren’t related to and sometimes don’t even know?


Even though common sense alone can tell us that our dispositions to extrafamilial generosity are significant, it’s equally obvious that this is rather negligible compared to our truly powerful dispositions to egoism and to nepotism. It also is apparent that these genetic dispositions don’t determine our actions. Rather, they set up the behaviors in question so that they will be exceptionally easy to learn.20 Thus, we must consider the interaction of genes and culture, and the influence of the social environment on how we behave should not be underestimated.21 For instance, actively preaching a “Do unto Others” ideology can powerfully reinforce the relatively modest innate tendencies that favor extrafamilial generosity and thereby enable groups to work better together.22 I will discuss my research findings in this area in Chapter 7, as well as in Chapter 12 toward the end of the book.

When individuals in a nomadic, egalitarian hunting band seek to promote generosity, they recognize that self and family will always come first and that therefore people will need some special “persuasion” to contribute robustly to the group as a whole. In short, band members understand that if they are to better reap the benefits of group cooperation, they’ll need to apply their local version of the Golden Rule manipulatively, as a refined type of social pressure designed to bring out the best in human nature.23

Keep in mind three things about classical hunter-gatherer bands. First, they always involve a mix of related and unrelated families.24 Second, they predictably cooperate in certain activities with no expectation of immediate or exact reciprocation.25 And third, they actively preach in favor of wider generosity within the group, precisely because human propensities to be selfish or nepotistic are so strong in our species.

In my research,26 I have found such strictures in favor of extrafamilial generosity to be both prominent and probably universal in these mobile band-level cultures—whose lifestyles are similar to those of the prehistoric foragers who basically had evolved our modern set of genes for us by 45,000 years ago. It would appear, then, that these strictures are fairly ancient. The people involved obviously know what they’re doing when they apply such pressure, and as an anthropologist I fully agree with the everyday intuitions of these socially manipulative hunter-gatherers. I, too, believe that our relatively modest propensities to engage in extrafamilial helping behavior can provide an important basis for human cooperation—and do so all the better if such propensities are being strengthened by prosocial socialization of children, by the application of positive social pressure on adults to behave with generosity, and by the discouragement (or elimination) of selfish bullies and cheaters, who hamper cooperation and also create conflict.

Of course, I have the anthropological advantage of knowing that in later, larger types of societies such as chiefdoms or early states, the same prosocial propensities can contribute to still greater community cooperation—and that today, as with both a ruthless Nazi Germany and Great Britain as Hitler’s wartime adversary, cohesive cooperativeness can at least approach the truly selfless, “eusocial” collaboration that takes place in anthills. In the case of these insects, however, the cooperating individuals tend to be close genetic relatives, so their apparently “selfless” contributions to group interests can be explained nepotistically by kin selection, combined with group selection.27 It is with the genetically “reckless” generosity of humans where generosity extends beyond nepotism to nonkin that the major evolutionary puzzle arises: How can such natural dispositions stay in place, especially if opportunistic free riders are poised to outcompete those who are extrafamilially generous?


Darwin saw this problem very clearly, even though he couldn’t begin to fully anticipate the sophisticated modern population-genetics models that began to emerge in the 1930s, which resulted in systematic theories such as those of Hamilton and Williams, and eventually led to Edward O. Wilson’s global redefinition of human social biology in terms of the altruism paradox we’ve been discussing. A century earlier Darwin simply wondered how he could ever reconcile his new theory, which was so “individualistic,” with the fact that patriotic young men so willingly went to war to sacrifice their lives for their countrymen. They were sacrificing not only their lives but also the lives of their future progeny, who otherwise would be inheriting these generous tendencies. The great naturalist was confounded.

Darwin had in mind the fact that free-riding cowards would be avoiding these same risks and that their greater numbers of surviving offspring would be inheriting the same selfish tendencies. In short, following his theories, generously self-sacrificial patriotism should always be on the wane, while dispositions to hold back and stay safe should always be proliferating. This meant that over the long run any tendencies to sacrifice personal interests for the good of the group should be automatically suppressed by natural selection—yet in practice young men were going to war, and many were doing so eagerly.

Darwin did offer a possible solution to this puzzle. Here are his famous, often-quoted, somewhat convoluted words, taken from The Descent of Man:

It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an advancement in the standard of morality and an increase in the number of well-endowed men will certainly give an immense advantage to one tribe over another. There can be no doubt that a tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to give aid to each other and to sacrifice themselves for the common good, would be victorious over other tribes; and this would be natural selection.28

This brilliant piece of reasoning still haunts the large community of scholars who study human social evolution. Group selection theory was for a long time spurned by the great majority of biologists, although today it has found its place in multilevel selection approaches.29 E. O. Wilson led the earlier charge against naïve group selection theories, but today one explanation for either nepotism or altruism is that groups having more or better cooperators will outreproduce lesser groups. This level of explanation will not be prominent in the pages that follow, because the emphasis will be placed on collective punishment and free-rider suppression as these affect selection taking place between individuals within groups.


I’m confident in saying that Darwin strongly desired an explanation of conscience and morality in a full natural-history context, which would make explicit how such remarkable human capacities could have developed over time. This would have required him to specify the type of favorable environmental conditions that would have prevailed and which mechanisms of selection could have contributed to this historical evolutionary process of moral origins. But Darwin was not able to accomplish this, not because of any lack of insight or ambition, but because in his time he lacked the necessary data from primatology, paleoanthropology, cultural anthropology, and psychology, along with explanations of brain functions from cognitive neuroscience. All of these fields have either emerged since Darwin’s time or else have grown by leaps and bounds so that today we may finally have the scientific information needed to put together a plausible evolutionary scenario.


  • "Christopher Boehm's Moral Origins is a tour de force of a sort rarely seen in any science."—Donald Black, university professor of the social sciences, University of Virginia, and author of Moral Time
  • "[An] engrossing work.... Boehm does a remarkable job of extending previous work and incorporating a historical approach."—Publishers Weekly, starred review
  • "What sets Boehm's approach apart is his effort 'to make the natural history of moral origins more historical'. In so doing he provides a new and coherent map of the evolution of morality.... It is a complex story..., but Boehm's experience doing fieldwork with humans and wild chimps makes him a wonderfully knowledgeable guide. And some of his ideas are truly revolutionary."—New Scientist
  • "How did evolution produce a species that blushes? To explain the uniquely human moral sense, Boehm teases a provocative neo-Darwinian theory out of cutting-edge archaeological, anthropological, and psychological research.... Those looking for a daring new application of empirical science will find it here."—Booklist
  • "[A] provocative scientific the millennia-long discussion about the nature of morality.... Thinkers everywhere will be forced--as they are in many arenas--to consider biology in realms that once seemed strictly matters of the heart and soul."—Michael Shermer, Wall Street Journal
  • "One rarely finds such a fully Darwinian, scientifically sound, and wisely accessible book for both professionals and lay audiences as Boehm's study of moral origins; it is far superior to any previous attempts to discuss the subject."—Choice
  • "Astronomers have the Hubble telescope to look back through time, and social scientists have Chris Boehm. Boehm's monumental accomplishment is to give us the most careful and compelling portrait ever created of how our ancestors lived, from three hundred thousand generations ago to five hundred generations ago. Boehm's work is vital for understanding why we are so tribal, punitive, gossipy, religious, and cooperative today."—Jonathan Haidt, professor of psychology, University of Virginia, and author of The Righteous Mind
  • "Few scientists have thought longer and harder about the origins of morality than Christopher Boehm, who brings to the issue a wealth of experience studying both humans and other animals. His thesis that our species has taken moral evolution into its own hands is new and refreshing."—Frans de Waal, author of The Age of Empathy
  • "Moral Origins is an exciting study on the evolution of human morality that is appropriate for scientific researchers and also of interest for the general public as well. Christopher Boehm brilliantly ties fundamental aspects of human cooperation such as altruism, free-riding, and bullying to both primitive and advanced societies. This book is a must for all who are interested in how human morality evolved and functions."—Ernst Fehr, professor of economics, University of Zurich
  • "In Moral Origins, Christopher Boehm uses his vast knowledge of the literature on primates and human hunter-gather populations to address the issue of the origins of human morality. It is a must-read for any social scientist, primatologist, or humanist studying human morality. Equally important, it is beautifully written in an easy and graceful style. Certainly the most informed and best work written by an anthropologist on this set of issues, Moral Origins is a book that I would recommend to any thoughtful person."—Jonathan Turner, distinguished professor of sociology, University of California, Riverside

On Sale
May 1, 2012
Page Count
432 pages
Basic Books

Christopher Boehm

About the Author

Christopher Boehm is Director of the Jane Goodall Research Center and Professor of Anthropology and Biological Sciences at the University of Southern California in Los Angeles. Boehm’ work has been featured in such publications as New Scientist, the New York Times, the Times (London), Natural History, Science News, and in films for National Geographic, Wild Kingdom, and the Discovery Channel.

He has lectured widely to groups as diverse as the Human Behavior and Evolution Society, the Chicago Academy of Sciences, the Sante Fe Institute, the Los Angeles and Cincinnati Zoos, and the Naval War College. Boehm is the author of many scientific articles and several previous books, including Hierarchy in the Forest (Harvard). He divides his time between Los Angeles and Santa Fe.

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