War, what is it good for?

At half past six on a Tuesday morning the alarm clock goes off in a bedroom in Roswell, New Mexico, where twenty-eight-year-old Tiffany McGregor had been sleeping peacefully up till now. She sighs as she gets up to take a shower. While she is doing this her husband, a pilot called Aiden McGregor, comes home from his night shift. He opens the back door to their detached house and enters the kitchen in a buoyant mood. Then it happens: lying in wait for him are two vicious looking attackers.

'Hands up!' one calls, threateningly pointing his pistol at him. The other intruder stands by, his firearm loose in his hand. Aiden starts. It's a cowardly ambush. They are armed and he is not.

'Don't shoot!' he calls, somewhat panic-stricken. He raises his hands in fear.

'Give me one good reason,' says one of them.

Aiden thinks.

'Because I'm your father?'

'Anyone could say that,' a six-year old boy shouts, and fires his toy pistol repeatedly. A toddler aged four also begins to shoot. Aiden collapses onto the sofa, his hand covering the bleeding hole in his chest. He rolls onto the floor. His children roar with laughter: dad is bleeding to death on the carpet!

When Tiffany enters the room, she sighs.

'We've killed dad,' her eldest son yells. She heaves another sigh.

Ten minutes later the boys are playing a war game on their computer, as Aiden buries himself in the morning paper which is full of reports about global conflicts. The game his sons are playing is a first-person shooter, an action game in which the player views the world from a 'first-person perspective'. Aiden has no problem with this, but after a few minutes his wife thinks enough is enough.

'Just leave them to it,' Aiden says. 'It's just a game.'

'How was work?' she asks, placing a breakfast of hot pasta with ham in front of him.

'Busy', he says, and turns a page of his newspaper. Atrocities in Syria and Nigeria; attacks in Iraq and Afghanistan.

Aiden did indeed have a busy night with his squadron, stationed at an air base half an hour's drive away from Roswell. They were one man short due to flu, so the remaining pilots were twice as frantic in their container. His shift had started with the usual observations of Afghan Taliban freedom fighters. Aiden and his colleagues moni­tored possible targets and suspects on twelve computer screens, ventilators buzzing all the while. Joystick in hand and headphones on his head for radio contact with people he did not know personally, Aiden studied the screens. At times, he felt like a voyeur. He had seen a bearded man in a robe who, overcome by diarrhoea, had been squat­ting for thirty minutes in a remote field whilst feverishly trying to shoo away playing children. He saw how a boy in a black waistcoat was being reprimanded by adult men in turbans. A woman was pre­paring a meal near her stone house. Everything was being registered.

Once they had fixed on the targets, one of his squadron leaders had issued the command to use the MQ-9 Reaper, an unmanned war plane able to transport around 1700 kilos of bombs and rockets. The aircraft took off and soon the drone had approached 'Target X'. It had been Aiden who steered the Reaper to the location of the hit.

Together with a colleague he made sure they had locked onto the right person on their computer screen, and fired. Sixteen seconds later a 100,000 dollar AGM-114M Hellfire rocket saw to it that one particular Taliban fighter would never have diarrhoea again. Aiden and his immediate colleague high-fived each other. When, an hour later, Aiden left the airless container and stepped into the fresh morning air, the sun was up. It promised to be a beautiful day. Driving back home in his Chevrolet Impala Aiden looked forward to his pasta breakfast and his newspaper. 

Primitive hooligans

At the time of writing, thirty-one official wars are being fought globally. This includes the Casamance conflict in Senegal, the skir­mishes in Balochistan and the independence intifada in the Sahara. Many of these conflicts are unfamiliar to us – both in terms of the regions in which they are being fought, the people and the causes.

The list of battles from the past is even longer, almost inexhaustible; hundreds of wars were waged that have vanished from our collective memory. Who apart from historians knows anything about the Lelantine War between 710 and 650 bc? The War of the Eight Princes (291-306)? Or the Dutch-Hanseatic War of circa 1440?

War – one group going to battle against another – is of all times. Historians believe the actual Trojan War took place as early as dur­ing the thirteenth or twelfth century bc, but there are many indications that well before that large-scale conflicts were being fought. Excavations in Egypt, Germany and America have uncovered mass graves from prehistoric times that are indicative of human violence. The bashed skulls and bone fractures suggest injuries from axes and sharp arrowheads. The mass graves denote organised violence.

Wherever people lived in proximity, evidence has been found of manslaughter and murder. Archaeological research shows that in 90 to 95 per cent of societies, traces of warring have been found. Peaceful societies are an exception in human history. But what is clear is that, in ancestral times, war did not involve two armies facing each other to wipe each other out. Any organised violence was above all 'cowardly'. Our ancestors were good at surprise attacks, which anthropologists also refer to as raiding and ambush killings. This might involve a group of men invading a camp at night to kill one or several victims, then retreating in silence (so-called raiding). Or laying an ambush at a river. When someone from the other tribe came by, this person was either killed (in the case of a man), or kidnapped (a young woman). These techniques of raiding and ambushing are as old as humanity itself. Worse still: probably much older.

Science sees 'coalition aggression', or organised violence, as the foundation of human warfare. Battles with many hundreds of thou­sands of fatalities, trench wars and massacres have their deep origin in our social ability to form coalitions of two against one. In Chimpanzee Politics (1982), Frans de Waal showed how chimpanzee males from the lower orders form mutual alliances to deprive higher-placed males of power or even to kill them. Several cases are known in which the beta and gamma males conspire against the alpha to dethrone him, often with the consent of the group's females. This behaviour also occurs amongst other species, from lions, hyenas and dolphins to other primates. The ability to form coalitions, paradoxically, underlies our propensity for organised vio­lence. Or if we want to refine it: our social and sometimes altruistic instincts enable us to wage war. Social behaviour and violence go hand in hand in human evolution.

In chimpanzees, the acts of violence not only take place between fellow group members, they also have a territorial quality. Groups of chimpanzees live in their fixed habitats, which sometimes border the habitats of other chimpanzees. Biologists have observed different groups defend their territory against intruders who come and steal their food. In order to stake out their area, chimpanzees form 'border patrols' to guard their boundaries. Border control is not typically human.

At times, groups of chimpanzee males venture forth to look for undesirable strangers. And when they do come across one in their ter­ritory, the heat is on. Primatologists have recorded video images of groups of chimpanzees attacking an unfamiliar male. Screeching, they bite and tug at limbs and sexual organs until little is left of the intruder. These are brutal murders. From a human moral perspec­tive, the violence used by apes could be called distinctly cowardly. The chimpanzees only go on the offensive when they are in a clear major­ity (for example five to one) and a victory is pretty much guaranteed. They limit the danger to themselves to the absolute minimum. This cowardly behaviour is something we see regularly in the media on CCTV images from big cities, usually around bars and clubs. Groups of young men beat and kick a motionless victim lying on the ground. A wave of moral indignation sweeps the country – yet another victim of senseless violence – but nothing apelike is alien to us.

In chimpanzees there is an evolutionary objective behind killing neighbouring counterparts. Research shows that groups of males systematically annihilate males from other groups. A desired outcome is that this increasingly weakens their neighbours. Science calls this the imbalance of power effect: killing the nearby group's males in particular can create a power gap. When this gap becomes too big, the females of the weaker group will end up migrating to their stronger neighbours. As they have a larger territory they are better able to gather food and everyone within the group benefits: males, females and the young.

In the end, cowardly murders of individuals from other groups pay out in an evolutionary advantage for the aggressor. The chim­panzees' violence happens without rational consultation; the apes have no generals or field marshals who map out a strategy for them. They have no armaments and they do not have to abide by the Geneva Convention. And they do run a minimal risk of getting injured.

To the chimpanzee, who by and large lives in one fixed place, his territory is much more important to him than to his fellow-primate, the human. Our ancestors, the hunter-gatherers, migrated several times a year along centuries-old routes across the savannah, sharing their living environments in the process. They would often have testy relationships with neighbouring tribes, and agreements had to be made about access to watering holes and other natural resources. This was obviously a breeding ground for conflicts.

Violence was prevalent in ancestral times. In War Before Civilization archaeologist Lawrence H. Keeley describes how primi­tive humans used more or less the same tactics as chimpanzees. Raiding and ambush killings were the order of the day. People did not shrink from surprise attacks on their neighbours and during fes­tive peace talks, adversaries might be ambushed. All in all the death rate amongst adult men as a result of organised violence in prehis­tory is estimated to be 25 per cent. Within this overall figure, big differences between traditional societies can be discerned. Amongst a people called the Jivaro (in Puerto Rico) the figures is 60 per cent, but amongst the Gebusi (in Papua New Guinea) there were just 7 per cent of male war casualties. By comparison: in Europe and the US, the percentage of men dying as a result of warfare during the twenty-first century is less than 1 per cent. Evolutionary psychologist Steven Pinker argued in his book, The Better Angels of our Nature: Why Violence Has Declined, that this reduction in violence is one of the most significant achievements of modern society.

The male warrior effect

Three principal motives can be found for organised violence in ancestral times: status, sex and salary (the famous three Ss in which salary was obviously not paid out in money or property, because they did not exist yet, but in social capital, for example friendships or exchange partners). When a tribe's men managed to defeat their neighbours, the warriors who had contributed most to the victory were awarded a higher status than the lily-livered individuals who had been looking on from the sidelines. The more enemies a man had killed, the greater his standing, which, in turn, was good for his reproductive success. Or in everyday language: for how many children he had. Science calls this the male warrior effect, a deeply rooted tendency in men to increase their reproductive success by taking part in organised violence.

The anthropologist Napoleon Chagnon has spent years conducting field-research amongst the Yanomami, a bellicose hunter-gatherer tribe in the Amazon rainforest. The highest honour men can earn is awarded for killing members of other Yanomami tribes. These men even have a special name, the unokai. Chagnon studied how many women and children the unokai had compared to other adult males in the group and found a clear distinction: the more warlike the man, the more sex and offspring.

Waging war was also a means to rouse sexual curiosity in women. Attacking other groups and defending one's living environment can be seen as comparable to a peacock's tail. Where a male peacock tries to impress females with feather splendour which is as imposing as it is affected and costly, men in prehistory tried to impress women with their warmongering expertise. By entering into conflicts with competing peoples as a group, men were able to acquire a larger, more fertile living environment, with the attendant chance to reproduce more successfully than their less belligerent counterparts. This probably meant that sexual selection occurred on war-waging traits amongst men.

In addition, waging war is what biologists call a 'costly signal' (just like smoking, which we referred to earlier). The battle is often dangerous and requires a lot of strength and energy. The winners show that they are able to withstand these hardships and are there­fore in possession of a decent physique and good genes. They exude the ability to produce healthy offspring and to protect and maintain their family. Recently, one of us conducted research into the question of whether waging war does indeed increase a man's sexual attrac­tiveness. This study was done at universities in the UK and the Netherlands. Female students were asked to read scenarios about a fictional soldier and to indicate whether they found him sexually attractive. Some women read a story about a soldier called John. In the first scenario John had stayed in the UK or in the Netherlands, in the second he had fought in a mission in Afghanistan and in the third scenario he had additionally been awarded a medal for bravery. What turned out to be the case? John was considered the most attractive when he had fought and acquired the status of hero, whereas there was no difference in the outcome between the first two scenarios. A follow-on study showed that John was considered more attractive if he had been awarded a medal for an act of bravery in war than if he had been awarded a medal for having executed a heroic role dur­ing a natural disaster. These results are striking, as soldiers in the Netherlands and the UK do not enjoy a particularly high status, judging purely by their training or income. And yet soldiers – and especially war heroes – are desired by women, our research shows. This applied to both short-term and long-term relationships.

Thus, the increased chance of status and sex appears to offer men significant evolutionary advantages that amply make up for the dis­advantages. That is the foundation of the male warrior phenomenon. In A Theory of Warfare, evolutionary psychologists Tooby and Cosmides demonstrate how this works using game theory. When, as a warrior, you have a one in ten chance that you will die by fighting doubly hard in battle, but the chance of extra offspring increases by 20 per cent, this produces an evolutionary advantage. It is in your genetic interest, after all, to join in the battle, provided that, for the average warrior, the benefits outweigh the costs.

According to Tooby and Cosmides a 'veil of ignorance' must hang over who will live or die in battle (the German language has an equally splendid version of this term: 'Schleier des Nichtwissens'). Game theory makes clear that you will not join in the fight when your chance of dying is 100 per cent. In order to be able to account for suicide missions during times of war, we should not be looking at biology, but at culture and religion. Game theory also demonstrates that you are best off as a member of a large coalition. When one group decides to send two warriors to battle, while the neighbouring group sends five or six, the second group is bound to win, and each individual within the group is less likely to be killed or injured. A game theory analysis of war shows that early in history there must have been an arms race between groups in order to grow and to be able to mobilise as many warriors with as much weaponry as possible, because 'size matters!' The army parades we see on TV in Russia, China or North Korea are a modern manifestation of this arms race. With it, the leaders give off the signal 'Look how strong we are . . . so don't fuck with us!'

Finally, game theory also explains why if you fight extra hard, you can look forward to an extra-large reward. This was recently demonstrated in a study into the Turkana, a nomadic people in eastern Africa who periodically set out to steal cattle from other tribes. The researchers asked Turkana men and women to assess scenarios of men who did not take part in such raids, because they lacked courage or were physically incapable. The men lacking in courage were judged less positively than men who were unfit, and they were punished more as well.

So for men there are clear evolutionary advantages to waging war. The qualities needed to win a war are physical (fighting aggressively), as well as social (showing courage) and political (ability to form coalitions). This male warrior effect presupposes that an entire range of male qualities, both positive and negative, have come into being as a result of a long history of waging war. We even like to speculate that psychopathy – the inability to respond with empathy to others' suffering, a phenomenon particularly prevalent in men – has not been selected away as it offered some advantages on the battlefield. A psychopathic warrior can reach great heights in battle victories, so psychopaths are tolerated in society in peacetime.

War and sex are also directly linked in human evolutionary history. Since time immemorial warfare has provoked excesses such as rape and bride kidnapping. In A Natural History of Rape, biologists Randy Thornhill and anthropologist Craig T. Palmer explain that rape is a fairly common form of procreation amongst many animal species. In humans, rape has been socially very undesira­ble and extremely reprehensible behaviour for as long as we can remember. As we saw, ancestral rapists could expect public shame, exclusion and often physical punishment within their own group. But in war situations, norms and values are different. Without incurring reputational damage, men are able to claim the enemy's women in an attempt to spread their genes, without facing reprisals. This resembles the evolutionary 'sneaky fucker strategy' (which we encountered ear­lier): if you can get away with it, have a go. War gives men opportunities to have offspring without running too many risks of being avenged.

Another aspect of waging war that points to an ancient relationship with sex is the role of the penis. Flawed Giant, a biography of American president Lyndon B. Johnson, contains an interesting story about an informal chat between Johnson and critical journalists. They asked him why the Americans were staying in Vietnam and simply did not admit defeat. Johnson lost his patience. 'Do you really want to know?' he asked, when his listeners continued to interrogate him too harshly. At which point the president undid his fly, got his penis out and declared solemnly: 'This is why.'

Lyndon B. Johnson exposed himself and in so doing manifested: 'Look how resolute we are, we have not been beaten yet!' Typical leader, Johnson. Even now we are still looking for the kind of leaders people would have followed in ancestral times. We have a deep-seated natural preference for physically strong leaders who avail themselves of brawny language.

The connection between penises and warfare goes back into deep human history. A while ago, a note from the pharaoh Merenptah (1224–1214 bc) was found during excavations. In it, he related how big his victory had been over his Libyan enemies. Following a grim battle with a Libyan army, the pharaoh was said to have been handed victory spoils comprising 13,320 chopped-off penises (six from Libyan generals, 6,359 from Libyan soldiers and the remainder from foreign mercenaries). The symbolic value of the chopped-off penis lies in the message that the enemy will no longer be able to have children and therefore not be able to bring offspring into the world who, in future, would set upon your tribe. Although no archaeological evidence has been found for such behaviour – a penis does not fossilise – it seems plausible that these excesses occurred in early tribal combat.

The tribal brain

For many men, waging war was and is a life-changing experience. Much has been written about the romantic nature of warriorhood. The American philosopher Jesse Glenn Gray fought in World War II and wrote about his experiences as a member of a platoon in his book The Warriors: 'Many war veterans who are honest will admit [ . . . ] that the experience of communal effort in battle [ . . . ] has been a high point in their lives. Despite the horrors, the weariness, the grime, and the hatred, participation with others in the chances of battle had its unforgettable side, which they would not want to have missed.'

War is physically addictive because of the huge adrenaline rush. Waging war produces deep, lasting social bonds between warriors, who experience their group as a family. In interviews, fifty years after World War II, soldiers related that the band of brothers forged during the war was the best thing to have happened to them. This is how deep the impact of going to battle is. Researchers at the University of Amsterdam revealed this 'band of brothers' effect in a hormone study. They were primarily interested in the bonding hor­mone oxytocin. This hormone is released during intimate emotional experiences, such as breastfeeding a child or making love. But it is clearly also responsible for enhanced group bonding. In the study, in which only men took part, researchers placed a snuff of oxytocin or a placebo in the noses of test subjects. They then made them play a game in which they competed as a group against another one. The result? The oxytocin group worked better together, they trusted each other more and the members of the other group less. The researchers concluded that oxytocin had a 'tend and defend' effect.

Warfare separates the men from the boys: only true heroes dare to go through the dust. There are warriors who become paralysed with stress and abdicate themselves from hostilities. This behaviour is not appreciated by the group. In science terminology this is called a clas­sic free-rider problem: what to do with men who experience the benefits of warfare (higher status, greater chance of offspring), but meanwhile refuse battle? In order to correct this behaviour, soldiers are subject to a system of norms, rewards and humiliations, mecha­nisms that continue to operate amongst nomadic people like the Turkana we encountered earlier. In modern warfare this behaviour applies just as strongly. The fact that under modern military law deserters can be shot forthwith, stems from an ancient instinct to keep the group strong and punish cowards. The disgrace of being regarded a deserter has such a profound effect that there have been several court cases in the UK in which family members of deserters during World War II wanted their loved ones to be rehabilitated. This can also explain the resistance to LGBT people and women in the armed forces: love relationships between soldiers might happen at the expense of unity within a group.

In other words, there are numerous examples of how our brain, and especially the male brain, has been shaped by a long history of warfare, the traces of which are still visible today. We continue to have a, chiefly male, fascination for warfare. News reports invariably open with accounts about hostilities when somewhere in the world a conflict breaks out. We watch war movies, read books about war and commemorate wars from the recent past. Our entire culture is imbued with images and metaphors related to war, whether in sport ('let battle commence') or politics ('we beat them!'). As children, we play many war games, as adults, fire paintballs until we see red, green and purple; and simulate violent situations for hours on end on our computers. Warfare is ingrained in the human (read: male) psyche.

In present times traces of our tribal brain can still be found in men especially, who continue to be tribalistic. Men, much more so than women, support a sports club in a way that goes far deeper than pur­suing a hobby. Likewise, men will be much more motivated to operate as a group and to defend their group against other groups (for exam­ple when going out in the evening or onto the football pitch).

These gender differences can be illustrated neatly in a study. We asked men and women to choose their favourite colour and to explain why they chose it. A greater percentage of men (22 per cent) than women (8 per cent) chose a colour for tribal reasons ('I choose red because it is the colour of my favourite football club', 'I choose white because it is the colour of my religion'). Women largely referred to nature or fashion ('I choose red because it looks good on me', 'I choose blue because it is the colour of the sky'). In another study, one of us made men and women play a game in which they were able to keep money for themselves or invest it in a group fund.

On average, men were more inclined to keep the money for them­selves than women, unless we told them that their group had to compete against other groups. From that point onwards they began to invest more in the group fund.

The question might be asked whether the status-enhancing effects of fighting wars in prehistory also apply in modern times. One of us has conducted research amongst American Veterans, whereby we looked at the difference between those who had been awarded high honours and regular veterans. The proposition was that a soldier with a medal on their chest had more children than the inglorious one. This proved to be the case. The decorated servicemen had 3.2 children on average and the regular veterans 2.7. Men who have displayed courage on the battle field are evolutionarily one up. When the results of this study were reported at length in the media, one of us received an email from Gijs Tuinman, the youngest Dutch soldier to be awarded the Military William Order, with a question about what inspired us to research this topic. Our reply: evolutionary psychology presents many interesting hypotheses.

Someone who has behaved with valour on the battlefield in his younger years can, as time goes by, increasingly live on his past. Generals themselves no longer take part in battle, for instance, but they do enjoy a high status and a great deal of respect. Societies, men and women, are forever looking for people who have special qualities, and wars lend themselves pre-eminently to displaying these qualities. It is not for nothing that generals who fought in World War II later became presidents or prominent politicians (Churchill, De Gaulle, Eisenhower). On the battlefield, they had won their spurs. Again an example of a costly signal (a peacock's tail): people who distinguish themselves by doing something for the group show that they have moral, physical and mental capabilities to serve the common good.

This sacrifice is appreciated more than the efforts of politicians, for instance, and, regrettably for us, scientists or writers. The question as to how heroic someone has been in his (or her) military career is still crucial in American politics especially. During the election battle between George W. Bush and John Kerry, their individual military histories surfaced. Bush had ducked out of military service, but Kerry produced all kinds of tales about his heroic actions during the Vietnam War. Major doubts were cast over this and the American right-wing press tried all manner of tactics to knock the bottom out of his stories.

Many American politicians have a war record. A stirring example is the American politician Tammy Duckworth, who was born in Thailand in 1968. As an American army helicopter pilot she lost both her legs and part of her right arm in Iraq. Her valour and sacrifice made her a reliable candidate par excellence to make a bid for a political position. She became the first Asian American woman in Illinois to be elected to Congress and the first disabled woman in the House of Representatives.

Women and war

What is the situation regarding women in war? There is little scien­tific knowledge as yet. But we can speculate. To begin with, women have far less of an evolutionary interest in fighting than men (just as female peacocks have no evolutionary interest in growing such a ridiculously costly tail). What they are able to do is to spur on men to fight for extra territory and food. Women can be calculating and switch loyalties when their group is tasting defeat. The American psychologist Shelley Taylor called this the 'tend-and-befriend response', the female response to threats and stress. Whereas men usually display fight-or-flight responses, women concentrate on the protection of their brood (tending) before anything else and join a partner or social group who can offer this protection (befriending). These might be the male warriors from their original group, but also from the enemy's group if they are winning the battle.

Women may also have developed psychological adaptations to prevent war being waged, or to end a war. Because women by and large have more to lose than men (as a war's evolutionary costs such as rape and the risks to offspring are greater for them), we might expect that women are more inclined to keep the peace. Research shows that women are more negative about the deployment of violence as a solution to conflicts. They are also less likely to go on the offensive in laboratory-simulated war situations. In addition, our own research shows that, in time of peace, we prefer female leaders – either actual women or men with a feminine appearance. It is perhaps not for nothing that the most recent American Secretaries of State included women, Madeleine Albright, Condoleezza Rice, and Hillary Clinton. We expect women, more than men, to be focused on maintaining peace.

Finally, there must have been circumstances in our evolution in which women exacerbated warfare. The best-known (fictive) story is that of Helen of Troy. Research by one of us into the sexual preference of women for war heroes signifies that women are fundamental to war. Sexual selection is the explanation for this. If women did not fall for war heroes, but for bird watchers, many men would spend large amounts of time with binoculars in the great outdoors. Statues would be erected for the best twitchers, and these people would be cheered on by a wild crowd, including countless young, attractive women, before setting out on another expedition.

Male Apache Native Americans were known only to venture out to loot and pillage from neighbours when women complained of lack of food. Women might also have played an active fighting role when they were forced to do so by circumstances. In the event that the tribe had too few male warriors (because they had been killed in earlier fights) women may well have actively taken part in battle in order to compensate for the lack of fighters. Throughout history, this has happened in various places around the world. A contemporary example is the state of Israel, which has been confronted with such superior numbers of enemies that women play an operational role in the army. Like men, women in Israel have to do national service. When there was a large shortage of men during the War of Independence in 1948, women took part in combat. Figures from the Israeli army show that in 2002 women comprised 33 per cent of the lower officer ranks, and 21 per cent were captains and majors. Conversely, they comprised just 3 per cent of the higher ranks, even though, in 2011, Israel appointed its first female Major General, Orna Barbivai.

Evolution plays a strange game with women. Sexual selection has made women fall for male warriors who might form a threat to them during times of war. The enormous scale of warfare has led to the increasing anonymity of soldiers and, with it, an increase in lawlessness and at times sexual violence on a massive scale. In 2008, the film Anonyma – Eine Frau in Berlin (The Downfall of Berlin Anonyma), directed by Max Fäberböck, was released. It was based on the diaries of an anonymous German woman, who recorded what happened to her and other German women during the months following the Russian liberation of Berlin: a massive wave of violent rape during a chaotic and extremely uncertain time.

The sexual assaults were more than barbarian, the American jour­nalist Cornelius Ryan chronicled in The Last Battle, a narrative about ordinary citizens and soldiers from both sides. Ryan recounted group rapes during which many women died and soldiers who forced their way into maternity wards in a drunken haze to rape women who had recently given birth or even some who were heavily pregnant.

In her 1992 documentary Befreier und Befreite (Liberators Take Liberties) filmmaker Helke Sander made an attempt to work out how many women were raped during the Russian advance. She did this using medical, abortion and birth records and verbal accounts. Sander came to a cautious estimate of 1.9 million Russian rapes in the whole of Germany and in excess of a hundred thousand in Berlin.

For a long time this subject was taboo in Germany, because many German women – to prevent worse – entered into relationships with Russian soldiers as a survival mechanism, often officers (the female tend-and-befriend instinct). Women offered themselves, to spare their children and their own lives. Once the Russians had moved on again and a large number of German soldiers had returned home traumatised, this created great tensions. Many raped women once again suffered greatly. The scale on which rape has been taking place in modern types of warfare has no parallel with prehistory. Because soldiers tend to fight far away from home, they can often get away with it, and at times are even encouraged by their officers, as during the break-up of Yugoslavia or amongst the foreign jihadists who are fighting in the IS-controlled areas of Iraq and Syria. In ancestral times, the attacked tribes would immediately retaliate. Now, the perpetrators are anonymous, the victims just as defenceless and any children stigmatised.

War over property

The agricultural revolution and subsequent population explosion had a significant impact on the scale and complexity of wars. Agriculture gave rise to something that had not been there two million years previously: property. Property had to be defended against people who would like to appropriate it. And so a soldier class appeared who came to protect belongings. Villages were given extra protection to make defending them easier. In every village or early city, in Turkey for instance, we see walls around houses. One of the first settlements in the world, Çatalhöyük in Turkey (7400 bc), has defences. Later, fortifications and castles were built. The size of communities exploded, and with it social complexity. Professions, trades and specialisations sprung up. Someone became a farmer, another a clerk, a third person an artisan and the fourth a soldier. Waging war became a profession.

Walled villages became states, with their own administration and economy. Old social orders disappeared and the group people belonged to became bigger and bigger and ever more abstract. Whereas in ancestral times the interest of individuals towards the group produced coherence, in an ever-expanding society the role of religion and patriotism grew in importance to create cohesion. War on account of abstract issues such as religion or nationality was an unknown phenomenon in prehistory, but became increasingly de rigeur in later times (the crusades fought by the European knights in the Middle East are a good example).

Warfare also increased in scale and became technically more refined, leading to all kinds of mismatches. The traditional three Ss, primordial motives for our ancestral conflicts, were greatly magnified by the population explosion. More people meant more sex, more status and a bigger salary for the winners of wars. The stakes were raised, which meant more interests had to be served. In terms of mismatch, the spoils of war became an exaggerated cue to which young men were attracted.

If one walled village occupied another, the booty (the earnings) were many times greater than during prehistory: large plots of land were taken, livestock was confiscated and many potential brides kidnapped. The status of war victor only rose. Winners became warlords, later barons, and even kings (the present Dutch king is a descendant of a war hero, William of Orange) and emperors who were in a position to maintain an even bigger army. The more soldiers someone was able to deploy in battle, the greater the chance of victory; the harder you fought, the greater the chance of large spoils.

Warfare became an increasingly effective means to acquire property. The demand for soldiers became so huge that many men fought alongside the highest bidder for decent pay. These mercenaries (a mismatch, because they did not exist in ancestral times when people always fought to protect their own group) were numerous on account of the population explosion. A well-known phenomenon during the Middle Ages was that of the first son pursuing academic study, the second becoming a skilled manual labourer and the third a soldier. Mercenaries were not in the slightest bit interested in for whom or for which objective they fought. A clear link between money and violence began to emerge: the richest rulers were able to afford the greatest number of soldiers and thus achieve the greatest number of victories (a principle that continues to live on in global football, a modern manifestation of ancient tribal disputes and the male warrior effect).

Peace for our time

Despite the growing military might of villages, cities and states, aggression gradually diminished in relative terms. Whereas in pre-agricultural times, around 25 to 30 per cent of the male popula­tion died as a result of violence, Harvard psychologist Steven Pinker believes that this subsided after the advent of agriculture. Now the figure in Western Europe and the US is less than 1 per cent. New, much more complex societies meant ever stricter standards and rules for the use of violence. States de-armed citizens and no more unnec­essary risks were taken to attack neighbouring communities. Religions that advocated peace rose up, at any rate within people's own local communities. The bellicose instincts of young men espe­cially were channelled and regulated much more in agricultural societies, and these instincts have emphatically come to the fore in modern society in the shape of hooligans, (motorbike) gangs, crimi­nal syndicates, the mafia, monopolists, and . . . CEOs.

Compare the pacification of humans against pigeons, who peck each other frequently with their beaks. Aggression is remarkably widespread amongst pigeons. They peck and peck each other to fight over hierarchy in the group. That's why biologists refer to this phenomenon as the pecking order, not to be confused with the length of the male member. Scientists once gave pigeons heavier weapons, by attaching knives to their legs and needles to their beaks. Aggression between the test pigeons dropped almost instantly, because the risk associated with violence was too great. The Cold War was based on this principle: if both the US and the Soviet Union had weapons of mass destruction, they would not attack each other. This geopolitical strategy was also known as MAD (Mutually Assured Destruction).

But there is another side to the story. If we do not look at the relative number of fatalities from war, as Pinker does, but at the absolute numbers, then we see an enormous rise in the number of casualties worldwide. This obviously has everything to do with the population explosion and the increase in lethal weapon technology, creating a mismatch. While the likelihood of dying in a war is many times smaller than before, in absolute terms, many more lives are lost than in earlier times. For the family and friends of the war victims statistics do not count, only individuals. This also applies to the hawkish leaders who send them to their deaths. The Russian dictator Stalin spoke these legendary words: 'The death of one man is a tragedy, the death of millions a statistic'.

The motherland is missing you

With the passing of time, the way in which war was waged changed. In ancestral times people fought with their fists, later with sticks, stones and axes. After the agricultural revolution, technology became an increasingly important part of warfare. Societies militarised, resulting in a large amount of effort being devoted to the manufacture of weapons. This, in turn, gave rise to an arms race. Weapons became ever more inventive and numerous, and the emphasis on crude, physical strength shrank. Moreover, people had to fight in wars further and further away from home for increasingly abstract ideals. This led to several mismatches.

The concept of 'love of one's country' (patriotism) has been invented purely for warfare and hints at mismatch. No normal biological organism would want to run great personal risk in order to protect an abstract concept like country or a state (only some bellicose ant species manifest something resembling this, but they do this while protecting hearth and home – at least their own nest). Humans have an instinct to protect immediate family and community in danger, but not to defend a religious objective or an abstract nation state whose inhabitants we do not know personally.

How have cultural innovations been able to counterbalance this fundamental mismatch between fighting for your family or your country? First of all, modern humans have a 'symbolic mind' at their disposal, the ability to make connections with genetic strangers, people who are not family or friends, but with whom we do have something in common. This symbolic brain is extremely useful, because it enables humans to join larger social networks. We have already seen how convenient this is in times of war, or when there was a threat of drought or water shortages. The larger your social network, the greater your chance of survival (this is probably what did it for the Neanderthals. Their networks were too small to survive in times of food shortages). The symbolic brain enables us to trust other people implicitly on the basis of a symbolic shared feature – such as belonging to the same church, nationality or football club. Patriotism is a corollary of this.

Rulers, politicians and generals can manipulate our symbolic brain by instilling in us the idea we belong to a group that needs defending. Millions of people have been united by the abstract notion of a homeland, even though they have no genetic interest whatsoever in fighting or dying for each other. Patriotism and religion are cultural constructs, which are intended, amongst other things, to organise and defend society. How many soldiers have died for something that had nothing to do with themselves or their genetic relations? A good example is both the World Wars of the last century, which saw millions of casualties.

But do people put up such a tough fight for abstract things like religion or one's country? Studies show that, in war situations, soldiers still primarily fight for their band of brothers, their small group of fellow soldiers. Hatred of the country and the politicians who send them off to war is huge. It also turns out that, despite the growing numbers of people taking part in combat, quite a number of soldiers do not play an active role. Research shows that only 20 per cent actually use their gun for shooting in battle. No wonder Pinker perceives a percentual decline in violence. Our instinct enables us to risk our life for our family or community, but perhaps to make less of an effort for our people and country.

In Bowling for Columbine, filmmaker Michael Moore shows that it is especially the disadvantaged in American society who fight the hardest and are most likely to die in battle. For a large group of disadvantaged young men, the army is one of the few opportunities to make something of life, acquire heroism and status and, when returning from battle, build a social existence and have children that will lead a respectable life. We see something similar in traditional nations. Bellicose Plains Native Americans make a distinction between peace leaders and war leaders, and these roles are fulfilled by different people. Peace leaders tend to be older and come from well-off families within the tribe, while the war leaders are younger, wilder and come from less-endowed families. So it appears that war continues to give disadvantaged young men a means to acquire status.

But the likelihood of becoming an actual hero and making a difference has decreased somewhat in modern complex wars between countries. In ancestral times, you would be instantly recognised as a hero; the five of you set out and those who returned, at the very least, had done nothing disastrous in the battle. Modern warfare, partly as a result of military specialisation, involves so many people that it is almost impossible to stand out above the rest. What's more, weapons are much more lethal these days, so walking out in front in order to become a hero tends to be a bad plan. In sharp contrast to the 4486 American soldiers who died in Iraq stand the tiny number of Medal of Honour recipients.

War at a remove

An important facet in the cultural development of warfare in recent history is that the distance between the fighting groups – and the perpetrators and victims – has been growing ever larger. We saw this in the earlier drone example. This increasing distance produces mismatch with far-reaching consequences. The entire weapon technology is aimed at widening the distance between perpetrator and victim, in order to reduce the risks to the aggressor. Moreover, by creating distance, empathy for the other party dwindles which in turn leads to an increase in the likelihood of atrocities and sadism. Greater distance means less empathy, an absent cue during modern conflicts with all its attendant consequences.

The psychologist Daniel Batson illustrated this in a study in which he told students in his lab that there was a student in another room who had to answer various questions, and every time he made a mistake would be given an electric shock. The researcher asked each student whether he wanted to swap with the victim. The reply depended on the similarity between the two people. If the victim was described as someone who was the student's equal in some respects – for example, someone with the same taste in music, or political views – then the student did not mind swapping places. In other cases he did mind.

When our ancestors were still travelling across the savannah, it was, as we saw, important to mobilise as many men as possible to – extremely cowardly – bump off individuals from a hostile tribe. Physically, men should get the better of one or two (unsuspecting) intruders. But when the attackers began to use spears and axes to defend themselves, it became important to stand further apart, out of self-protection. Swords emerged, and later guns and cannons, weapons that became more and more dangerous, used from an increasingly greater distance. And with that large distance, the abil­ity to feel another person's pain decreased.

The natural connection between perpetrators and victims which had been the deciding factor for hundreds of thousands of years, got lost completely. Thanks to the arms race, it was possible to catapult enormous boulders at castle walls and kill enemies at a huge distance, as well as to bomb entire cities. The number of warriors an army had no longer counted; what mattered was destructive power and tech­nological edge. There is an interesting anecdote about how technology can affect old-style warfare, chronicled by Jared Diamond. He describes how a tribal chief in New Guinea saw an airplane land for the first time, filled with missionaries. The chief asked whether he could fly in the bird and the missionaries agreed. Before getting on board, the man wanted to load up a pile of large rocks. The mission­aries were dumbfounded, until he explained he needed the rocks to drop from a great height on his enemies in the neighbouring village.

With increasing frequency, wars began to be waged far away from home, whether it was the Romans who hit a wall of hostility in Scotland, or Napoleon's soldiers who froze to death in the Russian arctic fury. This mismatch often ended up badly. An important biological mechanism is that of the home advantage. A robin protecting his garden puts up a greater fight than a robin invading a territory. The aggressor can try elsewhere, but a defender fights for his nest and offspring. Which is why many wars are won by the country with the home advantage. Waging war in nowheresville tends to end in tears. Whether Americans in Vietnam, Russians in Afghanistan or Germans in Russia, the further soldiers are away from home, the less motivated they seem to be to fight.

The role of leader as mismatch

Waging war on a large scale is most effective when a group is organised in a strictly hierarchical fashion, with delegating leaders at a distance. In ancestral history, leaders went first and led from the front, but the generals who sent their soldiers into the trenches and battles during World Wars I and II did so at a safe distance from the clashes. From an evolutionary perspective, leading from the back was a new phenomenon because, by tradition, the head of the battle was a better place to make assessments than miles away. Leading from behind the lines also caused millions of unnecessary deaths and historical blunders. We know from World War I that, from behind the front, British generals often took the erroneous decision to send their soldiers out of the trenches to attack the Germans, resulting in hundreds of thousands of needless casualties. The fact that the leaders did not experience the consequences of their mistakes for themselves is a mismatch. If there is a chance you will be killed, you think twice before you launch an attack.

In modern warfare, it is the leaders who run the least risk instead of the most, as in ancestral times. We are astounded when a general is prepared to take a personal risk or expose his descendants to risk. People were full of praise when Dutch General Peter Van Uhm lost his son in Afghanistan. This was an intensely personal drama, with the unintended consequence that Van Uhm revealed himself as a leader who was prepared to bear great sacrifices, just like past leaders. This has given him an unprecedented high status, and he is the best-known Dutch serviceman – if he had aspirations to enter Dutch politics, he would stand an excellent chance.

Psychological war complaints as mismatch

In 1980, the third edition of the DSM, the Diagnostic Statistical Manual of Mental Disorders, described the symptoms of post-traumatic stress disorder (PTSD). This is a psychological disorder which is classified as an anxiety disorder. The recognition of PTSD was largely associated with the Vietnam War, from which many veterans had returned unhinged. A remarkable number of young men became addicted to drugs, displayed maladjusted and often criminal behaviour, had hallucinations and frequently withdrew – armed – from society. Once the disorder had been included in the DSM, medical science threw itself at the condition. The number of publications in scientific journals exploded, from forty-three in 1980 to seventeen hundred in 1999. Since then, more than six thousand articles about the topic have appeared, with PTSD no longer solely relating to the problems caused by war, but to all types of trauma from aggression.

That war was an important cause of stress had been long known in world literature. Literary historians suggest symptoms of this psychological disorder can be found in the Epic of Gilgamesh, Homer's Iliad and the writings of Herodotus. The latter's Histories, for instance, feature a brave warrior who has to cope with blindness following an intense fight. Many examples of war neurosis exist in old books. In some Native American tribes, warriors have to live outside the group for a while when they have killed enemies, before being included into the community again. The objective is to ensure that they have recovered mentally in order to take part again in ordinary daily group-life peacefully.

PTSD can arise when people find themselves in life-threatening situations or have to contend with severe physical injury. There are many symptoms, including tiredness, shortness of breath, palpitations, sweating, chest pain and even fainting. PTSD is often accompanied by recurrent depression, anxiety, irritability, re-experiencing of the stressor, difficulty in concentrating, problems falling asleep, aggression issues, substance addiction, problems in forming and maintaining long-term relationships and social isolation. Here, too, our evolutionary history continues to affect us. Even if the drone pilot who creates long-distance casualties in the Nevada desert does not run a personal risk, it is still psychologically stressful to kill people, and probably even more stressful when you have not faced eyeball to eyeball the person who was actually out to finish you off. At one point, waging war was a very personal thing. You could see, smell and feel your enemy: now they are green specks on a screen.

War heroes continue to have a certain status, but for a long time veterans have not received the praise and financial compensation they are due. The earlier drone story is based on that of Brandon Bryant, a US Air Force operator who, in 2012, lifted the lid on the time he helped to kill people from a distance. During the six years that he worked as a drone pilot, his squadron was responsible for the deaths of no less than 1626 people.

When Bryant had killed a child in one of the attacks, he wrote in his diary: 'On the battlefield there are no sides, just bloodshed. Total war. Every horror witnessed. I wish my eyes would rot.' Partly because of this incident he began to cut himself off from his friends. He suffered from chronic bad temper and hardly slept. One day he collapsed: he fell over and vomited blood. Doctors diagnosed he suffered from PTSD. He is no longer in the army, but living in poverty. No war hero, in other words.

The atom bomb and other weapons of destruction

The ultimate consequence of the arms race – and the most alarming mismatch – is the development of the atom bomb, a weapon that has in fact only been deployed twice and has been such a terrifying deterrent that no one has ever dared to use it since, aware that dropping a nuclear bomb equals suicide. Military experts and political scientists talk of a MAD-strategy, which we discussed earlier: guaranteed mutual destruction. These days rockets can see to it that both the attacker and the defender are eliminated and this idea has – for the time being – proven sufficient to keep the peace. But it is still not a comfortable situation, least of all with a current Russian president with an ego problem.

Army bases around the world house enough nuclear weapons to destroy all life on Earth (and several times over if that were possible). At present, there are seven states with nuclear weapons. Two countries (Israel and North Korea) are believed to possess nuclear weapons, but the truth is unclear. Seventeen further countries, including the UK, France, and the Netherlands, have nuclear research programmes which could lead to the development of a nuclear weapon. In a word, if the aforesaid power-mad Russian president, the authoritarian Chinese party leader or the North Korean dictator gets the idea in his head, it could be the end of the blind process of organic re-arrangement of elementary components. It hardly needs stating; but our primitive brain finds it difficult to grasp that there are global powers in possession of weapons capable of wiping out a large part of humanity in one fell swoop. If our brain took this threat truly seriously, we would have ensured that countries like Russia, North Korea and Pakistan were nuclear-free.

Sport as a substitute for war

Where our evolutionary warring past manifestly lives on is in our fascination for sporting competitions. We could see team sports as a ritualised form of warfare, a positive mismatch, as the conflict rarely claims fatalities. The rules all players in a game have to adhere to ensure that the battle acts do not deteriorate into a true war. Just very occasionally it comes to grief.

On 10 October 2014, a European Football Championship qualifying match between Serbia and Albania was underway in the Serbian capital of Belgrade. Out of nowhere, a drone appeared over the pitch with an Albanian flag attached to it. The Serbian player Stefan Mitrović tried to grab the flag, whereupon a fight broke out as some of the Albanian players began to defend their flag. At this point the referee suspended the match. After the game, the brother of the Albanian prime minister was arrested, on suspicion of operating the drone from the stands.

The root of these skirmishes was the declaration of independence by Kosovo, which had been declared an independent republic by the Albanian majority in 2008 – against the will of Serbia.

When missionaries introduced football in Papua New Guinea this initially led to many scuffles as well, sometimes ending in full-blown tribal war. Thankfully a catholic solution was found to this problem by introducing a new rule to the game. All matches had to end in a draw, which meant there were times the teams had to keep on playing for a long time.

Sport is the channelling of our primitive instincts for warfare: we wear tribal colours, we fight for trophies, we experience home advantage and during play many hormones are released that are comparable to the hormones released when fighting. These hormones pump not only through the players on the pitch, but also through the spectators. Studies show that, amongst football supporters, changes in cortisol (the stress hormone) and testosterone (the status hormone) can be measured. In fans of both teams the cortisol level rises during the game. In fans of the losing team the testosterone level plummets, while that of the winning team soars.

In the times of our ancestors, wars did not have many spectators, so there is a case of mismatch as a result of exposure to a fake cue. In a conflict between two tribes, everyone took part in combat action, and those who did not were socially excluded or worse. Nowadays we sit in stands to watch clashes, often accompanied by stress, raised blood pressure and palpitations. Taking part in a sport may be healthy, but watching sport carries serious health risks. Our fight-or-flight response – useful when we are engaged in a pitched battle – is also activated in a full football stand where we have nowhere to go when our team threatens to lose. It is not for nothing that football violence spreads through the stands with some regularity. The most famous football conflict is possibly the so-called 'football war' between El Salvador and Honduras. After riots between supporters broke out during a game between the two sides in 1969, the countries fought each other for four days. Two thousand men lost their lives in this military conflict.

Break a lance for peace

It should be clear by now that modern warfare has created all kinds of mismatches.

We would like to turn our minds to the question of how we might be able to use the mismatch theory to promote peace. What should we do with all these male warriors? We could start by doing nothing. We could simply accept that there have always been generations of young men who find it exciting to take part in organised violence, whether they are hooligans, street gangs, the mafia, or IS. It is biology. We could stand by and watch how at some points in time a society turns into a version of Mad Max. And if we do not want to have them in our society, we could arrange a war for them and make sure they go and fight for us a long way from home.

The question is whether they would want to do that. As we have seen, soldiers primarily fight for their band of brothers, many hate the country or politicians who dispatch them, and a large proportion does not even take part in active combat.

Doing nothing also means that we, with our Stone Age brain, have to learn how to handle weapons which are becoming ever more lethal, with the distance between perpetrator and victim growing ever larger. In order not to run any risks itself, the American army is in the pro­cess of deploying robot soldiers to attack the enemy. But a widening distance leads to a decline in empathy, and consequently an increased likelihood of excessive violence and erroneous decisions. One of the reasons whistle-blower Bradley Manning (now Chelsea Manning) decided to leak to WikiLeaks secret video recordings of an extremely violent American helicopter attack on Baghdad was the excessiveness and inhumanity of the action. This act landed Manning a thirty-five-year jail sentence (although she was since pardoned). Another consequence of this brute force is that the enemy also starts to fight more aggressively in order to restore the imbalance of power. So, in asymmetric wars, violence will only increase, for example through combat with suicide platoons or by carrying out bioterrorist attacks.

A second solution to mismatch could be to make peace more important. Our ancestors had adaptations to wage war with other groups, but they also had adaptations to make peace. The Yanomami are not continuously at war either. Sometimes there is a conflict, but the villagers tend to live in relative peace with each other.

How can peace be safeguarded and what lessons can we learn from our evolution? One of the things that brings communities closer together is the exchange of marriage partners, which results in neighbours' genetic interests mixing. This also happens amongst hunter-gatherers, partly to enlarge social networks. During the Middle Ages, this was the way to unite royal families from different realms. One of the most successful ways for societies to counter prejudice and xenophobia is, not for nothing, mixed marriages with children.

One option is to have women play a more prominent role in poli­tics and the military. As previously shown, there are generally few evolutionary advantages attached to warfare and often only disadvan­tages (rape, for example). As leaders, women will therefore be less quick to launch a war. Studies indeed show that women are slower to initiate a war when, as leaders of a country, they have to solve a simu­lated crisis in a lab situation. Margaret Thatcher and Golda Meir are female leaders who started wars, but they appear to be the exceptions to the rule. It turns out that in lab-simulated wars, female participants opt for attack far less quickly than men and continue to negotiate with the 'enemy' for far longer before going to war.

Why don't we send so-called 'UN women's battalions' to the world's hotbeds? With weapons in their hands women are as deadly as men, but they have greater empathetic powers and arouse less aggression. The same could apply to men with feminine traits. The problem is that in a conflict with another country, we prefer masculine men to do the fighting for us.

Neuroscientists who work for the US Military are also investigat­ing whether it might be possible to spray substantial doses of oxytocin, the bonding hormone, from aircraft over war zones. Enemies would become friends and break off action.

Likewise, women could instigate a collective sex strike as a protest in order to change the minds of men who are waging war. This possibility was presented in a comedy in Greek Antiquity, Lysistrata by Aristophanes, as a solution to the protracted battle between Athens and Sparta. But sex strikes have indeed happened. There had been fighting between the separatists and the Philippine government army on the Philippines' second largest island, Mindanao, since the 1970s. The United Nations High Commissioner for Refugees (UNHCR) provided the battling village with emergency aid, but this had little effect. Until the warriors' wives threatened to withhold sex. Men who went off to fight would no longer receive a loving welcome in their marital bed. This turned out to be a more effective remedy than the UNHCR food parcels and fishing-nets.

Similarly in Africa, Togo women once called a sex strike. Women belonging to the Togolese human rights organisation Red Togo had copied the action from Liberian women, who in 2003 would only make love again if their men made peace with their enemies. 'We have many means to force men to understand what women want in Togo,' a lawyer said at a women's rally in the capital of Lomé.

Another way to solve mismatch in warfare would be to make leaders discover more for themselves what it is like to fight. Leading from the back has resulted in leaders no longer experiencing personal risks. They barely know what they put their soldiers through. Perhaps it is an option to force generals to take part in foot patrols and to lead in battle, in other words to lead from the front. That will teach them!

Finally, peaceful substitution for warfare could be pushed further. We know from studies that in terms of hormones (a combination of testosterone, cortisol and oxytocin) and group bonding, doing battle with a band of brothers has a comparable effect to a bout of paintballing or engaging in an exciting sports match. The battle being fought is a symbolic one without casualties. More sport means that a greater number of people can participate simultaneously. In order to prevent cheating and match fixing, it might be advisable to work with female referees only. Another substitute for warfare is already happening at home, where boys play World of Warcraft on their PlayStations or online on their computers with team members from different parts of the world. Doing something with people online across the world expands people's empathy and mutual understanding and reduces the chances of war. So, China and Russia, if you also read this: make the internet freely available.

- Ronald Giphart is an award-winning and best-selling novelist with a strong interest in psychology and human behaviour. Mark van Vugt is Professor of Evolutionary, Work and Organizational Psychology at VU University, and a research associate at Oxford University. Their book Mismatch, published by Robinson, is available now. This extract is reproduced with kind permission.