6. Death by Stress

In 1932 the director of the New York Aquarium, C. M. Breder, Jr., working with a colleague named C. W. Coates, performed an experiment with those small fish known as guppies that shook no worlds. Their conclusions were published in a little-read scientific journal, Copeia, and few people today are aware of their work. Yet the fifty-one guppies who participated in Breder's adventure should one day be memorialized by some watery monument, for they not only discredited a Pope but threatened with ruin a scientific doctrine as unquestioned as any in our time.

There are few of us unfamiliar with the tiny fish so common in our children's aquaria. Guppies multiply lavishly, and are born in a ratio of two females for every male. Breder initiated his experiment by arranging two tanks of equal size, each with an abundant food supply and aeration ample to tolerate a host of fish. Then in one tank he placed fifty guppies with an unnatural distribution of approximately one-third males, one-third females, and the remainder juveniles. In the other tank he placed a single gravid female -- one heavy with eggs already fertilized. What he expected to happen, I do not know. What happened defied prediction then, as it defies explanation today.

A remarkable character of the pregnant female guppy is that a single fertilization may give as many as three broods, born every twenty-eight days. The lone gravid female cooperated nobly with the experiment, producing broods as high as twenty-five. Yet at the end of six weeks there remained nine fish in her tank. She had eaten the surplus young. In the meantime the tank with an original population of fifty had witnessed a rapid and immediate die-off. Cannibalism of newborn was so rapid that it was seldom witnessed. The fish surviving at the end of six weeks had all belonged to the original population. Here too there were nine. In each tank there were three males and six females, the ordained proportion among guppies.

An ironic turn in the history of science took place when both Charles Darwin and Alfred Russel Wallace found their inspiration for natural selection in Malthusian doctrine, a thesis which sooner or later must be accepted as in large part false. Thomas Malthus was an English economist who in 1798 published his Essay on the Principle of Population, demonstrating that while human populations increase at geometric pace, food supply can increase only by addition. The multiplying population must therefore at some point overtake the supply of food. And at that point the population will reach its limit.

Darwin and Wallace saw in the Malthusian doctrine a natural law which must apply to all species, and so they deduced that through competition for a limited resource, food, selection must take place between fit and unfit. The Malthusian logic seemed inarguable, and, as we know, upholds the pessimism with which many view our contemporary population explosion. And undoubtedly supply of food places a theoretical limit on animal numbers, just as there must be cases in which deficiencies of quantity or quality of food contribute to a limiting effect. Yet the new biology provides no proposition more demonstrable than that of the self-regulation of animal numbers. Rare is the population that has ever expanded until it reached the limits of food supply. Rare are the individuals who directly compete for food. An infinite variety of self-regulatory mechanisms, physiological and behavioral, provide that animal numbers -- except in the case of climatic catastrophe -- will never challenge the carrying capacity of an environment. Birth control is the law of the species.

When Paul VI in 1968 shook the world both Catholic and non-Catholic with his condemnation of contraception, he made an error of fatal dimension. Had he and his advisors confined their condemnation to one of conflict with church doctrine, then a student of evolution could have nothing to say. But contraception was also condemned as a violation of natural law. And, whatever private interpretation the Vatican may give to the phrase "natural law," its invocation permits debate by the observer of natural arrangements. The conclusion which I shall present, drawn from the evidences of the new biology, is that contraception is the cultural implement enforcing a natural law. Papal condemnation, not contraception, stands as violator of natural designs.

In terms of the social contract, we may say that just as society must furnish the young with freedom to develop their genetic potential, so the breeding adult mitst not provide society with more young than the group can handle. The propositions are poised in equity, and the neglect of one must result in the nullification of the other.

Fifty-one guppies, controlling their numbers through a blend of cannibalism and infanticide which we must assume seems quite normal to guppies, can scarcely be regarded as furnishing a sufficient case for the toppling of a Malthus, the indictment of a Pope, or the elaboration of a social contract. But other evidence exists. And as we review the efforts of scores of scientists in recent decades, and as we identify ourselves with their successes small or spectacular, their failures comical or maddening, we shall gain, I believe, a proper mass of evidence. And we shall enjoy, too, participation in one of science's better detective stories.

Immediately after the First World War a burst of originality possessed us. Perhaps trench warfare, with its massive insult of collective death, brought to the human spirit a demand for individual daring. The literary consequences are famous, for these were the years of the uninhibited Left Bank, of Joyce, of Hemingway, of Fitzgerald. It was the time when unknown playwrights were popping up all over the Times Square area to create in the American theater its one golden age. Jazz overleaped all language barriers, and the American popular song became the musical currency of far markets. And in the sciences originality too was displaying its wares.

Out in Chicago the psychologist John B. Watson was founding behaviorism on the principles of Pavlov's conditioned reflex. His effort would wind up with today's reinforcement theory, and while I may deplore Watson's contribution to scientific confusion, I cannot dismiss his daring. Less conspicuously Eliot Howard, in England, was presenting us with the concept of territory, while in Norway Schjelderup-Ebbe's observation of barnyard pecking orders complemented Howard's to give us the foundations for a future ethology. Meanwhile the University of London's Carveth Read was publishing his Origin of Man with its prediction that the human ancestor, when found, would resemble in his life style more the way of the carnivorous wolf than the way of that inoffensive vegetarian, the forest ape. And at the same time, in the faraway Transvaal, Raymond A. Dart was discovering Read's predatory fellow in the person of Australopithecus africanus.

Most of these bursts of originality almost half a century ago disappeared for decades, leaving small trace. None went into a hiding more perfect than Sir Alexander Carr-Saunders' The Population Problem, an overwhelming attack on the Malthus doctrine. That was in 1922, and it failed to start even a backroom argument. But, fortunately, just two years later a paper appeared called "Periodic Fluctuations in the Numbers of Animals," by the pioneer ecologist C. S. Elton. It threatened directly no sacred assumptions, but it initiated a line of research that has progressed ever since. While Elton's study concerned largely the snowshoe hare, it was inspired by the lemming, an animal whose inexplicably suicidal tendencies qualified it as scientific box office. The rumpus was on.

The morbid activities of the lemming had been tantalizing human imagination for centuries. Travelers brought back grisly accounts of dead lemmings floating along the Norwegian coast. The earliest report to come to my attention was made by a Jacob Zieler in 1532. The first true study was made by a naturalist named I. G. Gmelin while observing animal populations in the Siberian tundra in 1760. He discovered the regularity of fluctuation in the numbers of both the lemming and the Arctic fox that preys on it. When the time of vanishing arrived, lemmings simply disappeared into the Siberian immensity. But in the confines of Scandinavia they did not always disappear. A ship off Trondheim in 1868 reported a shoal of lemming corpses so enormous that the ship took fifteen minutes to pass it.

As has frequently happened in the contemporary studies of animal behavior, the activity of a single species has led scientists on to broader and broader research, with conclusions of deepening significance. Carpenter's study of the howling monkey introduced us to the intricacy of primate society in a state of nature. Howard's warblers have given us today the territorial principle. The behavior of a few barnyard hens has led us on to a recognition of rank order as an organizing structure in most animal societies. Konrad Lorenz' imprinted ducks have brought into question all those learning theories dear to behav-iorist psychology. G. T. V. Matthews' preoccupation with homing pigeons, initiating a wave of investigation into animal navigation, has left us struggling with the problem of just how much we know about anything. If traditionalists have resisted the chain reactions of ethology, it has been with true intuition that their tidy explanations are in danger.

So the lemming today joins the ranks of the classic animals. A tiny beast weighing only a few ounces, it is a member of that largest of all mammalian families, the Muridae, including mice and rats, hamsters, gerbils, voles. And if the lemming's importance to man is minimal, then this is only because while existing in probable trillions in the sub-Arctic wastes, it exists where men are few. Yet the chain of investigations initiated by the lemming's bizarre behavior is taking its arrow's course toward a target of human affliction.

Why do the numbers of the lemming build up every few years, then crash? Sweden witnessed in 1963 one of the greatest "lemming years" in decades. Lapps in the far north first reported the disappearance of lemmings in the month of August. Originating in the mountains, they vanished, moving south. They moved mostly at night, and observers at a crossroads counted forty-four pass per minute. They moved as individuals, not as groups. Although food was abundant, if one died he was immediately eaten by others, the skull being opened neatly and the brain being eaten first. Of several hundred taken and examined, all proved to be the young of the year, and although sexually mature, not a female Was pregnant. The migration was a youth movement. At any water obstacle, like a lake, they massed on the beaches in such number that an observer could not move without squashing them. Fair enough swimmers, they were not good enough. From a dead-end peninsula on Lake Storsjon so many obeyed the unknown impulse compelling them that the shores of the lake, the following year, were carpeted with lemming bones.

Darwin, without the benefit of future observation, guessed that recurrent epidemics caused the periodic die-off. Through the years, however, most observers agreed that for reasons probably of food shortage, lemmings stage regular migrations out of an area. In Siberia's endless wastes they go elsewhere, whereas among Scandinavia's lakes and fjords and seas migration becomes suicide. The answer seemed good enough until a skeptic in 1921 demonstrated that, whatever the place or the environment, lemmings vanish everywhere simultaneously, appearing nowhere else. Then in 1924 Elton said: sunspots.

The answer might seem a touch cosmic. But what Elton had done was to correlate Scandinavia's peak lemming years with those years in Canada when snowshoe hares appeared in greatest abundance and staged similar population crashes. The years were about the same. Then, with a mighty stroke of ingenuity, he went back through the yellowing records of the Hudson Bay Company. Since the eighteenth century the company had kept season-to-season records of furs purchased. Lynx purchases, following the same peaks and valleys, had varied from 3,000 to 80,000.

Even more exclusively than the fox preys on lemmings, the Canadian lynx preys on the snowshoe hare. The great naturalist Enkest Thompson Seton once wrote that the lynx "lives on Rabbits, thinks Rabbits, tastes like Rabbits, increases with them, and on their failure dies of starvation in the unrabbited woods." Seton in 1886 estimated the number of hares as 5,000 to the square mile, yet after a crash there might be only one. Elton found that Seton had been right about the unrabbited woods, for pelts of the snowshoe hare in the Hudson Bay Company's records swung between 10,000 and 100,000, in accordance with the cycle of the lynx. And that cycle varied between nine and eleven years.

Now Elton had his second inspiration. The lynx-hare cycle corresponded with the cycle of sunspot activity. His investigations indicated that the lower the activity of solar flares, the colder and dryer die climate on earth. (Recent studies of British Columbia forests confirm that minimum timber growth corresponds with minimum sunspot activity.) Elton reasoned that in the marginal conditions of the sub-Arctic, declining sunspot activity would have its most drastic effect. If in good years fecund animals like the hare or lemming built up to huge numbers, then deteriorating climate and food supply would bring on the consequent decimation.

In the most funereal mood one must record the death of a hypothesis so brilliant. Some years later a Canadian scientist, D. A. MacLulich, a man one must assume quite devoid of compassion for fellow scientists, through most studious checking found that in the 174 years between 1751 and 1925 there had been eighteen lynx-hare cycles, and only fifteen sunspot cycles. The final crash was that of C S. Elton.

And yet MacLulich's victim was indeed not the ecologist whose originality had been of such order as to make even being wrong a triumph. The victim was the principle that it is food supply that limits population, and the corpse being secretly carried through science's back streets was that of Thomas Robert Malthus. A later authority, Dennis Chitty, could write just a few years ago: "No animal population continues to increase indefinitely and the problem is to find out what prevents it."

The food theory died hard, if it can be said to be dead even now. Kalela, a Finnish ecologist, conducting a three-year study of the red-backed vole in Lapland, recorded a devastating crash in a season of abundance. And yet in the same year a University of Helsingfors biologist could publish summaries of cycles of the Arctic fox and ptarmigan in Greenland, the partridge in England, the red grouse in Scotland, the goshawk and willow grouse in Norway, and the waxwing and red fox in Finland, to prove that all was climate. Chitty himself made an elegant study of the vole in Wales. The decimation of one population coincided with bad weather in 1938; but an adjoining population did not suffer until the following year, when the weather improved. A decade later, in the succeeding crash, neither weather nor food shortage contributed influence.

An experiment in 1965 with the California vole recalls Breder and his guppies. Two areas, each of an acre or so, were isolated. On the first was a population of voles increasing naturally at a rate of about 3 percent a month. On the other was a slim population of five males and eight females, and this became the experimental area. High-quality food was periodically scattered on it. Fertilizer was applied to enhance the natural growth. The population boomed to a springtime peak of forty-seven males and fifty-three females. But by August it had returned to precisely the original number -- five males and eight females.

Biology's nineteenth-century certainties were being replaced by the twentieth century's open questions. If it was not food supply that limited animal numbers, then what was it? The famous Iowa ecologist Paul Errington became absorbed by the problem. His long career, first as a hunter and trapper, later as research zoologist and teacher, denied him allegiance to orthodoxies. Errington's was the kind of mind that could distill long observation to primary-school simplicity: Muskrats, grouse, ring-tail pheasants, and snowshoe hares all reach a maximum population in years ending with 1 or 2, a minimum in years ending with 6 or 7. Mathematics, not environment, determines population. He recalled further Hudson Bay Company figures. In the mid-1930's a huge engineering project in Saskatchewan affecting three quarters of a million acres provided as a side effect more and better habitats for muskrats. The fur catch increased in consequence. But though the base was now higher, the fluctuations proceeded just as before.

An argument frequently advanced has been that the increasing number of predators -- as in the lynx and hare or in the fox and lemming -- at last decimates the prey population. Erring-ton dismissed it. The traditional enemy of the muskrat is the mink, as savage a little killer as the world affords. When the muskrat population is at the peak of its vitality, the most formidable attention on the part of the mink results merely in mother muskrats having more young. "Diminishing of population tensions affords one of the best stimuli for reproduction." Anything, in other words, that reduces the density of a healthy population, whether predation or drought or epizootics (that admirable word for epidemics so standard in zoology's vocabulary) , will increase the birthrate in compensation. But mathematics must favor the mother. Let drought fall in a year ending in 7, catastrophe may ensue.

Errington concluded that much in the resilience of natural populations lies beyond present knowledge, and that unknown factors may depress certain life processes. The Bergsonian conclusion carried .little appeal to a scientific community which tends to confuse the insoluble with^the insulting. But his concern with population density and its relation to reproduction, recorded in a paper published in 1951, contributed to a course that investigation has followed ever since. Muskrat litters vary in number, as likewise do the number of litters in a given season. In a time of low population density the mother muskrat may have as many as twelve to sixteen young in a year; in a period of topheavy numbers as few as two or three.

How self-regulation is accomplished remained as great a mystery as ever, but it related directly to density. The new clue exploded innumerable investigations. Somewhere in the population haystack was a needle, and in the scientific night one spied a host of detectives, each with flashlight, magnifying glass, and Sherlock Holmes cap, trampling through the hay with his shoes off. But to qualify for such a role of scientific private eye, you needed a combination of resources seldom known in the sciences. You needed the experience of ethology, with its emphasis on the relation of animal to animal. You needed the viewpoint of the ecologist, with his principal attention on the relation of the animal to its physical environment. And you needed command of physiology, with its studies of organic processes. If you were lucky, you knew about evolution too, and the relation of the past to the present. Out of all such exhausting demands emerged a new discipline called population dynamics. Few could qualify. Yet the hay suffered little from neglect.

In the following section of this chapter I shall explore the self-regulating devices which in many species prevent a buildup to such numbers that only a population crash can provide natural limitation. The species we have been considering -- in a sense, the freaks -- lack such mechanisms and so are subjected to cyclical control. And while there must remain a temptation to equate man with the lemming and the snowshoe hare, we had best defer our consideration of men until we know more about animals. And we had best defer too those questions facing the new devotees of population dynamics in the 1950's: How, when density reaches a certain point, does a form of birth control take place so that fewer young are born, or are even conceived? And why -- a more difficult question -- do the elders drop dead?

The mystery of death and life, brought to attention by the insignificant lemming, has scarcely been resolved by a Vatican decision.

John Calhoun, a director of our National Institute of Mental Health, is, like Maslow, a maverick's maverick in the field'of psychology. Physically slight, temperamentally elusive in the sense that elves are hard to get hold of, Calhoun is blessed with the capacity of slipping through the formidable fences of American psychology to escape without attracting undue notice. His first escape of which I have record was in 1952.

For two years the psychologist had been observing a population of wild Norwegian rats which he established in a large pen at Towson, Maryland. So large was the pen -- almost a quarter of an acre -- that under laboratory conditions of small separate cages it could have accommodated 5,000 healthy rats. At Tow-son, however, the undomesticated rats lived under approximately normal conditions. Calhoun established his population I with five pregnant females. In two years the theoretical number of possible descendants would be 50,000. Yet the population of the pen never exceeded 200, and gave every indication that, no matter how long the experiment might be extended, this would remain the approximate number.

As in Breder's experiment with the guppies, final numbers bore relation not to food supply but, in some fashion or other, to space. Mother guppies controlled numbers by the indelicate process of devouring surplus young. Calhoun's young suffered to a degree through adult fighting and neglect of maternal care. But as the population stabilized, it became evident that the critical factor limiting numbers was territorial behavior.

Norway rats form stable societies when nomore than a dozen adults share a territory and jointly defend it. Within this little world adults form a hierarchy led by an alpha male. The amity-enmity complex which I described in The Territorial Imperative turns hostility outward and preserves peace within the group. Calhoun wrote that the territories, and the buffer zones between, "seemed essential to the maintenance of group integrity." But they likewise divided up the available space into.homesteads for groups of limited number. So population control was achieved.

It was the Irish ornithologist C. B. Moffat who first glimpsed in territorial behavior a means of controlling animal numbers. That was in 1903, long before Eliot Howard introduced the whole territorial principle to biology. A portion of the earth's surface exclusively your own brings you as the proprietor many a material benefit. You are defended, since you know it better than do your enemies. Possession in some strange way enhances your energies. Through a process of animal justice, might no longer makes right and on your home grounds you are capable of resisting intruders stronger than are you. Territory may ensure a food supply for you and yours. If you share the property with your wife, then it will ensure also that you do not leave each other when the children need you both. These are benefits accruing to the proprietor, but there are two powerful benefits accruing to the population and the species. By the physical separation of individuals or groups, dangerous aggressive forces are reduced to shouted insults over common bounda: ries. And the distribution of available space among breeding couples or groups means that the number of offspring will be kept well below the carrying capacity of the environment.

Although with our present knowledge of the territorial principle Moffat's insight might seem self-evident, still only in recent years has the relation of territory to population control become accepted. Even in 1956 Cambridge's eminent ethologist Robert Hinde rejected the proposition as unproved. His rejection inspired at least two studies designed specifically to demonstrate limitation of births through territorial behavior.

Hinde's objection had real grounds: While the necessary possession of a territory quite obviously distributes breeding pairs throughout an environment, it does not follow that territory limits the numbers of such pairs. Space is seldom that scarce. The English robin, for example, must have its breeding territory, but there remain in England vast areas of suitable habitat unfrequented by robins. And so to meet the objection Adam Watson, a colleague of V. C. Wynne-Edwards at the University of Aberdeen, set up an experiment with red grouse on the Scottish moors. And David Carrick, of Australia's Division of Wildlife Research, began his observations of the Australian magpie in fields near Canberra.

The problem was to demonstrate that the territorial necessity actually eliminates healthy adult birds from the breeding population. Red-grouse males establish territories in the autumn, holding them till the following summer. Space for breeding in the moorland is truly unlimited, yet the competition for territories takes place only in restricted areas. Watson began by selecting a study area and marking all birds in the vicinity. He then cleared 119 territories by capturing or shooting the proprietors. Within a week 111 were filled by new males, only a dozen of whom were of unknown origin. All the rest had come from the marked population of the vicinity which constituted a non-breeding reserve. All bred successfully the following spring. Watson had demonstrated that at least in the red grouse it is the number of breeding territories that in fact limits the breeding population.

The Australian magpie is related to the crow, but it is a creature quite distinct in both appearance and behavior. Like the crow, it is a large bird but with vivid white markings on the rump, at the nape of the neck, and in the flash of outspread wings. Some, again like the crow, gather in large non-territorial flocks; but others form social bands surprisingly like Calhoun's Norwegian rats. Up to ten adults defend as a team a property of five to twenty acres. And these are the only birds that successfully breed.

Carrick's study area was about five square miles of savanna, broken here and there by eucalyptus clumps, supporting thousands of magpies. Both food supply and nesting sites were unlimited. A few non-territorial groups nested in trees, but never succeeded in raising young. The crow-like flocks in the fields never tried. Successful breeding was confined to that 20 percent of the total population within the territorial bands.

What, precisely, prevented normal reproduction in any but the propertied bands? Carrick made a surprising discovery. While all males in the total population produced motile sperm, only the hens in the territorial groups ovulated normally.

The physiological link between normal sexuality and territorial possession is demonstrable in many species. The most prevalent of the many arrangements was first conclusively demonstrated by Eliot Howard's observations of countless species of finches and buntings, warblers, lapwings, woodpeckers in which the female is sexually unresponsive to an unpropertied male. The Marxist mind may be properly revolted by such conduct, and gloomily conclude that the study of animal behavior can come to no good. But the way of the lapwing persists. Furthermore, later research demonstrated the converse of Howard's proposition: the unpropertied or dominated male tends to be psychologically castrated. Thus not only does female sexuality guarantee that breeding will be accomplished within a select circle, but sexual inhibition provides that the disenfranchised male will break up no homes, indulge in no rape.

We still have no certain answer concerning the physiological linking of territorial behavior and the sexual impulse. But the field research proceeding today leaves no doubt about its reality. In 1966, when I first investigated the territorial imperative, I could find only one species of African antelope to which I could responsibly ascribe the pattern earlier observed in birds. This was the Uganda kob, a species in which males occupy an arena of territorial competition to which females are attracted for copulation. Females will accept no other than the successful, and the masses of surplus males amuse themselves in their bachelor herds. In the few short years since I published my review, territorial systems of breeding have been described in the wildebeest and waterbuck, in the Grant's and Thomson's gazelle and the comparable southern springbok, in the harte-beest and topi and puku, and in the smallest of them all, the oribi and dik-dik and steenbok. Systems vary, from the modified arena competition of the wildebeest and puku, to the bird-like family territories of the steenbok. But, in all, the main propositions hold true: The female will be attracted only by a territorial male; the male who has failed in the territorial competition will retire into the careless existence of males in groups.

As we are only now discovering the prevalence of territorial sexuality in the large family of antelope species, we stand only now on the threshold of discovering the undoubted physiological explanations. But in our expanding efforts we come on some strange behavioral mechanisms of population control.

The wildebeest, one of the most common and certainly the most grotesque of African antelopes, possesses no social organization worthy of analysis excepting the incidence of territorial bulls who maintain a monopoly on copulation. Beyond that, wildebeest, like schools of fish, congregate in immense herds, offer the lion his favorite dish, and migrate with the rains in the hundreds of thousands. And population control takes place in an adjustment of unlikely instincts. The mother drops her calf without more emotional engagement than might take place with a bowel movement. But the calf has a following instinct regarding its mother. Miraculously, the newly born wildebeest within seven minutes can stagger to its feet and follow. Now the mother will lick it and proceed to recognize it as a being strange but her own. What, however, happens when herds are so dense that the unfortunate newborn after these minutes cannot recognize its mother? Let it make a wrong guess in the confusions of a wildebeest Times Square. The non-mother will butt it away. The mob will have swallowed the calf's identity. Lost, unprotected, it must in the end surrender its fate to the hyena or jackal.

The lion, preyed on by none, not too susceptible to disease or parasites, could in a few generations be a victim of overpopulation. The lioness produces her several cubs in a short period of gestation, and, should she lose them, comes into heat again at once. Yet in the Serengeti a stable population of about a thousand lions varies little in number from season to season. The area's immense numbers of prey animals, such as wildebeest, Thomson's gazelle, and zebra, could support far more lions. What keeps their numbers down? A subtle combination of behavior patterns, foremost among them maternal neglect, provides that only so many lions will reach a breeding age and situation.

The first control is territorial. As with the Australian magpie, only those females who are part of a permanently resident pride breed successfully. The second control is a dominance order like those of few other species. The young eat last. With Schaller I once watched a zebra kill where nine lionesses, rumbling at each other with the collective menace of a volcano, ringed the carcass flank to flank like daisy petals. In ninety minutes they ate some 450 pounds of meat, while a lone cub on the outskirts played with the zebra's tail, which he had somehow managed to secure. Had he sought a single bite before the lionesses were finished, quite probably he would have been killed.

This rank order of feeding, which places the males first though the lionesses have made the kill (and perhaps that is why our lionesses were eating in such a hurry, before males would show up), the females second, and the cubs last, compels no great deprivation so long as large game is available. A wildebeest or zebra will provide food for all. But the dry season brings a food shortage of a technical nature. The larger game migrates out of the grasslands into the woodlands. And the breeding prides, with their territorial attachment, refuse to follow. Through the dry season they live off the non-migrating animals, chiefly Thomson's gazelle -- and a Tommie weighs at most about forty-five pounds. Adult appetite is seldom sated, and cubs go hungry. Should you in August glimpse two wan cubs waiting while their mother goes hunting, you may be fairly sure that only one will remain in November when the rains and the big game return. Yet food exists in plenty scarcely fifty miles away.

Infant mortality in the lion runs to about 50 percent. And we may contrast that with the quite opposite behavior of the adult hunting dog, which I earlier described, who will touch no food till the young are finished. One may deplore the lion, praise the hunting dog, but either judgment would be anthropomorphic. The behavioral contrasts are expressions of population control. The hardy lion, once he reaches maturity, will be around for a long time. Control must fall on the young. But the delicate hunting dog, so susceptible to disease, must do all in his power to keep adult social numbers replenished.

Another animal virtually immune to predation is the elephant. Non-territorial, the elephant in herds has historically migrated over immense African areas in search of food, water, and perhaps even change of scene. No major animal has been so little studied, and none, as I earlier described, exhibits such mysterious capacities of behavior. But the developing needs, of developing peoples have taken away his freedom. Fields have spread. And the elephant, whose majestic presence once commanded the whole of Africa's majestic space, becomes today a prisoner of smaller and smaller protected areas.

Such an area is Uganda's Murchison Falls Park. Made famous by one of the world's most brain-numbing waterfalls, where the Victoria Nile passes through a rocky slot only nineteen feet wide, it has become even more famous for its elephants. They seem everywhere. Like a truck and trailer, a cow and her calf may thunder past your cabin door on the way to the camp's garbage cans. Once there was a great bull who acquired such a reputation as to become known as the Mayor of Murchison. Regularly he visited the tourists' cars in the parking lot, searching them for dainties. Visitors responded by leaving fruit in their cars, thus affording splendid snapshots to awe the folks back home. But the Mayor responded also. When he came to a car with no fruit, he turned it over. In the end, park authorities destroyed him.

A visit to Murchison Falls tempts the conclusion that the elephant is experiencing a population explosion. I was once so tempted, and I seem to have been wrong. Numerous they may be, but, in the opinion of Cambridge's Richard Laws, numbers are probably experiencing a slow decline. What the visitor witnesses is an elephant concentration camp. And the decline is the elephant's self-regulating mechanism responding to new conditions of density and restricted habitat.

The broad, crocodile-infested Victoria Nile separates Mur-chison's elephant herds into two distinct populations, each 7,000 or 8,000. The conditions on the South Bank are much the worse, both in crowding and destruction of natural habitat. An entire forest, its trees stripped of bark by the herds, stands today a leafless ghost. While in this well-watered land there is ample supply of grass, the elephant's traditional food, diminishing leafy browse may have brought on some nutritional deficiency. Or it may simply be the stress of density; we do not know. But through self-regulation the elephant is reducing his numbers to meet new conditions. The onset of fertility in the female is normally at the age of eleven. On the South Bank it is retarded to about eighteen. Calves are normally spaced about four years apart. On the South Bank spacing has reached nine.

The arrangements of lion and elephant illustrate the diversity of natural controls. But I present two rather different examples, ominous in human terms, derived not from any natural control but from human interference with natural arrangements.

That most sensitive of French zoologists, Francois Bourliere, has recorded two studies of deer that might be regarded as examples of the explosion-crash phenomenon were they not artificial. The first occurred on a large plateau in Arizona, just across the way from the Grand Canyon, where a stable population of 4,000 deer lived in balanced relationship with a fair number of wolves, pumas, and coyotes. The effect of predators on a prey population is almost always to weed out the sick, the malformed, the deficient. The net consequence, observed again and again, is to keep the prey population healthy. But early in this century human slaughter of the predators began and they were virtually eliminated. And with the slaughter the numbers of the deer began to rise. By 1920 there were 40,000, by 1924 over 100,000. Then in a year it crashed to 40,000, and by 1939 was down to ten thousand- Over-grazing and food shortage had undoubtedly contributed to the peak crash, but it could not explain the final decline.

The other example came about through efforts of the United States government to build up a herd of reindeer as food supply for the local inhabitants of St. Paul's Island in the Aleutians. Here there were no predators at all to exert a selective pressure on the herd, and for many years the experiment seemed a huge success. It had begun in the autumn of 1911 when four bucks and twenty-one does were place on St. Paul's. By 1932 they had increased in number to 500, by 1938 to well over 2,000. But then came what Bourliere well described as a cataclysmic decline. By 1950 eight remained.

While food shortage may have contributed to the Arizona collaipse, it could have entered little into the shattering of the reindeer experiment. The only possible conclusion is that failure fcy any agency to remove the weak and the deficient from the Ibreeding population gradually sapped the vitality of the whole gene pool.

It is a fate frequently predicted for the human species. The innocent egg, like some accident-prone bystander, seems always to be getting itself into the impossible middle of arguments. When at the end of the nineteenth century Charles Darwin's notions about evolution were passing through their darkest days, he had many a witty antagonist. Among them was Samuel Butler, who gloomily remarked that, according to Darwin, a hen was nothing but an egg's way of producing another egg. Butler's classic line will live always, as we may assume that the egg's predicament is other than temporary. And we shall not wonder if the egg is today cooking hopelessly in one of ecology's steamier arguments.

The natural regulation of animal numbers is a phrase introduced to science in 1954 with the title of a book by David Lack, Britain's celebrated ornithologist. In that book Lack's concern for natural controls was generated by the variation of number of eggs, from season to season, appearing in a clutch. Then in 1962 the Scottish ecologist V. C. Wynne-Edwards published his Animal Dispersion in Relation to Social Behavior, which so deepened and broadened the concept that the sad little egg was left far behind. The ensuing argument between Lack and Wynne-Edwards has only begun its spread beyond ecology into the whole biological realm.

Simple records show the year-to-year variation of clutch size in many bird species. It is as if the bird possesses some peculiar picture of how many eggs shquld be in the nest. An American experimenter -- who may or may not be described as a bird-lover -- by taking away each newly laid egg once induced a bewildered but determined woodpecker to lay seventy-one eggs in seventy-three days. Lack, more compassionate, contented himself with such observations as egg-counting in a great-tit population while determining food supply. The young are fed on caterpillars. And in the particular years of his observations he found a startling correlation. The years of highest clutch size, eleven and twelve, were those when later in the season caterpillars appeared in greatest profusion. In 1951, when clutch size dropped to eight, caterpillars dropped to a minimum.

Granted that the observations were persuasive, granted that great-tit foresight plus family planning kept the collective appetites of the young within the bounds of what nature would provide, the question still remained, How did they do it? Lack met the argument with an answer not too convincing: that optimum clutch size would be determined by the highest number of surviving young, which in turn would be determined by food supply. But we may recall what happened to Elton and the sunspot theory. While the control of numbers might not impossibly, as in Laws's elephants, be influenced by the quantity or quality of food supply, still students going back to Malthus for answers had a bad way of getting into trouble. And Lack got into trouble. Many years later, in 1965, C. M. Perrins reported on the continuation of the great-tit studies which Lack had initiated. In a decade and a half of observation, the correlation of seasons appeared as coincidence. What emerged as significant was the relation of clutch size to population density. If the numbers of great tits double in an area, clutch size the next season may be expected to be reduced by two.

The bird-watchers should perhaps have paid closer attention to what was happening to the rodent-watchers. By now, however, all watchers were coming to a single conclusion: It is space, not food, that stimulates controlling mechanisms in most species. It is the condition of over-crowding, not the condition of under-eating, that holds down numbers. (And it is of course at this point of advancing theory that the human condition attracts compelling notice.) But mysteries remain. We cannot say that animals learn from experience to reduce the ambitions of the clutch. Even had they the capacity to learn, as Perrins pointed out, among great tits only half of the adults alive in one year will be alive the next.

It was in the course of the heatening argument between iconoclast and traditionalist that Wynne-Edwards published his mammoth, iconoclastic book; and I cannot believe that all those who attack him have read it. In that book he accepted the resources of the environment as the final limitation on animal numbers. But he denied that food supply, or competition for food supply, presents the direct influence on our numbers. He presented instead the hypothesis that evolution has favored conventional modes of competition which limit numbers well below the carrying capacity of the habitat. Male animals do not compete for such direct rewards as food or females. They compete for symbols, like territory or high rank in a hierarchy, which in turn present them with first access to food or females. The territory may or may not present the successful proprietor with an assured food supply. Most definitely no female waits on it, like a feathered Mae West suggesting that the male come and see her sometime. But the gaining of such symbolic prizes -- limited in number -- presents the successful competitor with prior access to food and females. The female is attracted to the prize, not to the proprietor. And since the numbers of such conventional rewards are limited, so the numbers of the population are restrained.

The lay reader may inspect such differences of opinion and wonder what all the shouting is about. But he must remember that the sciences are dominated by materialism; it is impossible for many a contemporary scientist to conceive of animals competing for other than such material gratifications as sex or food. Yet ethology demonstrates that animals rarely compete for either. The dismal consequence of such scientific obsolescence was sharply demonstrated at a recent Washington symposium by one of the most able of American zoologists, Harvard's E. O. Wilson.

The conference was sponsored by the Smithsonian Institution, titled Man and Beast, and enlisted many of our foremost scientific minds to consider various new hypotheses linking the behavior of man and other animals. I consider it compulsory to confess a degree of prejudice, since among the hypotheses greeted by no unanimous acclamation were those advanced by Konrad Lorenz and myself that aggressiveness and consequent competition are innate propensities in the human as well as other species. If exceptions exist, then they do not include Homo sapiens. Wilson was invited to address the conference on competitive and aggressive behavior.

His was a paper to leave the evolutionist's mind temporarily blacked out. For its premise he chose a 1939 definition of competition as "the active demand by two or more individuals of the same species (intraspecies competition) or members of two or more species at the same trophic level (interspecies competition) for a common resource or requirement that is actually or potentially limiting." Cordially he simplified the language: "Competition arises only when populations become crowded enough for a shortage to develop in one or more resources." It was a premise of Triassic obsolescence leading logically to the conclusion that competition is infrequent in the natural world. The conclusion lent biology's endorsement to environmentalism's tattered dream. At this widely publicized conference, Wilson's was the paper most frequently quoted in the sentimental American press.

It was the old story of what a false premise can lead to, even in the work of a most able mind. Wilson's definition of competition had entered the scientific literature just two years after Konrad Lorenz' first paper was translated into English. The science of ethology had yet to be born, let alone to receive a name. A generation of students of animal ways in a state of nature had yet to return from field and forest, their notes in hand. Their reports would be unanimous that while competition occurs everywhere in nature (can one speak of natural selection without it?) the competition within a species is almost never for material resources. Whether or not observers accepted all of Wynne-Edwards' hypothesis, or even his description of prizes as conventional, it could hardly be denied that the goals of almost all animal competition exist not in the material environment but in the behavioral environment of the animal population itself. A territory, for example, cannot exist in nature; it exists in the mind of the animal.

The controversy that has arisen around Wynne-Edwards' work expresses far more than the reaction of the unsophisticated to a highly sophisticated hypothesis. The opposition is to his concept of group selection, and it has enlisted as fastidious a scientist as David Lack. The fundamental problem facing any theorist attempting to relate clutch size or territorial competition or social rank to population control is how to explain the willingness of the individual to accept certain rules and regulations that exist not in his interest, but in the interest of the whole population.

The nesting habits of seabirds provide a clear illustration. A final limitation on the numbers of the kittiwake is offered not by food supply but by a scarcity of cliff-hanging nesting sites which the species favors as a defense against predators. The kittiwake pair can easily raise three young to maturity, yet three quarters of all nests in a colony will show an egg clutch of two. The population is thereby kept within reasonable bounds. But if you are a kittiwake and you have a nest, then why not three? What process of natural selection has induced this self-imposed birth control?

Early in his career, when Wynne-Edwards was working as a biologist in Canada, he took a superb photograph of a large gannet colony on a Newfoundland headland. The photograph, published in Scientific American, required the shortest of cap tions to tell its enigmatic story. One bump of the headland is white with breeding gannets on their nests. An adjacent headland is just as white with "unemployed" birds, those excluded from breeding because they have no nesting territories. But nests can be built anywhere. Why are only a limited number of sites acceptable as breeding stations? We may of course immediately skip to the consequence, that the arbitrary limit placed on nesting sites arbitrarily limits the population. But why do the unemployed birds, having competed and lost in their efforts to gain territories, accept the rules and regulations? They resemble nothing so much as human children in some game who have been declared "out" by the umpire and have been relegated to the sidelines. And we may ask, also, what processes of natural selection could evolve and enforce such a natural treaty between a population and its members?

To the discomfort of more conservative biologists, Wynne-Edwards proposed group selection, resting on the new principles of population genetics. It is the same answer which I have suggested for the stotting Tommie. In the whole gene pool of a population may evolve a behavioral trait of-survival advantage to the group. A local population, in its capacity to surmount the hazards of its habitat for hundreds or thousands of generations, achieves a kind of immortality denied the individual. Any genetic change, whether or not of benefit to the short-lived members, if of benefit to the survival of the group should spread inevitably to become a part of the whole gene pool.

Let us think about Ellen Cullen's kittiwakes and presume that at some moment in kittiwake ancestry a mutation took place introducing a gene with a dominant allele limiting clutch size to two while the recessive remained the traditional three. The mutation would seem to be a disadvantage, since the parents would leave fewer offspring, and so should be eliminated. But would it not spread through the population with its problem of cliffside nesting sites? Group selection would say yes. And since the distribution of the gene in each generation is random, limitation of young lies beyond parental choice.

The significance of Wynne-Edwards' group selection -- the superior survival prospects of the population with a superior gene pool -- is that it provides a genetic explanation for the self-regulation of animal numbers. Such explanations are not easily come by. The traditional interpretation of natural selection in this century is differential reproduction, the proposition that superior individuals will leave more offspring to influence the succeeding generation's gene pool. But I suspect that the opposition to group selection goes back to a comment by Ernst Mayr that most biological controversies today are between those still thinking in terms of type and those who have moved on to think in terms of population.

Many biologists reject group selection as a concept unproved, others as one unnecessary, maintaining that the traditional interpretation of selection can explain everything. But the pathway of such explanations has been a tortured one, as we have seen in Lack's efforts to apply the traditional food theory. What seems at stake is less an explanation for a demonstrable phenomenon than a defense of an accepted if inconvenient definition. Perhaps the best comment was made long before the controversy became enflamed when M. E. Solomon reflected on the unreality of relating the fate of populations so exclusively to external environment. "The population functions in relation to a whole which includes itself."

The controversy will be resolved one day by the specialists involved. If Wilson was right at Washington, and competition occurs only when overcrowded numbers struggle for a scarce resource, then Malthus is confirmed. And humanity has little to look forward to but that chaotic day when in unlimited number we assassinate one another in our pursuit of inadequate resources. But if Wynne-Edwards is right, any population, human or non-human, has within its power the limitation of numbers through conventional rules and regulations and the capacity to abide by them.

While contemporary evidence seems to support Wynne-Edwards, there must always of course be those unlucky species who, lacking such powers and capacities, proceed on toward their unhappy rendezvous with decimation -- in all probability, I death by stress.

Readers of Alice in Wonderland have for generations accepted the March Hare in all his madness as a most ingratiating product of Lewis Carroll's imagination.-That he exists, regularly and in number, must seem unlikely. But the snowshoe hare, when his time comes, dies off in the spring of an affliction resembling nothing so much as a nervous breakdown.

We have concerned ourselves with species that succeed in regulating their own numbers, and just how they do it. Now let us return to those cozy species that do not, and with a prayerful thought for our own species consider just what happens to them. I left the detective story when a clue was found indicating that population density, not food supply, was responsible for population crashes. And at an early date the clue suggested that Darwin might have been right, and that crowded populations could be the victims of disease spreading at epidemic rate.

It was about the time in the late logo's when MacLulich was exploding the sunspot theory that a man named R. G. Green with various co-workers started picking up the corpses of snowshoe hares in Minnesota's Lake Alexander area. Few showed evidence of any infectious disease. Their manner of death, however, was odd. Some might be behaving normally, others might be in torpor, when suddenly they would be seized by convulsions and die. Another odd symptom was exhibited by hares captured, apparently healthy, and placed in captivity. The normal snowshoe hare tolerates the experience with indifference. But these in the springtime of the population crash died almost immediately. Autopsy showed a certain degeneration in the liver, a deficiency of blood sugar, and minor internal hemorrhages. Green described it as shock disease.

The description satisfied no one. Something specific enough to produce such similar deaths must be susceptible to definition. And why should it occur in the spring? Various hypotheses were advanced, the most persuasive by J. J. Christian, one of today's most earnest investigators. He saw the building up of a population as a time of intensifying stress. The increasing number of young, the increasing competition of adults, the increasing number of strangers in a massive, increasingly disorganized population at last brings on a state of exhaustion both psychological and physiological. It is as if the cycle's last winter with its normal hardships sets the stage for the entrance of the last straw. And that last straw comes with the sexual demands of the spring. Everybody drops dead.

Whether or not the hypothesis is correct remains still unproved. The notion that the mad March hare perishes at last from love, romantic though it may be, comes from one of our most skillful endocrinologists. More significant, however, than the disagreeable fate of the snowshoe hare was the introduction by such students as J. J. Christian and David E. Davis of the physiological consequences of social stress in high-density populations. Further evidence from the field emphasized the lethal relationship. Most studies had been made of rodents, particularly susceptible to population crashes. But the shrew, studied in Manitoba tamarack bogs, is an insectivore like the mole. During a population explosion in 1957 the excitability of animals was such that even early in the eruption they lived only four days in captivity, though, like the hare, they offer no normal captive problem. By autumn, and the peak of the explosion, they lived only eight hours. By then the average number of embryos carried by a pregnant female had decreased from seven to three. But the uncommon contribution of the shrew study was what happened to space. Population increased from less than one per acre to ten. And in the masked shrew, the species most affected by the explosion and crash, there was no increase in overlapping of territories. They remained defended, and shrank and shrank with ever more pressure on proprietors.

The increasing stress placed on an exploding population could not be better illustrated. And now the attention of science, with ample field material available, was shifting to the laboratory. And a single inspired experiment, confirmed and reconfirmed, has been enough to finish the notion that birth control violates natural law.

The house mouse is territorial, and the female under conditions of normal density encounters no strange males. The experiment, which exhibited what later became known as the "Bruce effect," was first conducted in Britain. A female mouse was impregnated by a stud male. If within four days she was mounted by a strange male, she aborted. The implication was that of a morality in mice previously unsuspected. But the investigation went further. If the impregnated female even saw a strange male within four days, the chances were fifty-fifty that pregnancy would be terminated. The final experiment -- of utmost significance to population dynamics -- demonstrated that the same failure of pregnancy would come about if she were placed in a cage where a strange male had been and she merely smelled his recent presence.

The experiment had been conducted under most elegant conditions, with ample numbers of subjects and ample controls who, sniffing no strange males, proceeded on with their normal pregnancies. Even so, stunned biologists suspected that something must be wrong and set up new experiments. Bruce had used an albino strain of laboratory mice, and such inbred creatures frequently yield untrustworthy conclusions. And so another investigator set up the same experiment with wild deermice. The results were the same. Physiologists demonstrated the cause: It is the smell, in all situations. The odor of the strange male frees the fertilized egg from implantation.

A last experiment performed at Oxford, and published in 1968, has shown what a powerful mechanism is the Bruce effect, and how widespread it must be in the control of animal numbers. Mice are known as spontaneous ovulators; that is, like most mammals, the female ovulates at regular intervals when fertilization must take place. But there are animals like the vole who are induced ovulators. Copulation releases the ovum to descend and meet the sperm already waiting. And so twenty female meadow voles were mated and permitted to remain with their males. Sixteen produced litters. But another twenty, after mating, were exposed to strange males. Only five produced litters.

The Bruce effect affirms natural birth control in its purest form. An overcrowded population, introducing strange males to the vicinity of a pregnant female, produces immediate abortion. In all probability, comparable effects of which we are yet unaware explain in many species, perhaps even the elephant, the reduction of embryos. But the simple effect of stress due to density cannot alone be responsible for the control of numbers.

A frequent observation has been the variation of response to growing density by different groups of quite the same creature, living under quite the same conditions. While all at some point must reach a point of reproductive breakdown, levels of tolerance may differ widely. It is as if the populations differed "temperamentally," to use Charles Southwick's word. Aggression may increase rapidly or slowly. Mother-infant relations may disintegrate with little increase of stress, or remain respectable at a much higher level of crowding. And the difference will probably be due to the presence or absence of a very strong alpha in a given group.

The relation of rank to stress has its grim side. The over-dominated animal may with small ado lie down and die. It has happened to cockroaches that the badly beaten animal, un-wounded, has died apparently of nothing but discouragement. Rats introduced to established groups suffer persecution and may die within days. In a Glasgow laboratory a rat died after ninety minutes of persecution. He had no significant wound nor had he suffered the least internal injury. He died of stress.

We believe that subordinated animals experience enlargement of the adrenal gland, and under the pressure of sufficient stress may, through adrenal exhaustion, sink into apathy or death. But a curious quality of the alpha is his relative invulnerability. We know that the true alpha male is born, not made, and perhaps it is a portion of his genetic distinction that he endures stressful situations with a glandular equanimity greater than others. The same may be true of the alpha female in those species where female rank orders exist. In Australian experiments Myers has shown that among rabbits subjected to density pressures it is the low-ranking female who suffers the greatest fetus mortality. We may speculate, then, that the "temperament" of a population may well be determined by the random incidence or absence of a powerful alpha, male or female, whose very presence acts to forestall the disintegration of social organization.

The relative immunity of the alpha and vulnerability of the omega was reported as early as 1952 by John Calhoun in his Maryland experiment with rats, and is suggested as late as 1968 in a study of men. In that year our American journal Science published a medical study of all 270,000 male employes of the Bell System Operating Companies, the telephone organization that in the United States is a near-monopoly. The mammoth investigation linked educational background, job achievement, and incidence of coronary heart disease. No credo could be more widely accepted than the belief that it is the striving, the intense competition, and the responsibilities of high achievement that in American life curtail men's lives. No credo, as it turned out, could be more false.

The Bell System offers, like a perfectly arranged laboratory condition, a single controlled environment. Operating units whether in Georgia or New York State have similar structures, fulfill similar functions, provide similar jobs. All is directed by a single top-management policy with the same system of pensions and security, insurance and medical practices, and, perhaps most important, record-keeping. And the 270,000 histories provide a sample so large that even small variations from the expectable would have statistical significance. The variations were not small.

Reading from bottom to top in the telephone company's pecking order, we find that workmen contract coronaries at the rate of 4.33 per thousand per year. Their immediate superiors, the foremen, have it slightly worse, 4.52. But supervisors and local area managers drop to 3.91. Then comes a bigger drop. General area managers have a mere 8.85. We then come to the high competitors, the high achievers, the high executives. Coro-naries occur at a rate of 1.85, about 40 percent of the level of workmen. And while we may say that many a coronary customer could have been eliminated before reaching the alpha rank, we must also reckon that the high executives are older.

There will be no problem of interpretation for those schooled in the population dynamics of animal groups. Certain environmental influences undoubtedly made a contribution. The study revealed that college men are a far better risk than non-college and one may fairly suspect the influence of better environmental backgrounds. But the investigators pointed out that the single worst record was made by college men who rose no higher than foremen, while non-college men who rose to the top shared the relative immunity of their fellow executives. The report ended up puzzled, but admitting that something biological must be going on.

Something biological was most distinctly going on. If man is an evolved animal, then the natural histories of alpha monkeys, of alpha rabbits, of alpha antelopes, of alpha fish must provide some hints about the natural endowments and deficiencies of the alphas and omegas among us.

Had Mai thus been right, and could food supply be demonstrated as the literal limitation on animal numbers, then we might reasonably interpret contraception as a violation of natural law. But in strange concord both Malthus and Paul VI were wrong. Throughout animal species self-regulatory mechanisms provide that population numbers will never challenge the normal carrying capacity of the physical environment.

It is an error to draw a clean line between the learned and the innate. Quite obviously the lion cub through unpleasant experience must learn to obey a law of subordinance which in itself is an innate social disposition in the species. Quite obviously the herring-gull chick, in one of Tinbergen's studies, must learn the territorial boundaries of its parents if it is not to stray too far and get pecked to death. Learned elements enter into almost all animal arrangements, and so to varying degree we may regard them as sub-cultural, just as Wynne-Edwards' conventional prizes are in part innate, in part traditional and learned. But in that most cultural of species, man, for whom tradition has so widely replaced patterns of innate behavioral or physiological command, contraception has become a cultural substitute for behavior that would otherwise have come so naturally.

We may regard it as a pity, perhaps, that our young females, unlike the lapwing, are sexually responsive to unpropertied males. We may sigh that our omega males, unlike the Uganda kob, do not cheerfully accept psychological castration. We may regard it as deplorable that in our family arrangements we do not, like the great-tit, respond to rising population by laying fewer eggs or, like the house mouse, spontaneously abort. We may with less certainty look askance at the lemming's,youth movements, under the stress of intolerable numbers, conducting suicidal marches, or at the snowshoe hare dropping dead; for we may just possibly resort to such lugubrious impulses ourselves one day.

However we may regard in human terms the gradual loss of such innate mechanisms, we cannot blame that loss with entire conviction on the mid-Pleistocene expansion of the human brain. Without any doubt the rapid enlargement of our cortical equipment exerted increasing inhibition on old forms of compulsive behavior. Even so, in our more primitive days we stayed with natural law and substituted social traditions for previously natural processes.

The American ecologist J. B. Birdsell has shown that by natural increase of numbers the aborigine would have reached the food limitations of Australia in two thousand years. But he was there far longer, and he never came close. Disease, territorial spacing of groups, tribal warfare may have made contributions. But the principal factor of population control was infanticide. The evidence is as conclusive in the Eskimo, observed before modern influences had modified his ways, as in the Australian aborigine. Both were hunting peoples with a pressing need for actiye males. In both, the proportion of young males to young females was approximately 150 to 100. Girl babies had been the chief object of destruction.

When in 1922 Carr-Saunders considered the population problem, he was unaware of the long evolutionary history of the animal control of numbers. His concern was with primitive peoples, and his assumption was that population control had begun in the Stone Age. His comprehensive review of almost all then known about primitive peoples led to his thesis of "optimum numbers." Within every group there is a number well under any threat by starvation, yet sufficient to gain a maximum yield from the environment. The number is sustained by varying traditions -- by infanticide or compulsory abortion, by cannibalism, head-hunting, human sacrifice, ritual murder, by tabus against incest, or against intercourse during the period of lactation. The environment is held to a constant size either through outright territorial defense or through traditional attachment to a familiar area, formalized as in certain aborigine tribes by belief that the home grounds are inhabited by thespirits of dead ancestors. Out of his conclusions concerning optimum numbers, and anticipating Wynne-Edwards' concept of group selection, Carr-Saunders wrote:

Those groups practicing the most advantageous customs will'have an advantage in the constant struggle between adjacent groups over those that practice less advantageous customs. Few customs can be more advantageous than those which limit a group to the desirable number.

With the coming ten thousand years ago of the agricultural revolution came a wrench to all those traditional forces that had severely limited numbers in the ancient hunting bands. Numbers of people were in demand. Yet even in a modern farming tribe one finds customs specifically regulating sexual and reproductive behavior. Jomo Kenyatta needs no introduction to the contemporary citizen. Few, however, are aware that his Facing Mount Kenya, written when he was a student at London University, is one of the most perfect monographs in the literature of ethnology. As a westernized mind, he brought scientific discipline to his subject. But as that rare anthropologist, a member of the tribe he describes, he brought the intimacy of birth and young experience to his analysis. He confirms population dispersal through territoriality with his comments on land tenure: that while the Kikuyu defended their country collectively, "the fact remained that every inch of the Kikuyu territory had its owner, with the boundary properly fixed arid everyone respecting his neighbor's." He considers customs of division of labor, and of education. But nowhere is there a passage more fascinating than his description of those traditions resolving adolescent sexual drives with limitation of young.

At the rites of puberty the male is circumcised, and the female subjected to clitoridectomy, thus reducing her capacity for sexual excitement. Until puberty, masturbation is accepted as a normal boyish practice, and, while indecent in the presence of elders, within an age group it may even be a subject for competition. After initiation, however, masturbation is regarded as babyish. Now the custom of ngwecko takes over, a restricted form of intercourse which Kenyatta describes "as a sacred act, and one which must be done in a systematic, well-organized manner." Ngwecko takes place in a special hut, the thingira, a rendezvous for the boys of an age group which girls may visit at any time. Here they eat and drink, and if the boys are in the majority, then the girl may choose her companion, although it is considered selfish for a girl always to choose her most intimate friends. When partners have been arranged, the boy strips, but the girl retains her mwengo, a soft little leather apron, which she pulls carefully between her thighs. Normally during the ngwecko the partners experience sexual relief, though since the girl has been circumcised she may not have equal necessity. What is quite tabu is disturbance of her apron. Any accident of conception is severely punished by tribal law, and if in later years the girl approaching marriage proves not to be a virgin, then her value is drastically reduced.

From Kenyatta's account we may see how finely balanced are those Kikuyu traditions which, accepting human sexuality, reduce the consequence of unwanted young. Yet with the breakdown of tribal discipline in our time must come the breakdown of such customs and a cultural degeneration leading to the population explosion.

In a sense it was not the eighteenth century's industrial revolution but the simultaneous cultural triumph of humanism that most effectively destroyed the older cultural institutions which, with small sentimentality, had replaced the still earlier biological institutions. Humanism's respect for the dignity of man, and its regard for every human life as sacred, while among the most powerful forces ever to advance the welfare of men along certain fronts, had ambiguous consequences on others.

Throughout a large world of primitive societies missionaries and colonial masters reacted with equivalent horror to such institutions as cannibalism, head-hunting, and human sacrifice. Tribal warfare, particularly in Africa, was put down. Infanticide was discouraged, at least within the limits of administrative process and missionary persuasion. While the destruction of twins, a custom throughout all of black Africa which effectively reduces the breeding population by 2.5 percent, has through parental cunning evaded authority even to this day; still almost all tribal ways affronting the humanist standard were reduced but not replaced. When I found myself in Kenya in 1955 a terrified observer of the Mau Mau rising, I came reluctantly to accept a Kikuyu fact of life. While all the world was aware of Kikuyu grievance concerning land, quite unreported -- perhaps because it was news unfit to print -- was Kikuyu anger at British efforts to suppress clitoridectomy.

Perhaps humanism's supreme triumph has been its transfer of guilt as a sense of sin against God to a sense of sin again fellow man. But again the consequences have been ambiguous. With the advent of modern medicine and biochemistry our regard for every human life as sacred received most miraculous tools. The rate of infant mortality dropped like a rock in a well. Life was so prolonged that a new class of senior citizen came into being. Breeding populations in the more advanced countries were now little reduced by the death of young mothers in childbirth. Strangely enough, with modern nutrition in the same countries the onset of menstruation and fecundity dropped three years in less than a century. Not at all strangely, however, the abortionist was condemned to surgery's red-light district. And driven on by our sacred mission, through mass-produced drugs and insecticides we extended the new breeding potential to all peoples, advanced or otherwise.

Religions are rarely humane, and certainly thus far humanism has been no exception. The guilt of the humanist in his preoccupation with the numbers game has been his sacrifice of human quality for human quantity. Life must be prolonged, whatever agony it presents to the dying. A child defective physically or mentally must somehow be saved sufficiently to join the breeding population. To restrict the reproductive rights of the genetically afflicted would be an act of discrimination. Not impossibly a sick society is one preoccupied by the fate of the sick, not the well.

We shall find out one day if, as many biologists fear, over-protection of the human being, like underpredation in the reindeer herd on St. Paul's Island, will produce a genetic collapse in those very populations most addicted to the compassionate way. If so, it will be an appropriate biological conclusion to a misapplied philosophy. Yet I find it a conclusion too appropriate. Human arrangements are seldom so tidy.

We should look for simpler answers. There is sufficient evidence, I believe, to warrant the conclusion that Malthus was wrong and that human numbers will never reach such magnitude as to encounter the limitations of food supply. Long before such a rendezvous can take place other forces will have affected our numbers. And if we take nature as a model, then the maximum probabilities are only two. The first is birth control.

There is sufficient evidence also, I believe, to warrant the conclusion that the papal decision should not have condemned contraception as a violation of natural law. Birth control, whatever form it takes, is a cultural substitute for biological mechanisms prevalent in the natural world. As our population problem has a cultural cause, so we are provided with a cultural answer. But that answer must be mandatory. I have suggested that as a portion of the social contract the individual has no right to expect society to provide equal opportunity for more young than the group can handle. We have seen that in animal species the numbers of young are not determined by parental choice. And so we must look for means of enforced contraception, whether through taxation on surplus children, or through more severe but more democratic means such as a conception license replacing or supplementing the marriage license. Abortion should be freely available to those suffering unintended pregnancy. In international relations, of course, any material aid to peoples who through ignorance, prejudice, or political hypnosis fail to control their numbers should, I believe, be forbidden.

The program sounds more formidable than it would prove in practice. The vast majority among us accept traffic regulations without resentment because we are aware of their necessity. Conscience too has a way of internalizing what has started with external pressure, and of transferring to the voluntary what was once the compulsory. Even fashion makes its contribution, so that what is socially unacceptable becomes something that is simply not done. Most hopeful of all is the demonstrable proposition that a cultural institution, such as private property, which accords with natural law rarely fails.

We have of course an alternative to a solution both sane and humane. But the alternative, death by stress, is a messy one indeed. If we recognize that population density, not food sup ply, is the chief factor limiting animal numbers, and if we recognize also that no population increases indefinitely, then, however unattractive the alternative control may be, we must come to accept it, even to applaud it. Such a program of madness is available.

The rising rate of automobile accidents is a quite perfect example of a form of population control mathematically determined by population density. Granted that we have accepted an insane solution as preferable to a sane one, then we must see that the automobile, which strikes most heavily at the young, is indeed an excellent instrument for reducing the breeding population.

Another agency striking hard at the young is drug addiction. While we cannot as yet be sure that drugs reduce reproductive potential, still we should be wise to gamble that they do, and to offer every encouragement to widespread addiction in the young.

The trouble with cardiac and other stress diseases is that they tend to reduce numbers in those who have passed the breeding age. Even so, we know that the omega is far more susceptible than the alpha. We should therefore encourage in business, for example, all those tendencies toward mergers and ever magnifying organizations that reduce in number the immune alpha and infinitely expand the ranks of the omega.

If life in the megalopolis discourages large families, then perhaps by discriminatory taxation falling most heavily on real estate we might reverse the flight to the suburbs and drive middle-class families back to the unpleasantness of urban reproduction. We should have nothing to lose by such a move, in any case, since further concentrations of city life must produce more stress, more broken marriages, more impotency due to acute alcoholism, more corpses, victims of crime in the streets, and more couples living together in unreproductive sin.

Homosexuality should not be neglected. Already it subtracts 4 or 5 percent from the American breeding population. We could do better.

Suicide too offers splendid vistas. We fall far behind such advanced peoples as the Swedes and the Swiss. Here too we could do better. Student suicide is rapidly increasing. But as stress and density close in upon us I feel a confidence -- or perhaps it iS(no more than patriotism -- that we Americans will catch up, and that suicide particularly in the young and the discouraged will make a significant reduction in our breeding numbers.

What at all times we must keep brightly in mind as, like thoughtfully mad March hares, we inspect the real possibilities of death by stress, is that while any reduction in numbers is a gain, significant reduction can only be accomplished in the young breeding group. The reader may wonder, with such an admonition, why I have so ignored war as an instrument. But war, in my opinion, has seen its best days. Its growing unpopularity with those who must fight it may turn out to be a passing whim. More serious is war's increasing preoccupation with the wastage of expensive machinery rather than with the traditional wastage of inexpensive men. Wars simply do not kill enough people. A nuclear entertainment would of course leave us with no population problem at all. But even as highly publicized a war as that in Vietnam has failed throughout its entire course to kill as many Americans as that magnificent engine of destruction, the automobile, kills in a normal year.

We must look to more imaginative agencies than war to dispose of the immense numbers who must someday die of stress. And I am sure that some future survey of likely instruments will reveal lethal conclusions of a wonder that the imagination cannot glimpse today. When our population has again doubled, when not a water supply remains unpolluted, when the traffic jams of tomorrow make today's seem memories of the open road, when civil disorder has permanently replaced war as a form of organized violence, when the air of the city can no longer be breathed and the countryside has vanished, when crime has become such that no citizen goes unarmed, when indigestion becomes a meal's final course and varieties of rage and frustration remain the only emotions man or woman can know, then perhaps, if we are young, we shall comprehend the lemming.

But of course future times of such stressful wonder may never come to be. Somewhere along the road we may have chosen compulsory contraception. And yet no one can make a sure prediction. Homo sapiens, that creature mad beyond the craziest of hares, lunatic beyond all lemmings, may go to the end of the road with no impulse more logical than to discover what lies there. How high is the mountain, how profound the stream? Which in the end will bend the ultimately defeated I knee, we or our world? Shall we embrace the logic of limited numbers, acceptable to elephants and mice, or shall we mount the hilltop and defy the winds?

One cannot say. The tragedy and the magnificence of Homo sapiens together rise from the same smoky truth that we alone among animal species refuse to listen to reason.