The Double Helix
On May 30, 1953 James Watson and Francis Crick published in Nature a correct interpretation of the crystalline structure of deoxyribonucleic acid, DNA. It was a great discovery, one which went far beyond merely spelling out the spatial design of a large, complicated, and important molecule. It explained how that molecule could serve genetic purposes—that is to say, how DNA, within the framework of a single common structure, could exist in forms various enough to encode the messages of heredity. It explained how DNA could be stable in a crystalline sense and yet allow for mutability. Above all it explained in principle, at a molecular level, how DNA undergoes its primordial act of reproduction, the making of more DNA exactly like itself. The great thing about their discovery was its completeness, its air of finality. If Watson and Crick had been seen groping toward an answer; if they had published a partly right solution and had been obliged to follow it up with corrections and glosses, some of them made by other people; if the solution had come out piecemeal instead of in a blaze of understanding: then it would still have been a great episode in biological history, but something more in the common run of things; something splendidly well done, but not done in the grand romantic manner.
The work that ended by making biological sense of the nucleic acids began forty years ago in the shabby laboratories of the Ministry of Health in London. In 1928 Dr. Fred Griffith, one of the Ministry’s Medical Officers, published in the Journal of Hygiene a paper describing strange observations on the behavior of pneumococci—behavior which suggested that they could undergo something akin to a transmutation of bacterial species. The pneumococci exist in a variety of genetically different “types,” distinguished one from another by the chemical make-up of their outer sheaths. Griffith injected into mice a mixture of dead pneumococcal cells of one type and living cells of another type, and in due course he recovered living cells of the type that distinguished the dead cells in the original mixture. On the face of it, he had observed a genetic transformation. There was no good reason to question the results of the experiment. Griffith was a well-known and highly expert bacteriologist whose whole professional life had been devoted to describing and defining the variant forms of bacteria, and his experiments (which forestalled the more obvious objections to the meaning he read into them) were straightforward and convincing. Griffith, above all an epidemiologist, did not follow up his work on pneumococcal transformation; nor did he witness its apotheosis, for in 1941 a bomb fell in Enders Street which blew up the Ministry’s laboratory while he and his close colleague William Scott were working in it.
The analysis of pneumococcal transformations was carried forward by Martin Dawson and Richard Sia in Columbia University and by Lionel Alloway at the Rockefeller Institute. Between them they showed that the transformation could occur during cultivation outside the body, and that the agent responsible for the transformation could pass through a filter fine enough to hold back the bacteria themselves. These experiments were of great interest to bacteriologists because they gave a new insight into matters having to do with the ups and downs of virulence; but most biologists and geneticists were completely unaware that they were in progress. The dark ages of DNA came to an end in 1944 with the publication from the Rockefeller Institute of a paper by Oswald Avery and his young colleagues, Colin MacLeod and Maclyn McCarty, which gave very good reasons for supposing that the transforming agent was “a highly polymerized and viscous form of sodium desoxyribonucleate.” This interpretation aroused much resentment, for many scientists unconsciously deplore the resolution of mysteries they have grown up with and have therefore come to love. It nevertheless withstood all efforts to unseat it. Geneticists marveled at its significance, for the agent that brought about the transformation could be thought of as a naked gene. So very probably the genes were not proteins after all, and the nucleic acids themselves could no longer be thought of as a sort of skeletal material for the chromosomes.
THE NEW CONCEPTION was full of difficulties, the most serious being that (compared with the baroque profusion of different kinds of proteins) the nucleic acids seemed too simple in makeup and too little variegated to fulfill a genetic function. These doubts were set at rest by Crick and Watson: the combinatorial variety of the four different bases that enter into the make-up of DNA is more than enough to specify or code for the twenty different kinds of amino acids of which proteins are compounded; more than enough, indeed, to convey the detailed genetic message by which one generation of organisms specifies the inborn constitution of the next. Thanks to the work of Crick and half a dozen others, the form of the genetic code, the scheme of signaling, has now been clarified, and, thanks to work to which Watson has made important contributions, the mechanism by which the genetic message is mapped into the structure of a protein is now in outline understood.
It is simply not worth arguing with anyone so obtuse as not to realize that this complex of discoveries is the greatest achievement of science in the twentieth century. I say “complex of discoveries” because discoveries are not a single species of intellection; they are of many different kinds, and Griffith’s and Crick-and-Watson’s were as different as they could be. Griffith’s was a synthetic discovery, in the philosophic sense of that word. It did not close up a visible gap in natural knowledge, but entered upon territory not until then known to exist. If scientific research had stopped by magic in, say, 1920 our picture of the world would not be known to be incomplete for want of it. The elucidation of the structure of DNA was analytical in character. Ever since W. T. Astbury published his first X-ray diffraction photographs we all knew that DNA had a crystalline structure, but until the days of Crick and Watson no one knew what it was. The gap was visible then, and if research had stopped in 1950 it would be visible still; our picture of the world would be known to be imperfect. The importance of Griffith’s discovery was historical only (I do not mean this in a depreciatory sense). He might not have made it; it might not have been made to this very day; but if he had not, then some other, different discovery would have served an equivalent purpose, that is, would in due course have given away the genetic function of DNA. The discovery of the structure of DNA was logically necessary for the further advance of molecular genetics. If Watson and Crick had not made it, someone else would certainly have done so—almost certainly Linus Pauling, and almost certainly very soon. It would have been that same discovery, too; nothing else could take its place.
Watson and Crick (so Watson tells us) were extremely anxious that Pauling should not be the first to get there. In one uneasy hour they feared he had done so, but to their very great relief his solution was erroneous, and they celebrated his failure with a toast. Such an admission will shock most laymen: so much, they will feel, for the “objectivity” of science; so much for all that fine talk about the disinterested search for truth. In my opinion the idea that scientists ought to be indifferent to matters of priority is simply humbug. Scientists are entitled to be proud of their accomplishments, and what accomplishments can they call “theirs” except the things they have done or thought of first? People who criticize scientists for wanting to enjoy the satisfaction of intellectual ownership are confusing possessiveness with pride of possession. Meanness, secretiveness, and sharp practice are as much despised by scientists as by other decent people in the world of ordinary everyday affairs; nor, in my experience, is generosity less common among them, or less highly esteemed.
It could be said of Watson that, for a man so cheerfully conscious of matters of priority, he is not very generous to his predecessors. The mention of Astbury is perfunctory and of Avery a little condescending. Fred Griffith is not mentioned at all. Yet a paragraph or two would have done it, without derogating at all the splendor of his own achievement. Why did he not make the effort?
It was not lack of generosity, I suggest, but stark insensibility. These matters belong to scientific history, and the history of science bores most scientists stiff. A great many highly creative scientists (I classify Jim Watson among them) take it quite for granted, though they are usually too polite or too ashamed to say so, that an interest in the history of science is a sign of failing or unawakened powers. It is not good enough to dismiss this as cultural barbarism, a coarse renunciation of one of the glories of humane learning. It points toward something distinctive about scientific learning, and instead of making faces about it we should try to find out why such an attitude is natural and understandable. A scientist’s present thoughts and actions are of necessity shaped by what others have done and thought before him; they are the wavefront of a continuous secular process in which The Past does not have a dignified independent existence on its own. Scientific understanding is the integral of a curve of learning; science therefore in some sense comprehends its history within itself. No Fred, no Jim: that is obvious, at least to scientists; and being obvious, at it is understandable that it should be left unsaid. (I am speaking, of course, about the history of scientific endeavors and accomplishments, not about the history of scientific ideas. Nor do I suggest that the history of science may not be profoundly interesting as history. What I am saying is that it does not often interest the scientist as science.)
JIM WATSON (“James” doesn’t suit him) majored in Zoology in Chicago and took his Ph.D. in Indiana, aged twenty-two. When he arrived in Cambridge in 1951 there could have been nothing much to distinguish him from any other American “postdoctoral” in search of experience abroad. By 1953 he was world famous. How much did he owe to luck?
The part played by luck in scientific discovery is greatly overrated. Ces hasards ne sont que pour ceux qui jouent bien, as the saying goes. The paradigm of all lucky accidents in science is the discovery of penicillin—the spore floating in through the window, the exposed culture plate, the halo of bacterial inhibition around the spot on which it fell. What people forget is that Fleming had been looking for penicillin, or something like it, since the middle of the First World War. Phenomena such as these will not be appreciated, may not be knowingly observed, except against a background of prior expectations. A good scientist is discovery-prone. (As it happens there was an element of blind-luck in the discovery of penicillin, though it was unknown to Fleming. Most antibiotics—hundreds are now known—are murderously toxic, because they arrest the growth of bacteria by interfering with metabolic processes of a kind that bacteria have in common with higher organisms. Penicillin is comparatively innocuous because it happens to interfere with a synthetic process peculiar to bacteria, namely the synthesis of a distinctive structural element of the bacterial cell wall.)
I do not think Watson was lucky except in the trite sense in which we are all lucky or unlucky—that there were several branching points in his career at which he might easily have gone off in a direction other than the one he took. At such moments the reasons that steer us one way or another are often trivial or ill thought-out. In England a schoolboy of Watson’s precocity and style of genius would probably have been steered toward literary studies. It just so happens that during the 1950s, the first great age of molecular biology, the English Schools of Oxford and particularly of Cambridge produced more than a score of graduates of quite outstanding ability—much more brilliant, inventive, articulate, and dialectically skillful than most young scientists; right up in the Watson class. But Watson had one towering advantage over all of them: in addition to being extremely clever he had something important to be clever about. This is an advantage which scientists enjoy over most other people engaged in intellectual pursuits, and they enjoy it at all levels of capability. To be a first-rate scientist it is not necessary (and certainly not sufficient) to be extremely clever, anyhow in a pyrotechnic sense. One of the great social revolutions brought about by scientific research has been the democratization of learning. Anyone who combines strong common sense with an ordinary degree of imaginativeness can become a creative scientist, and a happy one besides, in so far as happiness depends upon being able to develop to the limit of one’s abilities.
Lucky or not, Watson was a highly privileged young man. Throughout his formative years he worked first under and then with scientists of great distinction; there were no dark unfathomed laboratories in his career. Almost at once (and before he had done anything to deserve it) he entered the privileged inner circle of scientists among whom information is passed by a sort of beating of tom-toms, while others await the publication of a formal paper in a learned journal. But because it was unpremeditated we can count it to luck that Watson fell in with Francis Crick, who (whatever Watson may have intended) comes out in this book as the dominant figure, a man of very great intellectual powers. By all accounts, including Watson’s, each provided the right kind of intellectual environment for the other. In no other form of serious creative activity is there anything equivalent to a collaboration between scientists, which is a subtle and complex business, and a triumph when it comes off, because the skill and performance of a team of equals can be more than the sum of individual capabilities. It was a relationship that did work, and in doing so brought them the utmost credit.
CONSIDERED AS LITERATURE, The Double Helix will be classified under Memoirs, Scientific. No other book known to me can be so described. It will be an enormous success, and deserves to be so—a classic in the sense that it will go on being read. As with all good memoirs, a fair amount of it consists of trivialities and idle chatter. Like all good memoirs it has not been emasculated by considerations of good taste. Many of the things Watson says about the people in his story will offend them, but his own artless candor excuses him, for he betrays in himself faults graver than those he professes to discern in others. The Double Helix is consistent in literary structure. Watson’s gaze is always directed outward. There is no philosophizing or psychologizing to obscure our understanding; Watson displays but does not observe himself. Autobiographies, unlike all other works of literature, are part of their own subject matter. Their lies, if any, are lies of their authors but not about their authors, who (when discovered in falsehood) merely reveal a truth about themselves, namely that they are liars. Although it sounds a bit too well remembered, Watson’s scientific narrative strikes me as perfectly convincing. This is not to say that the apportionments of credits or demerits are necessarily accurate: that is something which cannot be decided in abstraction, but only after the people mentioned in the book have had their say, if they choose to have it. Nor will an intelligent reader suppose that Watson’s judgments upon the character, motives, and probity of other people (sometimes apparently shrewd, sometimes obviously petty) are “true” simply because he himself believes them to be so.
A good many people will read The Double Helix for the insight they hope it will bring them into the nature of the creative process in science. It may indeed become a standard case history of the so-called “hypothetico-deductive” method at work. Hypothesis and inference, feedback and modified hypothesis, the rapid alternation of imaginative and critical episodes of thought—here it can all be seen in motion, and every scientist will recognize the same intellectual structure in the research he does himself. It is characteristic of science at every level, and indeed of most exploratory or investigative processes in everyday life. No layman who reads this book with any kind of understanding will ever again think of the scientist as a man who cranks a machine of discovery. No beginner in science will henceforward believe that discovery is bound to come his way if only he practices a certain Method, goes through a certain well-defined performance of hand and mind.
Nor, I hope, will anyone go on believing that The Scientist is some definite kind of person. Given the context, one could not plausibly imagine a collection of people more different in origin and education, in manner, manners, appearance, style, and worldly purposes than the men and women who are the characters in this book. Watson himself and Crick and Wilkins, the central figures; Dorothy Crowfoot and poor Rosalind Franklin, the only one of them not now living; Perutz, Kendrew, and Huxley; Todd and Bragg, at that time holder of “the most prestigious chair in science”; Pauling père et fils; Bawden and Pirie, in a momentary appearance; Chargaff; Luria; Mitchison and Griffith (John, not Fred)—they come out larger than life, perhaps, and as different one from another as Caterpillar and Mad Hatter. Watson’s childlike vision makes them seem like the creatures of a Wonderland, all at a strange contentious noisy tea party which made room for him because for people like him, at this particular kind of party, there is always room.