The Unique Human Capacity for War

One characteristic that sets humans apart from other animals is the capability to organize sustained warfare against members of their own species, a troubling fact that connects to the problem of PTSD, says Michael Brenner.

By Michael Brenner

The question “why war?” has long inspired scholars to seek answers in human nature. Their findings invariably have been ambiguous and judgments inconclusive. While it is easy to make the case that humans do engage in violent behavior as part of their nature, there is no basis for arguing that they are “killers.” There is no propensity to kill fellow humans that prevails over other forms of social inter-action.

Moreover, the development of organized societies as their standard habitat introduces cultural and structural elements that produce a wide range of behavioral patterns. Simply put, humans in groups are capable of conducting their collective affairs just about any manner imaginable – as illustrated abundantly by the historical record.

Trench warfare during World War I.

Trench warfare during World War I.

The effort to make sense of the connections between human nature and the phenomenon of war is getting renewed attention thanks to the rising interest in understanding Post Traumatic Stress Syndrome or PTSS (also called Post Traumatic Stress Disorder or PTSD). That interest, in turn, reflects growing awareness that there is nothing new about PTSS or PTSD except that now we are chary about accepting cavalier explanations ascribing it to character flaws or the contradictions of socio-cultural conditioning.

One place to begin an exercise intended to unravel the puzzle is recognition that individual violence and war are not the same thing. All of God’s creatures engage in violence; only homo sapiens war with each other. Our ability to do so derives from the enlarged capacity of our brains that enables us to abstract, to conceptualize, to use language and – thereby – to organize joint enterprises sustained over time. Those activities engage the frontal lobes of the cerebral cortex.

That is why homo sapiens are the only species that fights wars. Other mammals, even primates, don’t have the mental ability to give meaning to others and events or to set objectives  – two preconditions for war. Their violent encounters have two distinguishing characteristics: a) all are brief, b) and all are keyed to matters of survival. They fight for food, for mates, and for territory, which is tied to the first two.

Reptilian Brain

Essentially, it is only the Reptilian brain (or R-complex brain) that is involved in those fights with a small contribution from the next evolutionary level of mental function that allows for a measure of memory, cunning and coordinated hunting. Hence, the susceptibility to mental impairment doesn’t exist, and the limited duration of the violence doesn’t even generate the stress necessary to create such an impairment.

Photos of victims of the My Lai massacre in Vietnam galvanized public awareness about the barbarity of the war. (Photo taken by U. S. Army photographer Ronald L. Haeberle)

Photos of victims of the My Lai massacre in Vietnam galvanized public awareness about the barbarity of the war. (Photo taken by U. S. Army photographer Ronald L. Haeberle)

By contrast, there is a discrepancy between the evolved brain capabilities that make war possible, on the one hand, and our core physiology that is little different from that of other mammals, on the other. In other words, our greatly enhanced capacity for organized violence has far surpassed the rest of our psychosomatic apparatus. No wonder we are vulnerable to stress.

Military technology that permits fighting at a distance far from the battlefield, and from the enemy, partially avoids this contradiction generated by sustained physical combat. People who push buttons, though, encounter another contradiction. Their Reptilian brain is not engaged in combat even as their brain’s higher functions are activated in killing people.

That means that the conceptual awareness, which is uniquely human (and the basis of mental stress) must be handled without benefit of the hormones and other physiological responses sparked by the Reptilian brain. They are dormant because the person involved is not at grips with the tangible enemy. This helps to explain the cause of the PTSD that some of the drone operators experience when snug in a Nevada cubicle.

At the other extreme, for soldiers engaged in hand-to-hand combat, the psychosomatic condition is comparable to that of other mammals – it is the Reptilian brain that engaged in the fighting. That probably was the experience on Saipan and Iwo Jima in World War II.

This analysis suggests that the prime question we should ask is not “why PTSD?” but rather “how is it that most humans are able to fight in wars without cracking up?

One answer is that the human propensity to abstract reality produces the ideologies, the religious beliefs, their symbolic representations, and thereby the objectification of the “other.” That permits communal mobilization, regimentation, and protracted war-fighting. They generate feelings able to override survival impulses – for most soldiers, for a certain period of time.

Organized Warfare

A complementary answer is that there is indeed always the lurking possibility that individual soldiers put in lethal situations will bolt. Bolt out of fear. Once under fire, the adrenaline et al kicks in, and that impulse may subside. It may also rise once again after experiencing a long string of such episodes.

President George W. Bush in a flight suit after landing on the USS Abraham Lincoln to give his "Mission Accomplished" speech about the Iraq War.

President George W. Bush in a flight suit after landing on the USS Abraham Lincoln to give his “Mission Accomplished” speech about the Iraq War on May 1, 2013.

Or, individuals cannot handle the accumulated stress – aggravated by the strain between the survival instinct to get the Hell out of there and the combination of conditioned loyalties/duties and bonding with one’s fellow “tribesmen.” Emotional dissonance ensues. That adds to the stresses that eventually can produce PTSD.

Which emotions prevail can be affected by the type of leadership provided by officers in the thick of things. Whether through example, inspiration or imposition an effective leader can get soldiers to take high-risk actions. The methods at their disposal vary from army to army. In the citizen armies of the United States or Great Britain during World War II, for example, there were limits on the coercive means available to officers.

It has been pointed out that up to a third of American infantry soldiers never, or rarely fired, their weapons at the enemy. That was due either to their impulse to hide in a ditch or behind a tree with their head down and/or to an aversion to killing at relatively close range a visible fellow human. That percentage probably went down around Bastogne or on Pacific Isles where the survival instinct took hold.

It often is remarked that for most of history, in most places, warriors moved in fixed step within serried ranks. That is explained, in military terms, as creating mass for both offense and defense. It also makes discipline much easier to maintain. The instrument for doing so was the threat of being killed by one’s officers (immediately or afterwards) for breaking ranks.

That practice continued right into the Twentieth Century, e.g. the Bolshevik commissars who patrolling behind the front lines shooting deserters or shirkers without inhibition. Surely, the ideal formation on strictly tactical military grounds was not to march across fields in brightly colored uniforms to be picked off by the enemy or shattered by cannon – as was the standard practice in the Seventeenth, Eighteenth and Nineteenth centuries.

The Victory of Horsemen

The drawback of that approach was demonstrated repeatedly over the centuries when the highly structured armies of great states were routed by horsemen from Central Asia. This occurred time after time: the Huns, the Seljuk Turks, the Mongols (mainly Turkish troops), Tamerlane, etc., etc. In fact, invading hordes of horsemen who operated with a fluidity and adaptability that gave them an enormous advantage, chalking up a streak of almost uninterrupted victories across the millennia.

Coffins of dead U.S. soldiers arriving at Dover Air Force Base in Delaware in 2006. (U.S. government photo)

Coffins of dead U.S. soldiers arriving at Dover Air Force Base in Delaware in 2006. (U.S. government photo)

The exceptions were some of their wars with Chinese dynasties, which were able to prevail by drawing on vast resources to marshal formidable armies – and also to build defensive fortifications exemplified by the Great Wall. Still, even Imperial China was overrun on four separate occasions.

Some might note other candidate “exceptions.” The most commonly referred to is the battle of Ain Jalut where the Crusaders entered into a tacit alliance with the Mamluks to defeat the Mongols in Syria. However, that was a case in which the invaders had been greatly diminished when their main force, led by Helegu, hastily left the Middle East to deal with a succession crisis back in Karakorum.

The other cited instance is the battle of the Catalaunian Plains near Chateaudun in modern-day France where the Huns were defeated by a coalition of Romans, Franks and Goths. That Hun army, though, was composed mainly of infantry drawn from what had become a sedentary population settled on the Hungarian plain.

But did these fierce horsemen of the Asian steppe suffer from PTSS. Any speculation should bear in mind that they were bred in a culture where killing and risking death in battle were taken to be what life was all about. That said, there probably were a few who did experience PTSS at some point in their wild perambulations across the continent.

What might their symptoms have been? How were they interpreted? Was the condition concealed? Perhaps the sufferers figured among those Mongols who settled in Afghanistan with their families in the Thirteenth Century rather than trek all the way back to Mongolia. They are the ancestors of today’s Hazara minority. Most settlers, though, probably just wearied of the tribulations they had endured year after year.

Michael Brenner is a professor of international affairs at the University of Pittsburgh. [email protected]

11 comments for “The Unique Human Capacity for War

  1. Peter Loeb
    October 22, 2016 at 07:22


    In major works of archeologist Thomas L. Thompson (eg THE MYTHIC PAST etc)
    he refers to the extreme polarity of men/women and the deity.(Thompson
    considers the Bible as literature, not history.) It is inevitably heaven or hell,
    following the path of righteousness (God) or complete destruction. And
    on and on. These views are reflected as well in many other ancient writings.

    The point being: This is the way we humans are taught to think. Good guys,
    bad guys. There is never a middle way.

    I would suggest that this method of perception of reality has become a
    quintessential part of our personality, whether we are talking about
    “American exceptionalism” or other policies involving war and peace.

    —Peter Loeb, Boston, MA, USA

  2. Zachary Smith
    October 21, 2016 at 22:12

    I’m going to give this essay a rating of “Close, But No Cigar”. Most of the jigsaw pieces are there, but they don’t quite fall into place. It’s my own opinion that humans fight wars because they’re presently the only species on the planet bright enough to do so. All the others engage in small scale territorial skirmishes. Some of those are a single individual (usually male) chasing out a rival, but other and brighter critters like the chimps do it in small groups.

    Rather than write my own essay, I’m going to recommend Dr. Brenner and others locate a copy of this book:

    Like with other creatures, humans are territorial. We have evolved a brain large enough to effectively compete, and the level of that competition depends not wholly on our IQ scores, but how well we can cooperate. This process feeds on itself, for ever larger effective groups will beat out smaller ones nearly every time.

    At the end Mr. Bigelow remarked that it’s going to be touch-and-go as to whether or not we’ve evolved to the point where we can overcome our well developed ability to fight with such terrible effectiveness. If we haven’t, the thermonuclear weapons will prevail, and all will be lost.

    Given how well humanity is handling the equally grave threat of climate change, the prognosis of our evolved abilities being adequate to cope with such extinction threats is not a hopeful one.

  3. backwardsevolution
    October 21, 2016 at 21:37

    Good article.

  4. October 21, 2016 at 21:32

    Humans are capable (genetically) of both aggressive and peaceful behaviors. The vast majority of all behavior at any give time is peaceful. I estimate that 99% of all behavior everywhere at any time is peaceful or neutral. It’s the 1% that ruin it for the rest of us.

    I’ve come to believe that Einstein was right when he became a world federalist. He concluded that the way to end war was to form a world government with enforceable world law. Violence doesn’t totally go away, but the worst of it (nuclear war) can be eliminated as can most wars. Peace activists are looking to the Earth Constitution to replace the faltering UN Charter in order to establish a democratically elected World Parliament, a viable world judiciary system, and universal rights including the right to peace. This is the Earth Federation. The Earth Constitution is ready to go. War and nuclear weapons become world crimes — against the law.

    • Zachary Smith
      October 21, 2016 at 21:51

      I agree with the ‘world government’ part, but the form of that government would take an awful lot of thought. Consider how thoroughly the US has subverted the UN for its own purposes. Consider also how the US Constitution has been turned into a vehicle to serve the Top .1% in this nation. You didn’t give a link to that Earth Constitution, so here it is:

      My first impression is that it’s WAY too brief – the word count is barely twice that of the US Constitution, and that’s not enough detail. Allowing the Court System of a government to dictate what the Constitution really means shows that the authors didn’t get it right in the first place.

  5. Zachary Smith
    October 21, 2016 at 21:22

    It has been pointed out that up to a third of American infantry soldiers never, or rarely fired, their weapons at the enemy.

    It has also been pointed out that the fellow who originated this nonsense was a fraud.

    IMO the story gained traction because us Americans are so darned exceptional. That’s something I was taught all my life, and swallowed the story hook, line, and sinker. And why not? Everybody everywhere wants to believe some version of this. If I’m living in a mud hut at the moment, at least I can point to a Golden Age when my bunch was top dog in the region. Failing that, someday God is going to make us great. Any time now…

  6. F. G. Sanford
    October 21, 2016 at 14:12

    Language and abstraction…per my October 10 comment under Dr. Davidsn’s article. The roots of some of human collective violence may have parallels in primate collective behavior, but it takes language, the subsequent abstracting process and the ability to share the imaginary doctrines based on abstract – often mythological, fanciful, delusional or even psychotic – ideas that characterizes human violence. Not every culture does it, suggesting it is not innate. The cultures that do it in a ritualized format have been demonstrated to do it in a way that maintains an ecological balance with the subsistence economy – like the ritual warfare based on wild pig hunting among indigenous South American tribes. The warfare only gets deadly when there aren’t enough pigs to go around. Unfortunately for us, we do it in a decidedly “non-survivalistic” way. Ours is not an ecologically, economically or biologically sustainable approach. We suffer from cultural psychosis induced by linguistically mediated pathological abstractions…such as Christianity, Islam, Judaism, capitalism, communism, exceptionalism, patriotism, racism, sexism…and all the other isms and itys. They’re all imaginary and delusional, folks, and our politicians are getting ready to prove they are also capable of producing mass extinction. Keep it up, and see if I’m wrong.

  7. October 21, 2016 at 13:46

    I like your caring perspective on the topic. I would like to propose a few extra ingredients. PTSD is not a disorder nor a cause of the problem. Those people exist to show the rest of us that something is very wrong.

    It is tempting to fall for the cultural trap where humans are assumed to be more important than anything but it is just that: a logic trap.

    The reality is that previous wars and efforts towards dramatically increased our precarious toxic garbage dumping habit. After each of our so called wars we’ve dumped such amazing amounts of toxic crap in the ocean that life expectancy for all life on this world is nothing short of wishful thinking. Air pollution and dumps on land aside.

    The only excuse to have nuclear reactors is in having the public pay for military grade refinement. Not officially of course but we can all do the numbers and we can all see how the equation is publicly made in the context of Iranian reactors.

    These reactors also work like a bomb strapped on the back of society. A tiny bombardment (or not even that) triggers a giant cloud of pure indiscriminate death.

    Why did we condition the general public to go into a rage of fury when someone proposes or claims an engine running on water or a reactor powered by permanent magnets? Why are so called scientific journals not interested in these things?

    The answer is simple and obvious: We classify all advanced technology for military purposes. In every country in the world we have teams of people specially hired to review such things. The inventor is either suicided, disappeared or (more recently) made to shut up about it.

    The usual post purchase rationalization is that no secrets can be kept on this world because secrets would always leak out. This is only partially true, those willing to look can find a ton of things and salvage little scraps of documentation. But when one seeks commercialization the show is quick to end.

    You have to envision tanks and gun boats that never run out of fuel, launchers that can fire any type of projectiles without the need for gun powder and 5$ rockets made of plastic tubes filled with water that in their most primitive implementation instantly expand 2000 times.

    If you believe such things to exist is irrelevant. All that matters is to keep such technology out of the hands of the “enemy”. Your believes should therefore be based on military ability to keep classified military technology secret.

    Humans in general have an incredible gift for guessing if they are trained on the right data set. History has shown that people guessing if a technology is possible or not will have as strong a tendency to guess negatively as a tendency to get it wrong. Skepticism all the way to the guy who actually invented it. You cant guess what is kept from you any more than you can guess what I ate for breakfast.

    But in the rare case something does come out you know there to be an enormous energy industry that can spend any amount of money to stop anything that challenges it. They can prevent anyone (except the military) from developing things.

    It isn’t that some exotic technology is kept from us but that all sufficiently advanced technology can be used for war. Developing dynamite for mining purposes is laughably naive.

    You may call it a model but the way I see it we’ve successfully created living entities. They are not non-corporeal beings, they exist out of large swarms of humans who like cells make up their body. Each cell has its purpose, the moment one doesn’t behave as desired its immune-system deals with the issue. You get a strictly defined job description, the moment you are unwilling to follow the written orders (your career) you are out and a new cell takes your place. Being a cell in a foot doesn’t mean you control the direction of locomotion.

    These entities might be very special creatures, their wars are simply animal fights.

    The solution becomes quite simple, we have to organize humanity into a creature that shares our values. It must be a big monstrosity intimidating enough to force the others into obedience. Big enough to only have to show its teeth and claws.

    And it cant be a country, those are as easy to burn as tissue paper.

    It has to start like little seeds in the back of our collective head then spontaneously convert to its ultimate form. All you have to do is read this comment and not do anything besides from having the thought live on.

    There are no forms to fill out, no demonstrations to show up at, no rocks to throw.

    Just look at the war victims of all kinds and do your thing.


  8. Dan Kuhn
    October 21, 2016 at 12:22

    Really good article.

  9. Bill Bodden
    October 21, 2016 at 12:19

    One of the interesting aspects of waging war and participating in the slaughter of other human beings is that PTSD seems only to afflict the military personnel on the front lines. People in the upper echelons of government and the military who initiate the wars and who should be the most guilt-ridden seem to be rarely affected. Presumably, to these truly barbaric people war is an abstract concept divorced from the barbarism that is the real face of war.

    • Alfred
      October 25, 2016 at 04:58

      Psychopaths do not get PTSD. Plenty of those in government and in the upper reaches of the military.

      “Political Ponerology (A Science on the Nature of Evil Adjusted for Political Purposes) ”

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