UNDER THE MICROSCOPE : A question of determination

I bet my DNA that I am right - whoever wrote that leader in a recent Economist editorial entitled the "Genetic Illusion" was no scientist and so, naturally, knew little about genetics. The core of the argument is that it is an illusion to think that our actions, and those of our fellow humans, are determined by their genes and not by free will; debates about whether intelligence is inherited or environmentally determined are called "vacuous". Genetics, it asserted, is not destiny.

I have a little sympathy with the writer as it is all too easy to be misled as to what genes actually do for us. There is no gene, for example, for the eye; many hundreds, if not thousands, are involved, but a fault in just one can lead to major abnormalities. The language in which many of the effects of genes is described leads to confusion. No sensible person would say that the brakes of a car are for causing accidents. Yet, using a convenient shorthand, there are numerous references to, for example, the gene for homosexuality or the gene for criminality. When the brakes of the car which are there for safe driving fail, then there is an accident. Similarly, if criminality has some genetic basis then it is not because there is a gene for criminality but because of a fault in the genetic complement which has resulted in this particular undesirable effect. It could have affected how the brain developed - genes control the development of every bit of our bodies - or it could be due to malfunction of the adult nerve cells.

There is clearly considerable resistance to accepting that much of our destiny is due to our genetic inheritance. But just think about the differences between men and women. Only a blinkered, unthinking feminist could believe that the differences are all cultural. There is evidence of male superiority in mathematically gifted children and that in women, unlike men, language and spatial skills are located in both sides of the brain. It seems that female attachment to infants is innate, whereas with men it has to be learned. There is no equivalent in men of the menstrual cycle and its psychological and physical effects.

Shortly after we are conceived, the embryo from which we develop is indifferent with respect to sexual differentiation. Female and male embryos look identical. Then, in males, a testis develops and secretes the hormone testosterone and it is its effects on the embryos' cells, activating numerous genes, that makes males different from females. The key controller is the Y chromosome with its package of genes. For a good example of genes determining our destiny the Y chromosome is the place to look. If you doubt that genes can determine criminality, look no further, for it is men who commit violent crimes, not women.

Why is there so much resistance to accepting that genes play an important role in our behaviour? It probably stems from the standard social science model of human behaviour which has, at its core, that most of our behaviour and beliefs are culturally determined. In opposition to this there is the model emerging in which biology is central but which does not deny the importance of culture. We are born with a much more sophisticated set of brain functions, all programmed by genes, than anyone previously thought. At birth we already have a concept of numbers and relate to human faces in a very definite way.

Such knowledge could be helpful to society. If we understood the biological basis of criminality we might be able to do something quite new about it and could treat such people in the light of that knowledge. And if there is found to be a genetic basis for homosexuality it could reduce, for some at least, parental guilt, as well as analysts' fees.

It is puzzling that the writer of that editorial did not read the excellent article a few pages later on the human genome project. I can only applaud its conclusion.

"Knowing thyself is not always a comfortable process. But it is better than ignorance." Free will is uncomfortably constrained by our biology, and so by our genes.

! Lewis Wolpert lectures at University College London