Personally, I prefer to believe that genes do not have much effect on what I am like. It has taken me decades to recognise the irrationality of this genophobia and my greatest aid in this has been the writings and advice of a behavioural geneticist, Professor Robert Plomin.
Plomin's focus is why we are different from our siblings, why humans are different from each other as individuals rather than why we are like we are as a species.
Before coming to London's Institute of Psychiatry to head a big new study of British twins, Plomin was in America. One of the main reasons that he is the world's leading behavioural geneticist has been his attempt to give proper due to both sides of the nature-nurture divide - without just producing the usual "it's a bit of both" cop-out.
In 1987 he co-authored a paper suggesting that the most important implication of twin and adoption studies is not that behaviour is partly heritable, but that they provide the strongest evidence that environment is also extremely important. Since identical twins have the same genes, he pointed out, any differences between them could not be inherited. Given that identical twins are very different in a great many respects, this proves the role of environment.
In recent papers, mostly co-authored by his colleague, the distinguished doyenne of child development Sir Michael Rutter, Plomin has been challenging the likes of me still further. Now he is claiming that we need not fear the implications of molecular genetics, the study of differences in DNA.
He takes as an example the association between a particular gene known as DRD4 and novelty-seeking. All of us have DRD4 but some have a long variant, and these people are more prone to novelty-seeking.
Nothing wrong with a bit of novelty-seeking, you may say. Large doses of it are essential to originality in many fields and it is highly probable that such people will turn out to be more likely to have the long DRD4. However, children with the long variant are more likely to suffer from Attention Deficit-Hyperactivity Disorder (ADHD). Heroin addicts are more likely to have the variant, and so are people suffering from major depressions.
What are the practical applications for the thinking liberal working in the welfare system or parent of a child who has ADHD? Plomin's answer is that nearly all the genes associated with behaviour confer susceptibility; they do not predict specific outcomes in individuals, only that there is a greater likelihood in some than others if they have a gene variant. This creates the potential for environmental interventions.
Suppose that a child has been identified as having the DRD4 long variant and has ADHD. The parents could be taught specific skills to divert the child's novelty-seeking to more creative, less destructive outlets.
Plomin argues that environmentalists like me who are convinced that the way parents treat their children and social class are the major determinants of how we turn out should recognise that genetic evidence can help us to focus more precisely on what to study.
Thus far, the amount of difference between individuals that molecular genetics can explain is tiny. This suggests even more than the findings of twin and adoption studies that environmental causes are critical. Indeed, if molecular genetics continue to find such small effects of genes on behaviour, it may require us to rethink the validity of twin and adoption studies (which sometimes show heritabilities of 60 per cent, as in manic depression) because molecular genetic findings are more to be relied upon.
Plomin says that environmental studies to date have been flawed and that more targeted research is needed as well as molecular genetic studies. I agree.
Take one example: the effects of leaving babies to cry versus picking them up. Given that many clinicians believe early infantile neglect is a big cause of mental illness in adulthood you would have thought this would have been established one way or the other. Not a bit of it. It would be a simple enough study, but very few of the relevant university academics would even consider it. They have a revulsion towards any theory which derives from Freud and psychoanalysis and so almost the only place at which scientific work is done to test these kinds of hypotheses occurs at one institution (University College London, overseen by the Professor of Psychoanalysis, Peter Fonagy).
The refusal to test the theory that early childhood experiences have long-term effects means that parents, and clinicians who treat troubled adults, are often shooting in the dark. It creates a vacuum liable to be filled by expedient prejudice.
A study comparing the beliefs of working and non-working mothers showed that the workers tended to believe that how we turn out has little to do with our childcare, more to do with genes. The non-workers believed that childcare is critical.
It is a massive indictment of child psychology academics that more than 50 years after this question was first raised as a scientific issue, we are so little nearer to a properly scientific answer. Their refusal to confront such fundamental issues means we are failing to capitalise on the work of Plomin and his colleagues.
With the help of genetic research we could be identifying what is and what is not crucial in the early environment for subsequent adult adjustment, using the results to influence parents, therapy and social policies.
Oliver James' book, `Britain On The Couch - Why We're Unhappier Compared With 1950 Despite Being Richer', is published by Century.