Religion and war

People bitch a lot about violence featured in movies and TV, but ignore a worse problem – how the sort of real (not make-believe) violence known as war is often associated with religion.

Now there may be a better theoretical understanding of how and why this association between religion and war may exist. Two articles in the October 26, 2007 issue of Science discuss evolutionary simulations which show that war drives the joint evolution of altruism and hostility to outsiders. Based on (but going beyond) this work, we will see how religion may be associated with warfare.

The first "perspectives" article gives an overview:

The Sharp End of Altruism

Which would you prefer: a society of selfish but tolerant freetraders, or a warrior society in which people help one another but are hostile to outsiders? If you value both altruism and tolerance, neither seems ideal. Societies of tolerant altruists, however, are exceedingly rare in the simulation presented by Choi and Bowles on page 636 of this issue. Instead, altruism flourishes only in the company of outgroup hostility (parochialism), with war as both the engine of this coevolutionary process and its legacy. For a compatriot, the parochial altruist who risks his life is a shining knight, whereas the outsider encounters the sharp end of this altruism.

The second article is a technical presentation of the research itself, which was the work of Jung-Kyoo Choi and Samuel Bowles:

The Coevolution of Parochial Altruism and War

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.

Unfortunately, both articles require a subscription for access.

Curiously, there appears to have been almost no reporting on this research in the usual places that report on scientific research for a general audience. (Wonder why that is....) And this is even though the Santa Fe Institute, with which one of the researchers (Bowles) is associated, did put out this press release:

The coevolution of parochial altruism and war

In "The Coevolution of Parochial Altruism and War" appearing in the October 26 issue of Science, SFI researcher Samuel Bowles and colleague Jung-Kyoo Choi of Kyungpook National University in South Korea suggest that the altruistic and warlike aspects of human nature may have a common origin.

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 to human nature, but we don't immediately think of them as working together hand in hand. In fact the unexpected combination of these two behaviors may have enabled the survival of each trait according to Bowles and Choi.

They show that the two behaviors – which they term "parochial altruism" – may have in fact coevolved. On the face of it joining parochialism to altruism is puzzling from an evolutionary perspective because both behaviors reduce one's payoffs by comparison to what one would gain by avoiding them. Aggression consumes resources and risks death; altruism, particularly toward those with whom we have no direct relationship, has the effect of helping other genes advance at our expense. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to the success of these conflicts.

Using game theoretic analysis and agent-based simulations Bowles and Choi show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans neither parochialsim nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

"But even if a parochial form of altruism may be our legacy," said Bowles, "it need not be our fate." He pointed to the many examples of contemporary altruism extending beyond group boundaries, and the fact that hostility toward outsiders is often redirected or eliminated entirely in a matter of years.

Now, none of this actually mentions religion. Choi and Bowles don't discuss it. So where does religion come into it? We'll get to that shortly. But first, let's review a bit about how altruism and cooperation in human cultures are thought to have evolved.

At first, it could seem that altruism and cooperation are unlikely to have evolved in humans at all, because they seem to be traits of an individual that are of more benefit to others than to the individual who happens to possess them.

However, there is a long history of evolutionary studies that have suggested how tendencies toward altruism and cooperation could have evolved in human groups. For example, starting in 1964 William D. Hamilton argued that altruism toward blood relatives helped to favor shared genes that fostered such altruism. This was termed "kin altruism".

Additional scientific consideration of the evolution of morality, altruism, and cooperation took off in the 1970s, in the work of people like Robert Trivers and Robert Axelrod. Using game theoretic arguments and simulations they showed how another type of altruism – "reciprocal altruism" – could arise in populations where individuals interacted frequently and could learn which others had earned a reputation for dependability in their dealings with other group members.

Many, many others have written on the subject since then, such as Edward O. Wilson (e. g. Consilience, published in 1998), and Steven Pinker (How the Mind Works, published in 1997). A very good history of the subject up until 1996 can be found in Matt Ridley's The Origins of Virtue.

On the other hand, in spite of arguments advanced showing the benefits to individuals of practicing altruism within a single tribe or cultural group, the fact remains that separate, unrelated groups could easily come into conflict over access to resources (e. g. water, game, other food sources, etc.), especially in times of scarcity due to overpopulation, unfavorable climate, etc. The result would be warfare.

Many people have also studied how evolutionary tendencies have contributed to aggression and warlike behavior between competing human groups. It seems that separate groups that have relatively low genetic similarity to each other and must compete for scarce resources have a notable tendency to come into conflict with each other, and to solve their problems of overpopulation or resource scarcity by killing as many members of the other group as possible. A good exposition of such ideas can be found in this article by Keith Henson: Evolutionary Psychology, Memes and the Origin of War.

It seems very reasonable to see such considerations as the source of the very human tendency to exhibit distrust and even hostility towards other humans who are noticeably "different", especially in physical characteristics, but also when there are simply cultural differences in taste, belief systems, etc.

Furthermore, when conflict between groups does occur and takes the form of open warfare, there is a distinct advantage for groups that have a high percentage of individuals who behave altruistically and cooperatively with each other. If you accept the (somewhat controversial) notion of evolutionary "group selection", this fact provides yet another evolutionary argument for the development of a third type of altruism – parochial altruism – within groups – because groups with the higher percentage of members who cooperate with each other will tend to prevail.

However, there is another side to this story. Individuals will not entirely lose a tendency to gain personal advantage through selfish behavior (such as hoarding food). Altruism can be disadvantageous for an individual if it goes too far, so there is some evolutionary pressure against it also. In an environment where scarcity of resources is not a large problem, individuals can serve their own interests by being open to interaction with members of other groups – especially for commerce and trading of "excess" goods. Individuals who are selfishly willing to trade their goods with members of other groups for the best exchange they can achieve will tend to do better for themselves since they are willing to "sell" to the highest bidder, regardless of group membership.

This, then, is the setting on which Choi and Bowles based their simulation. They considered two kinds of traits an individual could have. One related to altruism (A) vs. selfishness (N, for "not altruistic"). The other related to tolerance (T) vs. hostility (P, for "parochial") towards member of other groups. Any given individual could have one of four possible combinations (AT, AP, NT, NP). They started with groups having members with differing proportions of each possible combination.

Absent intergroup conflict, NT individuals (the most tolerant but selfish) tend to be most successful, and AP the least successful. But when intergroup conflicts occur, groups with the most AP types do better than groups with the most NT types. The simulations proceeded over thousands of generations, and a variety of parameters, all believed to be consistent with what is known about late Pleistocene hunter-gatherer human tribes, were tested.

The net result was that groups with many NT or AP individuals can both be successful, depending on how much warfare occurs (which depends on environmental conditions). But in most cases, groups with high proportions of NP or AT individuals lose out under any conditions. So one conclusion is that in order to have a lot of altruism within a group, you have to expect a lot of parochial intergroup hostility. Conversely, in order to have groups with a lot of tolerance towards other groups, you should expect less altruism and cooperation within the group. Choi and Bowles maintain that the same results tend to arise from a wide variety of different initial conditions.

True, this is "only" a simulation study. And it rests on the assumption that altruism and parochialism (or their opposites) are heritable traits (which alternatively might be transmitted culturally rather than genetically). But it seems to give results that accord well with what we know of human history. And that's where religion enters the picture. (Choi and Bowles do not discuss religion, so what follows is based on their findings, but also the contributions of others.)

In evolutionary terms, why is it that religion is so widespread in human societies? There are a variety of plausible explanations. One is that religion provides the rationale for moral and ethical principles that promote intergroup cooperation and altruism. The argument made by supporters of this idea – such as David Sloan Wilson in his book Darwin's Cathedral: Evolution, Religion, and the Nature of Society – is that societies and cultures with strong religion-based ethical and moral principles have a competitive advantage over other groups.

However, what the Choi-Bowles simulation suggests is that this advantage is realized only when groups often engage in conflict and war. For otherwise, there is an advantage for groups with lots of tolerance towards other groups, and lots of free-traders working for their own self-interest.

So, ironically, religion may have developed as a result of intergroup warfare, as a social artifact that helps justify intragroup altruism that actually was selected for because of the warfare. And at the same time, religion would also incorporate a justification for the intergroup hostility and aggression that arose from the same evolutionary process.

In other words, evolutionary pressures tend to bring about an association of religion and warfare. Note that this is not saying religion "causes" war. Indeed, evolutionary theory suggests that overpopulation and resource limits usually tend to be what "causes" war. But when such conditions prevail, it isn't too surprising to find a close association between religion and war. Just recall the slogan some religious believers are so fond of: "There are no atheists in foxholes." (In other words, most of the cannon fodder found in foxholes and military cemeteries is (or was) religious believers.)

Of course, most religions aren't pro-war full time. Many religious believers oppose war because of their faith. Nevertheless, most religions have their holy warriors, such as Mujahideen and Crusaders. (Military equipment of predominantly Christian nations is sometimes named a Crusader.) Most religions have their own versions of Onward Christian Soldiers. And most religions celebrate war in other ways.

But is there scientific evidence of a relation between religion and war? Yes. Consider this:

When God Sanctions Violence, Believers Act More Aggressively

Reading violent scriptures increases aggressive behavior, especially among believers, a new study finds. The study by University of Michigan social psychologist Brad Bushman and colleagues helps to illuminate one of the ways that violence and behavior are linked.

"To justify their actions, violent people often claim that God has sanctioned their behavior," said Bushman, faculty associate at the U-M Institute for Social Research and lead author of the article published in the March 2007 issue of Psychological Science. "Christian extremists, Jewish reactionaries and Islamic fundamentalists all can cite scriptures that seem to encourage or at least support aggression against unbelievers."

To be sure, this is hardly a new observation. Mark Twain, as well as many others before him, had already nailed it.

Update (11/13/07): I see that I missed one of the U. S. military's pricey toys proposed artillery systems (which was canceled in 2002) that used the "Crusader" moniker – the Crusader 155mm Self-Propelled Howiter. See here or here. Onward, Christian soldiers, indeed.