Evolution: Past and Future

by J. B. S. HALDANE

I AM asked to discuss one of the great problems of human biology. I do so gladly, but with one important reservation. I am going to treat of man from one point of view, the biological. This is wholly justifiable provided I do not leave you with the impression that this is the only point of view that matters. Only evil can come from forgetting that man must be considered from many angles. You can think of him as a producer and a consumer. You can treat him as a thinker, as an individual, as a member of society, as a being capable of moral choice, as a creator and appreciator of beauty, and so on. Concentration on only one of these aspects is disastrous.

A biologist can do two things besides discovering facts, such as the facts of human evolution and genetics. He can tell his fellows how to achieve ends which they desire already, such as the cure or prevention of a disease. He can tell them of possibilities at which they had not guessed, such as the possibility of making childbirth painless, or some of the possibilities of which I shall speak later. But he can never tell them what is worth doing. That is always an ethical, not a biological, question. In what follows, I shall say that I think certain things are worth doing, that it is better to be born with a normal mouth than a harelip, with a normal color sense rather than color-blind, and so on. These are my opinions as a human being. If you disagree with them, I cannot, as a biologist, persuade you to change your opinion. But if you agree, then, as a biologist, I may be able to help you to work for the ends on which we are agreed.

There are those who say that any attempt to apply biology to human affairs is mere Hitlerism. To my mind, that is as stupid as to say that when a tailor wants your measurement he is treating you as a mere lump of matter and no more.

Evolution is a process which has happened in the past, and is happening now. I may add in parenthesis that almost all biologists are convinced that it has occurred, though we differ a good deal as to how, and still more as to why, it has occurred. The very first point I want to make is the time scale of the process. Forty years ago we knew the sequence of events in our evolutionary history, but could only guess at their dates. It is as if we knew that Washington lived before Lincoln, but did not know whether Washington was born 200 or 2000 years ago. Now, thanks to the study of radioactive minerals, we know our dates with an error generally under 10 per cent when we are dealing with dates between about 30 million and 500 million years back. We know that somewhere around 350 million years ago our ancestors were fish, 270 million years ago amphibians somewhat like salamanders, 200 million years ago reptiles not very like any living forms, and 70 million years ago, mammals something like shrews.

Curiously enough we cannot date the last few million years quite so accurately, until we get to the last 20,000, when we have layers of mud laid down each year in water from melting ice. But we can say that Sinanthropus, the so-called Pekin man, lived about half a million years ago, and almost surely less than a million and more than 200,000 years. Further we can say that at that time there were no men of the modern types; so our ancestors must have been a good deal less human than any existing race, even though, as they used tools, they probably deserved the name of man.

Controlled evolution as an ideal

These Pekin men had queer-shaped heads, broadest about the level of the ears instead of much higher, brow ridges, no chins, and so on. In half a million years we have changed a bit. Certainly the difference between Sinanthropus and modern man is as great as that which separates many nearly related animal species (for example the coyote and wolf). It is doubtful whether it is as great as that between two nearly related animal genera (for example dogs and wolves on the one hand, and various kinds of fox on the other). In fact it has taken about half a million years for a change large enough for zoologists to give it a name with full certainty. Other animals, such as horses and elephants, of whose ancestors we have a far better record, have been evolving at about the same rate.

These facts suggest that, if we did not try to control the evolutionary process in any way, our descendants half a million years hence might differ from us, for better or worse, about as much as we differ from Pekin man, or a cat from a puma. Now at present I do not think we know how to control our evolution, even if we wanted to, or if biologists were granted all the powers which Hitler exercised for twelve years. But supposing a thousand years hence we know how to direct our evolution, and further that the vast majority of men accept this ideal, as the vast majority of Americans accept the ideal of sanitation today, what then?

The answer is rather curious. An unaided man can walk 20 miles a day with a fair load, and keep it up indefinitely. I have walked over 50 with a rifle and a few extras, but I couldn’t keep it up. At present one can easily fly 2000 miles a day, but a 5000-mile flight is more difficult. Roughly speaking, science has increased our speed of travel a hundred fold. It is reasonable to hope that we might speed up evolution a hundred fold if we knew enough. If so, we might achieve a change as large as I have indicated in 5000 years, or 200 generations. This is a long time. The earliest date in human history is 2283 B.C., or just over 4000 years ago. This is the date of a total eclipse of the sun which immediately preceded the capture and destruction of Ur by the Elamites. Five thousand years ago civilization had started in Egypt, Iraq, and maybe a few other areas, but most men were savages.

Is it worth while even talking about a change which we do not yet know how to bring about, and which would take 5000 years to accomplish if we did? Yes, it is worth while talking about it, for three reasons. In the first place we ought to discuss the right and wrong ways of using a power before we get it. The world would be a far safer and happier place today if we had discussed how to use nuclear, or so-called atomic, energy for a century, or even a generation, before we got it. If so, very likely almost all decent people would be agreed as to the rights and wrongs of this matter, which they certainly are not today. About 2500 years ago, the prophet Isaiah got the idea that one day all the nations of the earth would be at peace. Isaiah’s idea of universal peace was something like a Jewish world empire. Ours is an association of friendly democracies. The ideal has only just become possible of accomplishment because worldwide transport has been achieved. But if visionaries had not been talking about it off and on since Isaiah’s time, there would be no chance of achieving it now, when the alternative is, quite literally, destruction by fire from heaven.

Secondly, we shall not get the required knowledge in a hurry. Even now we can do a little to alter the unborn capacities of the next generation. Let us begin to think about what sort of changes we want, and criticize one another’s ideas, as democrats should.

Thirdly, if we put the ideal of controlling evolution before us, and try to accumulate the necessary knowledge, we may find out something even more important on the way. Columbus set out to find a sea route from Europe to China. A ship can get from Europe to China through the Panama Canal, but the discovery of America was a vastly more important result of his voyage than the opening of this route.

Slow development as a major evolutionary trend

Our first task will be to take a glance at human evolution, and to see how man differs from the other mammals, his nearest relatives, and how these differences have arisen. Man is an exceptionally brainy animal. The whale has a heavier brain, and the mouse has a brain which is a larger fraction of its body weight. But if we take a series of closely related animals, such as the cat, ocelot, puma, and lion, we find that their brain weight is proportional to the square root of their body weight. If we rate animals on the ratio of brain weight to square root of body weight, the great and small cats, for example, are about equal, and man comes out well ahead of any other animal.

We use our brains for thinking, but it is a mistake to suppose that the brain is primarily a thinking organ. Thinking is mainly, if not wholly, performed with words and other symbols, as the Greeks recognized when they used the word logic — from logos, a word — for the study of thought processes. From the study of the effects of brain injuries we know what parts of the brain are most concerned in thought and language. These areas are usually in the left cerebral hemisphere in the neighborhood of the area which controls the right hand. The human brain has two super-animal activities, manual skill and logical thought. Manual skill appears to be the earlier acquisition of the two, and the capacity for language and thought has grown up round it. If we bred for qualities which involved the loss of manual ability, we should be more likely to evolve back to the apes than up to the angels.

We develop far more slowly than any other mammal. Most mammals are mature at one year or less, a chimpanzee at about 9 years, a human being at 15 or more, while growth is not complete till over 20 years, and the skull sutures are often open till nearly 30, so that the brain can still grow. We are much more like baby monkeys than adult ones. In biological language we are neotenic, like the axolotl, a Mexican newt which, unlike most newts, never comes out of the water, but breeds without shedding its larval gills. Since a little thyroid hormone will make it grow up, and for other reasons, we may be pretty sure that its ancestors came out of the water. An obvious advantage of this neotenic tendency has been that man has a very long period of learning. As regards behavior he is the most plastic of all the animals. His behavior patterns are less fixed by heredity than theirs and more dependent on his environment.

If this tendency continues, whether by natural processes or human design, we should expect our remote descendants to have an appearance which we should describe today as childish. We should expect their physiological, intellectual, and emotional development to be slower than our own. We should not expect them to be born with an overpowering urge to any particular kind of conduct, good or bad.

For example, some birds are monogamous, others polygamous. Monogamy is just one of a series of fairly stereotyped behavior patterns. Man has evolved away from stereotyped behavior patterns, and can be monogamous, polygamous, or celibate. How he will behave depends largely on the impact of society on him. Even a cat is comparatively plastic in its behavior. A kitten which is brought up with mice, and does not see other cats kill mice in its first few months of life, will rarely kill them. But a child’s behavior is far less fixed in advance than a kitten’s.

This feature, which is so highly developed in man, and which we call plasticity of behavior when we look at it from outside, is called the freedom of the will when we look at it from inside. In any evolution which could be called progressive we are likely to develop it still further. Bernard Shaw, in Back to Methuselah, shows us a young lady emerging from an egg some thousands of years hence, and spontaneously talking very good English. She is like those birds which, without education, produce a fairly complex song characteristic of their species. I can imagine human beings bred for stereotyped behavior patterns. Perhaps if the Nazis had won they would have tried to do so. But any such step would be a step backwards.

Man is not only the brainiest species of mammal. He is the most polymorphic and polytypic if we exclude domesticated species such as the dog. Let me explain these words. We say that a species is polymorphic when in the same area there are several different types breeding together, the differences being genetically determined. For example, the fox Vulpes fulva of eastern Canada has three color types: the red, cross, and silver foxes. A polytypic species has different types in different areas. Your deer mouse, Peromyscus maniculatus, has a gray form inland, and nearly white forms on the white beaches of the Gulf of Mexico.

Human diversity desirable

Man is polytypic. For example, the peoples of tropical Africa have very dark skins and kinky hair. Those of Europe have light skins and wavy or curly hair. The pre-Columbian peoples of North America have intermediate colored skins, but straighter hair than the Europeans. Man is polymorphic. And at least as regards color, the European, the most successful of the human races at the present time, is also the most polymorphic. If anyone thinks that I am exaggerating this polymorphism, he will perhaps tell me of another mammalian species apart from domestic animals in which the hair color in a single geographical area ranges from black to pale yellow, the eye color from dark brown to pale blue.

This polymorphism is not necessarily, or even probably, due to race mixture in the past. For example, there is no reason to think that there was ever a race all of whose members had red hair. And the skull shape is as variable in cemeteries of 6000 years ago as in modern cemeteries.

Human polymorphism certainly extends to innate abilities as well as physical and chemical characters such as stature and hair color. For example, I am tone-deaf. I cannot distinguish between quite well-known tunes. I am pretty sure that this defect is congenital. I am also a better mathematician than the average, and have little doubt that I have abnormally high congenital ability for mathematics. No doubt I had good opportunities of learning mathematics, but so I had in the case of music. We know very little about the reasons for variation in human achievement, but we know enough to be reasonably sure that inborn differences play a great part in determining very high and low levels of achievement.

I believe that this psychological polymorphism has been a major reason for the success of the human species, and that a full recognition of this polymorphism and its implications is an essential condition for its success not only in the remote future but in our own lifetime. Let me make my meaning clearer. One of my colleagues, a man of greater manual ability than myself, and very likely of equal or greater intellectual ability, is also a musical executant who could have been a professional musician. If I had his musical gifts I might devote as much time as he does to music, at the expense of my scientific output. It is quite possible that my tone-deafness is an advantage not only for society but even for myself; though such a limitation would almost certainly be undesirable if my probable span of socially useful life were 400 years instead of 40.

The political implications of human diversity

I will now make a definition. Liberty is the practical recognition of human polymorphism. I hasten to add, because I recognize that your brains work differently from my own, that few of you will accept this definition. That society enjoys the greatest amount of liberty in which the greatest number of human genotypes can develop their peculiar abilities. It is generally admitted that liberty demands equality of opportunity. It is not equally realized that it demands a variety of opportunities, and a tolerance of those who fail to conform to standards which may be culturally desirable but are not essential for the functioning of society. If I lived in the Soviet Union I should not find its political and economic system irksome. I should be, and have been, irked by the assumption often made there that any cultured man enjoys listening to music and playing chess. If a nation were a pure line there would be little scope for liberty. Everyone between 45 and 50 would want so many hours a week at the movies, so much (or so little) liquor per week, and so on. These would be provided by rationing, as our needed food calories are provided in England, and everyone would be equally happy. There would be no freedom, no deviants, and no progress.

We are polymorphic not only in our aesthetic but in our intellectual abilities. Ways of describing the world as different as analytical and projective geometry may be equally true, even if at present one human mind cannot accept more than one of them at a time. Last year I saw for the first time Rubens’s and Breughel’s great picture of Paradise at The Hague. As a geneticist I noted with interest that the guinea pig had been created with at least three genes recessive to the wild type. But I was even more struck by the fact that the Tree of Knowledge was infested by only one serpent but no fewer than four parrots. Maybe in the long run the parrots are more dangerous than the serpent. Certainly we must so far recognize polymorphism as to realize that our own formulations of knowledge are not unique.

Domesticated animals such as dogs are more polymorphic than man. But greyhounds and sheep dogs differ only because they are reproductively isolated. The Indian caste system was an attempt to divide society into a set of reproductively isolated groups each with its peculiar function. This system broke down, as I believe and hope that any such system would break down. I believe that when our descendants plan the genetical future of man they will have to plan for high polymorphism without reproductive isolation. I don’t know how they will do it. Fortunately I shan’t have to do the planning.

Man is also polytypic. This does not mean that any two races differ as much in intellectual, aesthetic, or normal potentialities as they do in color. The darkest European has lighter skin than the lightest Negro. There is no overlap. But even in a society where Negroes have poor opportunities of education the most cultured Negro is far more cultured than the average European, let alone the least cultured one. Nevertheless polytypicism has so far been an advantage to humanity. Without postulating any over-all superiority of one race to another, we can be fairly sure that some desirable genotypes are commoner in one people than in others and that this difference is to some extent reflected in its achievements. For example, the genotype needed for long-distance runners is relatively frequent among Finns, that needed for short-distance runners among American Negroes, Doubtless the same is true for the genotypes needed for cultural achievement.

In the past a given people at a given time has usually specialized in a few fields of culture. Thus potential mathematicians had little chance in medieval Europe, but potential architects had a good chance. Very likely the contributions of a people to our common culture depend considerably on the genotypes available in it. If so, it is certainly desirable that, until all peoples have reached such a stage of liberty that rare but desirable genotypes can develop their faculties everywhere, man should remain polytypic.

If, however, 10,000 years hence we combine extreme tolerance with a psychology which will enable us to pick out human abilities at an early age, then I can see no need to foster or preserve polytypicism — though it may be desirable to do so for reasons which are not obvious at the present time. In discussing polymorphism we must not forget sex dimorphism — that is to say, the innate differences between the sexes. It is curious that in our existing society most men try to diminish them by removing their beards, while women try to exaggerate them by the use of cosmetics and other devices. Sinanthropus and related types seem to have been much more sexually dimorphic than ourselves. So it looks as if men conformed better than women with the evolutionary trend. It is not clear whether this trend should be encouraged to go much further. It is essential that the sexes should understand each other, but a certain difference in intellectual and emotional reactions may well be socially desirable.

The evolution of the meek

To sum up, I think that in the last million years man has become more cerebral, more neotenic, and more polymorphic. I think it probable that these are desirable evolutionary trends, while I suggest that judgment should be reserved concerning polytypicism and sexual dimorphism. Others will doubtless say that I have left out the one essential: namely, a bias towards their own canon of behavior, whether moral, religious, or political. However, I have at least given reasons why I believe that any hereditary fixation of behavior patterns is undesirable.

Even this moderate list of desirable qualities gives us food for thought. If it were shown, for example, that the median intellectual performance of English children at the age of 15 were diminishing, and that this was not due to environmental changes, this fall could be due either to the fact that, on the whole, we were reaching a lower intellectual level at maturity, which would be undesirable; or that we were reaching the same level as our ancestors, or a higher one, but reaching it more slowly, which would be desirable.

How are we to achieve these ends? I do not know. We do not know in detail for what human characters we want to breed. The experience of animal husbandmen will not help us much, for several reasons. We do know that the domestic breeds have been selected for highly specialized performances. But in gaining desired qualities they have lost others which would be desirable in a different context. The greyhound cannot hunt by smell, the dachshund is a poor runner, the husky is ill adapted for city life, and so on.

I think that the history of man’s ancestry, as revealed by the geological record, should also make us a little cautious. If a Martian zoologist who knew no more than we do now about evolution had been asked to pick the most progressive vertebrate at any time in the past, I think he would very rarely have picked on the line which was destined to give rise to man. During most of the last quarter-billion years they have been pretty small, inconspicuous, and unspecialized animals. Looking at the Jurassic and Cretaceous mammals, and most of the Tertiary Primates, one might be inclined to summarize the evolutionary story as “Blessed are the meek, for they shall inherit the earth,” and perhaps to suggest that peoples such as the British in the nineteenth century and the American in the twentieth, who have been successful in war, are dead ends from the evolutionary point of view.

However, if we go back to the Permian, we find that our ancestors were large and progressive reptiles. No one who looks at the skeleton and particularly the teeth of such a beast as Cynognatkus, which was not far from our own ancestral line, could possibly class it as meek. Why the descendants of large predatory theromorphs became small and vegetarian is very far from clear. It is possible that the giant forms discovered by Dr. von Koenigswald were actually our ancestors. If so, our ancestors a million years ago were monsters who could have torn up a tiger with their bare hands. In that case there was a second occasion on which our ancestral line tried physical dominance and gave it up again. It is also possible that the giants of Java and China were side branches from the human line, and represent an unsuccessful evolutionary experiment.

Negative eugenics

After all this caution, I believe we can make a start. Whatever else we may want our descendants to be, we do not want them to be blind, deaf, paralyzed, or brittle-boned. Now these conditions are sometimes due to dominant genes, which can be prevented from spreading further by negative eugenics. At first sight it might be thought that these genes could be eliminated. For example, in many pedigrees of juvenile cataract, affected persons pass on the gene for cataract to about half their children, and it very rarely skips a generation. It has been said that were they all sterilized, these conditions would be abolished. This was one of the ideas behind Hitler’s racial hygiene laws.

The idea is false, because these harmful genes constantly reappear as the result of mutation. Occasionally two normal parents will have a child with a harmful dominant gene, which is then handed on until natural selection or negative eugenics puts an end to its career. The two processes are roughly in equilibrium. Thus achondroplastic dwarfs have about one fifth the fitness of normal people. That is to say, they produce on an average about one fifth as many children. So only one fifth of the dwarfs alive at any time are the progeny of dwarfs, the others being the progeny of normal parents. If all dwarfs of this kind were sterilized we could only cut down the number of dwarfs by one fifth.

With hemophilia we could cut down the frequency to about one half by preventing the breeding of hemophilics and heterozygous women. With hereditary cataract we could cut down the frequency to much less than one half—perhaps to one tenth. Some, though not all, types of mental defect could be considerably reduced; so could harelip and many other physical defects. This would be well worth doing, but the battle would never be finally won, the race never finally purified.

We could, however, cut down the incidence of a great many congenital maladies to a large extent. Others, such as neonatal jaundice, or erythroblastosis fetalis, and perhaps mongoloid idiocy, are due to gene differences between father and mother. We could only abolish them by forbidding unions between people of different genotypes. A closed mating system based on skin color is bad enough, in the sense of making for the division and perhaps the instability of the community. One based on blood antigens, in which an Rh-negative woman might not marry an Rh-positive man, would perhaps be even worse. I should be the last to recommend it, even if it saved the lives of a few babies.

Nor at the present time can we do much to diminish the frequency of undesirable recessive conditions, whether they are lethal, like fetal ichthyosis, or merely a slight handicap, like albinism. The most efficient eugenic method is the introduction of good road transport into backward rural areas, thus encouraging outbreeding.

It may be that, if we knew enough, 1 per cent or even rather more of the population would be found to carry undesirable dominants or sex-linked recessives, which any sound eugenic policy would eliminate. How should we do it? Many people believe that carriers should be sterilized, either voluntarily as in Denmark, or compulsorily as in Nazi Germany. I do not, for the following reasons. Laws for compulsory sterilization are liable to gross abuse. Those for voluntary sterilization are only rather less so. I recall the case of a laborer in one of your Western states who was given an indeterminate sentence up to five years’ imprisonment for theft. The judge suggested that he be voluntarily sterilized. He agreed, and was not imprisoned. His agreement can only be called voluntary in a Pickwickian sense. However, I might be in favor of sterilization if it would finally rid us of these undesired genes. But it would not.

There is another reason, perhaps worthy of consideration. If we are ever to control our evolution we shall certainly have to overhaul our whole mating system. By this I do not mean that we shall have to abolish marriage or adopt polygamy. I do not know what we shall have to do. We shall only do what is right if people realize that we have a duty to beget and bear the best-endowed children possible.

It is of the utmost importance that the idea should not be spread abroad that we can improve the human race to any serious extent by sterilizing individuals who do not come up to certain standards. In England we are already beginning to persuade people with harmful dominants to refrain from reproduction, either by chastity or by contraception. We shall not improve the human race by compulsion. A prerequisite for doing so is the moralization of our sexual behavior — that is to say, making it subordinate to ideal ends, not to impulse on the one hand or superstition on the other.

Difficulties of positive eugenics

What about positive eugenics? In many human societies those types which are most admired are bred out. The Middle Ages admired holiness and courage. The holy men and women were celibate, the courageous men killed one another. Our age admires money-making. The men who make most money have least children. I am less worried by this than many of my contemporaries. I am not convinced that a business executive is a higher type than a saint or even a feudal knight. In any case, a differential birth rate lasting over a century need no more permanently affect the gene frequencies of a race than selection of certain chromosome orders for a few months per year affects a Drosophila species. And in Sweden the tendency has already reversed itself, and the poor breed rather more slowly than the rich.

Why, it may be asked, should we not encourage the breeding of rare and desirable genes as we can discourage the breeding of rare and undesirable ones? The answer is that we do not know of a single rare gene in man whose frequency we should increase. I have no doubt that such exist. But our analysis of the genetic basis of human abilities is so utterly rudimentary that we know nothing of them. Their discovery will need a vast program of collaboration between geneticists, physiologists, and psychologists. Until even one such gene is known, it seems to me rather futile to talk about a program for positive eugenics.

I would, however, suggest that among the genes whose spread we would want to encourage are those for the non-development of teeth, particularly wisdom teeth. Our cerebral development has caused a good deal of overcrowding of our teeth. I hope also that we shall do something about our noses, which are one of our weak points. (I have a nasal infection at the moment. No other organ lets me down so frequently.) The nose has of course been squashed out of shape by the growth of the brain. In consequence, while a sneeze takes a straight path in a dog or a horse, it has to take a hairpin bend in our own species. In a century or so we may know of detailed changes in our psychological make-up which are equally desirable.

In fact, while we can begin with negative eugenics, we cannot begin on positive eugenics until we have got a great deal more knowledge and a wider diffusion of the eugenic attitude. Probably the first requisites for the development of this knowledge are, on the one hand, the mapping of the human chromosomes, a task to which I have devoted some effort, and on the other, an attempt to analyze the psychological make-up of people judged to be exceptionally gifted, as Spearman in England and the Chicago school in America have tried to analyze that of more normal people. When these are accomplished it will be time to start research on the genetics of great intellectual or moral endowment. Much of it may turn out to be due to heterosis, and as unfixable as the good points of a mongrel dog, but I have little doubt that many rare and desirable genes for these characters exist.

Don’t make me world eugenic dictator

So far I have assumed that our descendants will take over the control of evolution in an intelligent manner. Let us consider the other possibilities. In the next century the human race may largely destroy itself. From the genetic point of view a war using atomic energy would be worse than one using old-fashioned weapons, or even pestilences. For the survivors of Hiroshima and Nagasaki have been so affected that their descendants will show a variety of abnormalities. Some will appear in the first generation and disappear within ten or so. Others will be recessive, and first appear after several generations, their evil (and very rarely good) effects continuing for many thousand generations. The killing of 10 per cent of civilized humanity by atomic bombs might not end civilization. The vast crop of abnormalities produced by another irradiated 10 per cent might do so, and even render recovery very difficult.

I hope that we shall avoid such an international war, or, what seems to me just as likely, a civil war in which a small group get control of some atomic bombs and hold up a whole nation. If so, we may settle down to some peaceful world order, but do nothing about our evolution. In such a case we might stay put for a very long time. Sewall Wright has shown that, on certain assumptions, which seem to me thoroughly sound, evolution goes on quickest in a species divided up into many groups of a few score or hundred individuals nearly, but not quite, sexually isolated from other groups. This was the human condition for thousands of centuries during the Old Stone Age. With agriculture and industry the community has grown, and probably evolution has slowed down. For some time there was heavy selection against crowd diseases, but the progress of hygiene has checked this tendency.

I do not know what we are selecting for now. Let me take an example. Until two generations ago large families were respectable in my country. Anyone who voluntarily restricted his or her family was a deviant. Selection favored genes making for conformity to mores in this respect. Now it is a deviation from the norm to have a dozen children. We are selecting in favor of deviation, instead of against it.

We may be favoring genes which make for high sexual activity, low intelligence, or lack of susceptibility to propaganda, to mention only three possibilities. Most eugenists regard the parents of large families as, on the whole, undesirable genetically. This may well be true. It is certain that on the whole they are economically unsuccessful. Before we equate economic success and long-term biological value, however, it might be desirable to read the Sermon on the Mount or the record of the dinosaurs. I do not know if the trend described is desirable or not, and I contend that no one else does.

Another possibility is that we shall control our evolution and choose the wrong path. If I had had to pick hopeful ancestors for a rational and skillful animal from past faunas I doubt if I should ever have got the right answer between the Pennsylvanian and the Miocene. I should certainly have picked Struthiomimus, a Cretaceous reptile like an ostrich, standing on its hind legs, but with arms in place of wings. I am equally sure that I should go wrong today. Dr. H. J. Muller has suggested a method for the radical improvement of the human race, involving the widespread use of artificial insemination. I guess that if I were made eugenic world dictator I should have one chance in a hundred of choosing the right path. Dr. Muller is ten times as good a geneticist as I, so he might have one chance in ten, but not, I think, much more.

I am convinced that the knowledge required, both of past evolution and present genetics and cytology, is considerably greater than the whole body of scientific knowledge on which our present civilization is based. We can get this knowledge if we want it. We may say that God is now enlarging the sphere of human choice, and therefore giving us new duties. Or we may say that the evolutionary process is now passing from the stage of unconsciousness to that of consciousness. But we have not yet got the knowledge.

Our immediate task is the remodeling of human society. This can be done in a few generations. The great men who founded your Republic based it on principles which had never before been applied to human societies but which nevertheless worked in practice. The great men behind the French and Russian revolutions made somewhat different but comparable experiments. No society is perfect, and the time scale of social change is so vastly less than that of evolutionary change that the duty to reform society is far more urgent than that to control evolution. The two duties must and will go together. But it would be fatal to think of the man of the future as one who would fit into contemporary American, British, Russian, or Chinese society, or into any society which we can even imagine today.

If I am right he would probably be regarded as a physical, mental, and moral defective. As an adult he would probably have great muscular skill but little muscular strength, a large head, fewer teeth than we have, and so on. He would develop very slowly, perhaps not learning to speak till 5 years of age, but continuing to learn up to maturity at the age of 40, and then living for several centuries. He would be more rational and less instinctive than we are, less subject to sexual and parental emotions, to rage on the one hand and so-called herd instinct on the other. His motivation would depend far more than ours on education. In his own society he would be a good citizen, in ours perhaps a criminal or a lunatic. He would be of high general intelligence by our standards, and most individuals would have some special aptitude developed to the degree which we call genius.

But just as, were we transported to the past, we should be unlikely to win the admiration of Sinanthropus, so, were one of these products of planned evolution brought back to our own time, we should probably judge him an unpleasant individual. This thought need not distress us. We shall not meet him.