Biology is not destiny. But it sure explains a whole lot of human activity, as Malcolm Potts and Thomas Hayden describe in their book, Sex and War: How Biology Explains Warfare and Terrorism and Offers a Path to a Safer World (Benbella Books, 2008), which I strongly feel is a must read for anyone dealing with conflict prevention and resolution today.

Chimpanzees, our closest cousins, share more than 98 per cent of our DNA, and many of our social, and antisocial, behaviours. Most disturbingly, we are perhaps the only two species that deliberately torture and kill their own kind. The evolutionary success of genes that enhance team aggression by small groups of males on others, both male and female, have bequeathed both species' descendants a dark side.

Male team aggression, aided by reinforcing the cohesion of an in-group and dehumanising the out-group, is as essential for warfare and terrorism today as it was for raids on neighbouring troops by our ancient ancestors. Chimpanzee males move around their territory in groups of four or five, foraging and patrolling the boundaries of that territory. If they run into a similarly sized group from a neighbouring territory, both sides will make a lot of noise and bluster, but it rarely leads to a real fight.

If, however, the party finds a smaller group or a lone individual from the next-door troop, they sometimes attack with shocking cruelty, with, for example, some males holding their victim down while others rip flesh off the hapless animal, stomp on it, bite fingers off or tear testicles off. Sometimes such a raid has a clear biological logic to it: the males may haul off young females from their neighbours, a behaviour which is obviously going to be passed on to the next generation rather immediately. Other times, there is no straightforward reason for a particular event.

However, behaviour that is evolutionarily successful need not demonstrate its gene-passing benefit on every occasion. It is enough for such male team aggression to bring evolutionary rewards only sometimes, and as long as it isn't detrimental to the likelihood of an individual passing on its genes it can be a successful trait. A tendency to initiate violence when there are even numbers in a fight might not be a trait you get a chance to pass on, but a behaviour of attacking when the odds are in you favour clearly is.

What's this got to do with us humans? Well, apart from the ganging up on individuals that will be familiar to anyone who was ever picked on in the school yard, there is a lot here to explain our propensity for conflict more generally. It's not that modern human conflicts are about stealing the females of a neighbouring troop, of course, but the tendency toward certain unconscious behaviours we share with chimps are still with us, coded in our DNA, and that affects our actions in some predictable ways.

Look at how fighting forces have been arranged over the course of recorded history: from raiding parties to massive armies, the core military unit has not been a group of hundreds or thousands but a tight band of four or five men -- a "fireteam" in current lingo, the unit that the modern infantry is based on. This small, core group engaging in destructive team aggression is repeatedly successful in war because it is reinforced by a variety of different behaviours, including the camaraderie that naturally (key word there) develops between men in such conditions. Whether an infantryman in a first world army, a street gang member in a blood feud, or a terrorist about to use a passenger plane as a mass murder weapon, the size of the basic attack unit is more or less the same, and there's a reason for that.

The authors go on to develop other aspects of evolutionary psychology and apply them to modern warfare, taking the reader through the World Wars, the Cuban Missile Crisis, Iraq, Lebanon, modern terrorism and much else besides. For example, our innate desire for revenge in certain situations and our tendency to distort the scale of threats under particular conditions can cause extreme, disproportionate and even self-damaging responses to attacks of far smaller size -- clear in the US reaction to 9/11. Our vulnerability to in-group/out-group mentality is also vital to warfare: dehumanising the enemy is as common to war as blood.

Again, the idea is not that modern soldiers or modern political leaders are after plunder and booty like barbarian raiders or chimpanzees -- though surely some consciously are in some current conflicts -- but that the underlying nature of human warfare is driven by factors of evolutionary psychology that are irrevocably part of us all.

Of course, no biological explanation excuses evil acts. But it is essential to conflict prevention and resolution to understand how these natures are in every human being: "It is tempting, but misleading, to try to make the rest of the world 'normal' by demonising Hitler. An evolutionary approach to understanding evil is at the same time both more humbling and more challenging. Hitler was a sociopath, but the Holocaust had millions of active participants and passive observers."

The authors continue a bit later: "...human beings are condemned to live in two ethical and behavioural worlds at once -- the morality of empathy for and reciprocity with ingroups, and the cold-hearted team aggression aimed at outgroups."

Of course, the cruel logic of team aggression applies almost exclusively to young men. And that's where the issues of population size and structure come in. Rapid population growth means a youthful demographic curve, and a larger proportion of young men means a greater natural propensity toward a violent and unstable society. Look around the world at states that manage to get their population growth under control, and you almost invariably find more peaceful and secure countries than those that don't.

Though stressing the genetic factors beyond our control, the authors are not deterministic or depressingly fatalistic about our future as a species. They are completely clear that, in an ever more vulnerably interconnected world with weapons of mass destruction, our "Stone Age" behaviours and potential for extreme violence have become hugely maladaptive. But we can manage to avoid disasters if we approach issues of conflict bearing our evolutionary psychology firmly in mind. Civilisation can, and quite often does, trump biology.

One hopeful tool is simply diplomacy, which has no parallel among chimpanzees. Working to keep arms out of the hands of potential enemies is also an obvious and frequently achievable goal. Reducing the level of conflict -- if not actually eliminating it as we have nearly done with slavery, another long-lived behaviour backed up by a number of our genetic predispositions -- will require some additional steps.

A key method for conflict reduction is empowering women. For one, women are generally less predisposed to violence, meaning that their social, economic and political equality should on average lead to less violent societies. The second point on empowering women is much more specific: provide easy access to birth control and reproductive health. When women can control the number of children they have, they invariably choose to do so, which constricts the demographic pyramid away from a bottom bulge of angry young men and towards a more stable and less violent society.

Another important idea is to keep expanding the concept of our in-group to include all of humanity. Aid and development workers like Potts have been doing this for years, but it goes beyond individuals, of course. The whole concept of universal human rights expands the in-group to everyone, for example. True, it too often remains just a concept, and enemies are all too easily dehumanised into an out-group with ease. But there are other evolved primate characteristics, such as a sense of fairness and a capacity for empathy, that mean we are not facing our darker natures completely unarmed genetically.

Despite its 400 pages and its extensive references to source material ranging from history to philosophy to psychology to genetics, Sex and War is only the start of a more complete view of human conflict, its prevention and its resolution. The field has strong promise: "The standard social science model looks for the causes of war; the evolutionary model seeks ways to make peace break out, while always expecting the worst."

I'm sure that part of the reason I find it so compelling is that, personally, it helps me tie together my biology degree, which had a focus on evolutionary theory, with my degree in politics/social science and my years of covering violent conflict around the world as a journalist and NGO-type. I suppose this book makes many points other people will want to argue with, but at its core, it holds up an uncomfortable mirror to our species that we would be ill-advised to put down.

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Note: This review is a much expanded version of a piece I wrote for the European Voice last week. The original short article is here.

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