Cooperative Killing, In-Group Identity, and God

Alpha God: The Psychology of Religious Violence and Oppression - Hector A. Garcia 2015

Cooperative Killing, In-Group Identity, and God


Cooperation is a fundamental quality of life on earth. Symbiosis provides a principle framework for biologic complexity, and there is evidence that some parts of cells were once free-living parasitic bacteria that managed to form mutualistic relationships with their hosts, ultimately merging into singular, cohesive units of life. Accordingly, unicellular organisms cooperate to form tissues, tissues to form organs, organs to form organ systems, and organ systems to form complex multicellular organisms, such as humans. Within our bodies there are trillions of organisms cooperating in vast networks that comprise living, breathing, thinking human beings. In this sense then, we are literally constructed of many levels of cooperation.

Just as cooperation is a fundamental quality of life on earth, demonstrable in life's most basic forms, so is enmity. Viruses, for example, are simple chemical compositions that, with no cell structure or metabolism, seem to teeter on the edge between life and nonlife; some are as basic as a single strand of RNA covered by a protective protein coating. Because viruses have no metabolism, they require host cells to survive and perform their replicative functions, which they do at the expense of the host cell's survival—essentially robbing that cell of energy. Most viruses eventually kill their host cells, often by exploding them (a process known as lysis). We find hostility even in life-forms more basic than a single cell.

In nature, cooperation and hostility often come together. In a world in which even the most minute life-forms are designed to kill, joining forces with other organisms provides a clear survival advantage. As such, we find cooperative warfare in the microbiologic world. The strategic complexities employed in microscopic warfare draw striking comparisons to their human analogues and reflect adaptations that speak to the fierce pressures of selection at life's most basic level of organization. Here one scholar enumerates the similarities:

…military alliances (could apply to synergistic pathologies, where more than one pathogen act in concert)…suicide mission (cells that self-destruct to kill the intruder), suicide bags (name applied to lysosomes that break open and release their contents destroying the cell…)…camouflage (coating on gram negative bacteria that inhibits recognition as foreign body by failing to provide earmarks of enemy)…wolf in sheep's clothing (could be applied to viruses which have envelope made from host cell membrane)…Trojan horses (bacteria which invade macrophages meant to destroy them and travel to other sites of the body protected from attack)…distress signals (chemicals released by injured and dying cells)…sabotage of communications (microbes commonly bind to cell signaling receptors on surface distorting or blocking communication…)…The key to a host's defense is being able to recognize its own cells and molecules from those of the pathogen (i.e. SELF from NON-SELF). In the military context, such recognition is accomplished by wearing different uniforms.1

On the human battlefield, the stakes are the same as in the microscopic wars waged inside us—survival and reproduction—and both theatres are ultimately administered by our genes. The analogy highlights another important point: a fundamental task of cooperative hostility is to recognize who is part of the cooperative alliance and who is against it.

For this task, humans have evolved a psychology to navigate interactions with both the in-group (a social group to which an individual belongs) and the out-group (a social group to which an individual does not belong). We have also developed cultures and religions as means to regulate in-group—out-group processes. Like secular culture, religions can engender great empathy and collaboration, but they can also bring about remorseless killing. This pattern of in-group altruism and out-group enmity has been termed parochial altruism.2

Religious enmity ultimately stems from the genetic strategies in which religion's out-group biases are rooted. Believers driven by religious hatred are for the most part unaware of the evolutionary designs of their behavior. Rather, they are often swayed by religious ideology that is modeled on their evolutionary psychology, which makes their stances and actions feel natural. To understand how this can come about, our task yet again is to make the natural seem strange.


In-group, Out-group

To begin, we revisit the idea of kin altruism. As a rule, cooperation is highly correlated with the amount of genetic material shared between individuals. Accordingly, kin altruism is a cornerstone of biological interaction, including that which occurs between humans. With brains shaped by eons of kin selection, the rules of kin altruism suffuse human thought, language, and behavior. Humans, with their unprecedented capacity for abstract thought and language, have even adopted the rules of kin altruism to influence each other—humans often symbolically exaggerate genetic relatedness in order to foster in-group cohesion and loyalty among nonkin. For example, fraternity members see themselves as “brothers,” and soldiers see themselves as “brothers-in-arms.” Similarly, countrymen share a common fatherland or motherland. Nonkin in-groups don't always require notional relatedness, but this strategy tends to strengthen affiliation.

As with in-group loyalty, this tendency to create fictive kin is pronounced in religion—for instance, God is called Our Father, his priestly representatives are addressed as fathers (or mothers), religious coadherents are brothers and sisters, and, collectively, the pious share a common ancestry as God's children. These designations tender a great deal of trust, compassion, and kindness between members of a shared faith. Creating notional brothers and sisters ends up being a powerful means of enticing people to close ranks.3

Contrarily, exaggerating genetic differences between others is a highly effective means of fomenting enmity. A common ideological strategy used in warfare is to regard the enemy as nonhuman; enemies are often seen as dogs, pigs, monkeys, monsters, or devils. Most people rallied to war by these images are hardly aware that their infrahumanizing rage is based on the logic of selfish genes.

Army psychologist David Grossman argues that humans are naturally disinclined to kill members of their own species. The “psychological cost of killing,” as Grossman describes it, is both pervasive and measurable in warfare and in its aftermath. A disinclination to kill one's own species, he argues, is characteristic of many animals that engage in ritualized combat. Piranhas, as one example, are equipped with razor sharp teeth designed to tear other animals to shreds, but these fish notably don't do this to one another. The contests between them are symbolic, and rarely result in serious injury. The weaker fish often submits, and the stronger fish is likely to pull back when a competitor yields. These behaviors allow competitors to avoid life-threatening injuries and suggest that animals (directed by genetic strategies) are able to exert an emotional brake on violence between members of their own species. Humans come equipped with similar brakes, which—considering our ability to cooperate—must be very powerful. When humans engage in lethal combat, Grossman argues, they disengage those brakes in part by using strategic terms designed to make the enemy seem less human (i.e., less genetically related). This is what we have been calling infrahumanization, and in Darwinian terms is akin to saying, “You share no genes in common with me, therefore I owe no loyalty to you, and I can kill you like an animal.”4

Philosopher David Livingstone Smith has compiled an extensive inventory of infrahumanization across the history of war.5 He begins with an observation made by English philosopher David Hume, who, in 1740, spoke to our tendency to dehumanize the enemy and also to our extreme bias toward actions of the in-group:

When our own nation is at war with any other we detest them under the character of cruel, perfidious, unjust and violent: But always esteem ourselves and allies as equitable, moderate and merciful. If the general of our enemies be successful, ’tis with difficulty we allow him the figure and character of a man.6

Smith goes on to cite early anthropological observations of aboriginal people who saw their enemies as nonhuman animals, which made them much easier to hunt and kill as prey. The propaganda of war offers another revealing look, which Smith argues taps an ancient fear of predation by outside species:

A Union poster from the American Civil War shows a heroic club-wielding General Scott of the Union army. He is poised to bludgeon a gigantic, nine-headed serpent. Seven of the monster's heads are those of leaders of the Confederacy.

An American cartoon from the Spanish American War represents Cuba as a huge, sinister ape-man, complete with protruding fangs, holding a bloody knife and hulking over the grave of U.S. Servicemen killed in the battleship Maine, which blew up in Havana Harbor in 1898.

A Taiwanese cartoon depicts a hapless man in a wooden boat about to be devoured by an enormous shark. The boat is labeled “Taiwan” and the shark is labeled “China.”

A Soviet poster from the 1950s shows a wolf dressed in a suit and tie, removing a mask from its grotesque, snarling face. The mask bears the countenance of the United States Secretary of State Dean Acheson.7

Similar out-group depictions, particularly during warfare, could be exemplified indefinitely. Thus, considering that people are so often prone to seeing outsiders as nonhuman while calling themselves the people, the human beings, the chosen people, the righteous people, or even people at the center of civilization, it should not surprise us that religious canon also embodies these contrived distancing strategies. This is seen across the Abrahamic religions. Here is an example from the Koran in which Allah, so disgusted with the Jews, transforms them into apes and pigs:

Those who incurrent the curse of Allah and his wrath, those of whom some he transformed into apes and swine, those who worshipped evil—these are [many times]worse in rank, and far more stray from the even path. (Koran 5:60)

And well ye know those amongst you who transgressed in the matter of the Sabbath. We said to them, “be ye apes, despised and rejected.” (Koran 2:65)

Clearly, Islamic doctrine includes infrahumanization, and it is not hard to understand how characterizations such as these could stoke the ancient coals of out-group mistrust, ultimately enflaming violence against Jews. With the main texts of Judaism predating Islam by hundreds of years, we would not find infrahumanization specifically directed toward Islam in texts such as the Old Testament or the Talmud—but finding the sons of Abraham infrahumanizing others in the modern age is not difficult. For example, when Israeli soldiers assault and torture Palestine children, they do so regarding them as “dogs.”8

For a case study of infrahumanization in religious violence among Christians, we look to the Thirty Years’ War (1618—1648). During this period Europe was ripped apart by bloody conflict, not between Christianity and Islam or Christianity and Judaism, but among Christians themselves; millions of Protestants and Catholics battled explicitly over theological differences of opinion. The divisions were not only between Catholics and Protestants; Protestants were divided into warring interests amongst themselves, with the Calvinists, Lutherans, Anabaptists, and Unitarians each fighting each other for religious supremacy and, importantly, the territories that it afforded.

When the Lutherans defined their doctrinal standard in the Book of Concord in 1580, they expelled the Calvinists from their territory in Germany. The Calvinists then drew up their own standard, the Heidelberg Catechism, which incensed both Catholics and Lutherans. The Calvinists in turn suppressed the Unitarians and sentenced to death those who questioned Calvinist doctrine. The Lutherans and the Calvinists began killing dignitaries and other people for alleged Calvinist or Lutheran leanings, respectively. Infrahumanization propelled the hatred. For example, in 1582 Lutheran pastor Nivander published a paper outlining forty characteristics of wolves and likened each precisely to characteristics of Calvinists. This tactic spread like wildfire across the various religious fiefdoms and readied Lutherans to butcher Calvinists. The Lutherans assaulted the Catholics in a similar manner. Historian Will Durant notes that “Words like dung, offal, ass, swine, whore, murderer entered the terminology of theology,” and that this sentiment was captured in the political art of the day—for example, in German woodcuts depicting the pope as a sow giving birth to Jesuit piglets.9 Theologians argued vehemently over the minutia of religious edicts and practices and used infrahumanization to artificially widen ideological differences. One Lutheran pamphlet read, “If anybody wishes to be told, in a few words, concerning which articles of the faith we are fighting with the Calvinist brood of vipers, the answer is, all and every one of them…for they are no Christians, but only baptized Jews and Mohammedeans” (italics mine).10

Each opposing group in the Thirty Years’ War took to slaughtering one another like the animals they portrayed. In Germany and Austria alone there were estimated to be some 7.5 million human lives destroyed.11 Like all wars, the Thirty Years’ War wrought immense human suffering, involving not only killing but large-scale rape, torture, starvation, and infanticide. It is worth emphasizing that these atrocities were Christian on Christian—groups of people worshipping the same god and the same Christ. In this case, exaggerating genetic differences by making fellow Christians into animals (as opposed to brothers) eased the way to their extermination.

While humans are unique in using religious ideology to bolster in-group—out-group boundaries, their ideological strategies are thickly veined with evolutionary significance. This is not to make the argument that infrahumanization causes war. Rather, it is an effective way to grease the gears of war in a manner that reanimates the emotions of our ancestors who rallied against outsiders for survival.

Because both recognizing kin and fearing outside threats are survival adaptations, it makes sense that infrahumanizing a perceived outside threat serves the function of terror management—doing so, and closing ranks within the tribe, must have afforded survival advantages to our ancestors. This intrinsic human tendency can be elicited in the research lab. Terror Management Theory (TMT) studies find that subjects will rate outsiders as having more animalistic traits and insiders, more human traits, when fears of death are artificially manipulated.12 The research also finds that subjects with lower self-esteem tend to infrahumanize more when mortality fears are activated than those with higher self-esteem.

Infrahumanization can be considered an ideological means to foster in-group cohesion based on logic that is evolutionarily familiar to us—the logic of kin altruism. Scholars in evolutionary sciences have operationalized other forms of cooperation that also help to explain why humans are so successful at extending cooperation beyond their genetic relatives. These mechanisms bear strongly on the emergence of cooperative hostility.


For humans, the advantages of cooperation materialize not just in things like hunting, gathering, childrearing, or warfare, but in virtually every avenue of survival imaginable. It is fair to say that the survival of the species as we know it would have been impossible without the cooperative enterprise.

Recall that in kin selection, genes “design” brains that entice cooperation between genetically related individuals. In doing so, genes “ensure” that copies of themselves (residing in genetic relatives) are replicated. Reciprocal altruism, a concept developed by American evolutionary biologist Robert Trivers, explains how seemingly altruistic acts between genetically unrelated (or distantly related) individuals evolved. Trivers defined reciprocal altruism as “behavior that benefits another organism, not closely related, while being apparently detrimental to the organism performing the behavior, benefit and detriment being defined in terms of the contribution to inclusive fitness.”13

As Trivers points out, the apparent detriment here often becomes a future benefit. Altruistic behaviors are offered with the expectation that help will later be reciprocated, thus conferring a survival advantage. The individual offering aid to another may not be acting to perpetuate shared genetic material in that moment, but is still relying on the expectation that—somewhere down the line—he or she will receive aid in return, which will benefit survival and reproduction. Reciprocal altruism strongly influences a wide variety of human interactions—from the human dyad to the world economy—and makes humans much more effective at solving adaptive problems, chiefly because it allows us to extend our networks beyond genetically related kin.

However, given the timeless propensity of genes and the people they program to be “self-interested,” some individuals inevitably attempt to take advantage of others’ altruism by seeking help without reciprocating. If successful, they increase their own fitness by being recipients of help without risking their fitness by providing it—for example, the hunter who has a personal barbecue out in the bush instead of bringing his quarry back to camp yet demands a split of his comrade's kills. Natural selection has responded by providing sensitive cheater-detection systems in species that reciprocate, but this in turn drives selection for individuals who are very good at cheating on the sly. From this dynamic arises another evolutionary arms race, with increasingly sly cheaters pushing the development of ever more sensitive cheater-detection systems and vice versa. In the end, people have become extremely crafty cheaters and are also very wary of cheaters in cooperative arrangements.

Indirect reciprocity is similar to reciprocal altruism, but can occur without the expectation of a reciprocal response directly from the person receiving help. This process relies on reputation. For instance, if an individual performs an act of altruism, and if the recipient informs others that he or she has been helped, then the helper accrues reputational capital. Having a reputation for helping pays off by making others more confident in cooperating with the helper—even those who have not directly observed the helping. Thus, indirect reciprocity can extend the reach of cooperation across even greater numbers, allowing us to build sprawling societies of cooperators capable of working toward common goals.

Across the various cooperative enterprises, cheater detection remains critical. The cost lies in investing time or resources in those with no intention of returning the favor. Clearly, in a world of limited resources (and where cheaters cheat), one would want to be cautious about being altruistic. We can all think of examples of those who would fake signals of commitment to gain trust, ultimately to take unfair advantage. Because deceit of this kind has historically impacted survival, humans continue to find it very threatening. For these reasons, humans expend great effort in cooperative undertakings to establish in-group membership, define codes of in-group reciprocity, and root out cheaters. One means of systematizing this process is by developing unique signals of commitment. Behavioral ecologist William Irons has argued that “for such signals of commitment to be successful they must be hard to fake. Other things being equal, the costlier the signal the less likely it is to be false.”14 In other words, when the cost of faking signals outweighs the benefit, then cooperation is on a safer footing. Costly signals therefore allow in-group members to cooperate with some degree of certainty, and eschew expending time and energy trying to determine the trustworthiness of their neighbors. This idea is known as Costly Signaling Theory (CST), and religion is replete with examples.

Anthropologist Richard Sosis writes about religion's “three Bs”—behavior, badges and bans—as forms of costly signals.15 Sosis's three Bs are easy to uncover. Many religions require behaviors that are difficult to fake, such as long pilgrimages and regular prostration, or time-consuming, such as praying the rosary or repeating religious verse. Similarly, religious life is filled with badges, such as ritualistic scarring, circumcision, long beards, curled locks of hair, burkas, et cetera. Finally, religions are filled with all sorts of bans—for example, restrictions on eating, sexual behavior, language use, or even substances such as coffee, tobacco, or alcohol.

Sosis offers the example of ultraorthodox Jews in Israel, known as Haredim—which means “[God] fearing or trembling ones”:

Women sport long sleeve shirts, head coverings or wigs (and occasionally both), and heavy skirts that scrape the ground. In their thick beards, long black coats, and black pants Haredi men spend their days fervently swaying and sweating as they sing praises to God in the desert sun. Many of them wear striemels, thick fur hats that were undoubtedly helpful in surviving the long and cold Eastern European winters where their ancestors had lived, but probably should have been left at the border when they immigrated to the Holy Land. By donning several layers of clothing and standing out in the mid-day desert sun, these men are signaling to others: “Hey! Look, I'm a Haredi Jew. If you are also a member of this group you can trust me because why else would I be dressed like this? Only a lunatic would spend their afternoon doing this unless they believed in the teachings of Ultra-Orthodox Judaism and were fully committed to its ideals and goals.16

Donning furs in the desert is a particularly difficult-to-fake signal of commitment. Precisely because of their difficulty, such behaviors create confidence in the sincerity of the signaler and allow trusting social networks to form around those willing to swelter together. Costly signaling eases the way for reciprocal altruism and indirect reciprocity, essentially demarcating who is safe to trust in cooperative exchanges and who is to be mistrusted, avoided, or sometimes even persecuted. The ubiquity of rituals qualifying as costly signals points to the fitness value of making in-group—out-group distinctions.


Patterns of Primate Alliance-Making

Like humans, the social lives of nonhuman primates are governed by rules of reciprocity. Rules of exchange in coalitional violence are clear. For instance, when calling for assistance during a fight, individuals are more likely to be aided by those they have previously helped in a fight (or groomed, or have shared food with).17 Reciprocating help in fights is an important social rule that is also enforced with violence. For instance, chimpanzees who fail to reciprocate with help in a fight will often be attacked (rather than helped) when they call for backup.18 Further, chimps will methodically isolate and attack group members who assisted their rivals in fights against them.19 Some researchers have concluded that the single most common cause of aggression within primate societies is perceived violation of social rules.20

Rank status plays an important role in alliance-making. To begin, primates appear to have an obsession with those of high status. In the research lab, for instance, male macaque monkeys will choose to view images of high-status individuals (and female genitalia) over food, but will require food overpayment to view lower-status individuals.21 Research shows that human toddlers also tend to prefer and emulate higher-status over lower-status individuals.22

The penchant for selectively focusing on high-status individuals may be traceable to the advantages of forming alliances with them—having “friends in high places” pays, particularly if you live in a world in which cooperative hostility is the norm. Accordingly, we find that primates spend disproportionate energy attempting to form alliances with higher-status individuals. For example, in the strict matrilineal hierarchies of vervet monkeys, macaques, and baboons, support in fights is often given to the higher-ranking female, who will later intervene in conflicts on behalf of the helper.23

Dominants also rely on alliances to assume or maintain their rank.24 Further, high-ranking primates will police relationships in their subordinates—for instance, by punishing behaviors such as sharing food with or grooming forbidden individuals.25 Frans de Waal has argued that this type of behavior is a strategy to interfere with possible alliance formation.26 When interfering doesn't work, alliances are punished with violence.

Human primates also make these kinds of patterned alliances and reenact them in their relationships with their man-based gods. Humans seek alliances with their (presumably higher-ranking) gods in battle and will ritualize food sharing (e.g., in the form of offerings, sacrifices, etc.) in order to secure them. Like any dominant primate, God is said to help those who ally with him and punish those who ally with the competition.

Humans will go to great lengths to secure alliances with God in battle, including making extreme and costly signals. However, this behavior violates central tenets of the Abrahamic-god concept, mainly omnipotence and immortality. Costly signals in coalitional violence are the mark of biological entities who risk being killed. Mortal beings generally cannot afford to behave altruistically without the reassurance that help will be reciprocated. But God is an immortal being; conceivably he could offer his alliance in battle with no risk to his existence. The same is true for omnipotence. According to scripture there is no being more potent than God. He therefore could never be harmed, and any alliance gestures that humans may make to him are inconsequential. Nevertheless, to secure his alliance humans will go to great extremes to demonstrate and enforce their association with God, often in a manner that generates grave human suffering—both among the enemy and among those who would refuse allegiance to him. The logical explanation for the illogic of making costly signals to God is that humans use the rules of reciprocity of their own societies to guide their “interactions” with him. Though transformed and elaborated upon through culture, such rules are grounded in the social structures of our primate ancestors and enacted unconsciously through our evolved psychology.

Costly Signals with God for Help in Killing

Charles Darwin recognized that warfare could be a powerful evolutionary force shaping in-group cooperation among humans.27 Indeed, although warfare would seem to be the very definition of human antagonism, it does require the most far-reaching, coordinated acts of costly cooperation across the vast repertoires of possible human group behaviors. Given the stakes involved, warfare requires immense trust in reciprocity, for relying on an unreliable comrade in war brings the ultimate price. Perhaps for this reason severe punishments are delivered to those who violate the rules of reciprocity in war—treason and cowardice, for example, have been punished not uncommonly with execution across the history of organized warfare. Accordingly, the alliances humans make with other humans in warfare are perhaps stronger than any other. It has been noted, for instance, that the bonds between fighting men can be stronger than the bonds between those men and their wives,28 and so reliant are brothers-in-arms on each other that the primary motivation for fighting becomes neither country nor cause, but one another, and the preservation of one's honor in the eyes of one's comrades.29

With brains shaped by millions of years of cooperative exchanges, humans are primed for making costly signals to secure alliances. This cross-cultural tendency extends to our concepts of God, with humans expecting God to operate on the premise of Costly Signaling Theory (CST)—a human means of establishing loyalty.

The ancient Mayans offer an example. Their supreme god Tohil demanded blood in exchange for the gift of fire. Worshippers would perform bloodletting—men, by piercing their penises, and women, their tongues and ears. By dripping blood onto paper and setting it aflame, the dutiful fanned their burnt offerings up to the heavens.30 The ancient Aztecs had similar arrangements with their gods. The supreme feathered serpent god Quetzalcoatl is believed to have created humans through an act of sacrifice—by piercing his own penis and sprinkling the world into existence with his blood. Dutiful Aztec lords would return the gesture by puncturing themselves about their bodies, penises included, with the spiny thorns of the maguey plant or filed bones.31

In a similar instance of genital mutilation, the first landmark act of costly signaling in Judeo-Christian creed is the covenant between Abraham and God. Indeed this covenant, this costly signal, is foundational to the Judaic religion. As the story goes, God asked Abraham to cut off his foreskin (and the foreskins of all his male descendants and male slaves) to prove his loyalty. In exchange for this painful act, God ceded the territories of Israel to Abraham and all his descendants in perpetuity. Per God:

You are to undergo circumcision, and it will be the sign of the covenant between me and you. For the generations to come every male among you who is eight days old must be circumcised, including those born in your household or bought with money from a foreigner—those who are not your offspring. Whether born in your household or bought with your money, they must be circumcised. My covenant in your flesh is to be an everlasting covenant. Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant. (Gen. 17:11—14)

Just as men of war form strong alliances with one another, they form alliances with their male god, projecting onto him their own reflection—for example, “The Lord is a man of war” (Exod. 15:3). Accordingly, God acts like a man of war and provides support in warfare. It should not be difficult to understand how primates would take courage from a battle alliance with the most powerful dominant male in the universe. Here are a couple examples of how this dynamic is described in the Bible:

Blessed be the LORD my strength which teacheth my hands to war, and my fingers to fight. (Ps. 144:1)

And the LORD said unto Moses, Fear him not: for I have delivered him into thy hand, and all his people…. So they smote him, and his sons, and all his people, until there was none left him alive: and they possessed his land. (Num. 21:34—35)

The Aztecs made similar costly signals to their god of war, Huitzilopochtli. Late in Aztec history, the powerful leader Tlacaelel began uniting disparate Aztec states through a series of military campaigns under Huitzilopochtli. Through those battles, Huitzilopochtli eventually ascended to become the most powerful male god of the Aztec pantheon. In exchange for success in war, the Aztecs provided food to Huitzilopochtli in the form of sacrificial blood from their conquered enemies. The practice became central to their religio-militaristic culture. In a conversation with the Aztec emperor Motecuhzoma, Tlacaelel discusses the plans for a grand temple for the supreme Aztec god of war:

There shall be no lack of men to inaugurate the temple when it is finished. I have considered what later is to be done. And what is to be done later, it is best done now. Our god need not depend on the occasion of an affront to go to war. Rather, let a convenient market be sought where our god may go with his army to buy victims and people to eat as if he were to go to a nearby place to buy tortillas…whenever he wishes or feels like it. And may our people go to this place with their armies to buy with their blood, their hearts and lives, those precious stones, jade, and brilliant and wide plumes…for the service of the admirable Huitzilopochtli.32

Huitzilopochtli was also regarded as the god of the sun, and the blood nourishment was also offered in exchange for his brilliance, which kept this world in existence. Often the hearts of sacrificial victims, many of whom were prisoners of war, were extruded with a jade knife while the victim was still alive. Like the Aztecs, the Mayans also sacrificed their prisoners of war. Ancient reliefs depict them decapitating, scalping, burning, or disemboweling their victims.33

In a similar vein, Abraham showed his loyalty to God by his unquestioning willingness to sacrifice his son Isaac (Gen. 22:1—19). God reciprocates in decidedly evolutionary terms by offering Abraham alliance in war (and progeny) in exchange for his submission:

Because you have obeyed me and have not withheld even your son, your only son, I swear by my own name that I will certainly bless you. I will multiply your descendants beyond number, like the stars in the sky and the sand on the seashore. Your descendants will conquer the cities of their enemies. (Gen. 22:16—19)

The blood sacrifice of another Old Testament figure, Jephthah, did not receive a last-minute reprieve. In exchange for alliance in warfare, Jephthah burned his daughter alive.

And Jephthah made a vow to the LORD: “If you give the Ammonites into my hands, whatever comes out of the door of my house to meet me when I return in triumph from the Ammonites will be the LORD's, and I will sacrifice it as a burnt offering.” Then Jephthah went over to fight the Ammonites, and the LORD gave them into his hands. He devastated twenty towns from Aroer to the vicinity of Minnith, as far as Abel Keramim. Thus Israel subdued Ammon. When Jephthah returned to his home in Mizpah, who should come out to meet him but his daughter, dancing to the sound of timbrels! She was an only child. Except for her he had neither son nor daughter…and he did to her as he had vowed. And she was a virgin. (Judg. 11: 30—34, 39)

So powerful is this idea of sacrificing one's child to signal alliance that it ultimately became the most fundamental premise of Christianity, which claims that God sacrificed his only begotten son to ensure his human followers would have an afterlife. As captured in verse:

God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. (John 3:16)

Here the Christian God allows his own son to be killed, an act which draws absolute awe from his followers. But the act is only astonishing to beings bound by genetic replication, to those for whom kin altruism has important survival implications. Remember that God does not need to perpetuate his line by genetic means; he is omnipotent. He is portrayed in scripture as creating by his voice, or by the Holy Spirit, and is not subject to the process of natural selection. God has the power to beget a billion sons, not to have only one begotten son. Perhaps more to the point, God as described has the power to support a billion sons without requiring reciprocity from puny humans. Therefore such a costly signal from God is an empty gesture, practically speaking, but it is deeply symbolic to followers who quite literally live and die on the basis of cooperation.

Once again pointing to the centrality of cooperation, God, like his primate counterparts, makes it absolutely clear that he does not like his followers to make costly signals to other gods, suggesting this may be considered cheating on the reciprocal exchange—for example, “He who sacrifices to any god, except to the LORD only, he shall be utterly destroyed” (Exod. 22:20).

Also like other primates, God requires alliance against his rivals (other gods) and against those who would ally with those gods in turn. His followers have been known to enforce alliance with God by slaughtering his rivals’ followers and offering their flesh as burnt offerings.

Suppose you hear in one of the towns the LORD your God is giving you that some worthless rabble among you have led their fellow citizens astray by encouraging them to worship foreign gods. In such cases, you must examine the facts carefully. If you find it is true and can prove that such a detestable act has occurred among you, you must attack that town and completely destroy all its inhabitants, as well as all the livestock. Then you must pile all the plunder in the middle of the street and burn it. Put the entire town to the torch as a burnt offering to the LORD your God. That town must remain a ruin forever; it may never be rebuilt. Keep none of the plunder that has been set apart for destruction. Then the LORD will turn from his fierce anger and be merciful to you. He will have compassion on you and make you a great nation, just as he solemnly promised your ancestors. “The LORD your God will be merciful only if you obey him and keep all the commands I am giving you today, doing what is pleasing to him. (Deut. 13:13—19)

The God of Islam also brokers deals with men in the manner of costly signals. What follows is an example how in exchange for lives in battle he gives a commodity highly valued among desert peoples (water) and also admonishes to eschew cooperation with those who don't cooperate with him:

Those that suffered persecution for My sake and fought and were slain: I shall forgive them their sins and admit them to gardens watered by running streams, as a reward from God: God holds the richest recompense. Do not be deceived by the fortunes of the unbelievers in this land. Their prosperity is brief. Hell shall be their home, a dismal resting place. (Koran 3:195—96)

The costly signal may also be literally a financial cost. In the Koran, God rewards men for using their riches to finance military expansion and for sacrificing their lives in combat by giving them either triumph or paradise.

Those who believe, and have left their homes and striven with their wealth and their lives in Allah's way are of much greater worth in Allah's sight. These are they who are triumphant. (Koran 9:20)

Allah hath purchased of the believers their persons and their goods; for theirs (in return) is the garden (of Paradise): they fight in his cause, and slay and are slain: a promise binding on Him in truth, through the Law, the Gospel, and the Koran: and who is more faithful to his covenant than Allah? Then rejoice in the bargain which ye have concluded: that is the achievement supreme. (Koran 9:111)

In exchange for fighting for his doctrine—“O you who believe! fight those of the unbelievers who are near to you and let them find in you hardness” (Koran 9:123)—God rewards with victory in battle, forgiveness, love, and Paradise:

O ye who believe! Shall I show you a commerce that will save you from a painful doom? Ye should believe in Allah and His messenger, and should strive for the cause of Allah with your wealth and your lives…. He will forgive you your sins and bring you into Gardens underneath which rivers flow, and pleasant dwellings in Gardens of Eden. That is the supreme triumph. And (He will give you) another (blessing) which ye love: help from Allah and present victory. (Koran 61:10—13)

Surely Allah loves those who fight in His way. (Koran 61:4)

He it is who has sent His Messenger (Mohammed) with guidance and the religion of truth (Islam) to make it victorious over all religions even though the infidels may resist. (Koran 61:9)

In short, as a dominant male, the god of the Abrahamic religions is turned to for coalitional violence, much as men turn to other men. Across cultures, geography, and epochs we find stories men of seeking cooperation with gods in exchange for alliance in warfare, which speaks to an ancient primate legacy reenacted in religious violence.


The act of taking another person's life with malice aforethought (as opposed to accidentally) has been considered the worst violation of all social rules since antiquity. Accordingly, we find prohibitions against killing within every society. This rule is so comprehensively enacted in humans, and so intuitive, that it appears to connote the moral consensus that humans fundamentally possess a right to not be killed by other humans. But while this ethic is seemingly universal, it is far from absolute—while strong proscriptions exist for killing in-group members, killing the out-group members has often been allowed, encouraged, or even obligated in every human society. Thus this seemingly universal injunction against killing ends up being one of the most selectively enforced taboos of human life. To be fair, this judicious hypocrisy has been a matter of survival with humans, much as it has with nonhumans; groups unwilling or unable to kill are typically either annihilated or subsumed by those who are.

Probably for these reasons, religions have adopted this logic with ease. For example, commandment number six of Judeo-Christian law, thou shall not kill—at least as it has been applied for centuries—really means thou shall not kill members of your own community. Religious scholar John Teehan nails this point34 by reminding us of the first thing Moses did when he descended from Mount Sinai; bearing a tablet freshly engraved with “Thou shall not kill,” Moses summarily began to slaughter all those who had committed sins while he was away:

Then Moses stood in the gate of the camp, and said, “Who is on the Lord's side? Come to me.” And the sons of Levi gathered themselves together to him. And he said to them, “Thus says the Lord God of Israel, ’Put every man his sword on his side. And go to and fro from gate to gate throughout the camp and slay every man his brother, and every man his companion, and every man his neighbor.’” And the sons of Levi did according to the word of Moses; and there fell on the people that day about three thousand men. And Moses said, “Today you have ordained yourselves in the service of the Lord.” (Exod. 32:26—29).

The morality of the seminal sixth commandment is predicated on in-group logic. Thou shall not kill establishes a rule that killing members of the in-group is considered murder, whereas different principles apply to killing out-group members—such killings are often acceptable, righteous, and regularly sanctioned by God. There are endless examples of out-group killing in the Bible. For example, when the lands of Heshbon were delivered to the Hebrews by God, the Hebrews did not passively receive those spoils. They boast that they “utterly destroyed every city, men, women and children; we left none remaining” (Deut. 2:34). From there they rampaged into Bashan where they,

smote him until no survivor was left to him. And we took all his cities at that time—there was not a city which we did not take from them—sixty cities…. And we utterly destroyed them, as we did to Sihon the king of Heshbon, destroying every city, men, women and children. (Deut. 3:4—6)

Teehan argues, rightly I believe, that these were not “weaknesses of humans perverting God's goodness and mercy, for these are all divinely ordered massacres.”35 By every definition of the word, the behaviors described above are genocide—committed at the explicit command of a dominant male god. In this way, in-group loyalty may be the moral blinder obstructing the eyes of the religious who commit horrors in the name of their faith while singing the praises of their own moral rectitude. Contrarily, out-group members are seen as devils, their religious practices, as witchcraft, and their cultures, as morally bankrupt—which makes killing them all the easier.

While parochial altruism strongly defines Judeo-Christian morality, it flourishes in Islam. First, the rules of parochial altruism are declared bluntly in the following verse: “Muhammad is the messenger of Allah. And those with him are hard against the disbelievers and merciful among themselves” (Koran 48:29). But there are also texts that seem to police every angle of this arrangement. For one, much as Judeo-Christians strive to create unity and notional siblinghood, the Koran (and Muslim culture) repeats notional brotherhood successively, for example, “The Believers are but a single Brotherhood: So make peace and reconciliation between your two (contending) brothers; and fear Allah, that ye may receive Mercy” (Koran 49:10); “And hold fast, all of you together to the rope of Allah, and do not separate” (Koran 3:103). With the alliance of insiders thus established, the next step is to foment distrust of outsiders, which the Koran also does at great length. For example:

Let the believers not make friends with infidels in preference to the faithful—he that does this has nothing to hope for from God—except in self-defense. (Koran 3:28)

Believers do not make friends with any but your own people. They [outsiders] will spare no pains to corrupt you. They desire nothing but your ruin. (Koran 3:118)

Believers do not seek the friendship of the infidels and those who were given the Book before you [i.e., Jews and Christians], who have made your religion a jest and a pastime. (Koran 5:57)

You see many among them making friends with unbelievers. Evil is that to which their souls prompt them. They have incurred the wrath of God and shall endure eternal torment…. You will find that the most implacable of men in their enmity to the faithful are the Jews and the pagans, and that the nearest in affection to them are those who say, “We are Christians.” (Koran 5:80—82)

And the Jews say: Ezra is the son of Allah; and the Christians say: The Messiah is the son of Allah; these are the words of their mouths; they imitate the saying of those who disbelieved before; may Allah destroy them; how they are turned away! (Koran 9:30)

Now with the out-group defined as unbelievers, the dominant male God of Islam prescribes out-group enmity by advocating retribution and assault against them:

Such are those that are damned by their own sins. They shall drink scalding water and be sternly punished for their own belief. (Koran 6:70)

No sooner will their skins be consumed than We shall give them other skins, so that they may truly taste the scourge. God is mighty and wise. (Koran 4:56)

They shall sigh with remorse but shall never come out of the Fire. (Koran 2:167)

Slay them wherever you find them. (Koran 9:5)

As with the genocide described in Deuteronomy, burning someone alive repeatedly (if only by magically reanimating their cooked skin), forcing one's victim to drink scalding water, and ignoring pleas for mercy and forgiveness are all behaviors that if perpetrated on in-group members would be considered the morally incomprehensible and macabre acts of a psychopath, someone with unspeakable disregard for in-group rules.

But in the eyes of many religious followers, the very concept of morality is synonymous with adherence to religious edicts and practices, including those as vicious as the above. Further, from the perspective of a religious insider, religious morality often reflects a higher order of moral reasoning, an unalienable set of ethical precepts that are principally sound (and righteous, etc.). But, again, these morals do not survive much past the periphery of the religious in-group, a fact that would seem at odds with their imagined transcendence. This limitation plays a hugely important role in facilitating religious warfare. Recall that warfare—defined as cooperative killing of out-group members—is by definition collectively sanctioned by the in-group members engaging in it.


Some crimes, such as rape, murder, and theft, are prohibited by law in every country around the globe. Such behaviors are universally abhorrent and are punished accordingly. Civilized, conscientious people obey the rules of their society, but within every society are some individuals with a propensity for rule-breaking. Often these people commit heinous acts with a shocking lack of remorse or compassion, thus violating the cooperative rules of societies. Because these behaviors are statistically abnormal and cause suffering to others, they are often deemed clinically pathological. Antisocial personality (here used interchangeably with the terms sociopathy and psychopathy) is a diagnosis that captures this phenomenon.

A thorough accounting for the current diagnostic criteria for sociopathy is in order. Note particularly how these symptoms are socially oriented (as the name implies) and consider the implications for a society of cooperators. To be considered a sociopath, a person must exhibit the following:

(1) failure to conform to social norms with respect to lawful behaviors as indicated by repeatedly performing acts that are grounds for arrest;

(2) deceitfulness, as indicated by repeated lying, use of aliases, or conning others for personal profit or pleasure;

(3) impulsivity or failure to plan ahead;

(4) irritability and aggressiveness, as indicated by repeated physical fights or assaults;

(5) reckless disregard for safety of self or others;

(6) consistent irresponsibility, as indicated by repeated failure to sustain consistent work behavior or honor financial obligations;

(7) and a lack of remorse, as indicated by being indifferent to or rationalizing having hurt, mistreated, or stolen from another.36

Prisons are filled with people with this disorder, including serial killers, serial rapists, and con artists; unsurprisingly, this disorder is much overrepresented in males. There is an interdisciplinary body of evidence supporting the heritability of antisocial personality disorder,37 suggesting that sociopathic behaviors may have been selected for, particularly in the evolutionary past of our male ancestors. A hallmark of the disorder is engaging in social deception. In a classic paper on the sociobiology of sociopathy, Linda Mealey described sociopaths as:

individuals of a certain genotype, physiotype, and personality who are incapable of experiencing the secondary “social emotions” that normally contribute to behavioral motivation and inhibition; they fill the ecological niche described by game theorists as the “cheater strategy.”38

In other words, those with antisocial personality disorder are the ultimate cheaters. Not only are they prone to aggression but they also tend to perpetrate fraud, pretending to be cooperative under false pretenses, usually as a means to steal from others.

Stealing is not only considered pathological by the standard of the American Psychiatric Association, but also by the Abrahamic god. Through commandment number eight (though shall not steal), the Judeo-Christian god made it clear that stealing was a prohibited behavior. There are many other references in the Bible addressing the problem of stealing:

You shall not steal; you shall not deal falsely. (Lev. 19:11)

If a man steals an ox or a sheep and slaughters it or sells it, he must pay back five head of cattle for the ox and four sheep for the sheep. (Exod. 22:1)

The LORD hates dishonest scales but accurate weights find favor with Him. (Prov. 11:1)

Let him that stole steal no more: but rather let him labour, working with his hands the thing which is good, that he may have to give to him that needeth. (Eph. 4:28)

While these rules seem morally sensible, they are not in fact unconditional; if the rest of the Bible is any guide, they were meant only to pertain to the in-group, arguably as rules of reciprocity aimed at maintaining group cohesion and cooperation. As for the out-group—it is fair game. Biblical patriarchs, for instance, were known to steal from outsiders, and such stealing was encouraged by God, even if it meant slaughtering the victims:

Whenever David attacked an area, he did not leave a man or woman alive, but took sheep and cattle, donkeys and camels, and clothes. Then he returned to Achish. When Achish asked, “Where did you go raiding today?” David would say, “Against the Negev of Judah” or “Against the Negev of Jerahmeel” or “Against the Negev of the Kenites.” He did not leave a man or woman alive to be brought to Gath, for he thought, “They might inform on us and say, ’This is what David did.’” And such was his practice as long as he lived in Philistine territory. (1 Sam. 27:9—11)

In the following example, God gives Jericho to Joshua. Joshua steals all the valued possessions of the citizens of Jericho and commits genocide in the process:

Joshua said to the people, “Shout; for the LORD has given you the city. And the city and that is within it shall be devoted to the LORD for destruction…. But all silver and gold, and vessels of bronze and iron, are sacred to the LORD; they shall go into the treasury of the LORD.”…Then they utterly destroyed all in the city, both men, and women, young and old, oxen, sheep, and asses, with the edge of the sword…. And they burned the city with fire, and all within it; only the silver and gold, and the vessels of bronze and iron, they put into the treasury of the house of the LORD…. So the Lord was with Joshua, and his fame spread throughout the land. (Josh. 6:16—27)

The Koran also prohibits stealing in no uncertain terms—“Now as for the man who steals and the woman who steals, cut off the hand of either of them in requital for what they have wrought, as a deterrent ordained by God: for God is almighty, wise” (Koran 5:38)—but it also holds the same double standard. Mohammed funded his very rise to power with wealth he sequestered from raiding desert caravans. He personally took part in twenty-seven raids, which are widely regarded by historians as having been offensive in nature (rather than in self-defense) and undertaken as a means to acquire resources.39 The spread of Islam would likely not have taken place without Mohammed's raids.

The ethical insularity of in-group logic, whether in religious or secular efforts to steal resources, seems to play out unconsciously, which evolutionary psychologists would regard as a sign of its evolved design. The same is true for killing.


In the summer of 1969, Charles Manson ordered his followers to murder the inhabitants of a Los Angeles suburban home, saying “totally destroy everyone in it, as gruesome as you can.” Sharon Tate, a young Hollywood actress, was among the victims. Though Tate was pregnant at the time and desperately pleaded for the life of her unborn child, she was stabbed sixteen times. With the blood of Tate's corpse, Manson's disciples smeared the word “Pig” on the front door of the home.40 Ted Bundy was another infamous sociopath who raped and killed at least thirty women, twelve of whom he decapitated. Ahmad Suradji was an Indonesian serial killer who murdered forty-two women and young girls. He was known for burying his victim up to their waists before strangling them with a cable. The list goes on, but I will not belabor the point.

If in reading these accounts you get cold chills up your spine or a sense of moral disgust, your moral compass is working properly. Acts so vile and so lacking in remorse, whether committed personally or ordered by a dominant individual, violate a code of morality so completely that in many societies these criminals are deemed undeserving of life—two of these men were executed with much support from the societies in which their atrocities were committed. Clinically, the behaviors of these men are the quintessence of sociopathy.

But this diagnosis, this class of cheaters so universally abhorred by in-group members, may lose its horror when the acts are committed against the outsider, as the outsider often fails to benefit from the established moral codes underlying prohibitions against rape, murder, torture, and infanticide. Again, men don't require religion to dichotomize morality in this manner. But among religious institutions, which worldwide are considered pillars of morality, dichotomous morality is enunciated in the most basic of foundational credos. We saw this earlier in Teehan's observation that “thou shall not kill” really means “thou shall not murder those with whom you have cooperative agreements.” Hypocrisy then, it would seem, is another violation of the moral code applying only to in-group cooperators.

I argue that bias toward the in-group, and toward the dominance structures therein, are among the most deeply embedded and most dangerous characteristics of the human race. These traits underlie warfare, oppression, torture, and other cruelties and allow most humans to be incredibly skilled at moral hypocrisy, given the right in-group—out-group manipulation. Of self-righteous bias, David Livingstone Smith observes:

Self-deception lubricates the psychological machinery of slaughter, providing balm for an aching conscience. By pulling the wool over our own eyes and colluding with our own deception, we can continue to think of ourselves as compassionate, moral and pious people, while endorsing or participating in the wholesale destruction of other human beings.41

While in-group bias is clearly a quality to which humans are already prone, religion too often legitimizes and encourages it in action. The Judeo-Christian god, for example, directly orders that compassion for fellow humans be suspended, perhaps as a means to lift the brakes on intraspecies violence (italics mine):

And thou shalt consume all the people which the LORD thy God shall deliver thee; thine eye shall have no pity upon them. (Deut. 7:16)

With compassion removed from the equation, all manner of killing is possible. Genocide, for instance, is not uncommon in the Bible. Through Moses, God helps Joshua decimate twenty kingdoms (as estimated by religious critic Steve Wells)42 and give the spoils to the Israelites:

He totally destroyed them, as Moses the servant of the LORD had commanded…. The Israelites carried off for themselves all the plunder and livestock of these cities, but all the people they put to the sword until they completely destroyed them, not sparing anyone that breathed. (Josh.11:12, 14)

Here is a snapshot of other acts of genocide committed on the order of God, reminiscent of the crimes of Manson and his disciples (killing men, women, and unborn children), only on a much greater scale:

Thus saith the LORD of hosts…go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass. (1 Sam. 15:2—3)

Genocide is truly one of the diseases of human existence, if only in its sheer capacity to cause human suffering. And yet scriptures praising genocide continue to be treated as holy texts in churches and cathedrals around the world because the killings are considered triumphs against evil, commanded as they were by a righteous god who is by his nature infallible.

The Crusades, too, were considered righteous campaigns in the era in which they were fought, even recalled centuries later by world leaders such as George W. Bush who called for a “crusade on terror.” In reality, the Crusades were a long series of battles with mindboggling destruction—much of it by Christians. As one example, on July 15, 1099, about twelve thousand crusaders descended upon Jerusalem, breeched the city's walls, and tore the city apart. The eyewitness account of priest Raymond of Aguilers should remind us of the strong in-group bias pervading human morality:

Wonderful things were to be seen. Numbers of the Saracens were beheaded…others were shot with arrows, or forced to jump from the towers; others were tortured for several days and then burned in flames. In the streets were seen piles of heads and hands and feet. One rode about everywhere amid the corpses of men and horses.43

Other documents wrote of women being raped and stabbed, suckling babies being wrenched from their mother's breasts and slammed against posts or thrown over the walls. As many as seventy thousand Muslims were killed, and the Jews who remained were thrown into a synagogue and torched alive.43

Islam is just as guilty of reverse logic on killing when it concerns the out-group, and the Koran seems ripe with passages that recount unspeakable acts in the name of religion. But first, as in like passages of the Judeo-Christian Bible, compassion must be set aside:

Be not weary and faint-hearted, crying for peace, when ye should be uppermost [have the upper hand] for Allah is with you. (Koran 47:35)

With this out of the way, all violence becomes possible:

I will cast terror into the hearts of those who disbelieve. Therefore strike off their heads and strike off every fingertip of them. (Koran 8:12)

The punishment of those who wage war against Allah and His messenger and strive to make mischief in the land is only this, that they should be murdered or crucified or their hands and their feet should be cut off on opposite sides or they should be imprisoned; this shall be as a disgrace for them in this world, and in the hereafter they shall have a grievous chastisement. (Koran 5:33)

If this kind of religion-inspired brutality simply reflected the sensibilities of a bygone era, a set of moral perspectives that we have matured out of since the biblical age, that would be one thing, but acts of remorseless killing or torture or mutilation in the name of religion are not confined only to the Abrahamic faiths, or to the ages of Abraham, Jesus, or Mohammed. In 2002, for instance, Hindu mobs in Gujarat, India, descended upon the Muslim out-group that lived there:

Mothers were skewered on swords as their children watched. Young women were stripped and raped in broad daylight, then doused with kerosene and set on fire. A pregnant woman's belly was slit open, her fetus raised skyward on the tip of a sword and then tossed onto one of the fires that blazed across the city.44

The mob rampaged through the Muslim neighborhood, stealing, raping, and burning 124 Muslims alive. These chilling acts bear the marks of primate territorialism, in-group loyalty, alliance with the alpha, and primate displays of dominance. The Hindu mob's atrocities were reportedly linked to a previous attack on a train car filled with activists from Vishva Hindu Parishad (the World Hindu Council). As the story goes, an ancient sixteenth-century Mosque was demolished to make room for a Hindu temple dedicated to the god Ram (a male supreme being and warlord). Stirred by their recent campaigning for construction of the temple, the council members rushed from the train, attempted to force a Muslim vendor to say “Hail Ram,” pulled his beard (we will discuss the evolutionary significance of beards in the next chapter), and beat him when he refused. Muslim mobs retaliated, attacking the train with stones, setting it on fire, and killing fifty-nine people. Most of the victims on the train were reportedly women and children. People operating under the rules of in-group loyalty and commitment are generally shocked by such acts of femicide and infanticide, though men feel much less obligation to see such actions as immoral when they are committed against the enemy.

For the best example of the double standard in religious killing, we must look to the Judeo-Christian god himself. The god of the Bible—while killing for reasons defensible by the standards of in-group morality—murders in the manner of the most remorseless sociopathic killer. In his book Drunk With Blood: God's Killings in the Bible, Steve Wells highlights the caprice of God's killings: “God buries the opposing party alive along with their families” (Num. 16:34); “God burns 250 alive for burning incense” (Num. 16:35); “God killed 14,700 for complaining about God's killings” (Num. 16:49).45 One could—and Wells does—populate many pages with similar examples. However, what is perhaps most revealing in Wells's work is his simple summation of all the killings numerated throughout the Bible, including the number attributed to God versus those attributed to Satan. God, it turns out, is directly described as killing two and a half million people—2,475,636 to be precise. Satan is listed as killing ten. When Wells includes estimates accounting for the probable size of towns and communities God is purported to have decimated, God killed over 24 million people (24,643,205)—and many were his own followers—while Satan killed sixty.46 Needless to say, as God's enemy, the devil is seen as vile, pernicious, and dangerous—the very epitome of evil. Yet the Christian god is seen as a righteous god, and his killings are censored, rationalized away, ignored, or simply disappear behind a wall of denial. But the most important point is that God didn't commit any of these killings. When not a result of mindless forces of nature (such as earthquakes, floods, disease), the killings were committed by the hands of men, as they always are in religious warfare.

The stated reason for religious (and secular) warfare often involves some sort of higher ideal. Such ideals give the religious moral justification for the acts they commit in the fields of battle. However, the engines of religious war, like other kinds of organized violence, have been forged from ancient patterns of primate alliance-making and shaped by the rules of in-group cooperation. God is given to play a central role, evoking the dominant males of our evolutionary history in a manner that is deeply intuitive to our evolved psychology. Nonhuman primates are obsessed with dominants and spend a disproportionate amount of time and energy trying to make alliances with them. Human primates are little different, and with God represented as the most powerful male in the universe, the religious experience an especially powerful pull to form alliances with him. To do so they make costly signals of cooperation, often by attacking his would-be enemies. They also make alliance by defending God's word, sometimes through extreme measures such as killing. At other times, alliance is made by offering sacrifice to God. The worst of these offerings come in the form of “food” from human corpses and blood. In all, following the patterns of primate alliance-making with God has wrought terrible human suffering.

It is clear how coming together under the aegis of deeply intuitive religious ideologies could have benefitted our ancestors, particularly those living in the brutal days during which the Abrahamic religions arose, when the need to rally under dominant males was a matter of life and death. However, like many aspects of our evolved psychology, becoming aware of our unconscious predispositions enables us to choose to abandon those which amplify human suffering. Once the biological mechanisms underlying moral hypocrisy are recognized, it may make it easier to disallow sociopathic behavior, even when it occurs outside the boundaries of our immediate circle. This should also be true for religious circles and should render questionable any “higher” ideals fomenting religious violence. Loyalty to a particular dominant male god should perhaps bear the most scrutiny, as such loyalty is often the ultimate mark of religious in-group identity and the progenitor of the most merciless atrocities against the out-group.