I HAVE SPENT—some might say wasted—most of my scientific career working on snails. A malacologist might seem a surprising 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 mollusks. Indeed, one of the few occasions when I thought of giving up biology as a career was when I first had to dissect one. Twenty-five 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 color 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 how and why they evolved.
At the time, the idea that it might ever be possible to do this 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 humans, there was scarcely a mention— usually just a short chapter tagged on at the end which described pedigrees of abnormalities such as hemophilia or color blindness.
Part of this reticence about human genetics 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, most of whom had a political ax to grind. Absurd pedigrees claiming to show the inheritance of criminality or of genius were the norm. Ignorance and confidence went together. Many biologists promoted the idea that it was possible to improve the human race by selective breeding or by the elimination of the genetically unfit. The adulteration of human genetics reached its disastrous end in the Nazi experiment, and for many years it was seen as at best unfashionable to discuss the nature of inherited differences among people.
After the Second World War, the United Nations was involved in publishing a book—Statement on 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 unconvincing and hard to follow, although its liberal message was clear enough. Re-reading it recently showed why: Ashley Montagu had tried, nobly, to make bricks without straw. The information needed to understand our own evolution was simply not available at the time and there seemed little prospect that it ever would be. Human genetics had moved from a series of malign to an equivalent series of pious opinions.
Now everything has been transformed. Humans, far from being the great unknowns of the genetical world, have become its workhorse. More is known about the geographical patterns of genes in the people of the world than about those of any other creature (snails, incidentally, still come second). By about the year 2000 we should have the complete sequence of the three thousand million letters in the DNA alphabet which go to make up a human being. Enough of the genetic message has already been read to make it obvious that the instructions are far more complicated than was ever thought. This knowledge is of more than merely scientific interest. Two out of every three people reading these words will die for reasons connected with the genes they carry; and the new genetics is giving the hope (and for the moment it is only that) of curing inherited disease. We are also beginning to 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 transformed views of our place in nature. At last it is becoming clear how humans are related to other animals and when and where they first appeared on earth. The idea that life was created—rather than having evolved—is now open to scientific test, and although creationism is still supported by millions of Americans, the test proves it wrong. The study of inheritance is giving new life to the theory of evolution. Most people believe that they descend from simpler predecessors but would be hard put to say why. As Thomas Henry Huxley, Darwin's great Victorian 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 this fate. It has killed many superstitions about ourselves. At last there is a real understanding of race, and the ancient and disreputable idea that the peoples of the world are divided into biologically distinct units has gone forever. Separatism may have gained a new popularity among racial groups anxious to assert an identity of their own, but they cannot call on genetics to support their views.
It is the essence of all scientific theories that they cannot resolve everything. Science cannot answer the questions that philosophers—or children—ask: why are we here, what is the point of being alive, how ought we to behave? Genetics has almost nothing to say about what makes people more than just machines driven by biology, about what makes us human. These questions may be interesting, but scientists are no more qualified to comment on them than is anyone else. In its early days, human genetics suffered greatly from its high opinion of itself. It failed to understand its own limits. Knowledge has brought humility to genetics as to other sciences; but the new awareness which genetics brings will also raise social and ethical problems which have as yet scarcely been addressed.
This book is about what genetics can—and cannot—tell us about ourselves. Its title, The Language of Genes, points to the analogy upon which it turns, the parallels between biological evolution and the evolution of language.
Genetics is itself a language, a set of inherited instructions passed from generation to generation. It has a vocabulary—the genes themselves—a grammar, the way in which the inherited information is arranged, and a literature, the thousands of instructions needed to make a human being. The language is based on the DNA molecule, the famous double helix, which has become the icon of the twentieth century. Both languages and genes evolve. Each generation there are mistakes in transmission and, in time, enough differences accumulate to produce a new language—or a new form of life. Just as the living tongues of the world and their literary relics reveal a great deal about their extinct ancestors, genes and fossils provide an insight into the biological past. We are beginning to learn to read the language of the genes and it is saying some startling things about our history, our present condition and even our future.
The book emerged from my series of Reith Lectures given on BBC Radio in late 1991. The lectures are named for the famously humorless John Reith, who was appointed as its first director-general soon after joining the British Broadcasting Corporation in 1922. They began with the philosopher Bertrand Russell in 1948 (and, some would argue, have gone downhill ever since). I would not dream of comparing myself with my illustrious predecessors but I hope that the lectures—and the book —can stand on the merits of their subject, the most fascinating in modern science. The BBC is under attack by those intent on becoming rich by dismembering its corpse. Perhaps my lectures in their small way helped to show that it can still fulfill its obligations, set forth by its founder, to instruct, inform and entertain. The last might seem an unexpected word to use for a series about science, but it is justified by the number of eccentrics and fools who have graced and disgraced the history of human genetics, and who appear sporadically in these pages in the hope of enlivening an otherwise bald narrative.
I would like to thank my producer at the BBC, Deborah Cohen, who did much to turn my ramblings into broadcast form. Cathy Abbott, Lesley Aiello, Sam Berry, David Hopkinson, Tom Jones, David Leibel, Ian Lush, Andrew Pomiankowski and Jenny Sadler read all or part of an early draft of the book and gave valuable advice, not all of which I took. My friend Norma Percy allowed me to work late when writing it without noticing as she was in her own office throughout. Much of the manuscript was written in the French village of Mas Canet, and I thank in particular M. Robert Rigaud for his hospitality. Finally, I should express my gratitude to the various government funding bodies whose determined refusal to support my work led me—as so many others—to abandon research, in my case for journalism. Perhaps, in time, human genetics will help to understand what is really happening in the world of snails, so that this temporary episode of reporting, rather than doing, will not be wasted.
JSJ, January 1994
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