Conflict resolution

Zoologists used to believe that violence in human society could be traced to higher primates' natural propensity for aggression. But a new theory says that apes are not antagonistic at all. Sanjida O'Connell investigates

In the opening scene of 2001: A Space Odyssey, a group of hominids are gathering food and quarrelling with a rival tribe over access to a waterhole. Violence erupts, and one male beats another to death with a bone. The murder weapon is thrown in the air, and we fast-forward millions of years of human evolution by cutting from the image of the flying bone to a spaceship in flight. The switch in scene has become an icon of how human endeavour can be traced back to a violent ancestry.

More recently, the author William Boyd used the warlike nature of chimpanzees as the background to his novel Brazzaville Beach, which explores the inherent aggression and competition in primate and human societies.

That apes and apemen lead lives that are nasty, brutish and short and thus paved the way for our violent society was the dominant belief among 19th-century scientists. More recently, primatologists such as Richard Wrangham and Dale Peterson have followed in that tradition. In their book Demonic Males, they describe the evil inherent in biology. Their fellow primatologist Alison Jolly, commenting on their work, says: "This book shows why border raids, rape and warfare are the natural inheritance of the human ape. It challenges us to shape human lives more wisely than the gang life of the chimpanzee, our heroic, demonic alter ego."

Now, two primatologists have come up with a new model of primate behaviour, which challenges the central tenet of much of primatology. They believe that apes and monkeys live co-operatively and affectionately with little antagonism.

Dr Robert Sussman, from Washington University, St Louis, and Dr Paul Garber, from the University of Illinois, Urbana, believe that current thinking in primatology is wrong. Sussman has been studying primates for 30 years, mainly ring-tailed lemurs in Madagascar, and it occurred to him that he really had not seen the level of sociability or aggression that most primatologists claim to have witnessed. What really crystallised the debate for him was Demonic Males. In the first chapter, Wrangham and Peterson write: "Killing was the reason we were in Africa. We were exploring the deep origins of human violence, back to the time before our species diverged from rain-forest apes." Sussman says: "They are emphasising things that are almost imaginary."

To prove their case, the two collected data from the vast literature of primate observations published in scientific journals. Sussman's theory is that people emphasise the spectacular. Primatologists, sitting in the field watching their monkeys for hours on end, take more notice of their bad behaviour. Sussman and Garber drily make the point in their paper: "Given that the most aggressive behaviours, such as chases and fighting, are loud and visually conspicuous, these events are unlikely to be missed or underrepresented in field studies." When they had collated their results, they discovered a startling fact: despite the portrayal of primates as incredibly gregarious animals, only 3 per cent of a gorilla's time is spent being social.

The figure is 4-15 per cent in gibbons, and chimpanzees spend a quarter of their time devoted to one another. A tiny fraction of that time was spent being aggressive – 0.6 antagonistic events an hour in monkeys, and only 0.09 events in apes. As the researchers point out, that includes life-threatening attacks but also any kind of aggression, from chasing to a hard stare. To test their results, Sussman followed individual ring-tailed lemurs in Madagascar and found the same pattern: very low rates of aggression and social behaviour. When the animals were interacting socially, they mainly played and groomed. Why, the scientists argue, would animals spend the time making up for fights most of them haven't had? Instead, they believe that affectionate behaviour, rather than aggression, is the driving force behind primate behaviour.

Professor Robin Dunbar, a primatologist based at the University of Liverpool, who has spent a considerable portion of his field research studying baboons, says: "If you don't have the risk of attack, then there is no point in spending all this time engaged in grooming. Grooming isn't there entirely for fun (and certainly not just for hygiene, because they do far too much of it); rather, it's there to bond groups together and build alliances. None of that makes sense unless there is a problem out there that you are trying to defuse by these social means."

Sussman's second line of reasoning comes from squabbles over what matters most to a monkey: food. Most primatologists think that food is the main source of antagonism between monkeys and apes. If groups reach a maximum size quickly, the addition of one or two new members would lead to an increased competition for food. A computer model showed that there is a range of group sizes where food competition will not be a problem, and many primate groups do fall within this range.

The model predicts that there will be few large groups, as they are unstable, a number of small ones, composed of individuals who have left the larger groups, and many intermediate groups. This "group fissioning" does take place in several species, from lemurs to apes. Sussman disagrees even with primatologists such as Professor Frans de Waal, from Emory University, Atlanta, author of Good Natured, which is about how primates need to co-operate and are essentially altruistic. De Waal wrote: "Individuals try to 'undo' the social damage inflicted by aggression; hence they will actively seek contact, specifically with former opponents."

Sussman says: "His book is based on the assumption that primates are good-natured in order to alleviate conflict." Dunbar points out that co-operation without conflict makes no sense. He says: "These views stem from people who seem to want us to be nice to each other and presumably fear that if we even hint at conflict behaviour in humans we'll all rush off and kill each other."

Unlike the majority of primatologists, who believe that social behaviour led to an increase in brain size and helped to enhance our intelligence as our primate ancestors had to deal with the increasing complexity and subtlety of a network of relationships, Sussman and Garber think that the environment played a far bigger role. However, they think that what we are watching are primates who have already been shaped by their environment. "My lemurs behave as they have for 20 million years, and there is no need for them to alter their behaviour unless the environment radically changes," Sussman says.

Dunbar sees two main problems with Sussman's and Garber's hypothesis. First, from an evolutionary point of view, co-operation and conflict must be important. He points out that a couple of quick attacks would have a highly detrimental impact on an ape's fitness, reducing its capacity to find food, escape from predators and produce offspring, and this possibility of an attack, even if it is not realised, has more of an impact than hours spent grooming, which do not hinder the animal's ability to survive.

Moreover, although the environment is important, that is because it creates competition. Dunbar says: "Animals have to bunch together into groups as a defence against predation – if they didn't have to do that, there would be no need to do any grooming." If Sussman is right, we have evolved from creatures who are not demonic at all, but peaceful and easy-going – but who mostly are surviving and not attempting to be social at all. As Sussman says, "When animals have evolved to live in a group, they live peacefully and they enjoy it. They have to."