Monday, June 21, 2010

The Coevolution of Parochial Altruism and War

How do we explain human heroism in war? Why are we willing to sacrifice our lives in war to advance our group against our enemies? And why do we honor those who die fighting in war as displaying the virtues of courage and patriotism? We can't presume to understand human beings if we can't explain this universal human propensity to warrior virtues.

Many people who agree with much of what I have to say about "Darwinian natural right" object to my including the desire for war as one of the 20 natural desires. These folks like the idea of their being a natural biological basis for love, morality, and cooperation. But they don't like the idea that such moral concern might be inseparable from the human disposition to war, because we have evolved to cooperate with members of our group in order to compete with those outside our group.

For many of my critics, this shows that my Darwinian view of morality cannot recognize the perfection of morality in universal love, which requires a religious belief in the equal dignity of all human beings as created in the image of God. These critics assume a religious pacifism that I reject as utopian in its denial of human nature and the tragic conflicts of interest that are always part of the human condition.

Another set of critics would be the libertarian anarchists who follow in the tradition of Herbert Spencer and Murray Rothbard, who foresee that human beings could live without government in perpetual peace by organizing social order through mutual aid and free trade, so that there would be no need for violent conflict. I see some suggestion of this libertarian pacifism in the work of Rasmussen and Den Uyl who sketch their conception of Aristotelian liberalism while saying nothing about war.

But I reject the pacifist view of morality, because it fails in two ways. First, it fails to recognize the history of morality as arising through war and violence. Second, it fails to recognize the partiality of morality as based on a love of one's own over strangers.

In The Descent of Man, Darwin offered a more plausible and realistic view of morality as arising from group selection in war. He wrote:

"It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an increase in the number of well-endowed men and an advancement in the standard of morality will certainly give an immense advantage to one tribe over another. A tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes; and this would be natural selection. At all times throughout the world tribes have supplanted other tribes; and as morality is one important element in their success, the standard of morality and the number of well-endowed men will thus everywhere tend to rise and increase" (Penguin ed., pp. 157-58).

Some anthropologists have rejected Darwin's scenario of morality evolving through warfare, because they have assumed that the earliest human ancestors who lived in small foraging groups were largely peaceful, and therefore warfare is mostly a product of the cultural history of the agrarian states that arose first about 5,000 years ago in large agricultural societies. But now, the anthropological and archaeological evidence surveyed by Lawrence Keeley, Samuel Bowles, and others suggests that warfare was common enough among foraging human ancestors to be a factor in human evolution. In fact, some estimates indicate that the rate of mortality in war among primitive human ancestors might have been higher than it was for the human community in the twentieth century, which we recognize as one of the bloodiest centuries in human history.

A few years ago, Jung-Kyoo Choi and Samuel Bowles used a computer simulation to work out the theoretical logic of how the evolution of war could have shaped the evolution of morality and cooperation. Here's the abstract for their article in Science:

"Altruism--benefiting fellow group members at a cost to oneself--and parochialism--hostility toward individuals not of one's own ethnic, racial, or other group--are common human behaviors. The intersection of the two--which we term 'parochial altruism'--is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one's payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly."

In Choi and Bowles' simulation, agents have two genes, each with two alleles. They are either tolerant (T) or parochial (P) and either altruistic (A) or not (N). So there are four possible combinations of traits. The selfish freetraders (TN) are not altruistic, but they are tolerant in trading with anyone inside or outside their group. The generous warriors (PA) are altruistic towards those in their group but violent towards those outside their group. The hostile bullies (PN) are selfish in refusing to be altruistic towards those in their group but also intolerant of those outside their group. The humanitarian philanthropists (TA) are altruistic towards everyone--those outside as well as those inside their group.

Under some plausible conditions as specified in their model, Choi and Bowles show that societies of selfish freetraders can evolve if there is a high proportion of tolerant agents in the groups. But even a low level of intergroup warfare--10 to 20% of encounters--favors parochial altruism, because the groups with greater numbers of generous warriors will win the spoils of war while the losing groups risk extinction.

A few humanitarian philanthropists can exist in trading regimes or warrior regimes, but their number can never be very great. The record of history bears this out. Traditions of pacifist thought persist, but the number of true pacifists is always small. Even most Christians have failed to live by the pacifist teaching of the Sermon on the Mount, because they recognize the practical necessity of war in defending one's group against attack from other groups, and so most Christians have adopted the tradition of "just war." Even Jesus departed from his teaching of universal love in teaching eternal damnation for those who rejected his message.

A recent article in Science (De Dreu et al. 2010; Miller 2010) suggests that the human brain is designed to promote the parochial altruism that has arisen from the evolutionary history of war. Here's the abstract for the article:

"Humans regulate intergroup conflict through parochial altruism; they self-sacrifice to contribute to in-group welfare and to ogress against competing out-groups. Parochial altruism has distinct survival functions, and the brain may have evolved to sustain and promote in-group cohesion and effectiveness and to ward off threatening out-groups. Here, we have linked oxytocin, a neuropeptide produced in the hypothalamus, to the regulation of intergroup conflict. In three experiments using double-blind placebo-controlled designs, male participants self-administered oxytocin or placebo and made decisions with financial consequences to themselves, their in-group, and competing out-group. Results showed that oxytocin drives a 'tend and defend' response in that it promoted in-group trust and cooperation, and defensive, but not offensive, aggression toward competing out-groups."

In Darwinian Natural Right, I surveyed the research on the importance of oxytocin for promoting the social bonding between sexual mates and between parents and children. A few years ago, Paul Zak and others won a lot of attention showing how inhaling a spray of oxytocin fostered trust that facilitated economic exchanges, which has become part of a whole field of research called "neuroeconomics," on the the neuroendocrinological basis of economic behavior.

This is the lovey dovey side of oxytocin. But we should expect that love of one's own--one's own mate, one's own children, one's own group, one's own trading partners--will be bound up with hostility towards those outside one's circle of loved and trusted associates.


Arrow, Holly. 2007. "The Sharp End of Altruism." Science 318 (October 26): 581-82.

Bowles, Samuel. 2009. "Did Warfare Among Ancestral Hunter-Gatherers Affect the Evolution of Human Social Behavior?" Science 324 (June 5): 1293-1298.

Choi, Jung-Kyoo, and Samuel Bowles. 2007. "The Coevolution of Parochial Altruism and War." Science 318 (October 26): 636-40.

De Dreu, Carsten K. W., et al. 2010. "The Neuropeptide Oxytocin Regulates Parochial Altruism in Intergroup Conflict Among Humans." Science 328 (June 11): 1408-11.

Gat, Azar. 2006. War in Human Civilization. Oxford: Oxford University Press.

Keeley, Lawrence. 1996. War Before Civilization. New York: Oxford University Press.

Miller, Greg. 2010. "The Prickly Side of Oxytocin." Science 328 (June 11): 1343.

Some related posts can be found here, here, here, here, here, here, here, here, here, and here.


Troy Camplin said...

I just included this research on oxytocin in a paper I am working on on Aeschylus' "The Suppliants." I make some of the same observations.

Bernie Fitzpatrick said...

I was fascinated by this article, but a male gender bias seems to be obvious. I understand that all societies have been male dominated, but could a female controlled society still follow the same patterns?

Troy Camplin said...

Have you ever seen a female protecting her young? And I'm talking female human. I have -- my wife, with our two children. My guess is that jealousy is not unconnected to this as well.