Violence in Ancient Rome: Behavioral and Ideological Evolution

Inside Rome’s Colosseum visitors can view the chambers that once held animals and contenders below the arena floor. / Photo by Senior Airman Alex Wieman, Wikimedia  Commons

The Roman state imposed a behavioral change that would over time alter the mix of genotypes, thus facilitating a subsequent ideological change.

By Dr. Peter Frost
Professor of Anthropology
Université Laval


Over the last 10,000 years, the human genome has changed at an accelerating rate. The change seems to reflect adaptations to new social environments, including the rise of the State and its monopoly on violence. State societies punish young men who act violently on their own initiative. In contrast, non-State societies usually reward such behavior with success, including reproductive success. Thus, given the moderate to high heritability of male aggressiveness, the State tends to remove violent predispositions from the gene pool while favoring tendencies toward peacefulness and submission. This perspective is applied here to the Roman state, specifically its long-term effort to pacify the general population. By imperial times, this effort had succeeded so well that the Romans saw themselves as being inherently less violent than the “barbarians” beyond their borders. By creating a pacified and submissive population, the empire also became conducive to the spread of Christianity—a religion of peace and submission. In sum, the Roman state imposed a behavioral change that would over time alter the mix of genotypes, thus facilitating a subsequent ideological change.


Natural selection has altered at least 7% of our genome over the last 40 thousand years. And it has been doing so at an accelerating rate, particularly after agriculture replaced hunting and gathering less than ten thousand years ago. At that time, the rate of genetic change may have risen over a hundred-fold (Hawks, Wang, Cochran, Harpending, and Moyzis, 2007).

By then, our species had colonized almost every biome on the planet: savanna, tropical rain forest, temperate woodland, boreal forest, and arctic tundra. It was not because we were adapting to new ecological environments that genetic change sped up. Rather, the cause was a proliferation of new social environments.

Many of these new social environments limited male behavior, particularly violent behavior. Previously, men could use violence more freely for self-advancement, notably to attract women and to sire children. This is still the path to male reproductive success among the Yanomamö, a horticulturalist people of Amazonia, among whom significantly more children are fathered by men who have committed homicide than by those who have not (Chagnon, 1988). Among the Ache, a hunter-gatherer people of Paraguay, “homicidal” men do not have more offspring but more of their offspring survive, either because strong fathers better protect their children or because some other factor makes both father and offspring healthier than average (Hill and Magdalena Hurtado, 1996, p. 445).

This situation reversed with the rise of State societies. Over circumscribed territories, power fell into the hands of a few “big men”, often only one, and violence became a privileged instrument of power. In such societies, reproductive success required compliance with the State, including its monopoly on violence. Successful men tended to have higher thresholds for violent behavior when acting on their own and relatively lower ones when acting under the command of authority (Milgram, 1974).

Initially, men complied by changing their behavior within the limits of phenotypic plasticity. This shift in the mean phenotype created a more peaceful society where violent males were less often imitated, celebrated, and accommodated. The more placid males were now the ones who enjoyed reproductive success, the result being a parallel shift in the mean genotype. In sum, once the State began to enforce its monopoly on violence, it favored not only certain phenotypes but also, indirectly, certain genotypes. Cultural evolution led the way for biological evolution, a process called Baldwinian selection.

Such selection was possible because male aggressiveness is moderately to strongly heritable. A heritability of 40% is suggested by a meta-analysis of 51 twin and adoption studies (Rhee and Waldman, 2002). A later twin study indicates a heritability of 96%, the subjects being 9–10 year-olds from diverse ethnic backgrounds (Baker, Jacobson, Raine, Lozano, and Bezdjian, 2007). This higher figure reflects the closer ages of the subjects and the use of a panel of evaluators to rate each of them. According to the latest twin study, heritability is 40% when the twins have different evaluators and 69% when they have the same evaluator (Barker, et al., 2009).

The historical economist Gregory Clark argues that this kind of behavioral selection shaped the English population. Once central authority had become established, male homicide fell steadily from the twelfth century to the early nineteenth. Meanwhile, there was a parallel decline in blood sports and other forms of exhibitionist violence (cock fighting, bear and bull baiting, public executions) that nonetheless remained legal throughout this period. Clark ascribes the behavioral change to the reproductive success of upper- and middle-class individuals who differed statistically in temperament from the much larger lower class. Although they were initially a small minority in medieval England, their descendants grew in number and gradually replaced the lower class through downward mobility. By the nineteenth century, such lineages accounted for most of the English population (Clark, 2007, pp. 124–129, 182–183; Clark, 2009). They now had the numbers to make their behavioral mean the norm for English society.

Formation of the Roman State

Roman bandits gambling / Creative Commons

Like its English counterpart, the Roman state created a central authority, monopolized the use of violence, expanded through military conquest, and enjoyed lengthy periods of internal peace.

In the Roman view, the State emerged from a loose group of individuals called latrones (singular latro, usually translated by “bandits”) who commanded respect through their charisma, access to prized resources, and ability to inflict violence (Shaw, 1984). To the extent that they gained control over a population and its territory, they also gained a stake in its well-being and ceased to be purely parasitic. An incipient state would take shape. As Augustine wrote in the fifth century:

And so if justice is left out, what are kingdoms except great robber bands? For what are robber bands except little kingdoms? The band also is a group of men governed by the orders of a leader, bound by a social compact, and its booty is divided according to a law agreed upon. If by repeatedly adding desperate men this plague grows to the point where it holds territory and establishes a fixed seat, seizes cities and subdues peoples, then it more conspicuously assumes the name of kingdom … [Augustine. De civitate dei 4.4]

Just as yesterday’s bandits could become tomorrow’s monarchs, the reverse was also true. Following a struggle for succession, the defeated factions would lose not only their legitimacy but also their sources of pay and provisioning. Many would turn to brigandage to support themselves (Shaw, 1984, p. 30).

The ‘Pax Romana’

Roman Relief depicting Gladiators in the arena, with lions / Utah State University, Creative Commons

The Roman state was supposedly founded by two bandit brothers, Romulus and Remus [Livy. 1.4.9, 1.5.4]. The next six centuries saw it expand from a small core to the limits of the Mediterranean world. As conquest gave way to pacification, the State sought to change the behavior of the newly conquered and even their character:

By humanitas the Romans meant two things: the adoption of the customs and the value system of the Roman people and material prosperity. The first was to be achieved by pacification, subjugation, and “Romanization”; the second was provided under the umbrella of the Pax Romana. By pacifying unruly elements, the Pax Romanaallowed for their integration into civilization itself: it promised urbanization, cultural refinement, and in some instances, even enfranchisement. (Parchami, 2009, p. 28)

The Pax Romana did not mean peace with rival empires. Nor did it really mean peace within the empire. Indeed, it meant regular use of State violence to quash revolts by slaves or the newly conquered and to fight brigands, bandits, pirates, and the like. Violence had become a state monopoly and any transgressors became enemies of the State.

Thus, pax did not exclude State violence, as Weinstock (1960) explains. “Pax, the root-noun of the verb pacisci, did not originally mean “peace” but a “pact” which ended a war and led to submission, friendship, or alliance.” With the establishment of empire, this meaning narrowed: “pax was no longer a pact among equals or peace but submission to Rome, just as pacare began to refer to conquest.” In short, pax was not the absence of war. It was the outcome of war. It was submission to a single authority, i.e., the State.

The Pax Romana was far more lasting and widespread than any previous pax. As Aristides, a second-century philosopher, observed: “Now total security, universal and clear to all, has been given to the earth itself and those who inhabit it” [Regarding Rome 104] (Parchami, 2009, p. 33). This pax did not simply benefit the elites by eliminating potential rivals. It made everyone wealthier by protecting life and property, by allowing traders to travel freely, and by keeping disputes between individuals or communities from erupting into violence.

But these benefits incurred a social contradiction. Whereas the State could achieve its ends violently, simple citizens had to achieve theirs peacefully. What was legitimate and even noble in one case was illegitimate and despicable in all the others. Initially, this situation seemed normal. It certainly seemed so to the ruling elites, particularly during the early years of empire when their subjects were mostly “objects”—the spoils of recent conquests. Nor did the general population see any hypocrisy. Were not the Gods themselves above the law?

A New Set of Selection Pressures

Mosaic of damnatio ad bestias from Zliten villa near Tripoli / Creative Commons

The Pax Romana punished those men who had previously enjoyed high reproductive fitness, i.e., the latrones. First, their access to resources, including women, was cut off through ostracism. They became non-persons without the rights of other lawbreakers. “The person stigmatized with the label of bandit did not have normal access to courts for judgements, a marriage was declared to be null and void if one of the partners was discovered to be a latro, and so on” (Shaw, 1984, pp. 22–23). The stigma even survived death, as indicated by Galen, a second-century physician:

On another occasion we saw the skeleton of a bandit lying on rising ground by the roadside. He had been killed by some traveller repelling his attack. None of the local inhabitants would bury him, but in their hatred of him were glad enough to see his body consumed by the birds which, in a couple of days, ate his flesh, leaving the skeleton as if for medical demonstration.[Galen. De anatomicis administrationibus 1.2] (Shaw, 1984, p. 5)

Second, the Roman state made violence against individuals an offense against the community. All citizens were given access to law courts and, more importantly, the courts could enforce their decisions (Liebeschuetz, 2006, p. 40). In the case of latrones, justice was summary and procedure minimal. Punishment likewise set them apart from other criminals, being typically a death sentence by one of the brutal methods allowed: throwing to the beasts, burning alive, and crucifixion (Shaw, 1984, p. 20).

Third, the State hunted down such people. In military districts, this function fell to the army (Shaw, 1984, p. 18). Indeed, the frontier defenses served not only to stop external enemies but also to police the semi-pacified local population (Shaw, 1984, p. 12). Areas under civil rule had stationes (guards, posts) and viatores (road patrols), but the bulk of policing was done by vigilantes in the pay of landowners or simply by private individuals. Here, the State mobilized the general population in the fight against latrones:

The laws also stress that it is the duty of private individuals to detect, to pursue and to betray bandits to local authorities. In the pursuit of this obligation the private individual was authorized to use force, to injure and even to kill such men. And they were also exempted, in doing this, from normal laws on iniuria and homicide. (Shaw, 1984, p. 19)

Pacified versus Unpacified Peoples

Barbarian invasion of Rome / Creative Commons

This legal environment stood in contrast to the one beyond the northern borders of the Roman state. “Barbarians” took the law into their own hands. Law courts did exist but their rulings had to be enforced by the aggrieved party. There was no State enforcement:

The injury was treated as an offense against the injured and his kin and it was left to the injured and/or his kin, not to the community, to compel the person who had caused the injury to give compensation for the damage he had inflicted. Unless the perpetrator or his kin paid compensation, it was the duty of the victim or his kin to take vengeance on the perpetrator or his kin. But the use of force was likely to start a chain of retaliation, in fact a feud. (Liebeschuetz, 2006, p. 39)

Feuding began easily and lasted indefinitely because of the readiness to meet violence with violence. For all these reasons, a private individual was much likelier to kill or be killed in barbarian society than under Roman administration (Liebeschuetz, 2006, p. 46).

This societal difference was commented on at the time. Barbarians were said to be inherently violent:

Both explicitly and implicitly late antique writers created a generic barbarian identity that was intimately associated with violent behavior. This was only consistent with a classical literary tradition in which barbarians were associated with several violence-related traits, including crudelitas (cruelty), feritas (wildness), immanitas(savagery), inhumanitas (inhumanity), impietas (impiety), ferocitas (ferocity), furor (fury), and discordia (discord). (Mathisen, 2006, p. 28)

Today, we might attribute such traits to external circumstances and not to internal predispositions. After all, these people were ancestral to today’s civilized Europeans. The picture is less clear if we read the Roman literature of the time.

Their violent nature also meant that barbarians were thought to be governed by their emotions rather than by their intellect. Seneca could claim that grief particularly affected “barbarians more than persons of a peaceful and learned people” and that barbarians were more likely to become angry. He also commented on barbarian lack of self-control: “Whom does one admire more than one who controls himself, who has himself under control? It is easier to rule barbarian nations and those impatient of alien rule than to contain and control one’s own mind.” Finally, Libanius suggested, “In this regard in particular I find the Greeks also to be superior to barbarians. The latter are akin to beasts in despising pity, while the Greeks are quick to pity and get over their wrath.” (Mathisen, 2006, p. 30)

Although barbarians were thought to be violent by nature, this predisposition was not understood in terms of selection for certain heritable traits. Instead, the cause was said to be the climate, i.e., if a country is too hot or too cold, its people will have a less balanced temperament (Goldenberg, 1999; Thompson, 1989, pp. 100–103). Furthermore, the Romans hoped to build a world empire and were thus inclined to believe in a single human nature.

Is it likely, then, that Romans and barbarians had differing temperaments because of differing selection pressures? To create and maintain a mean difference in temperament, such pressures need a barrier to the flow of individuals, and hence genes, between the two populations. Barbarians did enter the Roman world as mercenaries or foederati (allies who had to provide military forces for the emperor on demand), but this inflow was not substantial until the fourth century, when the army could no longer recruit enough soldiers within the empire (Swain and Edwards, 2004, pp. 156–157). Even as late as 350 AD, only 10–15% of the empire’s population seems to have been of external barbarian origin (Williams and Friell, 1994, pp. 37–38). Barbarians also entered the Roman world as slaves, but this source too seems to have been relatively minor. Slaves came mainly from two regions within the empire, one being Asia Minor and Syria and the other the lower Danube and the northern Black Sea coast (Gordon, 1924). Beginning around the time of Christ, there was a gradual increase in the flow of slaves from sub-Saharan Africa, particularly into the eastern provinces, but this inflow seems to have become substantial only in late antiquity (Goldenberg, 2003, pp. 131–138).

Thus, while the empire was not a closed system, there was relatively little gene flow from outside until the century before the fall of Rome. Long before then, observers were already commenting on the differing temperaments of Romans and barbarians.

Pacification and the Shift to a New Ideological Environment

Roman military illustration / Pennsylvania State University, Creative Commons

To maintain control, Rome had to preserve its martial values while instilling pacifism and submissiveness in its new subjects. This social contradiction would eventually become unsustainable.

First, the conquered assimilated into Roman society. Many became citizens and, as such, enjoyed certain rights and protections. Second, the State no longer had to be so violent with its subjects. Piracy largely disappeared following the battle of Actium in 31 BC. After the emperor Hadrian (117–138 AD), there were no new provinces to pacify and fewer rebellions in the older ones. The social climate had become so calm by the first century that Plutarch could write: “so far as peace is concerned the peoples have no need of statesmanship at present; for all war, both Greek and foreign, has been banished from among us and has disappeared” [Praecepta gerendae reipublicae 32].

Third, a profound behavioral change was spreading through the population. People were less willing to become soldiers than earlier generations had been, and many would pay gold or cut off their thumbs to avoid military service (Swain and Edwards, 2004, pp. 156–157; Williams and Friell, 1994, p. 37). A new kind of Roman was emerging, one less interested in violence and more submissive to authority. In fact, the new Romans were coming to see arrogant, aggressive conduct as wrong, even wicked. Yet this was how the Gods themselves behaved. Increasingly, people looked elsewhere for spiritual comfort.

Into this new behavioral environment came Christianity. Indeed, one of the early Church fathers, Origen (185–254 AD), explicitly linked the success of his faith to the Pax Romana:

God was preparing the nations for his teaching, that they might be under one Roman Emperor, so that the unfriendly attitude of the nations to one another, caused by the existence of a large number of kingdoms, might not make it more difficult for Jesus’ apostles to do what he commanded them when he said, “Go and teach all nations”. It is quite clear that Jesus was born during the reign of Augustus, the one who reduced to uniformity, so to speak, the many kingdoms on earth so that he had a single empire. It would have hindered Jesus’ teaching from being spread through the whole world if there had been many kingdoms, not only for the reasons just stated, but also because men everywhere would have been compelled to do military service and to fight in defence of their own land. This used to happen before the times of Augustus and even earlier still when a war was necessary, such as that between the Peloponnesians and the Athenians, and similarly in the case of the other nations which fought one another. Accordingly, how could this teaching, which preaches peace and does not even allow men to take vengeance on their enemies, have had any success unless the international situation had everywhere been changed and a milder spirit prevailed at the advent of Jesus? [Origen. Contra Celsum 2.30]

For the church father Eusebius writing in the fourth century, it “was not by mere human accident” but “of God’s arrangement” that the universal empire of peace came in time for the universal religion of peace (Mommsen, 1951, p. 361). Both strove to unify and pacify the world’s peoples:

Two great powers sprang up fully as out of one stream and they gave peace to all and brought all together to a state of friendship: the Roman empire, which from that time appeared as one kingdom, and the power of the Saviour of all, whose aid was at once extended to and established with everyone. [Eusebius. Theophania 3.2] (Mommsen, 1951, pp. 361–362)

Immediately after Augustus had established his sole rule, at the time of our Saviour’s appearance, the rule by the many became abolished among the Romans. And from that time to the present you cannot see, as before, cities at war with cities, nor nation fighting with nation, nor life being worn away in the confusion of everything. [Eusebius. Praeparatio Evangelica 1.4] (Mommsen, 1951, pp. 361)

This peace, however, was sustained by violence—a contradiction that Christians wished to end. Origen felt that Rome’s enemies were better fought through prayer [Contra Celsum 8.73]. Arnobius of Sicca thought it preferable to convert them. If everyone lent an ear to Christ’s commandments, the terms of peace treaties would be kept unbroken and “the whole world, long since having diverted the use of iron to more gentle pursuits, would be passing its days in the most placid tranquillity and would come together in wholesome harmony” [Arnobius, 1949 Adversus nationes 1.6].

Christians thus sought to demilitarize the concept of pax, by giving it a meaning closer to the one we now give to “peace” (Theissen, 1992).

Christianization of the Roman State

Colossal head of Constantine (4th century) / Photo by Katie Chao, Metropolitan Museum of Art, Wikimedia Commons

This question would no longer be semantic in the fourth century. In 313, Christianity was placed on a par with Roman paganism; then, gradually, it became the sole official religion. With its newfound power, the Church could now limit State violence.

The limits were spelled out by Ambrose, bishop of Milan (374–397). Christians could wage war only if it is defensive in nature, if no unfair advantage is taken of the enemy, and if mercy is shown to the defeated. Christians must nonetheless accept the inevitability of war with barbarians, who are to be treated as natural enemies (Swift, 1970, pp. 534–535). In all this, he was restating the concept of “just war” that pagan writers had earlier formulated.

Nonetheless, these limits now came from a higher spiritual authority that everyone had to obey, including the emperor. Barbarians would also be treated as being one with humankind, “sprung from the same womb of nature and bound by a single tie of blood” (Swift, 1970, p. 535). They were natural enemies only in a political sense. When the Visigoths revolted in 395, they did so not as barbarians but as mistreated foederati and, hence, as fellow Romans who deserve fair play.

Moreover, a true Christian could use violence only to defend others, and not for self-defense. This is made clear by Ambrose:

… a Christian man, a just and a wise man, ought never to try to save his own life at the cost of death to someone else. Indeed, even if he encounters an armed robber [latronem], he is not at liberty to hit back when his assailant hits him, lest in his anxiety to defend his own life he mar the sense of obligation he ought to feel towards the man. The principle given to us about this in the gospel records is crystal clear: “Put away your sword: for everyone who strikes with the sword shall perish by the sword.” Could any robber ever be more loathsome than the persecutor who had come to slay Christ? Yet Christ would not let anyone defend him by inflicting wounds on those who persecuted him: his desire was to heal all by being wounded himself. [Ambrose, 2001 De officiis 3.4.27]

Finally, Ambrose felt that the Church should remain aloof from war, however legitimate such action might be for individual Christians (Swift, 1970, pp. 537–538). This was a radical departure from pagan Rome, where religion had been key to rallying the people for war.

It is thus wrong to assume that Christianity ceased to be pacifist when it became the official religion. As Swift (1970, p. 538) observes, “if the realities of political and social development prevented Christians from maintaining the pacifist emphases of earlier centuries, pacifist arguments retained much of their old vigor.” There was likely a range of attitudes among Christians, with many interpreting their pacifism broadly. It is perhaps significant that when the Visigoths invaded Italy in 401 the Roman army responded not by conscripting civilians but by enrolling recently defeated barbarians (Liebeschuetz, 1993).

Nor can we assume that this pacifism was limited to the general population and did not penetrate the State administration. Ambrose himself had been governor of Northern Italy before becoming Bishop of Milan. Undoubtedly, other functionaries wished to bring their duties into line with Christian principles. This is apparent in a letter from a Roman magistrate who felt troubled by the death penalty and asked Ambrose for advice. In a long reply, the bishop defended this punishment, but then went on to argue that those who refrain from it deserve praise. In fact, most of his reply was an appeal for mercy on the grounds that the wrongdoer may end up repenting (Swift, 1970, p. 542).

Ambrose openly challenged State violence in 390 when a mob killed a Roman general in Thessalonica and thousands were slain in retaliation. The bishop denounced the massacre and forced the emperor, Theodosius I, to do public penance (Lenox-Conyngham, 2005). Through this gesture, what had once been simply the State’s prerogative—its monopoly on violence to ensure its monopoly of power—was raised to a moral principle that constrained not only the common people but also the State itself.

Interestingly, while Ambrose sought to limit State violence, he did not condemn the growing wave of violence by Christian individuals against pagan or Jewish places of worship. When a mob burned down a synagogue in 388, Theodosius I moved to have the wrongdoers punished and the synagogue rebuilt at the expense of the local bishop who had instigated the riot. This attempt at restitution was denounced by Ambrose in a long letter (Swift, 1970, p. 536).

The Church thus increasingly became a partner in the making of public policy, a partner that seemed to gain strength and vitality as the State declined. This was especially so in the western half of the empire, where the barbarian threat would weaken and ultimately overwhelm the Roman state.

The Christianized State and the Barbarian Threat

The statue of Victory on a coin issued under Augustus, matching its description by Prudentius. / Wikimedia Commons

The fourth century saw many barbarians enter the empire. They were let in largely out of expediency: they helped meet the army’s manpower needs and it was considered better to have them as allies on the inside than as enemies on the outside. Although some Romans feared the growing barbarian presence, others felt no cause for concern. The late pagan philosopher Themistius wrote in 383 that the Goths of Thrace “are now converting the iron from their swords and cuirasses into mattocks and scythes.” These sentiments were echoed in 417 by the Christian theologian Orosius: “the barbarians [in Spain], having forsworn their swords, have turned to the plow, and now nurture the surviving Romans as allies and friends” (Mathisen, 2006, p. 33).

During the same period, paganism lost all official status after one last clash with Christianity: the controversy over the Altar of Victory. “Victory” was a Roman goddess and incense was burnt at her altar whenever the Senate met. She represented not so much a divine being as a divine principle: the imperative to triumph over all enemies. The altar was removed in the mid-fourth century under Constantius II but then put back by Julian the Apostate. It was removed a second time, in 382, following an edict that made Christianity the sole official religion. Pagan senators pleaded for its return, arguing that it had helped make Rome a great empire. After the death of Valentinian II (392), the altar was restored on the condition of being treated as a work of art and not as an idol.

This controversy inspired the poet Prudentius to proclaim the true reason for the Roman Empire:

Shall I tell you, Roman, what cause it was that so exalted your labours, what it was that nursed your glory to such a height of fame that it has put rein and bridle on the world? God, wishing to bring into partnership peoples of different speech and realms of discordant manners, determined that all the civilised world should be harnessed to one ruling power … The untroubled harmony of human union wins his favour for the world; by division it drives Him away, with cruel warfare it makes Him wroth; it satisfies Him with the offering of peace and holds Him fast with quietness and brotherly love. [Prudentius. Contra Symmachum 2.583–597]

The poem portrays the empire as a woman, Roma, who dismisses fears of barbarian conquest:

Let those who din into my ears once more the story of past disasters and ancient sorrows observe that in your time I suffer such things no longer. No barbarian foe shatters my bars with his spear, nor with strange arms and dress and hair goes roving through my captured city, carrying off my young men to bondage across the Alps. [Prudentius. Contra Symmachum 2.690–95]

Those words were written in 403. Seven years later, the Visigoths entered Rome unopposed and sacked the city. The empire then imploded as one barbarian nation after another moved in. In 455, Rome was sacked by the Vandals, who likewise entered unopposed after promising not to kill anyone. With the return of piracy and brigandage, trade fell off, as did food production and maintenance of roads, ports, and aqueducts. Neither life nor property was safe. Urban life shriveled in the wake of disorder, pandemics, dwindling trade, and disruption of food provisioning. The weakened populace was then hit in the 6th and 7th centuries by plagues that killed three out of ten people (Seccombe, 1992, p. 57). So ended the Pax Romana.


Chi Rho monogramm on an altar. Marble, Comminges (Gascony, France), second half of the 12th century. From the Augustine convent of Montréjeau (Haute-Garonne, France). / Photo by Jastrow, Musée de Cluny – Musée national du Moyen Âge, Wikimedia Commons

Did Christianity destroy Rome? Or did Rome destroy itself by pacifying its subjects while more and more unpacified barbarians pressed on its borders? The answer probably lies somewhere in-between.

All State societies are prone to collapse because their existence depends on the State’s ability to repress individual and communal violence. Such repression permits a higher level of economic output and ultimately a larger population. It also alters the mix of behavioral genotypes by selecting out aggressiveness and selecting in submissiveness. If, however, the State falters, there will be a resurgence of both individual and communal violence. On the one hand, the State can no longer hold down the potential for violence that still exists among its citizenry. On the other, it can no longer keep out unpacified populations that lie beyond its borders. This new social environment reduces economic output, thus worsening the initial instability and causing a downward spiral that may spin out of control.

Nonetheless, when Rome faltered in the fifth century it did so as never before. Earlier, the third century had seen a similar crisis: civil war, foreign invasion, return of brigandage, and steep economic decline. Yet Rome fought its way back and reasserted its authority. There was no such response in the fifth century. Instead, the crisis was met with a strange mixture of complacency and willful naiveté.

We cannot understand this change without considering the ideology that now shaped the Roman worldview, i.e., all humans share the same potential for peaceful and submissive behavior. This was largely true among the pacified populations inside the empire’s borders. Outside, it was largely false. Tragically so.


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Originally published by Evolutionary Psychology 8:3 (07.01.2010), DOI:, under the terms of a Creative Commons Attribution-NonCommercial Unported 3.0 license.