Why Humans Fight
For many years, I wondered why people go to war as often as they do. I heard a number of theories about this, but they were all unsatisfying. They always left an element of unexplained irrationality. Not just immorality, mind you (which is understandable, if deplorable), but sheer, obvious imprudence. Then one day, I found out the answer. I learned it from Steven Pinker (but not from his recent book, The Better Angels of our Nature, which gives a false explanation; it was from an earlier book, How the Mind Works).
1. What’s Puzzling
What’s puzzling about war? The instinct for self-preservation (and pursuit of self-interest generally) is probably genetically programmed into us, for obvious reasons. So we don’t expect people to do things that are obviously very risky for the sake of much smaller benefits, or no benefits.
Wars usually have enormous costs for both sides, with many people winding up dead – especially able-bodied, young men who could otherwise be doing productive work – lots of property being destroyed, and lots of wealth expended. There’s also typically a significant risk of losing the war. All of which is well-known. So one would think that self-interested humans would generally avoid this.
2. Unsatisfying Explanations
So now I’m going to explain what I find unsatisfying about various explanations that I’ve heard or thought of. Btw, most of these can also be applied to fighting between individuals.
a. Disagreement
Maybe this is what happens: two countries have a disagreement about something that concerns both of them – say, the location of a particular border. They fight a war to resolve the disagreement.
Q: Given the destructiveness of war, why would this make sense? Whatever they’re fighting over is usually something of much less value than the amount of harm caused by a war.
A: Maybe each fights because they are afraid that if they don’t, they will look weak, then the other side, as well as other countries, will keep taking advantage of them.
Objection: The two nations could seemingly find other ways of resolving the dispute that would not make either look weak or invite others to take advantage of them. For instance, submit the dispute to a neutral, third-party arbitrator. Given the stakes involved, you’d think that people would try that more often.
b. Resources
Maybe nations fight largely to capture scarce resources. During the 2003 U.S.-Iraq war, protestors carried signs saying “No blood for oil,” implicitly claiming that the war was an attempt to secure our oil supply.
This made little sense, though. If you want resources to flow freely, the last thing you want is a war. Lots of stuff is liable to get destroyed, and supply of resources is liable to be disrupted. It’s completely unsurprising that oil prices spiked immediately following the U.S. invasion. Over the next five years, they rose to four times the pre-invasion level. (https://www.macrotrends.net/1369/crude-oil-price-history-chart)
If you want resources, maintain peace and just buy the resources from whoever has them. That is a much cheaper, more reliable way of getting resources.
c. Incentive Structures
A favorite libertarian explanation is that wars happen because the people who decide whether to go to war – government leaders – do not have to bear the main costs of war. They send other people off to risk their lives.
I’m sure this has a lot to do with the prevalence of war – if politicians had to fight in the wars that they started, we’d have a lot fewer wars. Nevertheless, this explanation fails to explain some important facts:
People in the military, who are at risk of dying in war, nevertheless appear to be more pro-war than the average citizen.
In primitive societies, inter-tribal wars are very common, and the people who start them also fight in them.
Anyway, even when you just look at our politicians, it’s not clear what their rational incentive is to start a war. They don’t personally get a bunch of loot. Sometimes they garner public support, but they also often get harsh public criticism. Obama didn’t suffer big political costs for being a hawk, but he didn’t get noticeable benefits either, nor did Trump suffer noticeable costs for not starting new wars.
d. Power
This seems more plausible: leaders start wars because they want more power. By defeating another country in war, the leader becomes more powerful, because he gets to rule over the defeated country, or at least to dictate terms to them.
This remains puzzling on its face, because:
There is also usually a risk of losing the war, whereupon one would become much less powerful. Surely war is never desirable for both sides, and very often (esp. when the combatants are about evenly matched), it will be irrational for both.
In primitive tribes, again, people voluntarily attack other tribes, and in doing so, they take on a serious risk of death. It just doesn’t seem worth it to possibly gain some power.
In modern societies, war is often supported by people (such as soldiers and right-wing citizens) who will not themselves gain any power even if their country wins.
e. Ideology
Maybe people are driven to war by ideology. For instance, the Marxists thought that they needed to spread Marxism across the world, to end capitalist exploitation, etc. George W. Bush thought that he needed to spread democracy to the Middle East. ISIS thinks that they have to spread Islam.
So this is definitely a factor. However, from an evolutionary standpoint, there is something odd about this. We should be genetically programmed to place our survival and prosperity above ideology.
You could say that we overcome our instincts when there is a sufficiently morally important cause. But how plausible is it that there are really compelling moral reasons for going to war, in a large class of cases where people actually go to war? It looks to me more like people are looking for excuses to go to war. Their ideology justifies it, but that ideology is usually extremely uncompelling from a rational standpoint.
You might say, “Maybe people are just very bad at figuring out political truth.” Okay, but why do they keep erring in this specific direction: thinking that violence is way more justified than it is? We have to explain why extremely unjustified belief systems that promote mass violence are attractive to human beings.
f. Hobbesian Dilemmas
Hobbes thought that in the state of nature, among other things, you would want to attack other individuals simply because you were afraid that they might attack you at some later time (and, presumably, because there is an advantage in combat for the person who attacks first). Since nation-states are in a state of nature with respect to each other (there is no world government), maybe something similar explains why they attack each other.
However, the Hobbesian reasoning is dumb and crazy. If there are really a lot of people around you who are worried about being attacked by other people, and who are therefore considering preemptive strikes, then what you want to do is try to appear as if you are not a threat. If you go around attacking other people without provocation, then other people (whom you haven’t yet had a chance to kill) are going to identify you as one of the biggest threats, and preemptively attack you. This is assuming that you can’t kill everyone at once.
Plus, if you attack another person pre-emptively, that guarantees a fight, which is typically very dangerous to you. Even if you get some advantage from surprise, this doesn't seem worth it just to address a chance that the other person might attack you.
In the case of nation-states, you’re not normally going to be able to finish a war without the other side fighting back, and thus without your own side incurring huge damage. If you don’t like being damaged, the smartest thing is to make peace treaties with your neighbors, where each side gets to verify that the other side isn’t mobilizing their military, etc. If both sides don’t really want a war, it shouldn’t be hard to not go to war.
3. Evolutionary Psychology
Now I’m going to give the explanation that I learned from Steven Pinker. First note two interesting facts about war:
War is common throughout human societies, from primitive tribes to modern nation-states, though getting less common in the latter. It would be good to have an explanation that applies to primitive tribes as well as modern nations; whatever it is in human nature that makes the primitive tribes fight is probably still present in members of modern societies.
War is mainly a male activity. It’s mostly men who start wars, fight in them, and die in them. In primitive tribes, it’s about 100% men doing the fighting, and almost all men doing the dying as well. (Modern societies have moved away from this to some extent, especially with the bombing of civilian population centers.)
Notice how the explanations in section 2 fail to accommodate this. Women are just as prone to disagreements as men are, have just as much need for natural resources, have just as much ideology, etc.
So here’s the theory about primitive tribes. In them, it’s common for the men to go attack a neighboring tribe in order to kill the men and kidnap the women, who would then become coerced wives of the victorious men. Nice, liberal people don’t want to believe this because it’s horrible. But the world is in fact a horrible place – and it used to be much worse than it is now.
Of course, starting such a conflict entails a large risk of getting killed. To see how this could be “worth it” from the evolutionary standpoint, consider a simple model in which there are two outcomes, each equally likely: you have a 50% probability of getting killed, and a 50% probability of surviving and capturing a new wife from the neighboring tribe.
Suppose you presently have no wife (which was common in primitive tribes, since most practiced polygyny). Then if you die in the conflict, your reproductive success goes to zero – but it was going to be zero anyway if you didn’t find a wife. If you succeed, you get some reproductive success. So you can see how going on this attack could increase your expected reproductive success.
Even if you already have a wife, going to war still isn’t so bad: if you lose the fight, your reproductive success goes to zero, but if you win, your reproductive success about doubles (as you go from one wife to two). So it’s a toss-up.
Women don’t go on such raids, because for a woman, capturing another husband does not increase one’s reproductive success (you can still only have one offspring per 9 months).
This explains why evolution would have men engage in this highly risky, aggressive behavior. But our genes don’t directly program complex behavior patterns; rather, they probably just endow us with certain vague attitudes and emotional dispositions. So, there were some genes that make men feel more aggressive, more prone to anger or hate toward foreign men, and these feelings often caused our ancestors to attack other tribes. The men who went on these raids, on average, were more reproductively successful than the men who didn’t have aggressive feelings and who therefore stayed home.
Fast forward to the present day. We no longer send soldiers to capture women from the countries we go to war with. So people who go to war no longer have increased reproductive success. But that doesn’t matter to the explanation, because we still have the emotional dispositions that evolved over the past 2 million years. Those emotional dispositions just make it easier for men to see all sorts of things as provocations for violence.
So that, I claim, is the fundamental factor behind the prevalence of war among humans. Note that I’m not saying we are genetically determined to go to war – we still have free will. It’s just that we (especially men) have a predisposition to find reasons for fighting when fighting is not really justified. This also has a lot to do with why men comprise about 96% of the world’s murderers and about 79% of the murder victims. (https://en.wikipedia.org/wiki/Homicide_statistics_by_gender)