The Ascent of Man

by Jacob Bronowski

  As the embryo develops the cells differentiate. Along the primitive streak the beginnings of the nervous system are laid down. Clumps of cells on either side will form the backbone. The cells specialise: nerve cells, muscle cells, connective tissue (the ligaments and tendons), blood cells, blood vessels. The cells specialise because they have accepted the DNA instructions to make the proteins that are appropriate to the functioning of that cell and no other. This is the DNA in action.

  The baby is an individual from birth. The coupling of genes from both parents stirred the pool of diversity. The child inherits gifts from both parents, and chance has now combined these gifts in a new and original arrangement. The child is not a prisoner of its inheritance; it holds its inheritance as a new creation which its future actions will unfold.

  The child is an individual. The bee is not, because the drone bee is one of a series of identical replicas. In any hive the queen is the only fertile female. When she mates with a drone in mid-air, she goes on hoarding his sperms; the drone dies. If the queen now releases a sperm with an egg she lays, she makes a worker bee, a female. If she lays an egg but releases no sperm with it, a drone bee is made, a male, in a sort of virgin birth. It is a totalitarian paradise, for ever loyal, for ever fixed, because it has shut itself off from the adventure of diversity that drives and changes the higher animals and man.

  A world as rigid as the bee’s could be created among higher animals, even among men, by cloning: that is, by growing a colony or clone of identical animals from cells of a single parent. Begin with a mixed population of an amphibian, the axolod. Suppose we decided to fix on one type, the speckled axolotl. We take some eggs from a speckled female and grow an embryo which is destined to be speckled. Now we tease out from the embryo a number of cells. Wherever in the embryo we take them from, they are identical in their genetic makeup, and each cell is capable of growing into a complete animal – our procedure will prove that.

  We are going to grow identical animals, one from each cell. We need a carrier in which to grow the cells: any axolotl carrier will do – she can be white. We take unfertilised eggs from the carrier and destroy the nucleus in each egg. And into it we insert one of the single identical cells of the speckled parent of the clone. These eggs will now grow into speckled axolotls.

  The clone of identical eggs made in this way are all grown at the same time. Each egg divides at the same moment – divides once, divides twice, and goes on dividing. All that is normal, exactly as in any egg. At the next stage, single cell divisions are no longer visible. Each egg has turned into a kind of tennis ball, and begins to turn itself inside out – or it would be more literal to say, outside in. Still all the eggs are in step. Each egg folds over to form the animal, always in step: a regimented world in which the units obey every command identically at the identical moment, except (we see) one unfortunate that has been deprived and is falling behind. And finally we have the clone of individual axolotls, each of them an identical copy of the parent, and each of them a virgin birth like the drone bee.

  Should we make clones of human beings – copies of a beautiful mother, perhaps, or of a clever father? Of course not. My view is that diversity is the breath of life, and we must not abandon that for any single form which happens to catch our fancy – even our genetic fancy. Cloning is the stabilisation of one form, and that runs against the whole current of creation – of human creation above all. Evolution is founded in variety and creates diversity; and of all animals, man is most creative because he carries and expresses the largest store of variety. Every attempt to make us uniform, biologically, emotionally, or intellectually, is a betrayal of the evolutionary thrust that has made man its apex.

  Yet it is odd that the myths of creation in human cultures seem almost to yearn back for an ancestral clone. There is a strange suppression of sex in the ancient stories of origins. Eve is cloned from Adam’s rib, and there is a preference for virgin birth.

  Happily we are not frozen into identical copies. In the human species sex is highly developed. The female is receptive at all times, she has permanent breasts, she takes an active part in sexual selection. Eve’s apple, as it were, fertilises mankind; or at least spurs it to its ageless preoccupation.

  It is obvious that sex has a very special character for human beings. It has a special biological character. Let us take one simple, down-to-earth criterion for that: we are the only species in which the female has orgasms. That is remarkable, but it is so. It is a mark of the fact that in general there is much less difference between men and women (in the biological sense and in sexual behaviour) than there is in other species. That may seem a strange thing to say. But to the gorilla and the chimpanzee, where there are enormous differences between male and female, it would be obvious. In the language of biology, sexual dimorphism is small in the human species.

  So much for biology. But there is a point on the borderline between biology and culture which really marks the symmetry in sexual behaviour, I think, very strikingly. It is an obvious one. We are the only species that copulates face to face, and this is universal in all cultures. To my mind, it is an expression of a general equality which has been important in the evolution of man, I think, right back to the time of Australopithecus and the first tool-makers.

  Why do I say that? Well, we have something to explain. We have to explain the speed of human evolution over a matter of one, three, let us say five million years at most. That is terribly fast. Natural selection simply does not act as fast as that on animal species. We, the hominids, must have supplied a form of selection of our own; and the obvious choice is sexual selection. There is evidence now that women marry men who are intellectually like them, and men marry women who are intellectually like them. And if that preference really goes back over some million of years, then it means that selection for skills has always been important on the part of both sexes.

  Eve is cloned from Adam’s rib.

  ‘The Creation of Eve’ by Andrea Pisano.

  Sex was invented as a biological instrument by the algae.

  Cell of the green alga, Spirogyra, in the process of fusion. Ancestors of this species produced the first evidence of cells fusing to form fertile egg cells.

  I believe that as soon as the forerunners of man began to be nimble with their hands in making tools and clever with their brains in planning them, the nimble and clever enjoyed a selective advantage. They were able to get more mates and to beget and feed more children than the rest. If my speculation about this is right, it explains how the nimble-fingered and quick-witted were able to dominate the biological evolution of man, and take it ahead so fast. And it shows that even in his biological evolution, man has been nudged and driven by a cultural talent, the ability to make tools and communal plans. I think that is still expressed in the care that kindred and community take in all cultures, and only in human cultures, to arrange what is revealingly called a good match.

  Yet if that had been the only selective factor then, of course, we should be much more homogeneous than we are. What keeps alive the variety among human beings? That is a cultural point. In every culture there are also special safeguards to make for variety. The most striking of them is the universal prohibition of incest (for the man in the street – it does not always apply to royal families). The prohibition of incest-only has a meaning if it is designed to prevent older males dominating a group of females, as they do in (let us say) ape groups.

  The preoccupation with the choice of a mate both by male and female I regard as a continuing echo of the major selective force by which we have evolved. All that tenderness, the postponement of marriage, the preparations and preliminaries that are found in all cultures, are an expression of the weight that we give to the hidden qualities in a mate. Universals that stretch across all cultures are rare and tell-tale. Ours is a cultural species, and I believe that our unique attention to sexual choice has helped to mould it.

  Most of the world’s literature, most of the world’s art, is preoccup
ied with the theme of boy meets girl. We tend to think of this as being a sexual preoccupation that needs no explanation. But I think that is a mistake. On the contrary, it expresses the deeper fact that we are uncommonly careful in the choice, not of whom we take to bed, but by whom we are to beget children. Sex was invented as a biological instrument by (say) the green algae. But as an instrument in the ascent of man which is basic to his cultural evolution, it was invented by man himself

  Spiritual and carnal love are inseparable. A poem by John Donne says that; he called it The Extasie, and I quote eight lines from almost eighty.

  All day, the same our postures were,

  And wee said nothing, all the day.

  But O alas, so long, so farre,

  Our bodies why doe wee forbeare?

  This Extasic doth unperplex

  (We said) and tell us what we love.

  Loves mysteries in soules doe grow,

  But yet the body is his booke.

  CHAPTER THIRTEEN

  THE LONG CHILDHOOD

  I begin this last essay in Iceland because it is the seat of the oldest democracy in Northern Europe. In the natural amphitheatre of Thingvellir, where there were never any buildings, the Allthing of Iceland (the whole community of the Norsemen of Iceland) met each year to make laws and to receive them. And this began about AD 900, before Christianity arrived, at a time when China was a great empire, and Europe was the spoil of princelings and robber barons. That is a remarkable beginning to democracy.

  But there is something more remarkable about this misty, inclement site. It was chosen because the farmer who had owned it had killed, not another farmer but a slave, and had been outlawed. Justice was seldom so even-handed in slave-owning cultures. Yet justice is a universal of all cultures. It is a tightrope that man walks, between his desire to fulfil his wishes, and his acknowledgement of social responsibility. No animal is faced with this dilemma: an animal is either social or solitary. Man alone aspires to be both in one, a social solitary. And to me that is a unique biological feature. That is the kind of problem that engages me in my work on human specificity, and that I want to discuss.

  It is something of a shock to think that justice is part of the biological equipment of man. And yet it is exactly that thought which took me out of physics into biology, and that has taught me since that a man’s life, a man’s home, is a proper place in which to study his biological uniqueness.

  It is natural that by tradition biology is thought of in a different way: that the likeness between man and the animals is what dominates it. Back before the year AD 200 the great classic author of antiquity in medicine, Claudius Galen, studied, for example, the forearm in man. How did he study it? By dissecting the forearm in a Barbary ape. That is how you have to begin, necessarily using the evidence of the animals, long before the theory of evolution comes to justify the analogy. And to this day the wonderful work on animal behaviour by Konrad Lorenz naturally makes us seek for likeness between the duck and the tiger and man; or B. F. Skinner’s psychological work on pigeons and rats. They tell us something about man. But they cannot tell us everything. There must be something unique about man because otherwise, evidently, the ducks would be lecturing about Konrad Lorenz, and the rats would be writing papers about B. F. Skinner.

  Let us not beat about the bush. The horse and the rider have many anatomical features in common. But it is the human creature that rides the horse, and not the other way about. And the rider is a very good example, because man was not created to ride the horse. There is no wiring inside the brain that makes us horse riders. Riding a horse is a comparatively recent invention, less than five thousand years old. And yet it has had an immense influence, for instance on our social structure.

  The plasticity of human behaviour makes that possible. That is what characterises us; in our social institutions, of course, but for me, naturally, above all in books, because they are the permanent product of the total interests of the human mind. They come to me like the memory of my parents: Isaac Newton, the great man dominating the Royal Society at the beginning of the eighteenth century, and William Blake, writing the Songs of Innocence late in the eighteenth century. They are two aspects of the one mind, and both are what behavioural biologists call species-specific.

  The brain and the baby is exactly where the plasticity of human behaviour begins.

  Leonardo da Vinci’s anatomical notes on the human foetus.

  How can I put this most simply? I wrote a book recently called The Identity of Man. I never saw the cover of the English edition until the book reached me in print. And yet the artist had understood exactly what was in my mind, by putting on the cover a drawing of the brain and the Mona Lisa, one on top of the other. In his action he demonstrated what the book said. Man is unique not because he does science, and he is unique not because he does art, but because science and art equally are expressions of his marvellous plasticity of mind. And the Mona Lisa is a very good example, because after all what did Leonardo do for much of his life? He drew anatomical pictures, such as the baby in the womb in the Royal Collection at Windsor. And the brain and the baby is exactly where the plasticity of human behaviour begins.

  I have an object which I treasure: a cast of the skull of a child that is two million years old, the Taung baby. Of course, it is not strictly a human child. And yet if she – I always think of her as a girl – if she had lived long enough, she might have been my ancestor. What distinguishes her little brain from mine? In a simple sense, the size. That brain, if she had grown up, would have weighed perhaps a little over a pound. And my brain, the average brain today, weighs three pounds.

  I am not going to talk about the neural structures, about one-way conduction in nervous tissues, or even about the old brain and the new, because that apparatus is what we share with many animals. I am going to talk about the brain as it is specific to the human creature.

  The first question we ask is, is the human brain a better computer – a more complex computer? Of course, artists in particular tend to think of the brain as a computer. So in his Portrait of Dr Bronowski Terry Durham has symbols of the spectrum and the computer, because that is how an artist imagines a scientist’s brain. But of course that cannot be right. If the brain were a computer, then it would be carrying out a pre-wired set of actions in an inflexible sequence.

  Man is unique not because he does science, and not because he does art, but because science and art equally are expressions of his marvellous plasticity of mind.

  The author at home, with an endocast of the Taung child’s skull. A copy of his book The Identity of Man is on the table. La Jolla, California, 1973.

  By way of example, think of a very beautiful piece of animal behaviour described in my friend Dan Lehrman’s work on the mating of the ring-dove. If the male coos in the right way, if he bows in the right way, then the female explodes in excitement, all her hormones squirt, and she goes through a sequence as part of which she builds a perfect nest. Her actions are exact in detail and order, yet they are untaught, and therefore invariable; the ring-dove never changes them. Nobody ever gave her any set of bricks to learn to build a nest. But you could not get a human being to build anything unless the child had put together a set of bricks. That is the beginning of the Parthenon and the Taj Mahal, of the dome at Sultaniyeh and the Watts Towers, of Machu Picchu and the Pentagon.

  We are not a computer that follows routines laid down at birth. If we are any kind of machine, then we are a learning machine, and we do our important learning in specific areas of the brain. Thus you see that the brain has not just blown up to two or three times its size during its evolution. It has grown in quite special areas: where it controls the hand, for instance, where speech is controlled, where foresight and planning are controlled. I shall ask you to look at them one by one.

  Consider the hand first. The recent evolution of man certainly begins with the advancing development of the hand, and the selection for a brain which is particularly adept at manipulati
ng the hand. We feel the pleasure of that in our actions, so that for the artist the hand remains a major symbol: the hand of Buddha, for instance, giving man the gift of humanity in a gesture of calm, the gift of fearlessness. But also for the scientist the hand has a special gesture: we can oppose the thumb to the fingers. Well, the apes can do that. But we can oppose the thumb precisely to the forefinger, and that is a special human gesture. And it can be done because there is an area in the brain so large that I can best describe its size to you in the following way: we spend more grey matter in the brain manipulating the thumb than in the total control of the chest and the abdomen.

  Only man can oppose the thumb precisely to the forefinger.

  Self-portrait, Albrecht Dürer.

  I remember as a young father tiptoeing to the cradle of my first daughter when she was four or five days old, and thinking, ‘These marvellous fingers, every joint so perfect, down to the finger nails. I could not have designed that detail in a million years’. But of course it is exactly a million years that it took me, a million years that it took mankind, for the hand to drive the brain and for the brain to feed back and drive the hand to reach its present stage of evolution. And that takes place in a quite specific place in the brain. The whole of the hand is essentially monitored by a part of the brain that can be marked out, near the top of the head.