Aging and Everyman

N. J. BERRILL

THROUGHOUT human history until recent times, most human beings have died in infancy, and no more than a very small percentage survived to ripe old age, carrying with them the wisdom of their experience or the foolishness of their years. Now all is changing, thanks to antibodies, antibiotics, the surgeon’s knife, and the welfare state. Demographers say that already one quarter of all human beings who have ever reached the age of sixtyfive are alive today. Yet not so long ago, Montaigne wrote that he rarely saw a man older than fifty; malnutrition, disease, and sudden death were the problems, not the weakening and failure of the body machinery as the result of staying alive.

Aging has many aspects. In some sense it begins before birth and is a quality of those processes we call development and growth. And from the cradle to the grave, it seems to be a continual fight against a progressive desiccation and the force of gravity, consequences perhaps of being fish out of water. If it were not so comic, it would be serious, but here we are, with much more time than any other mammal, reaching for every additional year though our teeth wear out, our hair falls out, our knees give out, and vision and hearing need artificial aid. There is in fact a society that proposes a long postponement of the inevitable end through quick deep-freezing of old but living human beings for subsequent resurrection by thawing in some distant future time.

Whether the problem is to understand the process of aging, to do something about age, or to extend the natural limits of human life, the trouble is that we know too little about what is really going on. More than three centuries ago Francis Bacon examined the relationship between longevity, growth rate, and gestation period for a number of animals and concluded that there were too few facts on which to build a general theory of aging. Since his time, mainly during the last fifty years, not only have facts mounted up but theories galore have been raised, only to be struck down or to wither away. And no amount of information will serve if key facts remain missing, or if the factual mountain is so great that we lack the ability to cull the trash. The cancer problem is comparable with this one, and possibly for much the same reason. In both cases the answer lies in the nature and mutual relationship of living cells, now the subject of the most concerted attack in the history of biological science.

One theory of aging, although it is more of a description than an explanation, has its roots in Aristotle, who saw life as the maintenance of a kind of internal heat or energy which had to be provided with fuel and could become exhausted, the heat of old age being a small feeble flame which could be extinguished by the slightest disturbance. This is fundamentally the same concept as that of the German embryologist C. S. Minot, who early in the present century described aging as development looked at from the other end; he saw senescence as a natural process inherent in the cell, resulting from the gradual loss of the energy stimulus originally present in the fertilized egg until none is left and the organism dies of old age. Although impugned by some biologists, this view of aging certainly calls attention to an overall waning process evident in all aging creatures and experienced by every human being who lives beyond the first flush of maturity. Nothing so disconcerts a man as finding himself unable to keep up with his sons, whether climbing a hill or learning the new mathematics. The heart is no longer what it used to be, and even the mind gets creaky. The heart, in fact, is a measure of sorts.

With each heartheat we are a little bit older, and what may seem paradoxical is true: the younger we are, the faster we grow old. At birth the heart beats about 140 times a minute. Even then it is already slowing down, and it continues to do so until the age of twenty-five, when the rate levels off at about 70 beats a minute when the body is at rest. Yet the rate of beat is by no means the whole story, for how fast the blood flows is the important thing, so that how much the heart pumps with each beat also comes into the picture. So we find that the actual amount of blood pumped by the heart in a minute in a ninety-year-old person is only half as much as it was at the age of twenty. Though the rate of heartheat remains steady, the flow of blood grows slower with each passing year, while the amount of oxygen the blood picks up in the lungs diminishes all the time.

Continuing this sad tale, the excretory capacity of the kidneys declines by about 55 percent between the ages of thirty-five and eighty. Muscle fibers and nerve fibers diminish in number, and even the brain comes to weigh less as age progresses. Much of the true loss of tissue weight is loss of water, a progressive desiccation natural to any fish out of water. The young, fresh from their aquatic sojourn in the womb, are comparatively juicy in a truly vital way, with that dewy look that is part of the charm. Baby fat, at first so appealing and later curvaceous, slowly slips in middle age, like a glacier, to come to rest where gravity calls a halt.

Yet quite apart from change in shape based on fat, the human form is forever altering, and here growth and age are one. We are born with a relatively enormous head, large eyes, small body, and short limbs. The proportions signal babyhood in a universal way, so definitely in fact that a similar disproportion between head and body when seen in other creatures has the same appeal to the maternal spirit of woman. Puppies and chicks are cute, and who could resist Bambi as portrayed by Walt Disney? Yet later, in man and beast alike, the body catches up, and the limbs stretch out until eventually seemingly small heads top tall and bulky bodies. This phenomenon, called relative growth, is general among backboned animals and many others but is not by any means well understood. It continues in man to the end of his days, particularly in males. The small button nose of the baby slowly transforms into a proboscis that trumpets when blown. There is at least some validity in the point of view that aging is fundamentally an extension and the inevitable outcome of development and growth. How else could it be unless the alternative were immortality itself?

THE inevitability of aging as a natural process has been challenged, although whether as the result of a cold objectivity or of unconscious desire for personal immortality on the part of the biologists concerned is a moot question. In fairness, at least, and for all our sakes, we should look to see who in the living kingdom ages and who does not. It is evident at once that all backboned creatures have a limited life-span, whether or not they age just as we do. Among warm-blooded creatures, the mammals and birds, man lives longer than any other, although elephants and parrots run him close. Apes, large cats, bears, horses with luck live half as long. Most medium-size mammals live shorter lives, while the smallest, such as mice, rarely more than two or three years. The general rule seems to be, the smaller the body, the shorter the life. This makes sense in a way because the surface area of any small body is relatively large and most of the heat produced by a living body is lost to the surroundings as though by a too effective radiator. The smallest of mammals, the minute shrew, has to eat like the shrill fury he actually is in order to keep body and soul hot enough to stay together.

Big fellows such as men, elephants, and hippopotamuses have to be sweaty and naked all over just to keep cool. Perhaps we can say with some meaning that in such as these the fires of life are banked and consequently last much longer. The trouble is that while man proposes, in his efforts to put nature’s house in order, nature usually disposes and upsets his little schemes. This is one of the joys of being a biologist, to whom the journey far transcends the goal. For here the whale comes into his own. The largest of all creatures, the great blue whale grows to a length of one hundred feet yet lives for only about twenty years. Large size is no insurance.

Longevity by itself, however, is not the main issue. The human question is not so much how to add extra time to the dilapidated end of life as it is to add luster to our waning years. Does the whale, for instance, age in any way as we do, or does it get bigger and bigger while it lives, until there is simply too much of it? However this may be, the performance is spectacular. After one year in the womb, not so very much more than our own sojourn, the baby blue whale at birth measures about twenty-four feet, and at the end of three years, more or less, it has grown to about seventy-five feet long and is sexually mature. Growth by then has slowed down, although it continues for a good while after. How does growth itself fit into the picture?

Although life certainly comes to an end in large fish, tortoises, and certain invertebrates such as mussels and sea anemones, aging has not been recognized. Carp, pike, halibut, and sturgeon all live well past the half-century and grow to large size. The remarkable thing is that they can breed year after year, and apparently grow for as long as they live. And so with the giant tortoises, which may live for one hundred and fifty years if given the chance. The absence of apparent aging may of course mean merely that these cold-blooded creatures are naturally extremely long-lived and never reach old age because death by accident, malnutrition, or disease cuts life short for all. For man to attain the same condition, growing and breeding to the end of his present natural time, raises a specter of awesome propensity.

GROWTH suggests youth in some degree wherever we encounter it, a freshness and promise of more to come. Aging suggests not only cessation of growth but an insidious regression of sorts. Yet the one slides into the other, and there is no real plateau in between where a man may feel he is a man for all that. When we poke into the human organism in earnest, or into any other, to put our scientific finger on what underlies the transformation, we come to the forefront of contemporary biological scientific endeavor — the relation of cells to the organism they constitute.

It is often said that an amoeba is immortal, barring accidents, taking amoeba as an example of single-celled organisms generally. This is a fallacy, for when an amoeba divides, two amoebas take the place of one, and the individuality of the original creature is lost. And most such cells die, from various causes, of which aging is certainly high on the list. So with the cells of the body. The marvel is that a human being or any other creature consisting of many billion integrated cells can hold on to its total life and individuality so successfully. Some of the most vital cells in the body live individually only a very short time. Red blood cells, for instance, live but a few weeks and are continually replaced from a source within the bone marrow. The basal layer of cells of the skin continually proliferates and gives rise to the layers that constantly rub off. All the inner membranes of the body, such as the intestine and lungs, are forever being renewed in a similar way. Hair falls out of its follicles and is continually replaced. And so it goes. Nerve cells, of the brain and elsewhere, stand somewhat apart, for there is no replacement, and in fact, no additions from infancy until death, which puts a high premium on conservation, although a process of renewal undoubtedly goes on within the confines of each such cell. There is a great deal of truth in what Chief Justice Holmes once wrote, that “we must all be born again atom by atom from hour to hour, or perish all at once beyond repair.”

What can happen when cell renewal or replacement suddenly comes to an end is seen all too clearly in those unlucky persons who have been accidentally exposed to large doses of radiation in atomic institutions, and could happen to much of mankind and other forms of life if nuclear war should ever be unleashed. Within a matter of hours, the maintenance of the body comes to a halt, a pernicious anemia sets in, the delicate internal membranes begin to seep bloody fluid, and a miserable sort of dissolution in the midst of life puts an end to existence. Even a relatively mild exposure to neutron irradiation shortens the life of mice and rats, and one theory of aging, sponsored more by physicists than biologists, is that aging results from the weak but continual radiation which reaches the tissues and cells of the body as cosmic rays from outer space, mainly from the sun, and as natural radiation from radioactive elements in the earth’s crust itself. There is no doubt that from the time of our conception to the hour of death, rays from both these sources are taking their toll, and that there is no safe level of radiation. Cell death is as characteristic of the growing fetus within the womb as it is of middle age or later. What matters more, however, is how fast new cells can be made to repair the damage or make new tissue.

It is on this level of analysis that youth and age link hands. As long as new cells are born faster than old cells die, the body grows. When cell birth and cell death are in balance, body growth is no longer apparent, although the basic process of growth continues. When cell production lags behind cell destruction, things begin to happen and we feel our age. Taste cells, for example, and probably those of smell, live each but a week or so and are continually replaced, yet the rate of replacement eventually fails to keep up with the loss. Taste and smell begin to fade, and gourmets require increasingly greater stimulation to satisfy their jaded senses.

All this is one of the great mysteries of life, at least to the biologist. Does the body age because its cells are aging and becoming fewer, or are the cells, so to speak, at the mercy of the body, or organism, as a whole? This is much the same question as was posed by the U.S. Surgeon General a good while ago at the beginning of the contemporary attack on the nature of cancer: did cancer arise because the growth-controlling forces of the body were abnormally or locally weak and so failed to control some of its elements, or were cancer cells so changed from the normal that they were true mavericks unable to recognize the call of law and order? We now know that it is the cancer cell that has changed, not the system. Yet here is the point. Cancer cells behave like outlaws among the tissues of the body, multiply without restraint, and migrate as far as possible, whereas normal cells appear to know their proper place and behavior. But outside the body, when cultivated in a satisfactory medium, normal cells grow, multiply, and wander as actively as malignant cells. Within the body they have the potential to show their youth but are obviously under restraint. In lower vertebrates such as salamanders, cells normally inactive rally to the occasion when a limb or a tail has been lost, and proliferate to form a new one.

What the normal restraint and what the new instructions for growth may be are among the foremost and most elusive problems in the whole of biology. At the turn of the century, Hans Driesch, the great German pioneer in experimental developmental science, finally threw up his hands in despair and turned to metaphysical, almost mystical, concepts for explanation. And today, although the mass of raw information is virtually overwhelming, insight is still lacking. The comment is that embryos are smarter than embryologists. This of course is frustrating. On the other hand, the challenge of the problem and the fascination of the phenomena remain, possibly for many generations of young scientists to come, which perhaps is as it should be, for who are we, at this time and age, that we should expect to have all the fun?

However, the paradox remains. In certain circumstances some tissues seem to be potentially immortal. About fifty years ago the scientistphilosopher Alexis Carrel started a culture of chick heart cells outside the body, and by a tedious procedure of subculturing every few days, managed to maintain a living culture of growing, proliferating, and rhythmical-beating heart tissue for something like twenty years. There is no reason to suppose it would not be living yet, as descendant fragments, had human incentive been adequate to the task. The important discovery is that aging and death of cells is not inevitable. And almost as striking is the fact that heart and other tissue cells taken from a tough two-year-old fowl show just as much youthful proliferative spirit as cells taken from a one-day-old chick, except that they require a few days to get going whereas chick cells are ready at once. There is a clue here, of course, for something has accumulated or is present in the fowl which is absent in the chick and seems to be the essence of age. But what it is, is still a question.

In later years Carrel, with the assistance of Charles Lindbergh, developed techniques for maintaining living organs, such as the kidney, outside the body, a direct extension of his work on tissue culture. And once more we see that the life of a part may persist beyond the life of a whole. The truth is that aging and death is a piecemeal affair. A heart may give out while all else is well. Kidneys may deteriorate and create havoc throughout the system. Cerebral arterial hardening may produce senility of mind in a still bouncy body.

ALREADY there is a tendency to regard the newly dead much as we do automobile graveyards, to be stripped of certain otherwise essential parts for repairing bodies not so far gone. When certain technical difficulties in grafting tissue from one human to another and in storing still living organs removed from spiritless bodies have been more fully overcome, so that organ banks join the ranks of corneal banks and blood banks, life extension by transplantation may soon be as commonplace as by transfusion. Borrowed time may be equated with borrowed parts. How far such reconditioning can be carried remains to be seen, although except for saving the life of the young, where so much remains to be saved, the picture of age takes on a rather grisly look. Even so it looks better than the description of age in As You Like It: “Last scene of all, / That ends this strange eventful history, / Is second childishness and mere oblivion,/ Sans teeth, sans eyes, sans taste, sans everything.”

For centuries past the world has belonged to youth, full grown and mature, to be sure, but not old. The postponement of death in human beings may be desirable. Certainly it is so for the individual, although meaningful postponement is very different from securing a rotting apple to its branch. On a planet with a limited capacity to support human or any other kind of life, a choice will eventually have to be made between an old and a not-so-old mankind. The slower the turnover of individuals, the older the average will be and the fewer there can be during a given time. We will add to our years at the expense of the young, and to what end? To wear better dentures for a longer time? If we remain content with our lot, or at least accept it as the bonanza it truly is, our goal should be the more restricted and reasonable one of improving the quality of body and mind in the later years already at our disposal.

Youth and age cannot be dissociated. The earlier search for the fountain of youth is the same as the present effort to postpone old age. The old long to regain youth, and the young wish to retain it. It may well be that the study of age and the aging process is a wrong emphasis and that the proper study of man should be youth, and that aging is merely its negation.

A half-century ago, C. M. Child, one of the pioneering American zoologists, wrote a book called Senescence and Rejuvenescence, which is now a classic. The title is indicative, for it reflects not only the close association of age and youthfulness but also the striking fact that whatever the process may be which embraces them both, the process is reversible and in either direction. This is unmistakably true of many lower forms of life, such as flatworms, and the question is how true it may be for the larger and more differentiated kinds. Flatworms are somewhat leaf-shaped, lowly aquatic creatures that have a remarkable capacity for reconstituting whole animals from body fragments. More than this, however, Child discovered that if individual flatworms were allowed to grow to about three quarters the maximum size, short of sexual maturity, and were then starved, they would shrink in an orderly and comfortable way to a half or a quarter of their original size, with every indication of such joy of youth as a flatworm might be expected to express. As long as feeding and starvation, growth and shrinking alternated, the animals remained young with an apparent potentiality for immortality under such circumstances. Yet once allowed to grow to full size and to attain sexual maturity, there was no turning back. The old had to die, and another generation took its place. When all was done, there was no more to do. In this light, life is a flowering of what is in the seed, to be fully expressed, delayed, or cut short as the case may be.

Reversal of growth and aging as in the flatworm experiments is compatible with bodies that are entirely soft. Whatever might have been possible in mice and men is prohibited by our mineralized skeleton, which refuses to budge and sticks out as the other tissues shrink. Periodic starvation for the sake of renewal or retention of youth is too uncomfortable, although certain recent experiments of this sort on growing rats raised on an alternating restricted and full diet should be considered. After two years, at a time when their well-fed colleagues were far into the sluggish decrepitude of old age, the retarded, undersized rats had a glossy coat, activity, curiosity, and general health that were clearly juvenile. The moral is there. Our affluent society adds bulk to our bodies and calluses behind but no luster to life or mind.

A quandary is now in the making. Death control, up to a point, is rapidly becoming worldwide. The population explosion, however uneven, is its consequence. Sooner or later everywhere, birth control will have to operate to bring some stability to human affairs. Proportionately the young will be fewer, man will be more middle-aged than ever, and the superannuated will be a major section of mankind. And as if this were not enough, automation, no new process but one that has kept pace with the human growth during the last few thousand years, is rapidly increasing the occupational vacuum. The great adjustment which lies ahead, apart from the maintenance of peace on earth, will be to cope with an all-pervading boredom detrimental to physical, mental, and social health. If life is to be long, it needs to be more meaningful than ever, even though untold billions inhabit the earth. Counteracting the physiological aging of the body, so far as this may be or may become possible, is little more than keeping the old ship seaworthy, which is pointless unless there is still a voyage to be done. Physical adventure is for the young, and in a congested and continually shrinking world is an increasingly uncommon experience. What is left for young and old alike is creativity in some form which utilizes our most distinctive attribute, some combination of hand and eye or ear.

Long ago Aristotle wrote that man thinks because he has a hand, a remarkable insight for his time, for ours is truly an eye-hand brain, inherited from our arboreal, subhuman ancestors, with an overlay of the sound of speech. The basic machinery may bias the potential mind toward sight or sound, for no two human beings are exactly alike in their personal equipment, but what the mind becomes depends on what comes into it and on what it does. Thoughts not put into action are ephemeral. Action may be expressive or creative, but what is expressed or created becomes permanently ingrained in the being of the person. And here if anywhere is the only fountain of youth we all can partake of, for the secret of true happiness lies not in having, nor in just being, but in becoming. It holds for youth, maturity, and the later years. It consists of self-discovery, sell-development, selftranscendence, creativity, and awareness in every possible manifestation. Self-renewal from first to last holds body and soul together, and only so is life worth living to the very end.