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Technology and Evolution
Sir Peter Medawar

Genetic and exogenetic heredity

The use of tools has often been regarded as the defining characteristic of Homo sapiens, that is, as a taxonomically distinctive characteristic of the species. But, in light of abundant and increasing evidence that subhuman primates and even lower animals can use tools, the view of now gaining ground that what is characteristic of human beings is not so much the devising of tools as the communication from one human being to another of the know-how to make them. It was not so much the devising of a wheel that was distinctively human, we may suggest, as the communication to others, particularly in the succeeding generation, of the know-how to make a wheel. This act of communication, however rudimentary it may haven been --- even if it only took the form of a rudely explanatory gesture signifying `It's like this, see', accompanied by a rotatory motion of the arm --- marks the beginning of technology, or of the science of engineering.

Everyone has observed with more or less wonderment that the tools and instruments devised by human beings undergo an evolution themselves that is strangely analogous to ordinary evolution, almost as if these artefacts propagated themselves as animals do. Aircraft began as birdlike objects but evolved into fishlike objects for much the same fluid-dynamic reasons as those which caused fish to evolve into fishlike objects. Bicycles have evolved and so have motor cars. Even toothbrushes have evolved, though not very much. I have never seen Thomas Jefferson's toothbrush, but I don't suppose it was very different from the one we use today; the Duke of Wellington's, which I have seen, certainly was not. To some Victorian thinkers, facts like these served simply to confirm them in the belief that evolution was the fundamental and universal modality of change. The assimilation of technological to ordinary organic evolution was not wholly without substance, because all instruments that serve us are functionally parts of ourselves. Some instruments, like spectrophotometers, microscopes and radiotelescopes, are sensory accessories inasmuch as they enormously increase sensibility and the range and quality of the sensory input. Other instruments, like cutlery, hammers, guns and motor cars, are accessories to our effector organs --- not sensory but motor accessories.

A property that all these instruments have in common is that they make no functional sense except as external organs of our own: all sensory instruments report back at some stage or by some route through our ordinary senses. All motor instruments receive their instructions from ourselves.

It was for reasons like this that the great actuary and demographer Alfred J. Lotka invented the word `exosomatic' to refer to those instruments which, though not parts of the body, are nevertheless functionally integrated into ourselves. Everybody will have realised from personal experience how closely we are integrated psychologically with the instruments which serve us. When a car bumps into an obstacle, we wince as much from an actual referral of pain as from a sudden premonition of the sour and sceptical face of an insurance assessor. When the car is running badly and labours up hills, we ourselves feel rather poorly, but we feel good when the car runs well. Wilfrid Trotter, the surgeon, said that when a surgeon uses an instrument like a probe he actually refers the sense of touch to its tip. The probe has become an extension of his finger.

I do not think I need labour the point that this proxy evolution of human beings through exosomatic instruments has contributed more to our biological success than the conventional evolution of our own, or endosomatic, organs. But I do think it is worth while calling attention to some of the more striking differences between the two.

Genetic and exogenetic programs

By far the most important difference is that the instructions for making endosomatic parts of ourselves, like kidneys and hearts and lungs, are genetically programmed. Instructions for making exosomatic organs are transmitted through non-genetic channels. In human beings, exogenetic heredity --- the transfer of information through non-genetic channels --- has become more important for our biological success than anything programmed in DNA. Through the direct action of the environment, we do in a sense `learn' to develop a skin thicker on the soles of our feet than elsewhere. But information of this kind cannot be passed on genetically, and there is indeed no known mechanism by which it could be. It is only in exosomatic heredity that this kind of transfer can come about. We can learn to make and wear shoes and pass on this knowledge ready-made to the next generation as readily as we can pass on the shoes themselves.

There is no learning process in ordinary genetic heredity: we can't teach DNA anything, and there is no known process by which the translation of the instructions it embodies can be reversed. No information that the organism receives in its lifetime can be imprinted upon the DNA, but in exogenetic heredity we can and do learn things in the course of life which are transmitted to the succeeding generation; thus exogenetic heredity is Lamarckian or instructional in style, rather than Darwinian or selective. By no manner of means can the blacksmith transmit is brawny arms to his children, but there is nothing to stop his teaching his children his trade so that they grow up to be as strong and skillful as himself.

Learning as a new stratagem

The evolution of this learning process and the system of heredity that goes with it represents a fundamentally new biological stratagem --- more important than any that preceded it --- and totally unlike any other transaction of the organism with its environment. In ordinary, endosomatic evolution and in cognate processes such as the so-called `training' of bacteria and, in immunology, antibody formation, we are dealing with what are essentially selective, as opposed to instructive, phenomena. The variants that are proffered for selection arise either by some random process such as mutation or by a process which is it not paradoxical to describe as a `programmed' randomness. By a `programmed randomness' I mean a state of affairs in which the generation of diversity is itself genetically provided for. Mendelian heredity provides for the preservation of genetic diversity for an unlimited period.

The reversibility of exogenetic evolution

Another important difference is this. Genetic evolution is conceivably reversible, just as it is thermodynamically conceivable that a kettle put on a lump of ice will boil. It's very unlikely, that's all. On the other hand, exosomatic evolution is quite easily reversible: everything that has been achieved by it can be lost or not reacquired. This is what specially frightens us when we contemplate the consequences of some particularly infamous tyranny that threatens to interrupt the cultural generation between one generation and the next. This reversion to a cultural Stone Age is what each political party warns us will be the inevitable consequence of voting for the other. To bring the idea of reversibility to life, one should contemplate the plight of the human race if for any reason it did have to start again from scratch on a desert island: it is not heaven, but the Old Stone Age, that lies about us in our infancy.

Popper's third world

I have been looking around in my mind for some one word or phrase to epitomize what I understand by our human inheritance through non-genetic channels --- through indoctrination, that is, and the conscious transfer of information by word of mouth and through books. Karl Popper's Objective Knowledge supplied the answer ready-made. Let me therefore introduce you to Popper's concept of a `third world'.

According to the philosophic views we specially associate with the name of George Berkeley, the apparently `real' world about us exists only through and by virtue of our apprehension of it. Thus sensible things and material objects generally exist only as representations or conceptions or as `ideas' in the mind --- hence the name `idealism'. Berkeley argued persuasively, but Boswell very well knew that Berkeley's argument was of just the kind that would enrage Dr Johnson. When Boswell teasingly said it was impossible to refute Berkeley's beliefs, `I refute it thus' said Johnson, kicking a large stone so violently that he `rebounded' from it, thus simultaneously refuting Berkeley and corroborating Newton's third law of motion (the one about actions' having equal and opposite reactions).

However, even those who take a sturdily Johnsonian view of Berkeley's philosophy as it relates to the real world of material objects sometimes hold a Berkeleian, or subjectivist, view of things of the mind. They tend to believe that thoughts exist by reason of being being thought about, conceptions by virtue of being conceived, theorems because they are the products of deductive reasoning, and beliefs because believed.

Popper's new ontology does away with subjectivism in the world of the mind. Human beings, he says, inhabit or interact with three quite distinct worlds: World 1 is the ordinary physical world, or world of physical states; World 2 is the mental world, or world of mental states; the `third world' (you can see why he now prefers to call it World 3) is the world of actual or possible objects of thought --- the world of concepts, ideas, theories, theorems, arguments and explanations --- the world, let us say, of all artefacts of the mind. The elements of this world interact with each other much like the ordinary objects of the material world: two theories interact and lead to the formulation of a third; Wagner's music influenced Strauss's and his in turn all music written since. Again, I mention for what it may be worth that we speak of things of the mind in a revealing objective way: we `see' an argument, `grasp' an idea, and `handle' numbers, expertly or inexpertly as the case may be. The existence of World 3, inseparably bound up with human language, is the most distinctively human of all our possessions. This third world is not a fiction, Popper insists, but exists `in reality'. It is a product of the human mind but yet is in large measure autonomous.

This was the conception I had been looking for: the third world is the greater and more important part of human inheritance. Its handing on from generation to generation is what above all else distinguishes man from beast.

Popper has argued strongly that, although the third world is a human artefact, yet it has an independent objective existence of its own --- and is indeed quite largely autonomous. I have already pointed out that the third world undergoes the kind of slow, secular change that is described as evolutionary, that is, gradual, directional and integrative in the sense that it builds anew upon whatever level may have been achieved beforehand. The continuity of the third world depends upon a non-genetical means of communication and the evolutionary change is generally Lamarckian in character, but there are certain obvious parallels between exosomatic evolution and ordinary, organic evolution in the Darwinian mode. Consider, for example, the evolution of aircraft and of motor cars. A new design is exposed to pretty heavy selection pressures through consumer preferences, `market forces' and the exigencies of function, by which I mean that the aircraft must stay aloft and the cars must go where they are directed. A successful new design sweeps through the entire population of aircraft and cars and becomes a prevailing type, much as jet aircraft have replaced aircraft propelled by airscrews.

I hope it is not necessary to say that the secular changes undergone by the third world do not exemplify and are not the product of the workings of great, impersonal historical or sociological forces. Just as the third world, objectively speaking, is a human artefact, so also are all the laws and regulations which govern its transformations. The idea that human beings are powerless in the grip of vast historical forces is in the very deepest sense of the word nonsensical. Fatalism is the most abject form of the aberration of thought which Popper calls `historicism'. Its acceptance or rejection has not depended upon cool philosophic thought but rather upon matters of mood and of prevailing literary fashion. There was quite a fashion for fatalism in late-Victorian and Edwardian England, admirably exemplified by Omar Fitzgerald's famous stanza:

'Tis all a Chequer-board of nights and Days
Where Destiny with Men for Pieces plays:
Hither and thither moves, and mates, and slays,
And one by one back in the Closet lays.
This is a comfortable doctrine, in so far as it spares us any exertion of thinking, but we may well wonder why it was so prevalent in England at that time.

This kind of fatalism sounds very dated now, but we should ask ourselves very seriously whether there is not a tendency today to take the almost equally discreditable view that the environment has already deteriorated beyond anything we can do to remedy it --- that man has now to be punished for his abandonment of that nature which, according to the scenario of a popular Arcadian day-dream, should provide for all our reasonable requirements and find a remedy for all our misfortunes. It is this day-dream that lies at the root of today's rancorous criticism of science and technologies by people who believe, and seem almost to hope, that our environment is deteriorating to a level below which it cannot readily support human life. My own view is that these fears are greatly and unreasonably exaggerated. Our present dilemma has something in common with those logical paradoxes that have played such an important part in mathematical logic. Science and technology are held responsible for our present predicament but offer the only means of escaping their consequences.

The coming of technology and the new style of human evolution it made possible was an epoch in biological history as important as the evolution of man himself. We are now on the verge of a third episode, as important as either of these: that in which the whole human ambience --- the human house --- is of our own making and becomes as we intend it should be: a product of human thought --- of deep and anxious thought, let us hope, and of forethought rather than afterthought. Such a union of the first and third worlds of Popper's ontology is entirely within our capabilities, provided it is henceforward made a focal point of creative thought.

The word `ecology' has its root in the Greek word oikos, meaning `house' or `home'. Our future success depends upon the recognition that household management in this wider sense is the most backward branch of technology and therefore the one most urgently in need of development. An entirely new technology is required which is founded upon ecology in much the same way as medicine is founded on physiology. A blueprint for such a technology is described in the book Only One Earth, by Barbara Ward and René Dubos, written in preparation for the United Nations World Conference on the Human Environment, held in Stockholm in 1972. If this new technology comes into being, I shall be completely confident of our ability to put and keep our house in order.

Typed on 26 June 1996 [CRS]