Genome - Matt Ridley

I promised not to bore you, but let me just take a quick glimpse at one of the effects of Cortisol. In white blood cells Cortisol is almost certainly involved in switching on a gene called TCF, also on chromosome 10, thus enabling TCF to make its own protein, whose job is to suppress the expression of another protein called interleukin 2, and interleukin 2 is a chemical that puts white blood cells on alert to be especially vigilant for germs. So Cortisol suppresses the immune alertness of white blood cells and makes you more susceptible to disease.

The question I want to put in front of you is: who's in charge?

Who ordered all these switches to be set in the right way in the first place, and who decides when to start to let loose the Cortisol?

You could argue that the genes are in charge, because the differentiation of the body into different cell types, each with different genes switched on, was at root a genetic process. But that's misleading, because genes are not the cause of stress. The death of a loved one, or an impending exam do not speak directly to the genes. They are information processed by the brain.

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So the brain is in charge. The hypothalamus of the brain sends out the signal that tells the pituitary gland to release a hormone that tells the adrenal gland to make and secrete Cortisol. The hypothalamus takes its orders from the conscious part of the brain which gets its information from the outside world.

But that's not much of an answer either, because the brain is part of the body. The reason the hypothalamus stimulates the pituitary which stimulates the adrenal cortex is not because the brain decided or learnt that this was a good way to do things. It did not set up the system in such a way that thinking about an impending exam would make you less resistant to catching a cold. Natural selection did that (for reasons I will come back to shortly). And in any case, it is a wholly involuntary and unconscious reaction, which implies that it is the exam, rather than the brain, that is in charge of events.

And if the exam is in charge, then society is to blame, but what is society but a collection of individuals, which brings us back to bodies? Besides, people vary in their susceptibility to stress. Some find impending exams terrifying, others take them in their stride.

What is the difference? Somewhere down the cascade of events that is the production, control and reaction to Cortisol, stress-prone people must have subtly different genes from phlegmatic folk. But who or what controls these genetic differences?

The truth is that nobody is in charge. It is the hardest thing for human beings to get used to, but the world is full of intricate, cleverly designed and interconnected systems that do not have control centres. The economy is such a system. The illusion that economies run better if somebody is put in charge of them - and decides what gets manufactured where and by whom - has done devastating harm to the wealth and health of peoples all over the world, not just in the former Soviet Union, but in the west as well.

From the Roman Empire to the European Union's high-definition television initiative, centralised decisions about what to invest in have been disastrously worse than the decentralised chaos of the market. Economies are not centralised systems; they are markets with decentralised, diffuse controls.

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It is the same with the body. You are not a brain running a body by switching on hormones. Nor are you a body running a genome by switching on hormone receptors. Nor are you a genome running a brain by switching on genes that switch on hormones. You are all of these at once.

Many of the oldest arguments in psychology boil down to misconceptions of this kind. The arguments for and against 'genetic determinism' presuppose that the involvement of the genome places it above and beyond the body. But as we have seen it is the body that switches on genes when it needs them, often in response to a more or less cerebral, or even conscious, reaction to external events.

You can raise your Cortisol levels just by thinking about stressful eventualities - even fictional ones. Likewise, the dispute between those who believe that a certain suffering is purely psychiatric and those who insist it has a physical cause - consider M E , or chronic fatigue syndrome - is missing the point entirely. The brain and the body are part of the same system. If the brain, responding to psychological stress, stimulates the release of Cortisol and Cortisol suppresses the reactivity of the immune system, then a dormant viral infection may well flare up, or a new one catch hold. The symptoms may indeed be physical and the causes psychological. If a disease affects the brain and alters the mood, the causes may be physical and the symptoms psychological.

This topic is known as psychoneuroimmunology, and it is slowly inching its way into fashion, mostly resisted by doctors and mostly hyped by faith healers of one kind or another. But the evidence is real enough. Chronically unhappy nurses have more episodes of cold sores than others who also carry the virus. People with anxious personalities have more outbreaks of genital herpes than sunny optimists. At West Point military academy, the students most likely to catch mononucleosis (glandular fever), and the ones most likely to get a severe illness from it if they do, are the ones who are most anxious and pressured by their work. Those who care for Alzheimer's patients (an especially stressful activity) have fewer disease-fighting T lymphocytes in their blood than expected. Those S T R E S S 153

who lived near Three Mile Island nuclear plant at the time of its accident had more cancers than expected three years later, not because they were exposed to radiation (they weren't), but because their Cortisol levels had risen, reducing the responsiveness of their immune system to cancer cells. Those bereaved by the death of a spouse have a less responsive immune system for several weeks afterwards. Children whose families have been riven by a parental argument in the previous week are more likely to catch viral infections. People with most psychological stress in their past get more colds than people who have led happy lives. And if you find these sorts of studies hard to believe, then most of them have been replicated in some form or another using mice or rats.1

Poor old Rene Descartes usually gets the blame for the dualism that has dominated western thinking and made us all so resistant to the idea that the mind can affect the body and the body can affect the mind, too. He barely deserves the blame for an error we all commit. In any case, the fault is not so much dualism — the notion of a separate mind detached from the material matter of the brain.

There is a far greater fallacy that we all commit, so easily that we never even notice it. We instinctively assume that bodily biochemistry is cause whereas behaviour is effect, an assumption we have taken to a ridiculous extent in considering the impact of genes upon our lives. If genes are involved in behaviour then it is they that are the cause and they that are deemed immutable. This is a mistake made not just by genetic determinists, but by their vociferous opponents, the people who say behaviour is 'not in the genes'; the people who deplore the fatalism and predestination implied, they say, by behaviour genetics. They give too much ground to their opponents by allowing this assumption to stand, for they tacitly admit that if genes are involved at all, then they are at the top of the hierarchy.

They forget that genes need to be switched on, and external events

- or free-willed behaviour — can switch on genes. Far from us lying at the mercy of our omnipotent genes, it is often our genes that lie at the mercy of us. If you go bungee jumping or take a stressful job, or repeatedly imagine a terrible fear, you will raise your Cortisol 1 5 4 G E N O M E