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|This was perhaps my father's greatest scientific talk, the perfect balance of genuinely exploratory scientific thought and a popular lecturing style that had earned him a place in Time magazine's cover story on the twenty greatest teachers in America. I only wish I had could include the slides he used to show, which ranged from scientific charts to cartoons from the New Yorker.|
|The Origin of Death
© 1970 George Wald
When one has wondered over the years about the origin of life, as I have done, one comes inevitably to ask oneself, just what kind of thing is one trying to bring forth? Need those first primitive organisms on the earth, for example, have had such complex apparatuses of reproduction as all organisms possess today? And then one comes to the curious question: Need those first organisms have died? Because if they didnt need to die, they neednt at least be in such a hurry to reproduce. And this brings one to this question of the origin of death.
For not all living creatures die. An amoeba, for example, need never die; it need not even, like certain generals, fade away. It just divides and becomes two new amoebas.
In fact, death seems to have been a rather late invention in evolution. One can go a long way in evolution before encountering an authentic corpse. This is the journey that I would like to make with you. What I should like to do, of course, is to begin with the first living organism on this planet and then pursue evolution onward, asking the question: When did the first organism appear that cultivated the habit of dying? But that is just what I cant do. As in so many other evolution stories, I have to be content with a poorer thing, and that is to discuss this transition in terms of contemporary organisms, of organisms alive today.
Let us begin with a familiar, single-celled organism, the amoeba. Its nucleus divides by pinching into two equal halves, then the whole amoeba divides. Thus we have two organisms where we started with one. This is the usual way singlecelled organisms, plant and animal, tend to reproduce, just by simple division: so called fission.
Occasionally they do something a little different. Reproduction in the single-celled organism Paramecium is usually by fission, but sometimes it engages in what we call conjugation. Two organisms, each containing a large nucleus (macronucleus) and a small nucleus (micronucleus), come together side to side. Then the cuticle breaks down between them. The macronucleus is by and large the working nucleus. The micronucleus represents a store of genetic material. The next thing that happens is that the macronuclei disintegrate and the micronuclei divide, and something very interesting happens that makes one think a little of sexual reproduction: there is an exchange of micronuclei, of genetic material. Then the Paramecia separate, the micronuclei divide repeatedly, then the Paramecium divides repeatedly. One ends up with eight brand new Paramecia just like the pair with which we started.
In the generation just before mine there was a very distinguished zoologist named Loren Woodruff. He began to publish a series of papers, the first of which was entitled something like Two hundred generations of Paramecium aurelia without conjugation. We waited a few years and another paper came out with a title something like Five hundred generations of Paramecium aurelia without conjugation. Finally this series reached its culmination in a paper entitled Eleven thousand generations of Paramecium aurelia without conjugation. So Professor Woodruff lived a happy and useful life, and convinced all of us that Paramecium can live indefinitely without conjugation.
But in the course of these researches Woodruff made another discovery. You see, every morning hed come into his laboratory and find two Paramecia where hed left one the night before; so hed carefully separate them. One Paramecium, he thought, cant conjugate. But thats where he was fooled, because watching these Paramecia so intently he discovered still a third wrinkle in this process which he called endomixis. Its a sort of do-it-yourself conjugation. In endomixis the macronucleus in a Paramecium disintegrates, the micronucleus divides, one of those new micronuclei grows up to a new macronucleus and you have a brand new Paramecium.
Then there is a fourth process, which is very interesting. It is called syngamy. In syngamy two cells fuse to make one; and that, of course, is essentially what happens in sexual reproduction. So, here we have, just among these single-celled organisms, four different ways of going about reproduction but no necessary dying, no corpses.
Let us now take an enormous jump in evolution, to a lower invertebrate, the sea anemone. Weve gotten from a single-celled organism to a very many-celled organism. It is not very highly specialized, having only two cell layers where we have three. It has only an ectoderm and endoderm; we also have a mesoderm. It is radially symmetrical, which we think rather primitive compared with our bilateral symmetry, our two-sidedness. Yet this is a big jump from single-celled organisms. The sea anemone splits down the middle, reproducing by simple division, simple fission.
That kind of process is rather a habit at this level of organisms. A close relative, the Hydra, reproduces by budding. A bud grows, finally separating from the parent Hydra, and that starts some new Hydras.
Next we take another enormous jump in the hierarchy of organisms. We have a flatworm named Planaria. Such an animal is bilaterally symmetrical, as we are. It has three germ layers, as we do. It has its nervous system concentrated at the head end. It has rather good sense organs. It represents a big jump from Hydras and sea anemones; yet we see this organism reproducing by simple division. It pinches in at the waist and separates into two parts, each of which then regenerates whatever it lacksthe tail end cultivates a new head, the head end a new tail, resulting in two brand new flatworms where we started with one. A number of flatworms go through this kind of process. One called Stenotomus breaks into five or six fragments; then each fragment regenerates whatever it lacks.
I thought that with Planaria perhaps I had finally found an organism that could just fade away. A Dutch worker named Stoppenbrink many years ago began to starve Planaria. As he starved them they began to consume their own substance, following a definite program First they absorbed whatever sex products there were. Then they went to work on their digestive systems, which werent doing them much good anyhow. Then they started absorbing their muscles. In this way the flatworms got smaller and smaller. The only thing they didnt absorb was the central nervous system; so that as they got smaller and smaller, they came to look highly intellectualall brain and no worm. By this time I was panting, waiting to read about the moment when Stoppenbrink went into his laboratory, and behold! there were no more flatworms. But to my great disappointment, instead he started feeding them again, and they rapidly regenerated everything they had lost. Then, however, Stoppenbrink made a discovery; for what you get back in this way is a brand new flatworm. He found that if you periodically starve flatworms and feed them again, they go on living forever. I am sure that theres a moral in this somewhere.
The furthest I have been able to pursue this way of reproducing by simple division was into the real worms, close relatives of our common earthworm. There is one with a beautiful name, Enchytraeus fragmentosus, that has no sex organs at all. It divides entirely by breaking up into many pieces; then each of the pieces regenerates anything it lacks, and one has that many new worms.
But long before this, organisms have taken up a quite different way of reproducing, the sexual mode of reproduction; and it is in the most intimate associations with the sexual mode of reproduction that death comes upon the scene.
I can describe the situation best in the terms in which a distinguished zoologist of the nineteenth century, August Weismann, described them. Any organism that reproduces sexually begins its life as a single cell, a fertilized egg. The single cell divides repeatedly, eventually to become an adult organism. In the course of its many divisions, there is a line of cells that constitutes what Weismann called the germ line, which will eventually produce the mature sex products, eggs or sperm. In the course of those repeated divisions there is also produced a body, what Weismann spoke of as the soma. At sexual maturity this organism mingles its eggs or sperm with the eggs or sperm of a similar adult of the opposite sex; so one has a new fertilized egg, which in exactly the same way, by repeated divisions, produces both sex products and a new body which at maturity, again, mingles its sex products with those of another adult organism. Thus one has the next fertilized egg that by repeated divisions produces the next adult generation. And so on and on, from generation to generation.
On this simple basis August Weismann stated two fundamental principles. The first he spoke of as the isolation of the germ plasm. I think the way we would say it now is that genetic information passes always in one direction, always from germ plasm to soma; never in the opposite direction, from soma to germ plasm. Thats why there can be no inheritance of acquired characters. An acquired character is a change in the body, in the soma, and there is no way that this can be transmitted into the germ plasm, and hence inherited.
The other principle stated by Weismann he spoke of as the potential immortality of the germ plasm. You see, germ plasm goes on making more germ plasm as well as bodies. The line of germ plasm goes on without a break. And now we see what death is. Death is the casting aside of the body, of the soma, after it has done its work. That work is to carry the germ plasm, to feed it, to protect it, to warm it in a warmblooded organism, and finally to mingle it with the germ plasm of the opposite sex. With that, it has completed its function and can be discarded.
The thought that life is through with the body once sexual reproduction has been accomplished is repugnant to us as men. I shall have more to say of this later. Yet now I should like to say that, repugnant or not, this would be no surprise to a salmon. For in salmon, and eels, and many such creatures, it is all too clear that reproduction is the last act of life, and that the preparation to reproduce is simultaneously the preparation to die.
I should like to speak of one such animal, the lamprey. So-called sea lampreys are probably not familiar to some of you, but they are quite familiar to us along the coasts. Thats because of their life cycle. Lampreys have the general shape of eels, and are frequently called lamprey eels, but they are not eels nor are they even fish. They belong to a small group of the most primitive of living vertebrates, the jawless vertebrates or Agnatha. They have no jaws, just a sucker disc with a kind of coarse rasp on it. When they get a chance, they attach themselves to a fish by that sucker disc and just begin to rasp their way in. If it is a big enough fish and the fish holds out, the lamprey may end up completely inside of it. A lot of this has been going on in the Great Lakes, as many of you perhaps know, because the digging of a canal persuaded the lampreys, instead of going down to the sea as they had done heretofore, to go into the Great Lakes. For a while they had almost cleaned out the whole Great Lakes fishery.
The lamprey begins its life as a wormlike larva, with no eyes, buried in the mud or sand of a swift-flowing stream. It stays that way for perhaps two or three years. Then it goes through a first metamorphosis, in the course of which, among other things, it acquires eyes. With that it gets itself out from the mud and sand and starts migrating downstream, usually to the sea, where it grows up. At sexual maturity it goes through a second metamorphosis. There are a lot of changes, but one of the most striking is a complete disintegration of the digestive system. That animal will never eat again; it loses its entire apparatus for consuming food. Then it starts its journey upstream.
I got my lampreys in the Exeter River in New Hampshire. A hydroelectric development and a dam had been built across the river. The good people of Exeter had been throwing bottles and tin cans into the water below the dam for generations. There wasnt much water and it was pretty perilous, but there were those lampreys still coming up with the first warm days of spring. How they got themselves over the dam I do not know. I suspect they took to the shore, because one of these animals on a sexual migration has only one thing on its mind, and that is to get up into its spawning ground. There it makes a nest of round stones, the females lay their eggs in the nest, the males shed their sperm over the eggs, and with that theyre through. All the adult lampreys then die; there is nothing more left in life for them.
The freshwater eels have a life cycle thats just the reverse of that of the lamprey. It was discovered by a great Danish oceanographer, Johannes Schmidt, many years ago. It had been a great mystery until then, where the eels reproduce. The eels of the shores of the Atlantic are of two different species, European and American. All of them come together to spawn in overlapping areas of the Sargasso Sea, the region of the South Atlantic that includes Bermuda. It represents the deepest and saltiest part of the Atlantic Ocean. Having made that enormous journey, the adult eels spawn and die. Then the baby eels make their way back alone. We have no idea how they get back. It takes the American eels about 15 months to come back to our shores, metamorphose, and head upstream. It takes the European eels three years to get back home. There is no record as yet of any baby eel ever getting mixed up and going to the wrong place. When they get into fresh water, they live there for five to fifteen years, growing up. Then at sexual maturity they go through a second metamorphosis. There are a lot of changes: the eyes blow up to twice their former diameter, four times their former area. This animal is getting ready for a deep sea journey. Among other things, there is a complete collapse of the digestive system. Before beginning this enormous journey that will take the adults to the Sargasso Sea, those animals have had their last meal. They will never eat again.
A more familiar organism, the Pacific Coast salmon, has a life cycle like the lamprey's. It begins its life invariably in fresh water, grows up a little way, and then goes through a first metamorphosis, losing its spots and nice colors. Up to that point it had looked like a freshwater trout. Now it turns silvery, and goes to sea, where it grows up. At sexual maturity it metamorphoses again, the flesh becomes pink, its color changes. There are all kinds of changes, including again a complete collapse of the digestive system. These salmon, before beginning their migration upstream, are through with eating. They will never eat again. In fact, in many of the males, the jaws become deformed, so that they can no longer meet. This animal isnt interested in jaws anymore. In this way it begins its journey upstream. It is no fun. The bears are waiting for it, the Indians are waiting for it, the sportsmen are waiting for it, the canning industry is waiting for it. Those handsome travel folders show you the salmon leaping over falls. That is no fun either. They beat themselves to pieces doing that kind of thing. The salmon that reach the spawning grounds are already dying organisms. Theyre all torn up, with great wounds in their sides which bacteria have invaded. They are capable only of that last act of reproduction, and thats the end of them.
So it is all too clear in these organisms and many others that reproduction is the last act of life, and that the preparation to reproduce is simultaneously the preparation to die.
Sometimes death doesnt wait for the act of reproduction to be accomplished, but takes part in the act. There was a golden period of insect observation in the second half of the nineteenth century. We had Henri Fabre in France, August Forel in Switzerland, Sir John Lubbock in England, and Maurice Maeterlinck in Belgium who wrote about the life of the bee. While these biologists were watching insects so intently, great interest was aroused in the habits of the praying mantis. The praying mantis is a voracious animal. It will tackle something much bigger and stronger than itself, and usually wins. It was observed that when a pair of mantises is copulating, the female, which is a much bigger animal, will occasionally just swing her head around on its beautiful, stalklike neck and quietly begin to devour the male. He goes right on copulating, while she goes right on eating him. As long as the males last two abdominal segments are left, they go on copulating.
Some years ago I visited my good friend, Professor Kenneth Roeder at Tufts College. When I got there and asked for him, a student told me, Youll find Professor Roeder down that hall, last door on the right. So I went down, and there I found Ken Roeder sitting on a soap box watching praying mantises. He offered me another soap box and we sat there, watching together. He told me he had been doing this for years. He told me that, if youve got a female mantis alone in a cage, and put in a male, that male instantly freezes. The praying mantis, like a lot of other animals, such as frogs, dont seem to be able to see anything unless it moves. The male knows that, and hes watching the female very carefully. If she looks away for a moment, he takes a hasty few steps forward. Then he freezes again as soon as she looks back. Roeder said that this can go on for hours. If the male is fortunate, he reaches the female, mounts her, and goes through a normal copulation. Incidentally, Roeder told me that once an American male mantis starts copulating, the female never bothers him. Its our better standard of living. But often the female sees him first. With that, she grabs him, always by the head. Then she begins to eat him, always starting with his head. As soon as she has eaten off the head, the male goes into a very interesting pattern of behavior. He plants his front feet squarely and begins to circle around them, meanwhile going through violent copulatory motions. In this way, Roeder told me, such a headless male will frequently succeed in mounting the female and going through a normal copulation.
Ken Roeder is a distinguished neurophysiologist. He was anxious to know that was going on here, and eventually worked that out. There is a copulatory center in the last abdominal segment. But there is an inhibitory center in the subesophageal ganglion that holds the copulatory center in check. Its all very simple. You dont need a female to remove this inhibition. Roeder used a razor blade to cut off the head. Once a male loses his head, the copulatory center is released. So here is an instance in which killing the male helps to stimulate the reproductive act.
At Harvard we have an arrangement whereby undergraduates
who feel like and seem to be up to it, can start doing research in their
last couple of years. Some years ago a Radcliffe girl came to me to do
a senior research. I had just found a few dozen activity cages in the
animal room that werent being used, so I put two and two together,
and dreamed up a beautiful problem for that Radcliffe girl.
Life brought me rather early to vitamin Abut sometimes I grow a little restless and want to expand my horizons. So I thought, why not do something with Vitamin B? Just then that Radcliffe girl turned up.
I wasnt going to be reckless, I was going to start with Vitamin B1, thiamine. Thiamine is an important vitamin. Pharmaceutical houses all over the world have to be ready to estimate how much thiamine is in various foods. I dont know exactly how they go about it now, but in those days they kept big animal rooms full of rats. They would put a group of rats on a thiamine-deficient diet and let them develop rat polyneuritis, which is the rat form of whats called beriberi in human beings. Every morning a bunch of girls would come in, put on white coats, and go down the line of cages. They would take each rat and would give it the twirl test: They would pick up the rat by the tail, hold it over a table, twirl it and drop it. If you do that with a normal rat, he just gives you a dirty look and runs off; but if you do this with a rat that is beginning to be thiamine deficientpolyneuritiche has trouble getting his balance back, righting himself again, and that is the first sign of polyneuritis. Once you saw that, you could begin to feed these animals various foods and estimate how much thiamine was in them.
It seemed to me that we could do better than that. I thought that if we took away a rats thiamine, as it went into polyneuritis, it would of course stop running. That way we would have an early and quantitative sign of thiamine deficiency.
Well, thats where I was fooled. I havent heard it cited lately, but we used frequently to quote to one another what we called the Harvard Law of Animal Behavior. It says, Under the most rigidly controlled conditions, an animal does as it damn pleases. Thats exactly what happened this time. As we took the thiamine away from these rats, instead of stopping running, they just began to run their heads off. They ran day and night, sometimes as much as forty times their normal running. Meanwhile they were losing weight. Occasionally, though we tried to keep that from happening, wed come in the morning and find a rat dead in the running wheel. The counter would show that somehow it had struggled out a last mile in the previous night.
Well, that seemed extraordinary, and got us pretty excited. So I wondered, how about Vitamin B2, riboflavine. If you take riboflavin out of the synthetic diet, again the rat begins to run its head off. If you take away its water, the rat runs; if you take its food away, the rat responds by running. If you take away both its food and water, it runsthough you cant keep that up very long and still have a rat. What was going on? All of us are told, usually by someone who is just about to pick our pockets, that self-preservation is the first law of nature. Here were animals going directly counter to that rule. If the animal had just gone to sleep in a corner of its cage, heaven knows what might have happened. The Radcliffe girl might have got married; or we might have just got bored with the experiment. Those animals were just killing themselves.
That made me plunge into the literature; and then I learned that the universal sign of hunger, of genuine deprivation of food, in all animals from protozoa (those single-celled animals) to man, is increased activity. You might think: Those animals are looking for food. But theyre not; they are just driven to run. In the heyday of this kind of experiment, people tried all kinds of things. They took the stomachs out of animals. Your sensation of hunger is just the response to a kind of deep, slow contraction of the upper part of the stomach, called hunger contractions. Those animals behaved just like the others. One could take the cerebral cortex out of an animal. Such an animal was incapable of recognizing food; yet when it was hungry, it ran. It couldnt feed itself, but if you poked food into its mouth, it swallowed and so was fed. Then it would go to sleep, then it would wake up and run until it was fed again, after which it would go to sleep. Our rats werent looking for food. Such a hungry animal is not asked to run; it is told to run. These are orders, not requests. They are forced to run.
I think that what we have here is a kind of small scale model for a well known phenomenon, a hunger migration. The most famous of the hunger migrations, one that all of you have heard about, is the migration of the lemmings. The lemmings are rodents that live high up on the mountainsides in Norway. There is a mythology about this that says that in a lemming year the lemmings come down from the mountains in hundreds of thousands if not millions, and go rampaging through the cities, driving people indoors, stopping all of the traffic. Theyre on their way to the ocean. When they reach the ocean they plunge in, and in an act of mass suicide, swim off and are never seen again.
Well, it isnt quite that way. Lemmings are rather cute-looking but unsociable organisms. A lemming ordinarily will tolerate no more than one other lemming of the opposite sex. When a pair of these, traveling together, meets another such pair they sort of growl at each other and each pair goes its way. Norway is of such a shape that for animals wandering off the mountainsides, many of them reach the sea; and it is true that many of them then go into the water and swim off never to be seen again. But they were not searching out the sea. The lemmings on the other side of the same mountains in the same way reach the plains of Lapland, and go wandering off across those plains to die.
That is the point. Its pretty well realized by now that that kind of migration is impelled by hunger. It happens in a population that has outgrown its resources. Animals are hungry, and a hungry animal has to run. Its driven to run. It isnt looking for anything. It just has to keep moving. You might think that the point of such a hunger migration is colonization. You might think such a horde of hungry animals leaving their home territory are looking for a better place to live. But there is no such place. If there were a better place to live, they would have found it long before. There is no place for them. The point of a hunger migration is not to colonize, but to remove the migrating animals. The end of every hunger migration is the death of the migrating animals.
Some of you may wonder why I include men in this pattern. You may say, Well, I dont run around when Im hungry. Thats because you are said to be civilized. That gets in the way of all kinds of sensible patterns. If you want to see men behaving this way you have to catch them in the raw.
One way to do that is to observe an infant. Every young couple knows what its like with a new infant. It is just the classic animal pattern. A new infant wakes up, starts to writhe, and yells its head off and grows red in the face, and is full of activity. Every muscle is working. Then you start feeding it. Usually it falls asleep in the middle of the feeding. You have to keep patting its bottom just to get it to finish feeding. Then it sleeps awhile, then it wakes up, writhes and yells and has to be fed again. Thats the way it starts its life; until that young couple civilizes it into eight hours on and eight hours off.
The other way to catch human beings in the raw is when theyre asleep. There was a golden period that I look back upon with great regret, in which the cheapest of experimental animals were medical students. Graduate students were even better. In the old days, if you offered a graduate student a thiamine-deficient diet, he gladly went on it, for that was the only way he could eat. Science is getting to be more and more difficult.
Some years ago, in the laboratory of Professor Curt Richter at Johns Hopkins, he offered a group of medical students the extraordinary privilege of a bed in the laboratory. There were a few formalities: Before the medical student got into bed, he swallowed a balloon attached to a rubber tube that came out of his mouth and went to a mercury manometer which recorded through the night the motions of his stomach. Then, that cot was not an ordinary cot. It was very carefully balanced, so that if that medical student moved in his sleep, that was all recorded on a revolving drum. Well, in just the classical pattern, in a four-hour cycle right through the night, the medical students stomach would begin to go through the slow, deep hunger contractions. As they reached their peak, the medical student began to toss around in his bed. Then the hunger contractions would die down, and the medical student go back to sleeping quietly, until four hours later he went through the same cycle.
As for a human hunger migration, there is a beautiful passage in Herodotuss Histories which has it in classic form. Herodotus is describing the origin of the Greek games, what we now call the Olympic Games. He says that in the reign of Atys, son of Manes, there was a great famine in Lydia. It persisted year after year. After seven years, the king ruled that all the people must spend every second day in athletic games and on alternate days they would eat. After seven years of this, the famine still persisting, the king divided the population in half, half to migrate, the other half to remain. That brings us at last to man.
Its rather odd that we regard mass suicide on the part of lemmings as an aberration, as a kind of psychopathic behavior; whereas our way of dealing with the same problem is considered normal. Where the lemmings go off to die, we go off to kill; for its equally true for the human migrants that there is no other place for them. Every place is occupied. Have you ever heard of people migrating to a place fit to live where there were no people before? There are always people. If the migration ends in a colonization, thats through conquest. It is strange that we look on that as normal and proper, whereas the lemmings seem to be doing something aberrant; for biologically there is much to be said for the way lemmings go about it.
On the one hand, the way the lemmings do it, there is a minimum of dying. As soon as enough lemmings have left the center of population, there is enough food for those that remain, so the migration automatically stops. Second, there is no destruction. The lemmings home territory is just as good as it ever was. Third, and whenever I say this I shudder, since I cant jump over my shadow, but a selection process is at work. Its the hungriest lemmings that go off to die; the ones that are doing better stay home. Whereas in the human way of doing things, we pick the flower of our manhood to go off to kill and die. The lemmings are exercising better biology.
I would like to return now to the repugnant thought that life is through with animals once reproduction has been accomplished. That is not true for man. To relieve this situation of the usual Pollyanna practice in which, whenever one describes something uncomfortable, one explains that its not true for us, let me talk about bees. All of you know that the heart of what goes on in a bee colony is what is done by the workers. The workers build the hive; they take care of the young, they forage for food, they clean the hive, they run the airconditioning system, everything. They do everything; and yet they are sexless females that have no part in reproduction. The only sexual female in the hive is the queen. And thats the point. If animals such as bees have a society, then individuals can serve the purposes of that society, and whether they reproduce or not becomes irrelevant. We human beings have a society, and thats the way it is with us. Beethoven, so far as we know, had no children; Bach had a lot of them. Who cares? That isnt the reason we go to Beethoven and Bach. Rembrandt had one boy; Isaac Newton had no children. Who cares? Its completely irrelevant. For organisms that have a society, this becomes a complete irrelevance.
Since we have had a history, men have pursued an ideal of immortality. I am speaking now, not of immortality of the soulI dont really know what that meansbut of fleshly immortality, of immortality of the body. Over the centuries and the millenia, one has searched for the Philosophers Stone, the Fountain of Youth, all of those efforts somehow to abolish death.
That age-old quest for fleshly immortality is a hoax. Peter Medawar has a book called The Uniqueness of the Individual, and in its first two chapters you will find this all laid out. Medawar points out that if we already possessed every feature of bodily immortality that one could want, it would change our present state very little. As Medawar says, wed all like to grow up, so lets be able to reach something like 20 years of age, and then never grow any older. Then he adds: let there be no natural death. Medawar says that at that point he got worried, and went about asking all his physician friends in London whether they had ever seen a person die of old age. All of us go about with the familiar concept of death of old age, of natural death. It turned out that none of the doctors he knew had ever observed it. I think if a physician wrote on a death certificate that old age was the cause of death, hed be thrown out of the union. There is always some final event, some failure of an organ, some last attack of pneumonia, that finishes off a life. No one dies of old age. Nevertheless, said Medawar, no natural death; and then he said, Lets give them a bonus of perpetual fertility. No matter how long this person lived, hed be as fertile as at age twenty. Thats about all one could ask for, isnt it?
Medawar points out that with all these conditions fulfilled, our lives would have changed very little, that is if one went on living a human lives, the way we are used to living them. Every time you cross a street you risk your life; there are cars, trucks, trains, and planes; there are viruses and bacteria. They need to live, too, and theyd be working away still. There are electric circuits, and all the other hazards. All the insurance actuaries would have to do is hang around for awhile, and pretty soon theyd send you the new rates. Matters would have changed so little, says Medawar, that possibly our patterns of old age and death are essentially following the inevitable patterns, were we, in fact, immortal.
The strange thing about all this is that we already have immortality, but in the wrong place. We have it in the germ plasm; we want it in the soma, in the body. We have fallen in love with the body. Thats that thing that looks back at us from the mirror. Thats the repository of that lovely identity that you keep chasing all your life. And as for that potentially immortal germ plasm, where that is one hundred years, one thousand years, ten thousand years hence, hardly interests us.
I used to think that way, too, but I dont any longer. You see, every creature alive on the earth today represents an unbroken line of life that stretches back to the first primitive organism to appear on this planet; and that is about three billion years. That really is immortality. For if that line of life had ever broken, how could we be here? All that time, our germ plasm has been living the life of those singlecelled creatures, the protozoa, reproducing by simple division, and occasionally going through the process of syngamy -- the fusion of two cells to form onein the act of sexual reproduction. All that time, that germ plasm has been making bodies and casting them off in the act of dying. If the germ plasm wants to swim in the ocean, it makes itself a fish; if the germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to Harvard, it makes itself a man. The strangest thing of all is that the germ plasm that we carry around within us has done all those things. There was a time, hundreds of millions of years ago, when it was making fish. Then at a later time it was making amphibia, things like salamanders; and then at a still later time it was making reptiles. Then it made mammals, and now its making men. If we only have the restraint and good sense to leave it alone, heaven knows what it will make in ages to come.
I, too, used to think that we had our immortality in the wrong place, but I dont think so any longer. I think its in the right place. I think that is the only kind of immortality worth having -- and we have it.