Only three types of creatures engage in warfare: humans, chimpanzees and ants. In the case of ants, we assume war is instinctually driven. Many have concluded that the same is also true of humans. After all, the earliest archeological evidence of human war is from 12,000 years ago, dating back to the very beginning of settled, agricultural life, and well before such innovations as capitalism and cities.
Sweeping through recorded history, you can find a predilection for warfare among hunter-gatherers, herding and farming peoples, industrial and even postindustrial societies, democracies and dictatorships. The old pop-feminist explanation -- testosterone -- would seem, at first sight, to fit the facts.
But war is too complex and collective an activity to be accounted for by any warlike instinct lurking within the individual psyche. Violent battles are only one part of war, most of which consists of preparation for battle, of things like training, weapons manufacturing and organizing supply lines. There is no plausible instinct, for example, that could impel a man to leave home, cut his hair short and drill for hours in tight formation. "The hypothesis of a killer instinct," concluded some of the world's leading anthropologists of war at a 1989 conference, "is not so much wrong as irrelevant."
Furthermore, contrary to the biological theories of war, it is not easy to get men to fight. In recent centuries, men have often gone to great lengths to avoid war -- fleeing their homelands, shooting off their index fingers, feigning insanity. So unreliable was the rank and file of the famed 18th century Prussian army that military rules forbade camping near wooded areas: The troops would simply melt away into the trees. Even when assembled for battle, killing is not something that seems to come naturally to men. As Lt. Col. Dave Grossman argued in his 1995 book "On Killing: The Psychological Cost of Learning to Kill in War and Society," one of the great challenges of military training is to get soldiers to shoot directly at individual enemies.
If not human nature or testosterone, what is it then that has made war such an inescapable part of the human experience? Each war, of course, appears to the participants to have an immediate purpose -- to crush the "Hun," to preserve democracy, to disarm Saddam Hussein -- that makes it necessary and even noble. But those who study war dispassionately, as a recurrent event with no moral content, have observed a certain mathematical pattern: that of "epidemicity," or the tendency of war to spread in the manner of an infectious disease. Obviously war is not the work of microbes, but it does spread geographically in a disease-like manner, usually as groups take up warfare in response to warlike neighbors. It also spreads through time, as the losses suffered in one war call forth new wars of retaliation. Think of World War I, which broke out for no good reason at all, drew in most of Europe as well as the United States, and then "reproduced" itself, after a couple of decades, as World War II.
In other words, as the Dutch social scientist Henk Houweling puts it, "one of the causes of war is war itself." Wars produce warlike societies, which in turn make the world more dangerous for other societies, which are thus recruited into being war-prone themselves. Just as there is no gene for war, neither is there a single type or feature of society -- patriarchy, for example, or hierarchy -- that generates it. War begets war, and shapes human societies as it does so.
War puts its stamp on human societies by requiring that they possess two things: some group or class of men (and in quite a few historical settings, women) who are trained to fight; and the resources to arm and feed them. These requirements have often been compatible with patriarchal cultures dominated by a warrior elite, as with the knights of feudal Europe or the samurai of Japan. But not always. Different ways of fighting seem to lead to different forms of social and political organization.
Historian Victor Davis Hanson has argued that the phalanx formation adopted by the ancient Greeks, with its stress on equality and interdependence, was a factor favoring the emergence of democracy among nonslave Greek males. And there is no question but that the mass, gun-wielding armies of Europe in the 17th century contributed to the development of the modern nation-state -- if only as a bureaucratic apparatus to collect the taxes required to support and arm so many nonproductive men.
Marx was wrong: It is not only the "means of production" that shape societies, but the means of destruction. In our own time, the costs of war, or just war readiness, are daunting. Not only must nations maintain a mass standing army -- the United States supports about a million men and women at arms -- they must also keep up with an extremely expensive, ever-changing technology of war. The resulting cost squeeze has led to a new type of society, perhaps best termed a "depleted" state, in which the military has drained resources from all other social functions. North Korea is a particularly ghoulish example, where starvation coexists with nuclear weapons development. But the Soviet Union also crumbled under the weight of militarism, and the United States, in order to brandish its military might around the world, is at this moment cutting assistance to the poor, from school lunches to health care to food assistance.
If war can be likened to an epidemic, it is a particularly tough one to eradicate, behaving more like a parasite than a virus. It cannot exist without humans (or, in the nonhuman cases, chimpanzees or ants), and it thrives at our expense, a beast attached to the neck of living prey, feeding on human effort, heroism and blood.
It can't be conquered merely by trying to uproot whatever violent or warlike inclinations may dwell within our hearts. Abjuring violent speech and imagery, critiquing masculinist culture and promoting respect for human diversity, though worthy projects, will make little contribution to the abolition of war. It would be far better to think of war as something external to ourselves, something that has to be uprooted and dismembered, multilaterally, everywhere, down to the last weapon and bellicose pageant.
The "epidemicity" of war has another clear implication, one George W. Bush and his "coalition of the willing" would do well to heed: War cannot be used as a means to prevent or abolish war. True, for some time to come, urgent threats from other heavily armed states may require armed force in response. But these must be very urgent threats and extremely restrained responses. To continue the metaphor of war as a kind of living creature, a parasite on human societies: The idea of a war to prevent war is one of its oldest, and cruelest, tricks.