Prehistoric Capital Punishment and Parallel Evolutionary Effects

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Here I explore the possibility that morality could have impacted natural selection, as well as vice versa. There is little doubt that mechanisms of natural selection can be invoked to explain the individual human conscience and the fact that, collectively, we mete out punishment to our moral deviants. Far less obvious is the fact that being moral may have enabled prehistoric people to participate, actively but indirectly and unknowingly, in the very process of natural selection.

Righteous morality has a dark and, for many of us, an emotionally upsetting and ethically unfair underbelly—namely, capital punishment. In the state of Texas alone, the plentiful miscarriages of justice are more than tragic—they are truly outrageous. However, this is a debate we moderns can afford to engage with, because we have a viable alternative. Today’s citizens can protect themselves by locking up society’s truly dangerous deviants for life, but in our human past this was hardly the case.

Before five or six thousand years ago it is very doubtful that even the notion of incarceration existed, for that was when taxation-based states and civilizations came along to provide the necessary infrastructure. Before that, if a socially endangered group could neither cope with nor escape from a dangerous or oppressive group member, physical elimination was the only way to handle the situation.[1]

Prehistorically, killing group members was morally condemned, for the belief that “thou shalt not kill” long preceded the writing of the Bible. However, this ancient and universal condemnation was subject to important exceptions. Mercy killing was tolerated, as was infanticide as a form of birth control, while capital punishment was legitimate as a group strategy to cope with extreme, intolerable, and otherwise inescapable acts by social deviants. Such killings were the result of community intentions, and to work they had to be strongly approved—or at least be morally countenanced—by the entire group.

Hunter-gatherers are apt at intuitive political analysis and at social problem solving, and today these moralistic foragers use capital punishment mainly to eliminate bullies.[2] Although this puts the main focus on serial killers and dangerously malicious shamans, they also may kill people who endanger the group cosmologically by breaking major taboos, or individuals who are extremely disruptive socially and seriously endanger cooperation and social harmony.

As Ara Norenzayan writes, non-literate hunter-gatherers have had no institutionalized religion to help them organize and enforce their moral rules.[3] However, my research has shown that supernatural beliefs have had some important connections with morality. For instance, incest has been universally punished by either realistic social sanctions that may include ostracism and execution or by supernatural forces that (in belief) inflict birth anomalies or other costs, and sometimes by a combination of the two.[4] However, if antisocial dominators wouldn’t reform, the only sanctioning that worked against the worst socially insensitive or arrogant bullies was actually to kill them.

Some of the worst bullies would have been psychopaths. In the brains of these “natural deviants” the connections with moral emotions (paralimbic system–based) are tenuous, resulting in a lack of conscience and its markers: the strongly-felt internalization of rules, shameful blushing, and feelings of remorse over past transgressions. As a result, such people show little identification with moral rules; rather, they merely have a manipulative cognitive understanding of them.[5]

A conservative estimate of male psychopaths in our modern population would be 1 percent. This would suggest that prehistorically, at any given time, perhaps one out of every twenty foraging groups of about twenty-five men, women, and children was likely to face a problem with an adult male psychopath’s expressing his inborn domineering tendencies. Such dispositions are very predictably associated with these deviants,[6] and their expression creates enormous hostility in egalitarian communities. In addition, highly-aggressive, antisocial non-psychopaths could have added significantly to this percentage, and whenever one of these domineering upstarts could not be reformed, he (they are mostly “he’s”) had to be killed.

Because of psychopaths alone, we humans surely have been resorting to capital punishment for at least 45,000 to 80,000 years or more, depending on when you believe we became behaviorally modern and, hence, morally modern. This means that in our small and usually nomadic prehistoric hunting groups, for at least the past several thousand generations we have been acting as judgmental, self-protective moral communities—groups that can form a consensus and moralistically agree to take extreme measures whenever a social problem becomes bad enough.

Before exploring the possible effects of capital punishment upon gene selection, I must tell you how such punishment works, on the ground, in these small, egalitarian human groups. When a social deviant is deemed seriously dangerous to other group members, they must decide how to eliminate him without causing the group to fission through conflict. Actually, there are two predictable problems. One is such internecine conflict, which damages group cooperation; the other is blood revenge, whereby an angry relative of the person killed takes vengeance on the executioner, even though he acted on behalf of the group. This can destroy the group.

My studies with a dedicated hunter-gatherer database I am developing suggest that a group consensus is necessary, even though close relatives of the victim may make for reluctant participants. They also suggest that to obviate revenge killing by grieving relatives, either the entire community must participate in the execution, or else (and more usually) the group will delegate a close kinsman of the target to do the killing.

We can project these specific patterns backwards in time by using systematic “ethnographic analogy.” This is still a developing aspect of prehistoric research, but my conservative version of it holds that if a behavior is found in all six of the regions where hunter-gatherers have been studied by anthropologists over the past several centuries, essentially the behavior can be projected back to include all behaviorally modern humans.[7]

Today, hunter-gatherers practice capital punishment in all six of the world regions they inhabit—North and South America, Africa, Asia, Australia, and the Arctic—so, minimally, this practice qualifies as being very widespread, both now and in the past. Of course, the sampling afforded by an extensive but imperfect ethnographic record is necessarily spotty for such a relatively rare behavior, so we cannot speak empirically of capital punishment’s having been universal. However, the fact that foraging groups killed serious political deviants in all parts of the world is highly significant, and we may be confident that worldwide, humans have been picking out certain types of deviants and regularly eliminating them over thousands of generations.

Deliberate capital punishment has had obvious, immediate effects on social life; nobody would dispute that, for it enabled egalitarians to maximize cooperation and avoid dangerously disruptive interpersonal domination leading to conflict within the group. However, at this point I would like to raise a profound question about evolutionary process itself. Is it possible that some modest degree of purposiveness has worked its way into what is supposedly a “blind” biological process?

What is of great interest, in terms of possible evolutionary teleology, is that, even as such punishment was reducing bullying behavior in the here and now, at an ultimate level it could have been acting on the human genome to create what might be called “parallel effects” that went in exactly the same direction. This is a clearly matter of causation, in that fewer bullies procreating today would mean weaker bullying tendencies tomorrow.

How do we know these parallel effects could have been in force for long enough to modify our genome, and therefore our very social nature? One would expect no direct evidence for capital punishment prehistorically, but as the Pleistocene ended in France and Spain, African Homo sapiens immigrants had already been painting on the walls of European caves for twenty millennia. Mostly they painted the animals they liked to hunt, but as the Mesolithic transition took place, increasingly they were depicting themselves as well.

Near the Altamira district of Spain we have several unique paintings with groups obviously killing individuals. The best one shows, to the right, ten men evocatively holding their bows over their heads; the impression is one of assertive jubilation. A moderate distance behind and to the left lies a man on the ground with exactly ten arrows sticking out of his body or on the ground. A few other paintings are similar, but with fewer executioners and fewer matching arrows.[8]

Execution Group, Remigia, Castellón, Spain Execution Group, Remigia, Castellón, Spain

The victim could have been a stranger, perhaps a prisoner of war. But given what we know about today’s foragers, it is most likely that this was a member of the same group—a deviant who grossly went against the moral code and may well have broken the egalitarian rule against throwing one’s weight around. Such actively collective executions by entire groups are rather rare in contemporary ethnography, but earlier the feuding tribal Serbs I studied in the 1960s had stoned a pair of deviants to death, a practice that kept kinsmen of the slain individual from targeting any single executioner for revenge. In an adjacent culture area group stonings are mentioned in the Bible, and they also are reported recently in the Moslem Middle East and in Africa.

When the entire group participates actively and simultaneously, no one will know who cast the first stone, and this precludes blood revenge by angrily grieving relatives. However, the predominant hunter-gatherer pattern is for the group to delegate a close kinsman of the deviant to kill him because that, too, obviates a revenge killing.

If we wish to look back beyond those remarkable paintings from the Spanish Levant, we have the aforementioned ethnographic analogy method to work with. And if we follow a maximally conservative methodology and insist that only behaviors reported at least once in all six forager-regions qualify for projection into the past, it is possible to reconstruct the prehistoric moral code that guides such punishment and to do so with some confidence.

As today, these prehistoric hunter-gatherers morally decried a range of behaviors, including not only serial murder or sorcery that led to undue domination, but theft and cheating, failure to cooperate, and breaking of taboos, including incest. All of these strong prohibitions qualify as being widespread in the past, and any or all of them may have been cultural universals.

As for methods, coping with these deviants comes mainly in the form of gossiping, exerting mild social pressure, active group shaming, ostracism, and, finally, execution. If we look for worldwide distributions, perhaps surprisingly the widest geographic distribution is for capital punishment, which is reported in all six regions. Although I believe that all of these sanctions may be universal, group killings are so widely reported that I am tempted to say that, when really extreme social problems arise, more often than not a small group’s only way out is to kill the deviant.

To arrive at these patterns I have created a hunter-gatherer database of sixty-five foraging societies,[9] chosen because they are suitable for analogizing to the Late Pleistocene. Some of the reports are detailed enough to reveal political dynamics, which tell us that these executions were intentional, well calculated, and highly patterned. One major, short-term effect was that an egalitarian lifestyle could be maintained, with none of the hunters being in a position to dominate his fellows. The long-term effects were that genetic tendencies that favored bullying behavior were being reduced, which would have resulted in some significant reduction of bullying dispositions, in general, and also a lowering of rates for psychopathy. However, it is obvious that these monsters didn’t go out of business entirely.

Capital punishment definitely existed in the Late Pleistocene, but what about ancestral precursors? Both chimpanzees and bonobos are prone to occasional lethal gang attacks within their groups against aggressive high-ranking males, and while their motives appear to be mixed and sometimes unclear, the overall similarity to human capital punishment is apparent in the collective and patterned nature of these assaults.

In A Natural History of Human Morality, Michael Tomasello argues that our morality is based on the kind of collective intentionality that philosopher John Searle talks about, and that chimpanzees must be denied such a capability.[10] This would mean that somehow humans developed this capacity without ancestral pre-adaptations, which amounts to an unexplained evolutionary saltation.

Tomasello’s experience is with captives, and perhaps more important it is with experimental captives behaving as dyads. In the more natural-sized captive groups studied by de Waal,[11] coalitions of females will go up against even their alpha male in a coordinated way, and de Waal makes their shared hostile intentions and their awareness of one another’s support quite apparent. They are making sure that the males who need to redirect aggression because they are in a bad political mood won’t use females as scapegoats and beat on them, and they know exactly how to put on a united front.

Wild chimpanzees show similar evidence of collective intentions at work. In working for eighteen months in the field at Gombe, I was able to analyze via videotape both the community mobbing a large python and chimpanzees on patrol. With the python the group appeared to act in a coordinated way, but with very little leadership. On patrol, the alpha male had a leadership role, but it was shared with other high-ranking males, and sometimes their positions became interchangeable. The patrol’s mission was to proceed quietly, surprise a stranger, and make a vicious assault, and they acted as though they shared both knowledge and intention. Their direction of gaze also suggested that before they responded vocally to the enemy patrol that spotted them, they were observing one another for cues. All of this argues for collective intentions at work.

I stopped my African field work in 1990, but two years later I could have observed the very first chimpanzee equivalent of deliberate ostracism. Gombe’s alpha male Goblin had recently been deposed, and when he went to rejoin the group, a gang of males mounted an attack almost as ferocious as those against strangers. They allowed Goblin to escape, and he wisely stayed away for several months. Finally he was able to return, but only in a very submissive role.

Since 1992, almost a dozen further published reports have come in about chimpanzees being gang-attacked in this way by other group members throughout much of Africa. In seven of fourteen cases, the individual attacked fled to temporary exile. Because six of them are known to have died (and there is also a suspected case of a gang-attack death among bonobos), this pattern also can be seen as reminiscent of capital punishment of the aforementioned, actively-collective human type that today relies on group stoning. This suggests that collective, coalitionary attacks against high-ranking group members may have a long evolutionary history, and that in turn this means that humans did not invent either collective intentionality, or capital punishment, out of whole cloth.

Returning to the issue of intention, let me clarify something important. Non-literate hunter-gatherers are and were totally unaware of their actions’ impact on ultimate evolutionary processes. The closest they got to such reflection was when some of their origin myths suggested that humanity developed in stages. For instance, as desert foragers the Navajos believed that our insect-like predecessors lived underground, and that “earth surface people” evolved from them. Otherwise, however, people-without-science have been blissfully unaware of evolutionary processes as we know them.

Suggesting that intentions at any level have affected our biological evolution is highly controversial, and this has a long history going back to the great Darwinian shakeup of 1859, when Deistic origin theories were challenged. In fact, as evolutionary theory was developing over the past century, there were two noteworthy scientific taboos that have acted as a damper on evolutionary theorizing. One relegated to the scientific scrap heap the imaginative group selection theory created by Charles Darwin, both because initially it didn’t seem to agree with mathematical models, and because some group-selectionists misused the theory. Over more than a quarter of a century David Sloan Wilson[12] fought a major battle for this theory, with only a handful of active allies (I include myself, as of several decades ago[13]). Group selection helps to explain the mystery of altruism, and for a decade now, multi-level selection theory has brought group-selection models into the fold.

The other evolutionary proscription has been the outlawing of teleological thinking of any kind. The history of this taboo is equally deep, and so far the subject has not really been engaged with aside from in The Deep Structure of Biology, a fascinating edited book on evolutionary convergence and the possibility of built-in “directionality.”[14]

Ever since Darwin, conservative scientists who study natural selection have considered this to be a totally random process, a point persuasively emphasized by Dawkins in The Blind Watchmaker. Dawkins made his case as a vehement advocate of atheism, but more neutrally the evolutionary psychologist Donald T. Campbell said it all, in 1965, in just a few quiet words: evolution is a process that involves blind variation and selective retention.[15] All you need is varying individuals, a means of inheritance, and an agency that can select among their traits; that’s it. Later, Campbell[16] did become open to the possibility of some lower-level teleology[17] being operative in natural selection, while Dawkins remained an absolutist to the end.

In the wake of the earlier, Templeton-funded symposium on evolutionary convergence and “directionality,” archaeologist Robert Foley decided that:

the processes of selection and adaptation give the illusion of purpose through the utter functionality and designed nature of the biological world, but I have also argued that the illusion of purpose is further enhanced by the fact that selection has clearly favored strongly motivated behavioral abilities and that, in that sense, purpose resides in the genome and phenotype of organisms.[18]

Foley seems far more open-minded than Dawkins. Of course, Dawkins was mainly worried about denying God as purposeful creator, as he upheld a taboo that often serves as a useful curb on the scientific imagination. This was not the case with William Hamilton, however, when he semi-seriously suggested that playful (and apparently omnipotent) extraterrestrials might actually have created natural selection and were using planet earth as a kind of experimental zoo for their observations.

It is quite different to ask if there could have been some more realistic, less comprehensive purposive agencies within the natural selection process, for instance, having to do with the “strongly motivated behavioral abilities” mentioned by Foley. Could they have introduced some degree of purposefulness into a process that everyone had been agreeing was totally blind?

Some rather subtle distinctions are involved. Ernst Mayr distinguished between teleonomy, which characterizes processes that appear to solve problems purposefully but in fact are purely mechanical, and teleology, which means that purposeful agencies (supernatural or otherwise) are, in fact, influencing evolutionary outcomes.[19] Mayr’s view would be that when Darwin’s finches acquired a variety of task-dedicated beaks, the process was entirely “mechanical.” The evolutionary biology community would agree with him, and for all practical purposes so would I, but only as long as this restriction does not carry over 100 percent to animals with much larger brains.

This evolutionists’ venerable taboo against teleological thinking may basically hold for analyzing smaller-brained species, and overall it makes a great deal of sense. But I shall suggest that outlandishly powerful brains make human purposes quite different from those of finches whose hungry beaks are selected straightforwardly on the basis of feeding efficiency. We need only to look at capital punishment and its long-term effects on the human genome to see that something more complicated can be at work.

When a group purposefully singles out a domineering bully to eliminate him in the prime of life, that bully’s procreative career will end. He will also be unable to support his breeding partner, offspring, and relatives. This definitely can change a gene pool, and it is the social and not the physical environment that is at work. Such a culturally and morally-based behavior obviously relies upon a great deal more brain power than being a well-fed finch does.

Here, in the same breath, we are speaking in terms of both evolutionary theory and philosophy of science. What links certain moralistic purposes of hunter-gatherers to biological evolution is that the long-term, ultimate genetic effects of social sanctioning go in exactly the same direction as the short-term, intended effects, which are simply to suppress bullying behavior in the here and now. In the face of these parallel effects, I believe we must at least be open to the possibility that just for humans, not all natural selection processes are antiseptically devoid of purpose.

The quotation from Foley places this reasoning in perspective because it suggests that in many species, short-term purposes are inherent in the psychology of making decisions. When a lizard chooses one ant rather than another to flick its tongue at, this is a decision, and the making of such very immediate decisions is an evolved property of many species with modest brains. A question I shall not try to answer is whether this amounts to intentional input writ very small; what I do believe is that humans are the obvious venue in which to open the debate and that capital punishment is a most suggestive example.

Humans consistently make genetically impactful, collective decisions, ones which reduce the fitness of certain types of individuals such as born psychopaths and others unusually disposed to dominant aggression. This provides some major food for thought. Also worth considering is the larger fact that, in an indirect but important way, our species seems to have been domesticating itself through purposive capital and other punishment.

The first recorded instance of domestication has us turning wolves into the dogs we love, and very likely some kind of “passive” domestication began at least 15,000 years ago, when we began to feed predators lurking around our camps. At some point they became pets, and domestication became more active as promising litter members were chosen as suitable future pets. We obviously would have gone for the nice individuals, not the nasty. Capital punishment has had similar consequences, and for a much longer period of time, but the process is much more complicated. As an effective type of social problem solving, this killing of fellow group members is very well focused. When humans crack down on bullies, we do this through concerted social cooperation, in order to solve specific problems we understand and know we can cope with. The cognitive assessments have to be quite sophisticated.

In killing off such troublemakers we surely have been “domesticating” ourselves, but I emphasize that this genetic consequence has been far from being on our minds. In spite of this ignorance, however, it is equally emphasized that our very immediate intentions can be effective, sometimes, in shaping the human genome. This takes place when the immediate and the long-term, ultimate effects are very similar.

It is by using symbols that we can reach a group consensus, and engage in purposive, highly focused, and consequential collective action that has reproductive consequences, while the continuity of cultural traditions ensures that over evolutionary time, we will be continuing to solve the same problems in the same ways. It is this continuity that has made it possible for our everyday problem-solving to help to shape the human genome.

For exemplification of such lower-level teleology, capital punishment was a real find. However, there is another, less obvious moral example that also is suggestive. In The Biology of Moral Systems, Richard D. Alexander came up with the idea of indirect reciprocity, which explains altruism as follows: in theory, altruists are doomed genetically because by definition they give away resources to non-relatives, which means that free-riders who don’t reciprocate should flourish at their expense.[20] However, in small human groups the obvious altruists gain superior moral reputations, and when other people select spouses to breed with or other partners in cooperation, altruists with good moral reputations are chosen preferentially. This more than compensates for the costs of being generous to non-kin, and in humans this would have been a very significant factor in the evolution of our unusual altruistic traits.

Altruism appears to provide the more limited example of lower-level teleology at work, since the decisions are individual, and the genetic effects seem less extreme. Collectivized capital punishment is far more impactful and dramatic. But in both cases purposeful decisions are shaping the genome in ways that make us more pro-social. In effect, this inadvertent self-domestication has made us nicer as a species, and it has done so precisely because our evolved psychological preferences reveal a dislike of being dominated and also a desire to associate with altruists.

Now let us return to the larger philosophical issue I have raised, that of teleology. Kill a bully today, and—whether you realize it or not—you will be subjecting the human genome to modification precisely because, causally, you are reducing species-specific tendencies to act the bully. From the standpoint of philosophy of science this suggests that with our large-brained species, some lower-level teleology could be creeping into evolutionary process, at the level of both collective intentions and collective decisions.

With both capital punishment and altruism, patterns of sophisticated choice have been working consistently over evolutionary time to create these parallel effects in our genome. Hopefully, faced with this information, the taboo against even asking this type of question will begin to lift.


Photo credit: Execution Group at Remigia, Castellón, Spain from N. K. Sandars, Prehistoric Art in Europe. 2nd revised ed. (New Haven: Yale University Press, 1995), 162.

[1]. C. Boehm, “Impact of the Human Egalitarian Syndrome on Darwinian Selection Mechanics,” American Naturalist 150 (1997): 100-121. See also C. Boehm, “Bullies: Redefining the Human Free-Rider Problem,” in J. Carroll and E.O. Wilson, eds., Darwin’s Bridge: Uniting the Humanities and Sciences (Oxford, U.K.: Oxford University Press, 2016).

[2]. C. Boehm, “A Biocultural Evolutionary Exploration of Supernatural Sanctioning,” in R. Bulbulia, R. Sosis, E. Genet, et al., eds., Evolution of Religion: Studies, Theories, and Critiques (Monterey, CA: Collins Family Foundation, 2008).

[3]. A. Norenzayan, “What Can Cultural Evolution Tell Us About the Human Conquest of the Planet?” at; accessed April 29, 2017.

[4]. W.H. Durham, Coevolution: Genes, Culture, and Human Diversity (Stanford, CA: Stanford University Press, 1991).

[5]. K.A. Kiehl, “Without Morals: The Cognitive Neuroscience of Criminal Psychopaths,” in W. Sinnott-Armstrong, ed., Moral Psychology, Vol. 1: The Evolution of Morality: Adaptations and Innateness (Cambridge, MA: MIT Press, 2008).

[6]. C. Boehm, Hierarchy in the Forest: The Evolution of Egalitarian Behavior (Cambridge, MA: Harvard University Press, 1999).

[7]. C. Boehm, Moral Origins: The Evolution of Altruism, Shame and Virtue (New York: Basic Books, 2012). See also C. Boehm, “The Moral Consequences of Social Selection,” Behaviour 171 (2014): 167-83.

[8]. L. Pericot, “The Social Life of Spanish Paleolithic Hunters as Shown by Levantine Art,” in S.L. Washburn, ed., Social Life of Early Man (New York: Aldine, 1961).

[9]. Funding for this project has come from the John Templeton Foundation and the Goodall Research Center, University of California.

[10]. M. Tomasello, A Natural History of Human Morality (Cambridge, MA: Harvard University Press, 2016).

[11]. F.B.M. de Waal, Good Natured: The Origins of Right and Wrong in Humans and Other Animals (Cambridge, MA: Harvard University Press, 1996).

[12]. D.S. Wilson, “The Group Selection Controversy: History and Current Status,” Annual Review of Ecology and Systematics 14 (1983): 159-87. See also D.S. Wilson and E.O. Wilson, “Rethinking the Theoretical Foundation of Sociobiology,” Quarterly Review of Biology 82 (2007): 327-48.

[13]. C. Boehm, “Rational Pre-selection from Hamadryas to Homo sapiens: The Place of Decisions in Adaptive Process,” American Anthropologist 80 (1978): 265-96. See also a discussion of guided variation and guided selection in C. Boehm, “Emergency Decisions, Cultural Selection Mechanics, and Group Selection,” Current Anthropology 37 (1996): 763-93.

[14]. S.C. Morris, ed., The Deep Structure of Biology: Is Convergence Sufficiently Ubiquitous to Give a Directional Signal? (West Conshohocken, PA: Templeton Foundation Press, 2008).

[15]. T.D. Campbell, “Variation and Selective Retention in Socio-cultural Evolution,” in H.R. Barringer, B.I. Blanksten, and R.W. Mack, eds., Social Change in Developing Areas (New York: Schenkman, 1965).

[16]. D.T. Campbell, “The Two Distinct Routes beyond Kin Selection to Ultrasociality: Implications for the Humanities and Social Sciences,” in D. Bridgeman, ed., The Nature of Prosocial Development: Interdisciplinary Theories and Strategies (New York: Academic Press, 1983).

[17]. C. Boehm, “Lower-Level Teleology in Biological Evolution: Decision Behavior and Reproductive Success in Two Species,” Cultural Dynamics 4 (1991): 115-34.

[18]. R. Foley, “The Illusion of Purpose in Evolution,” in Morris, ed., The Deep Structure of Biology.

[19]. E. Mayr, “The Multiple Meanings of Teleological,” in E. Mayr, ed., Towards a New Philosophy of Biology (Cambridge MA: Harvard University Press, 1988).

[20]. R.D. Alexander, The Biology of Moral Systems (New York: Aldine de Gruyter, 1987).

  • Christopher Boehm

    Christopher Boehm is Professor of Biological Sciences and Anthropology and Director of the Goodall Research Center at University of Southern California.

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