The Roman State and Genetic Pacification

Did the human “domestication” inherent in civilized society cause genetic changes? Could that partially account for the acceptance of Christianity and the rise of the more submissive male? Could this have applied not only to Rome, but to all advanced European societies?


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

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

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 Romana allowed 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

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

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. …

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Source: read the full article at Research Gate

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Andover 8
Andover 8
31 January, 2018 10:20 pm

In reading history, there seems to be something much more civilized in two men stepping outside and settling a situation immediately, rather than dragging something through the courts for years, which can be its own kind of cruel and unusual punishment, especially where murder is concerned. In reading the Norse sagas, it’s clear they definitely operated under a system of immediate and personal justice. It might be called the wild west of the North. Even as late as the 1830’s in the U.S., duels were still happening. Andrew Jackson was in a few, barely surviving one. Yes, there is much to be admired in a man who takes sh*t from no one, has a sense of honor and knows how to defend it, and understands that violence is sacred and… Read more »

Diaethria Anna Anna
Diaethria Anna Anna
Reply to  Andover 8
9 October, 2021 1:36 am

In “Table Talk” Hitler says one of his journalists was killed in a duel over an insult toward their wife. I take that to mean dueling was still going on in Weimar Germany.