Steve Jones is Professor of Genetics at the Galton Laboratory, University College London. The first edition of this book was based on the Reith Lectures he gave in 1991. The Language of the Genes won both the Rhone-Poulenc prize for the best science book of [994 and the Yorkshire Post Prize for Best First Work. In 1996, the Royal Society presented him with the Michael Faraday Award, given annually to the scientist who has done the most to further the public understanding of science. Professor Jones was born in Wales, educated in Scotland and lives in London. He is author of two other books. In the Mood (1996) and Almost like a Whale (1999), co-editor of the Cambridge Encyclopaedia of Human Evolution and joint author of Genetics for Beginners and of the Open University' final-year genetics textbook. On balance he prefers snails to humans.

Steve Jones. The Language of the Genes

ISBN 0-00-655243-9

I have spent — some might say wasted — most of my scientific career working on snails. A malacologist may seem an unlikely author for a book about human genetics. However, my research, when I was still able to do it, was not driven by a deep interest in molluscs. Indeed, one of the few occasions when I thought of giving up biology as a career was when I first had to dissect one. Thirty years ago snails were among the few creatures whose genes could be used to study evolution. They carry a statement of ancestry on their shells in the form of inherited patterns of colour and banding. By counting genes in different places and trying to relate them to the environment one could get an idea of how and why snail populations diverged from each other: of why and how they evolved.

At the time, the idea that it might ever be possible to do the same with humans seemed absurd. Genetics textbooks of the 1960s were routine things. They dealt with the inheritance of pea shape, the sex lives of fungi and the new discoveries about the molecular biology of viruses and their bacterial hosts. Of ourselves, there was scarcely a mention — usually just a short chapter tagged on at the cud which described pedigrees of abnormalities such as haemophilia or colour blindness.

Part of this reticence was due to ignorance but part came from  the dismal history of the subject. In its early days, the study of human inheritance was the haunt of charlatans, nio.st of whom had a political axe to grind. Absurd pedigrees purporting to show family lines of criminality or genius were the norm. Ignorance and confidence went together. Many biologists argued that it was possible to improve humankind by selective breeding or by the elimination of the unfit. The adulteration of the science reached its disastrous end in the Nazi experiment, and for many years it was seen as at best unfashionable to discuss the nature of inborn differences among people.

After the Second World War, the United Nations published a book — Statement of Race, by the American anthropologist Ashley Montagu — which tried to kill some of the genetical myths. I read this as a schoolboy and found it unpersuasive and hard in follow, although its liberal message was clear enough. Re-reading it a few years ago showed why: Ashley Montagu had tried, nobly, to make bricks without straw. The information needed to understand ourselves was simply nor available and there seemed little prospect that it ever would he. I luman genetics had moved from a series of malign to an equivalent set of pious opinions.

Now everything has been transformed. Homo sapiens is no longer the great unknown of the genetical world but has become its workhorse. More is known about the geographical patterns of genes in people than about those of any other animal (snails, incidentally, still come second}. The three thousand million letters in the DNA alphabet have, at last, been read from end to end and, so it seems, the century of genetics that began with the rediscovery of Mendel's laws has ended with a new and revolutionary insight into ourselves.

The completion of the DNA map marks the triumph of genetics as a science. Its success as a technology — or, at least, as a medical technology — has yet to be established. Everyone, in the end, dies; and genes are nearly always involved in that unpleasant process. Nobody escapes the fate coded into the double helix. Much of the damage arises anew, either in body cells or as a result of errors in parental sperm and egg. Indeed, most pregnancies end because of such errors. Science has given the hope of finding those at risk of inherited disease and, perhaps, of treating it. At last we understand what sex really means, why we age and die, and how nature and nurture combine to make us what we are.

Most of all, biology has altered our view of our place in the universe of life. For the firsr rime, it is clear how humans are related to other animals and when they first appeared. The idea that Man did not evolve is open to scientific examination: and although crcationism is supported by millions the test proves it wrong. Most people believe that they descend from simpler predecessors but would be hard put to say why. As Thomas Henry Huxley, Darwin's great protagonist, said of the idea of evolution: "It is the customary fate of new truths to begin as heresies and to end as superstitions." Genetics has saved Darwinism from that fate. It has killed many old and disreputable superstitions. At last there is a real insight into race, and the ancient idea that the peoples of the world are divided into distinct units has gone for ever. Separatism has gained a new popularity among groups anxious to assert an identity of their own, but they cannot call on genes to support their views.

It is, though, the essence of scientific theories that they cannot resolve everything. Science cannot answer the questions that philosophers — or children — ask: why are we lure, what is the point of being alive, how ought we to behave? Genetics has nothing to say about what makes people more than just machines driven by biology, about what nukes us human. These questions may be interesting, but a scientist is no more qualified to comment on them than is anyone else. Human genetics has suffered from its high opinion of itself. For most of its history it failed to understand its own limits. Knowledge has brought humility to genetics, but its new awareness raises social and ethical problems that have as yet scarcely been addressed.

This book is about what genetics can — and cannot — tell us about ourselves. Its title, The Language of the Genes, points to the analogy upon which it turns, rhe parallels between biological evolution and the history of language.

Inheritance is a discourse through time, a set of instructions passed from generation to generation. It has a vocabulary — the genes themselves — a grammar, the way in which the information is arranged, and a literature, the thousands of instructions needed to make a human being. It is based on the DNA molecule, the famous double helix, the icon of the twentieth century. Johann Miescher, the Swiss discoverer of that marvellous substance, himself wrote in 1892. that its message might be transmitted 'just as the words and concepts of all tongues can find expression in twenty-four to thirty letters of the alphabet.' A century of science shows how right he was.