Peter Medawar on the pace of scientific change

'Named' Lectures like the Herbert Spencer and the Romanes can be a grievous headache to those responsible for arranging them. It is almost always difficult to find suitable people to give them and very often the man they are designed to honour or at least to commemorate is either ignored or dismissed with a patronising nod. Moreover the endowments that provide for the Lectures • necessarily in trustee securities now hardly pay a lecturer's stipend, let alone provide the bounteous dinner given ostensibly in the lecturer's honour by the organiser and his friends: many a 'Named' lecturer must have looked on with dismay while gluttonous colleagues have munched their way through what would otherwise have been his stipend.

For these and many other reasons it was a happy thought to replace the Herbert Spencer Lectureship by a little symposium such as this one*, particularly as the organisers contrived to assemble an all-star cast. In the outcome, they are more like the Herbert Popper than the Herbert Spencer Lectures because many of the contributors are avowed Popperians and Popper himself brings the symposium to a close.

Hermann Bondi opens the series by describing with special authority how Einsteinian

theory came to supersede the Newtonian (-we

can certainly speak of its disproof now"). The story is familiar but has not yet lost its power to shock, so solid and irrefragably right did Newton's theories seem to be. It is not surprising therefore that very serious attempts were made to explain the anomalies in the orbit of Mercury within the framework of Newtonian theory: treating them as the consequence of an asymmetry of the Sun, or perhaps of the existence of an undiscovered planet, Vulcan, between Mercury and the Sun. The usual fate of theories which have long been thought unsatisfactory is not so often outright disproof as becoming a theorem in in effect a special case of a theory of wider compass. Another reason why unsatisfactory old theories disappear, Bondi says, is that their supporters die out. Some of Bondi's asides are amusing and illuminating:

I always find it intriguing to think that what is so often called the revolution in physics in the last decades of the last century (what with the discovery of electrons and X-rays and so on) . . .• owes its particular timing in history entirely to the fact that . . . a reasonably reliable vacuum pump , became available then for the first time.

Bondi attaches equal importance or so he says, to the introduction of modelling wax (plasticine) as a means of stopping leaks.

Herbert Spencer and John Stuart Mill were two of Monod's father's heroes, so he was

brought up in the beliefs that evolution was the fundamental mode of change .in the universe and that progress was inevitable. Monad has a very thorough understanding of the history of ideas in science and philosophy in the nineteenth century. He describes it as a curious characteristic of evolutionary theory that everybody thinks he understands it — meaning ;philosophers, social scientists and so on, while in fact very few people do understand it and Spencer, he adds, was one of those who did not.

Monod raises some methodological objections to evolutionary theory that I am not wholly in sympathy with. To my mind the principal objection to the modern 'neo-Darwinian' theory of the mechanism of evolution is the great difficulty we have in thinking of anything it cannot explain. Great explanatory facility is a weakness in a theory, not as is sometimes thought a strength. Monod re-expresses the evolutionary theory in the language of molecular genetics, "which has enriched tremendously and made explicit a great deal that was implicit in the theory of evolution." He proceeds from there to the etiology of the anti-Darwinism of Driesch, Polanyi and others. Monod has no doubt of the immense biological importance of language and of ideation generally the endowments that make possible the creation of Popper's World III or "royaume des idees" that which, propagated from one generation to the next in a process of exogenetic or exosomatic heredity, distinguishes man from beast.

Walter Bodmer, the Professor of Genetics at Oxford, contributes the best short discussion known to me of the possible threats associated with advances in medical genetics. He illustrates the widespread fear of genetical engineering by recording that when a Customs Officer challenged him and learned that he was a professor of genetics, he said -Hm, I'd better let you go hadn't I, otherwise you might turn into a frog!" He dismisses the more extravagant possibilities of molecular genetics sometimes discussed by science journalists as if they were on the verge of practical realisation and turns to the much more important and realistic eugenic problems of coping with the so-called inherited diseases' a philosophically quite unacceptable term though everybody knows in effect what it means. Eugenically the most manageable of these diseases are those of 'recessive' determination those in which the offending gene must be inherited from both parents if the disease is to become manifest. , Among such diseases are phenylketonuria, 'sickle call anaemia and, particularly among .Askenazi Jews, Tay-Sachs disease. The genetic carriers of all such diseases can be identified

and as most victims of the disease are children of carriers of the same offending gene, some measure of control can be achieved by dissuading its carriers from marrying each other — a suggestion first made, I think by J. B. S. Haldane. When, in addition, examination of cells from the amniotic fluid makes it possible to identify those children of carriers who will be horn *ith the disease, the way is open to offering the parents of an affected child the possibility of an abortion. (In general, only one quarter of the children of carriers will be victims of the malignant gene they carry.)

In discussing this very problem I have been the victim of the idiotic misinterpretation by an anthropologist that I have advocated the prohibition of reproduction by carriers of

recessive genes. This would be tantamount to advocating that human reproduction should cease, because as Bodmer points out nearly all of us carry on average up to four or more abnormal recessive genes. Needless to say, the

prohibition or discouragement would applY only to carriers of the same deleterious recessive gene.

Bodmer gives a learned and statesmanlike discussion of the rights and wrongs of AID, i.e. artificial insemination by the sperm of voluntary donors, and apropos of the difficulty of choosing such donors he recalls a story about Herman Muller so full of morals it deserves never to be forgotten. Muller was a passionate champion of Soviet Russia and of AID, and his first list of exemplary sperm donors included the names of a number of prominent Communists who were quietly dropped from his list sometime after the Twentieth Party Congress at which Stalin's malefactions were revealed to the world.

In discussing human diversity, Bodmer deals with numbers large enough to make even Hermann Bondi envious: . . . the probable minimum number of different types of eggs or sperm that an individual can produce is or

Iff""l, namely 1 followed by 3000 zeros. This can

be compared with the total number of sperm that have ever been produced by all human males that have ever lived, which I estimate to

be approximately 10' to ICI'''. Thus the number of different types of eggs or sperm that one individual can produce is some 10 '''fold more than the total number of sperm ever produced. Only a very, very small proportion of potential

genetic combinations are ever realised. We are all genetically' unique, and this genetic uniqueness Clearly must apply to behavioural and( . other attributes as well as to blood type, though specific genetic factors that may be involved in these other traits have not been defined." In short, the number of possible people is overwhelmingly larger than the number of actual people.

In putting to himself the question: are biochemical advances a mixed .blessing, Bodmer declares himself, like all sensible people, a meliorist — seeing it as our own responsibility to 'ensure that biomedical advances are turned to good account.

Professor Ravetz's contribution begins promisingly with the engraving that belies the defeatist doctrine ne plus ultra: it shows ships riding majestically through the pillars of Hercules showing t\at there was more bertibtil (The New Philosophers of the seVenteetith century accordingly took plus ultra for their motto.) Ravetz is an historian and philosopher of science but so far from being a camp folldwer of science he adopts an almost Gddel-like posture in undertaking to demonstrate . . . that there is no absolute measure within science for the 'progress of science'. Still legx•dd the fields of application of science have autonomous criteria for progress. Hence we cannot look to natural science, in itself or in its applications, either for an independent measure or for a perfect model for progress in human affairs."

Ravetz says a good deal that no sensible scientist would disagree with, e.g. that "quantity in science is not the same as quality" and that a large number of scientific publications are quite worthless. Clearly Ravetz is riled by those simplistic measures of scientific progress that turn on, for example, the number of pages in an encyclopaedia devoted to science in each century of history a measure first used, I think, by A. J. Lotka, or alternatively using the

act ual number of scientific papers published in the journals. I think Ravetz may have been underestimating his audience in not taking it for granted that they themselves felt the same. Certainly no scientists in the audience would have denied that many scientific publications are dull, repetitious or frankly bad — though all are given equal weight in the kind of idiotic quantification of progress at which Ravetz protests. Yet there is progress in science, "a continuous enrichment and correction of it self Also we may have new theories and explanations not only encompassing new facts and surviving new critical tests but also explaining why earlier theories were Madequate. In this . . . we can locate a genuine asymmetry from which a unique direction of 'progress can be inferred quite naturally'." This is all very well, Ravetz feels, for retrospective judgments upon some fairly limited domain of science, hut the problem changes when we ask ourselves such a question as "Is science progressing?" The answers are "inevitably intuitive and value-laden" and lie outside the domain of science in the conventionally 'objective' or 'scientific' sense.

My own view about all this, which I believe could illustrate very convincingly in my -own branch of science, imainnolog.y, is that it is in the nature of science to progress in the genuine sense admitted by Ravetz unless it is actively impeded. The main impediments are an undeveloped technology (like Bondi's machines for producing high vacua), an unlucky lagging behind of sonic other branch of science that turns out to be necessary for progress in the one we are interested in, a faulty methodology, maladministration leading to the misapplication of public funds — as when Flore:yr's great work on the development of . penicillin was handicapped by an officai judgment that the future of antibacterial therapy lay with synthetic organic chemicals like sulphonamide and not with mediaevalsounding concoction* like penicillin and bacterial extractives such as streptomycin. Whatever the cause it usually boils down to human error or fallibility, something of which not even scientists can be acquitted. And I fully agree with Ravetz's judgment that Judgments of the present and future progress of individual branches of science which themselves influence the future through their early decision making are made in a style that is 'political' rather than 'scientific' though still fully 'rational'." Ravetz will have everybody with him again when he says that contributions to national prestige are not evidence of progress and has some sharp things to say about what he calls "runaway technology", but I think he might have admitted that technological sophistication is also directional and thus satisfies at least one of the criteria of progress, for having now got aircraft and telephones they can't very well be dropped because the entire tempo and style of life has been fashioned around them. I don't think this little Symposium would have been possible if modern means of transport were not available. The book itself might not have been published unless the telephone had been used to remind deliquent contributors that their contributions were overdue.

Nevertheless, Ravetz concludes his lecture by moralising on a Baconian text in a spirit. which I hope will become increasingly common ,nowadays, which must indeed become more common unless the benefactions that Bacon and most scientists hope and expect from science are to come to nothing after all.

These first four lectures are agreeable to read, but with B. F. Skinner's The steep and thorny way to the science of behaviour' the style changes. It is so painfully literary in intention but so clumsy and awkward in execution that it is not really easy to discern What Skinner intends to say. He does, however, say some rather strange things. I wonder what he can mean, for example, by asking how the genetic endowment changes during the lifetime

of an individual. It doesn't. I am equally bewildered when Skinner recalls his having pointed out that in his epoch-making Integrative Action of the Nervous System Sherington had analysed the role of the synapse, but that he had never -seen a synapse in action.Considered as a specialised interface between neurones it is not clear what one could expect to see that would lay bare how the synapse delays and polarises the passage of a nervous impulse. It is of couse perfectly true to say that the synapse was known to Sherington and his contemporaries only in terms of the characteristics it must have in order to display the properties we all recognise. Exactly the same was true until recently of the 'gene', but what of it? With Skinner's piece I have the uneasy feeling throughout that he has a message to impart without the expository skill to impart it.

Karl Popper's contribution is frankly Spencerian: -from the biological or evolutionary point of view of science progress in science may he regarded as a means used by the human species to adapt itself to the environment, to invade new environments and even to invent new environmental niches." A scientific discovery is a special case of adapative behavioural learning, itself one of the principal stratagems of adaptation. Popper sees a common formal structure in all forms of adaptation: tentative solutions of whatever problem the organism may be confronted with are thrown up by random variations that arise within a pre-existing structure which is in some sense inherited, whether genetically or in the form of received ideas or institutions passed on from generation to generation in a cultural heredity. A critical process figuratively akin to natural selection now weeds out those solutions that don't work or don't work well enough. All this applies to ideation too: "scientific discovery is akin to explanatory storytelling, to myth making and to poetic imagination." New theories often explain why the old ones don't work. Popper here is close to Ravetz in seeing this process as one which confirms asymmetry and therefore a directional change upon science in its ever closer approximation to the truth.

Because scientific theories are continuously under critical scrutiny scientific progress is revolutionary in character. Moreover, scientific revolutions are rational in the sense that the processes bywhich scientific theories are tested and by which one comes to supplant another are fully accountable to reason. This is not to deny the importance of an intuitive or inspirational element in devising theories. It appears to me that through his lecture the way in which Popper makes his case carries complete conviction.

It is sad to think that a very large market does not exist for original and deeply reflective works on ideas — particularly the ideas that lie on the interface between science and philosophy. This struck me as an excellent book and a credit to all concerned with is. It reinstates reason at a time and in a context in which it has been fashionale for philosophic mavericks and other bores to depreciate it.

Sir Peter Medawar, the Nobel prize winner, has most recently written The Hope of Progress