Ridley - Nature via nurture genes, experience and what makes us human

For Jim

Perverse Mankind! Whose wills, created free,

Charge all their woes on absolute Decree;

All to the dooming Gods their guilt translate,

And follies are miscalld the crimes of Fate.

Homers Odyssey, translated by Alexander Pope

Revealed: the secret of human behaviour, read the banner headline in the British Sunday newspaper the Observer on 11 February 2001. Environment, not genes, key to our acts. The source of the story was Craig Venter, the self-made man of genes who had built a private company to read the full sequence of the human genome (his own) in competition with an international consortium funded by taxes and charities. That sequence a string of three billion letters composed in a four-letter alphabet containing the complete recipe for building and running a human body was to be published later in the week. The first analysis had revealed that there were just 30,000 genes in the human genome, not the 100,000 that many had been estimating up until a few months before.

Details had already been circulated to journalists under embargo.

Seeing the Observers first edition, other newspapers followed suit. Genome discovery shocks scientists: genetic blueprint contains far fewer genes than thought DNAs importance downplayed, proclaimed the San Francisco Chronicle later that Sunday. Not only had McKie scooped the story; Venter had set the theme.

This was the making of a new myth. In truth, the number of human genes changed nothing. Venters remarks concealed two massive non sequiturs: first, that fewer genes implied more environmental influences, and second, that 30,000 genes were too few to explain human nature where 100,000 would have been enough. As Sir John Sulston, one the leaders of the Human Genome Project, put it to me a few weeks later, just 33 genes, each coming in just two varieties (such as on or off), would be enough to make every human being in the world unique. There are more than ten billion ways of flipping a coin 33 times. So 30,000 does not look such a small number after all. Two multiplied by itself 30,000 times produces a number larger than the total number of particles in the known universe. Besides, if fewer genes meant more free will, that made fruit flies freer than people, bacteria freer still, and viruses the John Stuart Mills of biology.

Fortunately, there was no need for such sophisticated calculations to reassure the population. People were not seen weeping in the street at the humiliating news that our genome had less than twice as many genes as a worms. Nothing had been hung on the number 100,000, which was just a bad guess. But it was fitting after a century of increasingly repetitive argument over environment versus heredity that the publication of the human genome should be broken on the Procrustean bed of nature-versus-nurture. It was, with the possible exception of the Irish question, the intellectual argument that had changed least in the century just ended. It had divided fascists from communists as neatly as their politics. It had continued unabashed through the discovery of chromosomes, DNA and Prozac. It was fated to be just as bitterly debated in 2003 as it was in 1953, the year of the discovery of the structure of the gene, or in 1900, the year modern genetics began. Even the human genome, at its birth, was being claimed for nurture-versus-nature.

For more than fifty years sane voices have called for an end to the debate. Nature-versus-nurture has been declared everything from dead and finished to futile and wrong a false dichotomy. Everybody with an ounce of common sense knows that human beings are a product of a transaction between the two. Yet nobody could stop the argument. Immediately after calling the debate futile or dead, the protagonist would charge into the battle himself and start accusing others of overemphasising one or other extreme. The two sides of this argument are the nativists, who I will sometimes call geneticists, hereditarians or naturians; and the empiricists, who I will sometimes call environmentalists or nurturists.

Let me at once play my cards face up. I believe human behaviour has to be explained by both nature and nurture. I am not backing one side over the other. But that does not mean I am taking a middle of the road compromise. As Jim Hightower, a Texan politician, once said: There aint nothing in the middle of the road but a yellow line and a dead armadillo. I intend to make the case that the genome has indeed changed everything, not by closing the argument or winning the battle for one side or the other, but by enriching it from both ends till they meet in the middle. The discovery of how genes actually influence human behaviour, and how human behaviour influences genes, is about to recast the debate entirely. No longer is it nature-versus-nurture, but nature-via-nurture. Genes are designed to take their cues from nurture. To appreciate what has happened, you will have to abandon cherished notions and open your mind. You will have to enter a world where your genes are not puppet masters pulling the strings of your behaviour, but are puppets at the mercy of your behaviour; a world where instinct is not the opposite of learning, where environmental influences are sometimes less reversible than genetic ones, and where nature is designed for nurture. These cheap and seemingly empty phrases are coming to life for the first time in science. I intend to tell bizarre stories from the deepest recesses of the genome to show how the human brain is built for nurture. My argument in a nutshell is this: the more we lift the lid on the genome, the more vulnerable to experience genes appear to be.

I imagine a photograph taken in the year 1903. It is of a group of men gathered at some international meeting, in a fashionable spot like Baden-Baden or Biarritz, perhaps. Men is not quite the right word, for though there are no women, there is one little boy, one baby and one ghost; the rest are middle-aged or elderly men, mostly rich and all white. There are 12 of them and, as befits the age, there is a great deal of facial hair. There are two Americans, two Austrians, two Britons, two Germans, one Dutchman, one Frenchman, one Russian and one Swiss.

It is, alas, an imaginary photograph, for most of them never met each other. But, like the famous group photograph of physicists at Solvay in 1927 the one that includes Einstein and Bohr and Marie Curie and Planck and Schrdinger and Heisenberg and Dirac my picture would capture that moment of ferment when a scientific endeavour throws up a host of new ideas. My 12 men were the ones who put together the chief theories of human nature that came to dominate the twentieth century.

The ghost that hovers overhead is Charles Darwin, dead for 21 years by the time of the photograph, and with the longest beard of all. Darwins idea is to seek the character of man in the behaviour of the ape and to demonstrate that there are universal features of human behaviour, like smiling. The elderly gent sitting bolt-upright on the far left is his cousin, Francis Galton, 81 years old but going strong; his whiskers hang down the sides of his face like white mice. Galton is the fervent champion of heredity. Next to him sits the American William James, 61, with a square, untidy beard. He is a champion of instinct and maintains that human beings have more impulses than other animals, not fewer. On Galtons right is a botanist, out of place in a group concerned with human nature, and frowning unhappily behind his straggly beard. He is Hugo De Vries, 55, the Dutchman who discovered the laws of heredity only to realise he had been beaten to them more than 30 years before by a Moravian monk named Gregor Mendel. Beside him is the Russian, Ivan Pavlov, 54, his beard full and grey. He is a champion of empiricism, believing that the key to the human mind lies in the conditioned reflex. At his feet, uniquely clean-shaven, sits John Broadus Watson, who will turn Pavlovs ideas into behaviourism and famously claim to be able to alter personality at will merely by training. To Pavlovs right stands the plump, bespectacled, moustachioed German, Emil Kraepelin, and the neatly bearded Viennese, Sigmund Freud, both 47 and both in the throes of influencing generations of psychiatrists away from biological explanations and towards two very different notions of personal history. Beside him is the pioneer of sociology, the Frenchman Emile Durkheim, 45 and especially bushy in beard, busy insisting on the reality of social facts as more than the sum of their parts. His soulmate in this is standing next to him: a German-American (he had emigrated in 1885), the dashing Franz Boas, 45, with his drooping moustaches and duelling scar and his growing insistence that culture shapes human nature, not the other way round. The little boy in the front is the Swiss Jean Piaget, whose theories of imitation and learning will come to fruition, beardless, in mid-century. The baby in the pram is the Austrian Konrad Lorenz, who will revive the study of instinct and describe the vital concept of imprinting in the 1930s, while growing a fine white goatee.