A year ago, together with Sergey Gavrilets and Laura Fortunato, we organized a conference at the National Institute for Mathematical and Biological Synthesis in Knoxville. The main theme was how we build and test theory of the evolution of social complexity. After the end of the conference we held a public debate on this question:
In the last 10,000 years, human societies have evolved from highly egalitarian bands of a few dozen people to huge societies of today with great economic and social divisions, thousands of professions, and elaborate governing structures. How this transition occurred is one of the greatest puzzles in science. To throw some light on this fascinating topic, NIMBioS will host a debate, focusing on the role of warfare in explaining the transition from simple to complex societies.
Thesis: Warfare has transformed us from living in villages to living in huge states, building cities and civilizations, and ultimately making our lives more peaceful.
Antithesis: Warfare is an unfortunate side-effect of the evolution of social complexity, but it was other evolutionary mechanisms that resulted in highly complex human societies.
For the thesis: Peter Turchin (University of Connecticut), Jeremy Sabloff (Santa Fe Institute)
For the antithesis: Sander Van Der Leeuw (Arizona State University), Tim Kohler (Washington State University)
At the end, the audience voted on who won the debate. Can you guess the outcome?
You can watch the debate to find out the answer here. However, as I am not a great public speaker, I would prefer that you read my argument, rather than listen to it. I myself hardly ever watch videos, always preferring the text for any serious argument. So here it is. Comments welcome!
Argument for the Thesis (Peter Turchin)
Here we are in this nice auditorium. Most of you are perfect strangers to me, yet I am not worried that you’d decide to kill me and cook my flesh over the fire. But if I lived 10,000 years ago, I’d be well advised to fear strangers. In fact, if I could shoot you from the bushes without risk, this would be a good idea, because it would ensure that you wouldn’t kill me.
A cannibalism scene from a 1592 painting by Theodore de Bry (source)
Today we live in huge societies of millions of people, most of whom you’d never meet in your life. We often forget how much we depend on the ‘kindness of strangers.’ Strangers will help with directions when you are lost, but they are also responsible for the bread arriving in the supermarket. It is strangers that generally ensure that our lives are free of hunger and fear, that we can have fulfilling jobs – and that we can ask questions about how societies evolve. How did we make the transition from living in villages, surrounded by friends and neighbors, to huge societies of strangers, with thousands of professions and elaborate governance structures?
Remarkably, science still does not have a satisfactory answer to this question. Today I will present one way of resolving this puzzle – but as you will see, other participants in this debate have their versions. My answer has three parts. First, the critical glue that holds societies together is cooperation. Second, the reason humans learned how to cooperate is – paradoxically – warfare, lethal conflict between groups. And third, by creating a selective pressure for ever-larger societies warfare will eventually put itself out of business, when we learn to cooperate at the level of the whole humanity.
Let’s start with cooperation. I use the strong version of this word – when people’s actions contribute to the common good, even though at personal cost. This is also known as altruism. One of the most striking examples of cooperation is volunteering for the army when your nation has been attacked. The common good is clear – if nobody serves in the army, your country will be overrun by the enemy, with catastrophic consequences for all. The costs are also clear – a high risk of getting killed or maimed. The problem is, the benefits of cooperation are shared amongst all, but costs are born by each individual privately. This is the ‘cooperator’s dilemma.’ By volunteering for the army, you don’t materially change the outcome. Your additional contribution to that of millions of others is miniscule and does not matter. But if those millions don’t join the army, you would be even more foolish to volunteer, for you will be killed with no benefit to anybody. So a rational selfish person should never volunteer. This means that a society consisting of rational selfish people will not be able to generate enough collective action to repel the enemy.
Although the choices facing one are particularly stark in matters of war, the same logic operates in times of peace. Economists have long agreed that it is ‘irrational’ to help strangers, vote, go to a demonstration, and obey laws when there is no danger of being caught. Yet most people do such things most of the time. And without these folks who do prosocial, cooperative things a society couldn’t exist. Selfish people cannot cohere in a functioning society – this is the fundamental theorem of social life. Ayn Rand and those who say that “greed is good” are very, very wrong.
So it is very fortunate that the majority of us are not ‘rational agents’ imagined by economists. We can count on the kindness of strangers not because others will make a rational calculation that it pays to be cooperative, but because people have prosocial emotions and follow prosocial rules of behavior. To give an example, I am not worried that you here would decide to kill me. And not only – primarily not! – because there are police, courts, and prisons. I know that the great majority of people have a very strong aversion to killing a fellow human being. There are very few who lack this aversion, and the army tends to recruit snipers from them. This aversion is so strong, it is physiological – which is why normal people throw up when they commit even a justifiable homicide. More generally, cooperation is ultimately based not on logic, but on emotions, feelings, and beliefs; we cooperate because it is ‘the right thing to do.’
But how did we evolve to be that way? Humans are unique in our ability to cooperate in huge groups of genetically unrelated individuals; this is known as ‘ultrasociality.’ The puzzle of ultrasociality is the central question of social evolution. By the way, social evolution has both a genetic and cultural components, and both are important. In early human evolution the genetic component predominated, now the cultural one is much more important, but both continue to be relevant.
This takes us to the second part of my argument – the role of warfare. The logic is very simple. Groups of people who can’t cooperate to put together an army, will be overrun by those who can. The result is that genetic and cultural traits for noncooperation will go extinct.
More generally, cooperative traits are spread by the process of group selection. Selfish traits win in competition within groups, but altruistic, cooperative traits are favored by competition between groups. If between groups selection is strong enough, cooperative traits will spread.
Human groups can compete in many ways, but historically the most extreme form of such competition has been warfare. Warfare is the main engine of social evolution and it explains how small bands of hunter-gatherers (a few dozen people) evolved over the last 10,000 years into the huge societies of today. Because warfare pushes cooperating groups to become larger. As Napoleon said, “God favors big battalions.” The tribe that could mobilize more warriors had a better chance of surviving in war. This is the basic logic that drove the evolution of ever greater societies and states, and ever greater scale of warfare.
The story is of course much more complex than that. First, before warfare could do its thing, humans had to invent agriculture. Agriculture is a necessary condition for the evolution of truly complex societies. Why is absolutely obvious, and all scientists, including the participants of this debate, agree on it. But agriculture is only a necessary, not sufficient condition – many regions of the world had agriculture for milennia and did not make the transition to complex societies until they were colonized by European Great Powers.
Second, evolution had to solve a multitude of problems in order to ensure that large societies would not simply split apart at the seams (in fact, most early states and empires did just that). So such cultural traits as monumental architecture; records, writing, and literacy; division of labor; professional bureaucracies, taxation, and formal legal systems; state rituals and ideologies, and so on, evolved to enable megasocieties to function without falling apart. But the fundamental driver was warfare.
However not any kind of warfare has this ‘creative’ nature. It doesn’t matter how many people are killed, what is important is the high chance of group extinction. This is what drives social evolution. In the mountains, for example, warfare does not drive evolution of social complexity. So you lose a battle, but you can always survive by retreating to a mountain fastness. The chance of extinction is small, and in rugged areas complex societies do not evolve. The opposite thing happens. People living there evolve away from the state.
In the plains, on the other hand, if you lose the war, you are history. Things got even more hairy when Central Asians domesticated horses, learned to ride them and to shoot arrows from the horseback. This weapon of mass destruction was invented in the early first millennium BC, and the agrarian societies south of the Eurasian steppe found themselves under enormous pressure from the horse archers. The only way they could match the nomad power was by increasing their size and swamping the horse archers with soldiers. So they did, and that is why starting in the first millennium BC we see an ‘imperial belt’ developing south of the steppe, from the Middle East to North India to China. Then the empires also adopted the horse and gradually spread the aggressive way of war to the rest of the Old World. The spread of complex societies followed in the wake of such warfare.
Around 1500 the Europeans took over from the steppe archers. Instead of horses and archery they used sailing ships and guns. But the evolutionary logic was the same. Europeans traveled to the ends of the world, bringing genocidal warfare to all societies. When the dust settled, complex societies organized as states took over the whole planet.
So there is an intimate connection between warfare and civilization. This seems a gloomy conclusion. I am not a war-monger, and I certainly would like warfare to disappear in the humanity’s future. Actually, the chances of this not so bad.
Although large societies fight big wars (think World War II), paradoxically citizens in such societies have a much lesser chance of being killed by other human beings. One reason is that strong states suppress internal warfare, banditry, and murder. Another is that among hunter-gatherers everybody (at least, all males) had to be a warrior, but in large-scale societies, typically, only a small proportion fights in wars. The chances that you or I will get killed are much smaller.
More importantly, social evolution molded humans in ways that reduce violence. Earlier I mentioned that most people have a very strong aversion to killing fellow human beings. It was the same at the dawn of humanity, except ‘fellow human beings’ were only those personally known to you – relatives and friends. Or members of your tribe. Others were subhumans who needed to be exterminated.
A big evolutionary step in expanding the definition of ‘human’ occurred 2.5 thousand years ago. Remember that these were the times when horse-riding nomads pushed farming societies to the verge of extinction. So farmers had to scale up the size of their societies to resist this pressure. Social evolution had to break through the barriers imposed by tribalism and ethnicity. The rise of world religions – Zoroastrianism, Buddhism, and Confucianism, later Christianity and Islam – was the answer. These world religions made possible cooperation between different tribes in the new multiethnic empires. Suddenly the definition of ‘human’ was enlarged way beyond those who spoke the same dialect. But it was still limited to those who practiced the same religion. So a Muslim couldn’t enslave another Muslim, but enslaving a nonbeliever was OK.
We are now in the midst of the final transition, with the definition of a ‘human being’ expanding to any member of Homo sapiens, whatever their religion, race, etc. This transition is far from complete, but we are moving in the right direction.
To sum things up. The all-important glue that holds our wonderful complex societies together is cooperation. Cooperation evolved as a result of competition among societies, which historically took the form of warfare. But by driving the evolution of complex societies warfare also made our lives less violent and more secure. And if this trend continues, warfare will eventually put itself out of business.