Alas, the evidences of mortality are all about us; the other day our little parakeet died. As nearly as we could make out, it was a trifle over five years old, and we had always taken the best of care of it. We had fed it, watered it, kept its cage clean, allowed it to leave the cage and fly about the house, taught it a small but disreputable vocabulary, perrffltted it to ride about on our shoulders and eat at will from dishes at the table. In short, we encouraged it to think of itself as one of us humans.
But alas, its aging process remained that of a parakeet.
During its last year, it slowly grew morose and sullen; men tioned its improper words but rarely; took to walking rather than flying. And finally it died. And, of course, a similar process is taking place within me.
This thought makes me petulant. Each year I break my own previous record and enter new high ground as far as age is concerned, and it is remarkably cold comfort to think that everyone else is doing exactly the same thing.
The fact of the matter is that I resent growing old. In my time I was a kind of mild infant prodigy-you know, the kind that teaches himself to read before he is five and enters college at fifteen and is writing for publication at eighteen and all like that there. As you might expect, I came in for frequent curious inspection as a sort of ludicrous freak, and I invariably interpreted this inspection as admiration and loved it.
But such behavior carries its own punishment, for the moving finger writes, as Edward Fitzgerald said Omar
Khayyam said, and having writ, moves on. And what that means is that the bright, young, bouncy, effervescent infant prodigy becomes a flabby, paunchy, bleary, middle-aged non-prodigy, and age sits twice as heavily on such as these.
It happens quite often that some huge, hulking, raw boned fellow, checks bristling with black stubble, comes to me and says in his bass voice, "I've been reading you ever since I learned to read; and I've collected all the stuff you wrote before I learned to read and I've read that, too.",
My impulse then is to hit him a stiff right cross to the side of the jaw, and I might do so if only I were quite sure he would respect my age and not hit back.
So I see nothing for it but to find a way of looking at the bright side, if any exists...
How long do organisms live anyway? We can only guess.
Statistics on the subject have been carefully kept only in the last century or so, and then only for Homo sapiens, and then only in the more "advanced" parts of the world.
So most of what is said about longevity consists of quite rough estimates. But then, if everyone is guessing, I can guess, too; and as lightheartedly as the next person, you can bet.
In the first place, what do we mean. by length of life?
There are several ways of looking at this, and one is to consider the actual length of time (on the average) that actual organisms live under actual conditions. This is the
"life expectancy-)I
One thing we can be certain of is that life expectancy is quite trifling for all kinds of creatures. If a codfish or an oyster produces millions or billions of eggs and only one or two happen to produce young thal are still alive at the end of the first year, then the average life expectancy of all the coddish or oysterish youngsters can be measured in weeks, or possibly even days. I imagine that thousands upon thousands of them live no more than minutes.
Matters are not so extreme among birds and mammals where there is a certain amount of infant care, but I'll bet relatively few of the smaller ones live out a single year.
From the cold-blooded view of species survival, this is quite enough, however. Once a creature has reached sexual maturity, and contributed to the birth of a litter of young which it sees through to puberty or near-puberty, it has done its bit for species survival and can go its way. If it survives and produces additional litters, well and good, but it doesn't have to.
There is, obviously, considerable survival value in reach ing sexual maturity as early as possible, so that there is time to produce the next generation before the first is gone.
Meadow mice reach puberty in three weeks and can bear their first litter six weeks after birth. Even an animal as large as a horse or cow reaches the age of puberty after one year, and the largest whales reach puberty at two.
Some large land animals can afford to be slower about it.
Bears are adolescent only at six and elephants only at ten.
The large carnivores can expect to live a number of years, if only because they have relatively few enemies (al ways excepting man) and need not expect to be anyone's dinner. The largest herbivores, such as elephants and hip popotami, are also safe; while smaller ones such as baboons and water buffaloes achieve a certain safety by traveling in herds.
Early man falls into this category. He lived in small herds and he cared for his young. He had, at the very least, primitive clubs and eventually gained the use of fire. The average man, therefore, could look forward to a number of years of life. Even so, with undernourishment, disease, the hazards of the chase, and the cruelty of man to man, life was short by modern standards. Naturally, there was a limit to how short life could be. If men didn't live long enough, on the average, to replace themselves, the race would die out. However, I should guess that in a primitive society a life expectancy of 18 would be ample for species survival. And I rather suspect that the actual life ex pectancy of man in the Stone Age was not much greater.
As mankind developed agriculture and as he domesti cated animals, he gained a more dependable food supply.
As he learned to dwell within walled cities and to live under a rule of law, he gained oTeater security against hu man enemies from without and within. Naturally, life ex pectancy rose somewhat. In fact, it doubled.
However, throughout ancient and medieval times, I doubt that life expectancy ever reached 40. In medieval
England, the life expectancy is estimated to have been 35, so that if you did reach the age of 40 you were a revered sage. What with early marriage and early childbirth, you were undoubtedly a grandfather, too.
This situation still existed into the twentieth century in some parts of the world. In India, for instance, as of 1950, the life expectancy was about 32; in Egypt, as of 1938, it was 36; in Mexico, as of 1940, it was 38.
The next great step was medical advance, which brought infection and disease under control. Consider the United
States. In 1850, life expectancy for American white males was 38.3 (not too much different from the situation in medieval England or ancient Rome). By 1900, however, after Pasteur and Koch had done their work, it was up to
48.2; then 56.3 in 1920; 60.6 in 1930; 62.8 in 1940; 66.3 in 1950; 67.3 in 1959; and 67.8 in 1961.
All through, females had a bit the better of it (being the tougher sex). In 1850, they averaged two years longer life than males; and by 1961, the edge had risen to nearly seven years. Non-whites in the United States don't do quite as well-not for any inborn reason, I'm sure, but because they generally occupy a position lower on the economic scale. They run some seven years behind whites in life ex pectancy. (And if anyone wonders why Negroes are rest less these days, there's seven years of life apiece that they have coming to them. That might do as a starter.)
Even if we restrict ourselves to whites, the United States does not hold the record in life expectancy. I rather think
Norway and Sweden do. The latest figures I can find (the middle 1950s) give Scandinavian males a life expectancy of 71, and females one of 74.
This change in life expectancy has introduced certain changes in social custom. In past centuries, the old man was a rare phenomenon-an unusual repository of long memories and a sure guide to ancient traditions. Old age was revered, and in some societies where life expectancy is still low and old men still exceptional, old age is still revered.
It might also be feared. Until the nineteenth century there were particular hazards to childbirth, and, few women survived the process very often (puerperal fever and all that). Old women were therefore even rarer than old men, and with their wrinkled cheeks and toothless gums were strange and frightening phenomena. The witch mania of early modern times may have been a last expression of that.
Nowadays, old men and women are very common and the extremes of both good and evil are spared them. Per haps that's just as well.
One might suppose, what with the steady rise in life expectancy in the more advanced portions of the globe, that we need merely hold on another century to find men routinely living a century and a half. Unfortunately, this is not so. Unless there is a remarkable biological break through in geriatrics, we have gone just about as far as we can go in raising, the life expectancy.
I once read an allegory that has haunted me all my adult life. I can't repeat it word for word; I wish I could. But it goes something like this. Death is an archer and life is a bridge. Children begin to cross the bridge gaily, skipping along and growing older, while Death shoots at them. Ms aim is miserable at first, and only an occasional child is transfixed and falls off the bridge into the cloud-enshrouded mists below. But as the crowd moves farther along, Death's aim improves and the numbers thin. Finally, when Death aiins at the aged who totter nearly to the end of the bridge, his aim is perfect and he never misses. And not one man ever gets across the bridge to see what lies on the other side.
This remains true despite all the advances in social struc ture and medical science throughout history. Death's aim has worsened through early and middle life, but those last perfectly aimed arrows are the arrows of old age, and even now they never miss. All we have done to wipe out war, famine, and disease has been to allow more people the chance of experiencing old age. When life expectancy was
35, perhaps one in a hundred reached old age; nowadays nearly half the population reaches it-but it is the same old old age. Death gets us all, and with every scrap of his ancient efficiency.
In short, putting life expectancy to one side, there is a "specific age" which is our most common time of death from inside, without any outside push at all; the age at which we would die even if we avoided accident, escaped disease, and took every care of ourselves.
Three thousand years ago, the psalmist testified as to the specific age of man (Ps. 90:10), saying: "The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labor and sorrow; for it is soon cut -off, and we fly away."
I And so it is today; three millennia of civilization and three centuries of science have not changed it. The com monest time of death by old age lies between 70 and 80.
But that is just the commonest time. We don't all die on our 75th birthday; some of us do better, and it is un doubtedly the hope of each one of us that we ourselves, personally, will be one of those who will do better. So what we have our eye on is not the specific age but the maximum age we can reach.
Every species of multicellular creature has a specific age and a maximum age; and of the species that have been studied to any degree at all, the maximum age would seem to be between 50 and 100 per cent longer than the specific age. Thus, the maximum age for man is considered to be about II S.
There have been reports of older men, to be sure. The most famous is the case of Thomas Parr ("Old Parr"), who was supposed to have been born in 1481 in England and to have died in 1635 at the age of 154. The claim is not believed to be authentic (some think it was a put-up job involving three generations of the Parr family), nor are any other claims of the sort. The Soviet Union reports numerous centenarians in the Caucasus, but all were born in a region and at a time when records were not kept. The old man's age rests only upon his own word, therefore, and ancients are notorious for a tendency to lengthen their years. Indeed, we can make it a rule, almost, that the poorer the recording of vital statistics in a particular region, the older the centenarians claim to be.
In 1948, an English woman named Isabella Shepheard died at the reported age of 115. She was the last survivo 'r, within the British Isles, from the period before the com pulsory registration of births, so one couldn't be certain to the year. Still, she could not have been younger by more than a couple of years. In 1814, a French Canadian named Pieffe Joubert died and he, apparently, had reliable records to show that he was bom in 1701, so that he died at 113.
Let's accept 115 as man's maximum age, then, and ask whether we have a good reason to complain about this.
How does the figure stack up against maximum ages for other types of living organisms? if we compare plants with animals, there is no question that plants bear off the palm of victory. Not all plants generally, to be sure. To quote the Bible again (Ps. 103:
15-16), "As for man his days are as grass: as a flower of the field, so he flourisheth. For the wind passeth over it, and it is gone; and the place thereof shall know it no more."
This is a spine-tingling simile representing the evanes cence of human life, but what if the psalmist had said that as for man. his days are as the oak tree; or better still, as the giant sequoia? Specimens of the latter are believed to be over three thousand years old, and no maximum age is known for them.
However, I don't suppose any of us wants long life at the cost of being a tree. Trees live long, but they live slowly, passively, and in terribly, terribly dull fashion. Let's see what we can do with animals.
Very simple animals do surprisingly well and there are reports of sea-anemones, corals, and such-like creatures passing the half-century mark, and even some tales (not very reliable) of centenarians among them. Among more elaborate 'invertebrates, lobsters may reach an age of 50 and clams one of 30. But I think we can pass invertebrates, too. There is no reliable tale of a complex invertebrate liv ing to be 100 and even if giant squids, let us say, did so, we don't want to be giant squids.
What about vertebrates? Here we have legends, par ticularly about fish. Some tell us that fish never grow old but live and grow forever, not dying till they are killed. In dividual fish are reported with ages of several centuries.
Unfortunately, none of this can be confirmed. The oldest age reported for a fish by a reputable observer is that of a lake sturgeon which is supposed to be well over a century old, going by a count of the rings on the spiny ray of its pectoral fin.
Among amphibia the record holder is the giant sala mander, which may reach an age of 50. Reptiles are better.
Snakes ma reach an aoe of 30 and crocodiles may attain y t,
60, but it is the turtles that hold the record for the animal kingdom. Even small turtles may reach the century mark, and at least one larger turtle is known, with reasonable certainty, to have lived 152 years. It may be that the large Galapagos turtles can attain an age of 200.
But then turtles live slowly and dully, too. Not as slowly as plants, but too slowly for us. In fact, there are only two classes of living creatures that live intensely and at peak level at all times, thanks to their warm blood, and these are the birds and the mammals. (Some mammals cheat a little and hibernate through the winter and probably ex tend their life span in that nianner.) We might envv a tiger or an eagle if they. lived a long, long time and even
- as the shades of old age closed in-wish we could trade places with them. But do they live a long, long time?
Of the two classes, birds on the whole do rather better than mammals as far as maximum age is concerned. A pigeon can live as long as a lion and a herring gull as long as a hippopotamus. In fact, we have long-life legends about some birds, such as parrots and swans, which are supposed to pass the century mark with ease.
Any devotee of the Dr. Dolittle stories (weren't you?) must remember Polynesia, the parrot, who was in her third century. Then there is Tennyson's poem Tithonus, about that mythical character who was granted immortality but, through an oversight, not freed from the incubus of old age so that he grew older and older and was finally, out of pity, turned into a grasshopper. Tennyson has him lament that death comes to all but him. He begins by pointing out that men and the plants of the field die, and his fourth line is an early climax, going, "And after many a summer dies the swan." In 1939, Aldous Huxley used the line as a title for a book that dealt with the striving for physical im mortalit y
However, as usual, these stories remain stories. The oldest confirmed age reached by a parrot is 73, and I imagine that swans do not do much better. An age of 115 has been reported for carrion crows and for some vultures, but this is with a pronounced question mark.
Mammals interest us most, naturally, since we are mam mals, so let me list the maximum ages for some mammalian types. (I realize, of course, that the word "rat" or "deer" covers dozens of species, each with its own aging pattern, but I can't help that. Let's say the typical rat or the typical deer.)
Elephant 77 Cat 20
Whale 60 pig 20
Hippopotamus 49 Dog 1 8
Donkey 46 Goat 17
Gorilla 45 Sheep 16
Horse 40 Kangaroo 16
Chimpanzee 39 Bat 15
Zebra 38 Rabbit 15
Lion 35 Squirrel 15
Bear 34 Fox 14
Cow 30 Guinea Pig 7
Monkey 29 Rat 4
Deer 25 Mouse i
Seal 25 Shrew 2
The maximum age, be it remembered, is reached only by exceptional individuals. While an occasional rabbit may make 15, for instance, the average rabbit would die of old age before it was 10 and might have an actual life ex pectancy of only 2 or 3 years.
In general, among all groups of organisms sharing a common plan of structure, the large ones live longer than the small. Among plants, the giant sequoia tree lives longer than the daisy. Among animals, the giant sturgeon lives longer than the herring, the giant salamander lives longer. than the frog, the giant alligator lives longer than the lizard, the vulture lives longer than the sparrow, and the elephant lives longer than the shrew.
Indeed, in mammals particularly, there seems to be a strong correlation between longevity and size. There are exceptions, to be sure-some startling ones. For instance, whales are extraordinarily short-lived for their size. The age of 60 1 have given is quite exceptional. Most cetaceans are doing very well indeed if they reach 30. This may be because life in the water, with the continuous loss of beat and the never-ending necessity of swimming, shortens life.
But much more astonishing is the fact that man has a longer life than any other mammal-much longer than the elephant or even than the closely allied gorilla. When a human centenarian dies, of all the animals in the world alive on the day that he was born, the only ones that re main alive on the day of his death (as far as we know) are a few sluggish turtles, an occasional ancient vulture or sturgeon, and a number of other human centenarians. Not one non-human mammal that came into this world with him has remained. All, without exception (as far as we know), are dead.
If you think this is remarkable, wait! It is more re markable than you suspect.
The smaller the mammal, the faster the rate of its metabolism; the more rapidly, so to speak, it lives. We might well suppose that while a small mammal doesn't live as long as a large one, it lives more rapidly and more intensely. In some subjective manner, the small mammal might be viewed as living just as long in terms of sensation as does the more sluggish large mammal. As concrete evidence of this difference in metabolism among mammals, consider the heartbeat rate. The following table lists some rough figures for the average number of heartbeats per minute in different types of mammal.
Shrew 1000 Sheep 75
Mouse 550 Man 72
Rat 430 Cow 60
Rabbit 150 Lion 45
Cat 130 Horse 38
Dog 95 Elephant 30
Pig 75 Whale 17
For the fourteen types of animals listed we have the heartbeat rate (approximate) and the maximum age (ap proximate), and by appropriate multiplications, we can determine the maximum age of each type of creature, not in years but in total heartbeats. The result follows:
Shrew 1,050,000,000
Mouse 950,000,000
Rat 900,000,000
Rabbit 1,150,000,000
Cat 1,350,000,000
Dog 900,000,000
Pig 800,000,000
Sheep 600,000,000
Lion 830,000,000
Horse 800,000,000
Cow 950,000,000
Elephant 1,200,000,000
Whale 630,000,000
Allowing for the approximate nature of all my figures,
I look at this final table through squinting eyes from a dis tance and come to the following conclusion: A mammal can, at best, live for about a billion heartbeats and when those are done, it is done.
But you'll notice that I have left man out of the table.
That's because I want to treat him separately. He lives at the proper speed for his size. His heartbeat rate is about that of other animals, of similar weight. It is faster than the heartbeat of larger animals, slower than the heartbeat of smaller animals. Yet his maximum age is 115 years, and that means his maximum number of heartbeats is about 4,350,000,000.
An occasional man can live for over 4 billion heartbeats!
In fact, the life expectancy of the American male these days is 2.5 billion heartbeats. Any man- who passes the quarter-century mark has gone beyond the billionth heart beat mark and is still young, with the prime of life ahead.
Why? It is not just that we live longer than other mam mals. Measured in heartbeats, we live four times as long!
Why??
Upon what meat doth this, our species, feed, that we are grown so great? Not even our closest non-buman rela tives match us in this. If we assume the chimpanzee to have our heartbeat rate and the gorilla to have a slightly slower one, each lives for a maximum of about 1.5 billion heartbeats, which isn't very much out of line for mammals generally. How then do we make it to 4 billion?
What secret in our hearts makes those organs work so much better and last so much longer than any other mam malian heart in existence? Why does the moving finger write so slowly for us, and for us only?
Frankly, I don't know, but whatever the answer, I am comforted. If I were a member of any other mamxnalian species my heart would be stilled long years since, for it has gone well past its billionth beat. (Well, a little past.)
But since I am Homo sapiens, my wonderful heart beats even yet with all its old fire; and speeds up in proper fashion at all times when it should speed up, with a verve and efficiency that I find completely satisfying.
Why, when I stop to think of it, I am a young fellow, a child, an infant prodigy. I am a, member of the most un usual species on earth, in longevity as well as brain power, and I laugh at birthdays.
(Let's see now. How many years to 115?)