The Pima Indians in Arizona, US, are a particularly dramatic example. They maintained a traditional way of life, relying on farming, hunting and fishing for food, until the late nineteenth century. Then, diversion of their water supply by American farmers upstream drove them to poverty and malnutrition, even starvation. The Second World War brought both prosperity and contact with Caucasian Americans, which westernised their dietary and lifestyle habits. Since then, the Pima Indians as a group have put on an unhealthy amount of weight. Half of the adults have diabetes and 95 per cent of those are overweight. Scientists from the US Government’s National Institute of Health have studied the Pima Indians for more than thirty years, looking for genetic causes of diabetes and obesity.
Just as the Pima Indians are physically adapted for a traditional lifestyle, our minds may be geared to deal with traditional dangers. We still eat as if food shortages were imminent; perhaps we are also still on the look-out for predators and natural threats. Certainly, evolutionary psychiatrists Randolph Nesse at the University of Michigan, and Isaac Marks, from London University, believe that we are all programmed to react to threats. Anxiety and fear are necessary, they say, and have been essential for our survival throughout evolution.
At the simplest level, mild anxiety boosts performance. It prompts the student to revise for exams, the musician to practise, the sales rep to rehearse a presentation. But evolutionists say it is far more sophisticated than that.
We could improve our understanding of anxiety at a stroke if we stopped thinking of it as a disorder, and considered it a defence that regulates and orchestrates our reactions to every threat and opportunity, say Nesse and Marks. The anxiety system is as important to our survival as is our immune system. It protects against threats to our whole body, and life, in the way that the immune system fights off specific physical threats. Both defence systems have developed within our species as we evolved. The individuals with appropriate reactions to danger or to micro-organisms are most likely to survive, produce offspring and pass on these traits to future generations.
Both have a range of reactions to meet specific threats. The immune system creates a scab to heal a cut finger and produces antibodies to deal with viruses. Similarly, at least some of our reactions to danger are clearly adaptive and matched exactly to the threat, say Marks and Nesse. For example, people who are afraid of heights may ‘freeze’ if they have to walk along a ledge or cross a narrow bridge. They cling to the side, unable to move. They may need a companion’s reassurance and physical assistance to get going again. This sort of reaction is not helpful if it stops you climbing stairs but in natural surroundings someone who became immobile by the side of a sheer drop might avoid a bad fall.
Blushing often seems to make a difficult situation worse. People who lack confidence in social gatherings dread being the centre of attention and burning cheeks do not help anyone blend into the background. But if, as has been argued, blushing signals social submission, a red face could be a plea for continued membership of the group. In ancient times, membership of a group would have been near-essential for survival. Anyone expelled and left alone would become vulnerable to cold, starvation and attack. They would also be unlikely to pass their influence on to the next generation if they could not reproduce.
Blood and injury phobias provide an intriguing physiological example of the possible benefits of an anxiety response. People with these phobias may faint at the scene of an accident or even at the sight of a syringe or needle. These are the only phobias associated with fainting. Someone with agoraphobia may feel extremely dizzy or uncomfortable in a crowded street and believe they are going to pass out, but they almost never do. As the agoraphobic prepares to flee the difficult situation, rising blood pressure effectively prevents a faint. By contrast, the blood and injury phobics’ blood pressure drops at the sight of blood, and they often do pass out. Nesse and Marks argue that this, again, could be adaptive. If a hunter saw blood, it was more likely to be his own than anyone else’s. An injured man loses less blood if his blood pressure drops. Even if he fainted, this could conceivably be useful. Some animals only attack moving creatures and lying still might just discourage further attack by predators.
Many animals are known to play dead while remaining conscious. Charles Darwin himself once caught a robin in a room and said it ‘fainted so completely, that for a time I thought it was dead’. David Barlow, an eminent psychologist in Albany, New York, says there may be a human parallel. Women who have been raped frequently describe being paralysed, rigid and cold during the attack. They are not unconscious because they can later remember details of what happened. In the past, this freezing has been wrongly taken by courts to mean that the women somehow consented to sex. Barlow says their immobility may in fact be an ancient defence mechanism. Remaining still may reduce further violence by a more powerful assailant and could conceivably reduce his sexual arousal.
In this way, the nature of a reaction is matched to the threat. Blushing is not likely to scare off a snake and freezing would not help in a difficult social situation. Normal phases of development also fit the evolutionists’ model. Babies may suddenly become afraid of strangers between six and twelve months old, just when they are starting to crawl and coming into more contact with unknown people. Animal fears peak at about four years old, the age when they may start meeting and playing with animals unattended. Social phobia typically starts in the late teens, just when young people are establishing their identities and facing all sorts of social pitfalls. While it would be unwise to take the argument too far – even Marks and Nesse have admitted that imaginative thinkers could come up with an adaptive use for virtually any human reaction – there are many compelling examples.
The strength of a reaction to a threat is every bit as important as its nature. Both the anxiety and immune systems are tightly regulated and over- or under-reaction causes problems. The human immunodeficiency virus, HIV, does not itself kill, but its destruction of immune defences means normally harmless bacterial and viral infections can become fatal. At the other end of the scale, allergies and hay fever develop when the immune system is overreacting to irrelevant stimuli like dust or pollen.
Anxiety is similar, argue Marks and Nesse. An underactive anxiety system may create real problems, as demonstrated by Max Klein in Fearless. A lack of concern about the future sounds wonderful, but not if this destroys all ability to plan for it. Never worrying about the consequences of your actions may mean you speak out when it would be diplomatic to say nothing. Telling your boss exactly what you think of him or her is a fantasy for many of us, but we never do it. A moment of extreme satisfaction could cost you your job. Similarly, you might feel like objecting loudly when someone pushes past you at a bar, but if they are big, drunk and bad-tempered, you probably keep your feelings to yourself. Those without normal levels of anxiety may lack basic caution and end up losing jobs and getting into fights where others simply sidestep trouble. Without the push of anxiety, it may be difficult to revise for exams or apply yourself to any long-term project. Marks has termed this hypophobia. It is interesting but speculative. It has not been studied much because those who lack anxiety often don’t imagine they have a problem and tend not to come forward for help. However, New Zealand researchers have some evidence to back the idea and at the same time, challenge the widespread assumption that a traumatic experience can trigger a phobia. They looked for height phobias among children who had serious falls between the ages of five and nine. They found that, at eighteen, these children were much less – not much more – likely than others to have height phobias. This study implies that temperament (discussed in chapter 7) may be all-important and suggests that children without fear, those who have never worried about heights may be hypophobic, and most likely to injure themselves in a fall.
The over-reactive