The Language of the Genes

Biology, History and the Evolutionary Future

Revised Edition

DEDICATION

To my parents and my brotherwho share my genes and my affection

CONTENTS

Cover

Title Page

Dedication

Preface: A Malacologist’s Apology

Introduction: The Fingerprints of History

1 A Message from our Ancestors

2 The Rules of the Game

3 Herodotus Revised

4 Change or Decay

5 Caliban’s Revenge

6 Behind the Screen

7 The Battle of the Sexes

8 Clocks, Fossils and Apes

9 Time and Chance

10 The Economics of Eden

11 The Kingdoms of Cain

12 Darwin’s Strategist

13 The Deadly Fevers

14 Cousins under the Skin

15 Evolution Applied

16 The Modern Prometheus

17 The Evolution of Utopia

Appendix: A Bibliographic Sketch

Index

Adout the Author

Praise

Copyright

About the Publisher

Preface A MALACOLOGIST’S APOLOGY

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 end 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, most 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 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 unpersuasive and hard to 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 not available and there seemed little prospect that it ever would be. Human 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 first time, 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 creationism 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 here, 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 makes 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, the 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.

Both languages and genes evolve. Each generation makes errors in transmission and, sooner or later, enough differences accumulate to produce a new dialect – or a new form of life. Just as the living tongues of the world and their literary relics reveal their extinct ancestors, genes and fossils are an insight into the biological past. We have learned to read the language of the genes and it is saying remarkable things about our history, our present condition and even our future.

The first edition of this book emerged from my Reith Lectures, given on BBC Radio in the early 1990s. Those lectures began with the philosopher Bertrand Russell in 1948 (and, some argue, have gone downhill ever since). I would not dream of comparing myself with my illustrious predecessors but I hope that the series – and the book – can stand on the merits of their subject, the most fascinating in modern science. Perhaps my lectures in their small way helped to show that the BBC can still fulfil its obligations, set forth by its founder Lord Reith, to instruct, inform and entertain. The last might seem an unexpected word to use about science, but it is justified by the number of eccentrics and fools who have graced and disgraced the history of human genetics. They appear sporadically in these pages in the hope of enlivening an otherwise bald narrative.

Since that first edition, seven years ago, genetics – and public concern – have each exploded. What was then remote is here today. In spite of the complaints of Prince Charles, millions of acres of genetically modified crops have been planted; and Dolly the Cloned Sheep, with her penchant for standing on a trough and bullying her inferiors, has been joined by many other domestic animals born without benefit of sex. Some contain genes that make human proteins, as a statement of the new free trade in DNA which makes it possible to move genes from any part of the world of life to any other. We have, with the exception of a few footnotes, read the book of human inheritance. In 2000 it was announced that the order of the DNA bases for every one of the genes needed to make a human being had been established. The rest (small scraps of the ‘junk’ as it is optimistically called) will be read off within a year or so.

Nobody should disparage this work. The impossible has become commonplace. To decipher the DNA has been an enormous task. It was, briefly, the privilege of a professor (or his technicians). Then came the time of the postgraduates, with doctorate after doctorate awarded for one or other piece of the genetic jigsaw. Soon, the machines took over – cheaper, less subject to emotional upset, and far faster than even the most dedicated student. Brute force (helped by ingenuity) triumphed and the pace of discovery accelerated in a fashion more associated with computers than with biology. Part of the rush came from the excitement of a science armed with a goal and the technology to reach it, but part emerged from an attempt to make millions from patents and a competing effort to keep the information in the public domain.

The need for funds and the prospect of fortune has given birth to an era of exaggerated hopes and fears about inheritance. The public is obsessed with genes. In part that is because they come close to questions that lie outside science altogether; issues of sex, identity and fate that have occupied sages since the days of the Old Testament, the first genetics text of all. Genetics is more and more involved with social and political questions such as those of abortion, cloning, and human rights. It puts medical issues into sharp and sometimes uncomfortable focus, with much concern about problems of privacy, blame and the nature of disease. Many inherited illnesses are expensive to treat and hard to cure. They raise unwelcome questions about the balance of responsibility between individuals and populations.

Much has been spent in the past decade. Those who paid for the map of the genes are anxious for some return. It can be hard to translate theory into practice. Vesalius worked out the anatomy of the heart in 1543; but the first heart transplant was not until 1967. Although it will not take as long before gene transplants arrive, they are further away than most people realise, and one important task that genetics faces (and one of the aims of this book) is to tailor public demands to reality.

The new genetics sounds (and is) both beguiling and alarming. Some of those involved have been quick to take advantage of public naiveté and have maintained a stream of promises as to what they will soon achieve. Few have been fulfilled; and some will not be. The molecular biology business promotes its wares as well as any other, and the four letters of the genetic code might nowadays well be restated as H, Y, P and E. Even so, in genetics, more than most sciences, fantasy has a habit of turning into reality in unpredictable ways, even as much-heralded breakthroughs do not appear. At the time of my first edition, the idea that inherited disease would be cured with gene therapy was just around the corner, where it remains. At that time, though, the idea that animals – perhaps even humans – might routinely be cloned, or that lengths of DNA could be moved around at will seemed beyond belief. Now, genetic engineering is a business worth billions a year.

The biggest change in the past seven years has been in attitude. In the public mind, genetics is no longer a science but a faith; a curse or a salvation. It promises or threatens, according to taste. In fact, biology has told us little about human affairs that we did not know before. Both have had plenty of publicity. Dozens of works of exegesis now offer salvation in a molecular paradise or (choose your Church) eternal damnation to those who take the broad path down the double helix to Hell. Some are accounts of the latest advances, but too many are in that weary penumbra of science inhabited by sociologists, who wander like children in a toyshop, playing with devices they scarcely understand. Biochemistry has become a branch of the social sciences and, some say, life will be explained in genetic terms. Many welcome the idea, some are filled with horror, but few pause to consider what, if anything, it means.

The public needs a fairer statement of what science can and cannot do. Reality is harder to sell than hopes or fears; but DNA deserves more than the Frankensteins and designer babies that fill the press. The problem is, at all levels, one of unreasonable expectation, both positive and negative. In this revised version of The Language of the Genes I try to cover the many advances since its first version; in the map of human DNA, in the genetic manipulation of plants and animals, and in our new abilities to screen for inborn disease. I have tried to keep the book to size and have thrown out several sections to allow space for the developments of the past decade.

Since this work first appeared, my malacological career has taken second place to journalism. Perhaps, in time, human genetics will help to understand the world of snails, so that this episode of reporting, rather than doing, will not be wasted.

JSJ, June 2000.

Introduction THE FINGERPRINTS OF HISTORY

In 1902, in Paris, a horrible murder was solved by the great French detective Alfonse Bertillon. He used a piece of new technology which struck fear into the heart of the criminal community. Eight decades later two young girls were killed near the Leicestershire village of Narborough. Again, the murderer was found through a technical advance, although the machinery involved would have been beyond the comprehension of Bertillon. These events link the birth and the coming-of-age of human genetics.

The Parisian killer was trapped because he left a fingerprint at the scene of the crime. For the first time, this was used in evidence as a statement of identity. The idea came from ancient Japan, where a finger pressed into a clay pot identified its maker. The Leicestershire murderer was caught in the same way. A new test looked for individual differences in genetic material. This ‘DNA fingerprint’ was as much a statement of personal uniqueness as Bertillon’s clue or the potter’s mark. As usual, life was more complex than science. The killer, a baker called Colin Pitchfork, was caught only after DNA fingerprints had eliminated a young man who had made a false confession and after Pitchfork had persuaded a friend to give a fraudulent blood sample under his name.

The idea that fingerprints could be used to trace criminals came from Charles Darwin’s cousin, Francis Galton. He founded the laboratory in which I work at University College London, the first human genetics institute in the world. Every day I walk past a collection of relics of his life. They include some rows of seeds that show similarities between parents and offspring, an old copy of The Times and a brass counting gadget that can be hidden in the palm of the hand. Each is a reminder of Galton. As well as his revolution in detective work Galton was the first person to publish a weather map and the only one to have made a beauty map of Britain, based on a secret ranking of the local women on a scale of one to five (the low point, incidentally, being in Aberdeen).

His biography reveals an unrelieved eccentricity, well illustrated by the titles of a dozen of his three hundred scientific papers: On spectacles for divers; Statistical inquiries into the efficacy of prayer; Nuts and men; The average flush of excitement; Visions of sane persons; Pedigree moths; Arithmetic by smell; Three generations of lunatic cats; Strawberry cure for gout; Cutting a round cake on scientific principles; Good and bad temper in English families; and The relative sensitivity of men and women at the nape of the neck. Galton travelled much in Africa, regarding the natives with some contempt and measuring the buttocks of the women using a sextant and the principles of surveying.

Galton’s work led, indirectly, to today’s explosion in human genetics. His particular interest was in the inheritance of genius (a class within which he placed himself). In his 1869 book Hereditary Genius, he investigated the ancestry of distinguished people and found a tendency for talent to crop up again and again in the same family. This, he suggested, showed that ability was inborn and not acquired. Hereditary Genius marked the first attempt to establish patterns of human inheritance with well-defined traits – such as becoming (or failing to become) a judge rather than with mere speculation about vague qualities such as fecklessness.

Galton and his followers would be astonished at what biology can now do. It still does not understand attributes such as genius (and reputable scientists hardly concern themselves with them), but DNA is much involved in mental and physical illness. Half a million DNA samples have been taken by police in Britain since the test was invented, and the government has a scheme to follow the genes – and the ailments – of the same number of its citizens over two decades in the hope of finding the biological errors responsible for killers like cancer and heart disease. New tests mean that parents can sometimes choose whether to risk the birth of a child with an inborn defect. Ten thousand such illnesses are known and if we include, as we should, all ailments with an inherited component, most people die because of the genes they carry.

Genetics does more than reveal fate. Humans share much of their heritage with other creatures. As Galton himself illustrated with the appropriate impression pasted near that made by Gladstone, the prime minister, chimpanzees have fingerprints. Now we know that much of their DNA is identical to our own (as indeed is that of bananas). All this suggests that humans and apes are close relatives.

Genetics is the key to the past. As every gene must have an ancestor, inherited diversity can be used to piece together a picture of history more complete than from any other source. Each segment of DNA is a message from our forebears and together they contain the whole story of human evolution. Everyone alive today is a living fossil and carries within themselves a record that revisits the birth of humankind. The Origin of Species expresses the hope that ‘light will be thrown on the origin of man and his history’. Darwin’s hint that humans share a common descent with all other creatures is now accepted by all scientists, because of the evidence of the genes.

Evolution, the appearance of new forms by the alteration of those already present, is no more than descent with modification. The same is true of language. As a boy, I was amused by the tale of the order going down the line of command to soldiers in the trenches. ‘Send reinforcements, we’re going to advance’ changed to ‘Send three and fourpence, we’re going to a dance’ as it passed from man to man. This simple tale illustrates how accidents, as an inherited message is copied, can lead to change. Because of mutation, life, too, is garbled during transmission.

This book is about inheritance: about the clues of our past, present and future that we all contain. The language of the genes has a simple alphabet, with not twenty-six letters, but four; the DNA bases – adenine, guanine, cytosine and thymine (A, G, C and T for short). They are arranged in words of three letters such as CGA or TGG. Most code for different amino acids, which are themselves joined together to make proteins, the building blocks of the body.

The economy of life’s language can be illustrated with an odd quotation from a book called Gadsby, written in 1939 by one Ernest Wright: ‘I am going to show you how a bunch of bright young folks did find a champion, a man with boys and girls of his own, a man of so dominating and happy individuality that youth was drawn to him as a fly to a sugar bowl.’ This sounds somewhat peculiar, as does the rest of the fifty-thousand word book, and it is. The quotation, and the whole work, lacks the letter ‘e’. An English sentence can be written with twenty-five letters instead of twenty-six, but only just. Biology manages with a mere four.

Although its vocabulary is simple the genetical message is very long. Each cell in the body contains about six feet of DNA. There are so many cells that if all the DNA in a single human body were stretched out it would reach to the moon and back eight thousand times. Twenty years ago, the Human Genome Project set out to read the whole of its three thousand million letters, and to publish perhaps the most dreary volume ever written, the equivalent of a dozen or so copies of the Encyclopaedia Britannica. The task is now more or less complete. The sequencers followed a grand scientific tradition: the Admiralty, after all, sent the Beagle to South America with Darwin on board not because they were interested in evolution but because they knew that if they were to understand (and, with luck, control) the world, the first step was to map it. The chart of the genes, like that of the Americas, has been expensive to make; but – like the theory of evolution itself – it may change our perception of ourselves.

Powerful ideas like inheritance and evolution soon attract myths. Impressed by his studies of genius, Galton founded the science (if that is the right word) of eugenics. Its main aim was ‘to check the birth rate of the Unfit and improve the race by furthering the productivity of the fit by early marriage of the best stock’. He led the new field of human genetics into a blind alley from which it did not emerge for half a century. At his death, he left £45,000 to found the Laboratory of National Eugenics at University College London and, in fine Victorian tradition, £200 to his servant who had worked for him for forty years. His research institute soon changed its name to the Galton Laboratory to escape from the eugenical taint. What became of his servant is not recorded.