2. The Accident of the Night

Diversity is the material of evolution, since it is from a diversity of beings that natural selection makes its choice. Our genetic endowment differs, as must differ our innate capacity to challenge or adapt to our environment. And no step in the development of life has so contributed to diversity as that reproduction which comes as a consequence of the sexual embrace. The subject of inequality may be unfashionable. But so then was the subject of sexuality itself in Victorian times. If we have today transferred our taboos of discussion from sex to its consequences, then perhaps the progression has come naturally to the puritan mind.

The lower the organism, the less is the distinction of individual identity and the slower the rate of evolutionary advance. As we turn our exploratory steps back through the subdued passages of time, pressing through curtain after fading curtain into the shadowy chambers of life's early mansions, we come to those once-living beings who existed before the coming of sex. The earliest we know left their fossil souvenirs in southern Africa's rocks just over three billion years ago. Life of a sort must have had its beginnings not too long after the formation of the earth itself. Our earliest ancestors have comparable descendants in such durable beings as the amoeba who discovered a way of life so successful that they will be with us always.

Diversity developed in those times that we call Pre-Cambrian, but it was not as we know it in higher organisms. Reproduction took place through division, so that mother and daughter cells contained precisely the same genetic material. A clone would develop -- an aggregation of single-celled creatures or perhaps, as in algae, a chain of connected cells -- and since all members were descended by division from a common ancestral cell, so all were constructed from the same genetic stuff. Change could take place through the random, infrequent action of mutation when some accidental outward force replaced an old gene with one of novel yet workable order. And diversity could come about when clones thus equipped with novel capacities could adapt to novel environments. Perhaps other means of change which we do not quite understand came about, and so other paths to diversity. We may be sure only that change on the whole was slow, and diversity slight.

Our knowledge of Pre-Cambrian times -- the ages before the coming of hard-bodied creatures who could leave clean fossil records for the future -- has been growing rapidly in recent years but is still of small order. We cannot be sure, for example, just when the first glimmerings of sexual reproduction made their entry into our evolving way. It may be longer ago than we know. But by half a billion years ago sexual reproduction had replaced cellular division as the fashionable means of begetting offspring. Many a conservative organism, while tentatively experimenting with the new way, still clung to the old. But the union of two individuals in contrast to the splitting of one brought mathematical possibilities of diversity to the gamble of survival so decisive as to sweep the living world in behalf of sex.

The American geneticist Sewall Wright showed that an unfavorable change of environment would destroy an entire clone of identical members; but its effect on a population of varying individuals would be to destroy only those least capable of adaptation, while the remainder survived. Species of protozoa and rotifers have been reported that cling to cellular division so long as conditions are favorable, but turn to sexual reproduction when times become hard. The Pre-Cambrian world of backwater slimes, therefore, was one in which offspring tended to be identical and of equal merit. But for the last half-billion years of sexual ascendancy our young have been various, and of unequal potential. And this world of diversity is the world we know.

Such a world was the object of Charles Darwin's observations, as it was of his contemporary Alfred Russel Wallace. How total is the variation of individuals within a species might receive adequate testimony today from the Federal Bureau of Investigation, since no two human beings, not even identical twins, have the same fingerprints. Neither Darwin nor Wallace needed the FBI to inform them, however, concerning a truth observable by any naturalist. But it was Darwin who first suffered the inspiration that was to lead to Origin of Species. He was aware of Thomas Malthus' famous work, An Essay on the Principle of Population, in which the proposition was advanced that since the number of young in any population must proceed far faster than available food supply, then environmental resource must place a constant check on numbers. As early as 1839, shortly after his return from the cruise of H.M.S. Beagle, Darwin put two and two together: varying individuals encountering limited food supply must compete, the most successful and best adapted to their environment thus leaving more offspring for the next generation. This of course was natural selection, among the farther leaps in the history of human thought.

Darwin was not only a perfectionist; he was a procrastinator. To the exasperation of his friends, Origin of Species lay still unfinished nineteen years later. Wallace meanwhile was working in the Far East. And in February 1858, bedded by fever in the Moluccas, he seems to have had nothing better to do than think. He too had read Malthus years before, but he was unaware of Darwin's long preoccupation with natural selection. Now, pondering the question of differential mortality, it came to him too that those animals best suited by chance to meet the demands of an environment would be those to survive. "Then it suddenly flashed upon me that this self-acting process would necessarily improve the race, because in every generation the inferior would inevitably be killed off and the superior would remain -- that is, the fittest would survive."

On the following three evenings Wallace wrote his essay and with a flourish of excitement sent it off to Darwin in England. Transportation was slow in those days. Darwin received it on June 18, and the sky promptly fell down. For years intimate friends had warned him that just such a catastrophe might take place. Now the same friends, including the greatest geologist of the time, Sir Charles Lyell, came to the rescue. They insisted that one man's devoted labors of almost twenty years must not be destroyed by the priority of another man's flash of inspiration. Darwin must as rapidly as possible draw extracts from his manuscript and present his view.

On the historic if neglected night of July l, 1858, both papers were presented to a meeting of the Linnaean Society in London. Thomas Bell, president of the society, was in the chair, and the papers, according to custom, were read by the secretary. Darwin was at his home in the country, Wallace was still in the Far East. No discussion followed the reading. For some the subject may have been too new to grasp, for others too traumatic. The president seems to have suffered no shock, for he could later report that "the year has not, indeed, been marked by any striking discoveries which at once revolutionize, so to speak, the department of science on which they bear." But rumors of impending crisis spread through scientific and religious circles.

Wallace withdrew all claims to scientific priority, and almost half a century later recalled, "The one great result which I claim for my paper of 1858 is that it compelled Darwin to write and publish his Origin of Species." This it did. The following year, on November 24, 1859, the first edition was published and sold out in a single day. And the fires of controversy, ignited by Wallace, have not yet been extinguished.

Natural selection in time took its proper place not only in biology but in any study of life's processes. It offended many in Darwin's day, as its implications offend many in ours. Yet its prime offense is remarkable. Darwin looked to Malthus when he wrote that "the amount of food for each species must, on an average, be constant whereas the increase of all organisms tends to be geometrical." Few objected to the harsh rule of starvation. In our contemporary concern with the population explosion we witness few doubts cast on the proposition that human numbers will expand until meeting the limitation of food supply.

That Malthus was almost surely wrong will concern us heavily in a later chapter. It was not, however, the role of starvation but the role of accident that repelled our thoughts. It offended the religious convictions of the nineteenth century as it offends the social convictions of the twentieth. Perhaps something in our nature finds unendurable the thought that we are accidents of random creation, not portions of some grand design. And while natural selection is in itself a design of magnificent order, perhaps a cowardice within us shrinks from the chore of eternally creating order from eternally re-created disorder. It is all too much.

Yet the random and inevitable variation of beings underlies the theory of evolution as hidden mountains and abysses underlie the seas. Darwin could not explain diversity; he could only observe it. And since he believed that the variations of parents should blend in their offspring, how variation persists became the final puzzlement and frustration of his career. He could not know that only six years after the publication of Origin of Species an Augustinian monk, Gregor Mendel, experimenting with common peas which he grew in his monastery garden in Austria, had presented his conclusions to the local Brunn Society for the Study of Natural Science. The Society was polite enough about it and printed his report in their obscure Proceedings. But they probably regarded the monk as mad. When two years later he was appointed abbot of his monastery, Mendel, like a stray scientific cat, vanished from the world's' back doorstep as unnoticed as when he had arrived.

While Mendel was precise enough in his description of genes -- he called them elements -- and of their working in pairs received each from a parent, and of the continued shuffling and reshuffling of these unblending determinants through inheritance, I doubt very much that when he died he knew quite what he had discovered. But the mystery of conception's accident awaited only its resolute detectives. In 1900, as if to outdo the coincidence of 1858, no less than three continental scientists came upon the forgotten paper at once. With the rebirth of Mendel came the birth of genetics. And the accouchement occurred none too soon.

By the end of the nineteenth century the theory of evolution had fallen on evil days. Too many sociologists, following Herbert Spencer's early intimations, transported Darwin's struggle for existence into the human arena, there, in the name of social Darwinism, to consecrate as natural law the more brutal consequences of human might. And too many zoologists, unable to close the gaps in Darwin's thinking, had turned their exclusive attention to the endless chores of species classification. Sir Julian Huxley has described this period with the magical line: "Intoxicated with such earlier successes of evolutionary phylogeny, tliey proceeded (like some Forestry Commission of science) to plant wildernesses of family trees over the beauty-spots of biology."

With the resurrection of Mendel, life flowed in biology as never before. The theory of evolution began its long move from the status of a persuasive speculation toward the structure of a modern science. Zoologists turned from classifying bird skins in unventilated museums to planting primroses, a healthier devotion. Experiments proliferated. In America, Thomas Hunt Morgan established the cult of the fruit fly, an unattractive beast but worthy of a geneticist's veneration, since it grows to reproductive maturity in ten days. With every experiment, however, complexities developed, contradictions appeared. Then about 1930 the three wise men of population genetics -- Fisher, Haldane, and Wright -- through mathematical complexity brought mathematical order to the problems of heredity. And population genetics -- the heriditary potential of an interbreeding group -- provided the solid foundation for modern evolutionary theory.

It has been a long road from a monastery garden to the still later demonstration of the double helix of the DNA molecule. Yet as Charles Darwin, despite the dubious validity of Malthus and his own inability to explain variation, had nonetheless been right about natural selection, so Gregor Mendel out of unaccountable luck had chosen characters in his garden peas that could reasonably demonstrate his laws. Had he chosen others of more complex genetic determination -- a character produced by several genes acting in concert, or several characters influenced by a single gene -- his calculations would have failed, his experiments would have been abandoned, and we should have had no Mendel to resurrect. Yet despite the simplicities of its one-gene-one-consequence origins (what Huxley with his gift for phrases has called "billiard-ball genetics"), and despite the complexities that later calculations would contribute, Mendelian law explained variation in living beings, and we need look no deeper.

The principle is that of recombination. In the action ot sexual conception, two parents with different combinations of paired genes contribute half of the resources of each to what! becomes a new genetic proposal. The fertilized egg, this randomly determined recombination of parental possibilities, is the accident of the night.

Theodosius Dobzhansky, an inheritor of Morgan's fruit flies and today, philosophically, the most equalitarian of geneticists, has described the theoretical Mendelian consequences this way: If the parents have 5 pairs of genes, then there are 32 possible recombinations. If they have 20 pairs, then the possibilities amount to 1,048,576. If they have 32 pairs, then over two billion new opportunities confront the offspring. Yet the simplest of animals has genes in the hundreds, and the human being has far over ten thousand. We have no comprehensible mathematics to describe the chances against recombination producing two identical human beings.

We are speaking of theoretical possibilities according to Mendelian law. There are practical limitations. Genes tend to recombine in groups, reducing the chances. Some combinations are so far-fetched that fertilization will not even take place. The British philosopher of science, L. L. Whyte, has described this as internal selection, a process in which the genes, like members of a conservative club, blackball the entry of a fellow too strange. And there is a broad restriction brought about by evolution itself to reduce the waste of accident by limiting the genetic disparity of parents. We shall come back to this later.

Granting all the reductions of theoretical possibility, we must remember that we are reducing odds beyond comprehension to odds still lying beyond comprehension. Let us consider brothers and sisters, the offspring of a single pair of adults. We may, of course, find identical twins, conceived by the union of a single egg with a single sperm. Otherwise, the chance is one in a trillion that any two siblings will be genetically alike.

The accident of the night, which determines in such large part what you or I will be, prohibits identicality. Every month a new egg slips into the female womb, and no two eggs are alike. At the climax of the sexual embrace the male ejects sperm beyond counting into the female genital tract. No two are alike, and in the first trial of natural selection there is no determination as to which sperm will have the superior luck or vigor to win the race to the egg and fertilize it. The magnitude of the competition is such that although only one human being will be the normal consequence of the achievement, still a single teaspoonful of male sperm would be sufficient to father every member of Homo sapiens alive today, and all would be different.

Every being conceived by sexual recombination is a genetic accident. Every individual being is thus a pioneer, a biological adventure. No one quite like you can exist in your species. Common heredity may provide a common disposition among contemporaries, or a limited likeness between ancestor and descendant. But the strategy of sex denies the prison of identicality. If you were not created equal, you were yet created free.

Henry Allen Moe was for decades director of America's Guggenheim Foundation. I met him for the first time over thirty years ago, when I was a proud possessor of a Fellowship, and I thought that I had never met so gentle, so perceptive, so sensitive a man. A time came when Moe retired to become president of the American Philosophical Society. And a night came, in 1965, when he rose to address Washington's Cosmos Club in response to its award for his contribution to science, literature, and the arts in America. The address might have been delivered from history's most thundering barricade. Few Americans but this gentle, sensitive, perceptive man could have had the courage to pronounce such heresies. In part he said:

In his History of English Law, F. W. Maitland, the most lucid and far-sighted of English legal historians, quotes a text from St. Paul: "It is better to marry than burn." And then Maitland dares to comment, on a text from Scripture, mind you: "Few texts have done more harm than this."

Similarly, from the scriptures of the United States, I shall quote Thomas Jefferson's "All men are created equal" and shall dare to comment that few texts have required more explanation than this. . . . There is no doubt that, at the time it was said, the saying that "All men are created equal" needed to be said, and especially that it needed to be said in the context of the Declaration of Independence. Nevertheless, I shall dare to say flatly now that few unqualified statements have done more harm than this. . . . To say that all men are created equal is -- as everybody knows and nobody doubts nowadays, but nobody says -- the apotheosis of error.

In his published address Moe points out in a footnote that Jefferson's phrase, which was to become the holy unity of the American secular religion, was made in 1776; and that only thirteen years later, in the Declaration of the Rights of Man, even French revolutionary thought had backed away sufficiently to state: "Men are born equal and remain free and equal in rights."

The French declaration, while false in its premise, left room for maneuver. Jefferson's phrase, presented as a self-evident truth, was false and left none. And so for almost two centuries American thought, with increasing agony and distortion, has been nailed to a cross of revolutionary propaganda, a passing political slogan which its sophisticated author would have been the last to take seriously. Fundamentalist we may no longer be in our religious contemplations. Yet contemporary social theorists can yield nothing to mumbling, illiterate, forgotten multitudes in their cringing devotions to antique screeds.

Sexual recombination imposes diversity on living beings. Evaluated by environment, that diversity becomes inequality.

I have described each differing recombination as a genetic proposal. It is the offering of a new, unique being to the test of development in a particular environment. This being, this fertilized egg, this genotype as yet unaffected by dusty skies or the problem of serpents, meets its first tests in the world of the womb. Here it divides and re-divides according to the coded instructions of its genetic material. Fetal life may reveal error in the original instructions; the proposal will be withdrawn and the being aborted. But granted that development is true, and that what once was a genetic proposal has survived life's first sortings to become through birth an independent being, then already we confront superiority. The live are superior to the dead, the born to the stillborn.

Already, too, we confront the phenotype. It is a geneticist's term of salient importance. The genotype is that most independent of beings, the accidental egg, owing allegiance to none but the genetic memories that have combined to create it. The phenotype is the egg plus experience. The womb itself may have failed to protect the developing fetus from experience: undernourishment, drugs, disease, accident, stress or perhaps alcoholism in the mother. Even in the womb, environment will have imposed certain alterations on genetic destiny. The newborn infant is already a phenotype, a genotype modified by environment. And as a world of diverse experience opens up before the newly independent being, so will the interactions of genetic determination and environmental persuasion bring new courses, new colors to the phenomenon of individual existence.

The accident of conception commands that no two beings be genetically identical; equally so, the accidents of existence command that no two lives proceed along identical ways. The diversity of our beginnings is compounded by the diversity of our histories. But there is a difference of large order: whereas randomness dictates the accident of our origins, nothing like randomness dominates the paths, however various, that our lives will pursue. Any population of men or deermice, of vervet monkeys or herring gulls, faces in a state of nature approximately the same environment presenting approximately the same demands, the same hazards, the same opportunities. A diversity of beings encounters a singleness of being. Disorder encounters order.

It is this singleness of the playing field that reveals the inequality of the players. To a degree, the environment promotes equality in the elimination of hopeless variants. If you are a young zebra who cannot keep up with your family, then the lion will get you. If you are an ailing caribou, then you belong to the wolf. All survivors have something in common: that they have survived. To a degree, also, environment promotes equality in its shaping of phenotypes. Various though we may be in our beginnings, we learn our lessons from the same master. Yet the shaping of muscles and manners and mind to uniform environmental demands can go only so far. Experience may fulfill or reduce the potentialities of the accidental egg, but it cannot create what was never there. And we cannot leave to our descendants the mind or muscle we have acquired in the exercises of survival; every egg comes fresh.

That acquired characteristics may be inherited, as most of us know, was the interpretation given to evolution by the French naturalist Lamarck. In Darwin's inability to explain variation he was frequently tempted to embrace the idea, yet, fortunately, for the most part resisted it. Lamarckism has been disproved in the laboratory over and over again. Generations of mice have surrendered their tails, only to grow new ones. It has been acidly observed that the sacrifice of mouse tails has been unnecessary since for thousands of years the Jewish people have been cutting off foreskins without noticeable effect on their male offspring. Even so, it is today a portion of the naivete of Marxism that a new kind of social system will produce, permanently, a new kind of man. It is Lamarckism, and Lysenko was his Soviet prophet, installed with halo and power by Stalin. The power banished Western genetics from Soviet science, as it banished N. I. Vavilov, among the world's greatest geneticists, to a Siberian labor camp, where he died in 1943. Lysenko may today have vanished from Marxist power; yet his memory lingers as a portion of Soviet agricultural inadequacy. Vavilov may be dead of arguable causes; his memory fails to linger in those minds who in adolescent reverie equate Marxism with progressivism, and competition of men and ideas with the political counterrevolution.

A science as mathematically remote as genetics may become the wheel of political fortune. Yet one must admit that, were it not for a force of pervasive disposition, temporal power in all brutality might by environmental harshness reduce even the newborn, in terror, to phenotypic mediocrity. To safety, to conformity, we might flee days after birth. But it is an evolutionary impossibility described by Konrad, Lorenz in On Aggression. Whatever environment's iron hand, as Lorenz sees it, every being will challenge such rule, will seek to achieve non-identi-cality and to fulfill its diverse genetic potential through an aggressiveness inborn. The drive to fulfill oneself, to perfect if possible the genetic potential of one's unique endowment, is itself coded in our genetic instructions.

We might say, in the context of this inquiry, that aggression is the natural guarantee placed in species that disorder -- the richness of diversity generated by sexual recombination -- will not fail of development. The London psychoanalyst Anthony Storr, brilliantly expanding the Lorenz thesis in his Human Aggression, writes of children:

There is the need to cling to the mother, to be sure of her affection and support. But there is also a drive to explore and master the environment, to act independently. . . . One important function of the aggressive drive is to ensure that the individual members of a species can become sufficiently independent to fend for themselves, and thus in their time to become capable of protecting and supporting the young which they beget.

Aggression is not necessarily destructive at all. It springs from an innate tendency to grow and master life which seems to be characteristic of all living matter. Only when this life force is obstructed in its development do ingredients of anger, rage, or hate become connected with it.

Aggressiveness, we may then suggest, brings to life as its partners rebellion and competition. We need not think in terms of the Darwinian "struggle for existence," or the nineteenth century's "survival of the fittest." No such lethal stakes are involved, and Lorenz rightly points to the rarity of corpses decorating the scene of animal decision. The vindication of the individual, not the annihilation of enemies, is aggression's goal. But such aggression commands competition. I return to Storr:

The normal disposal of aggression requires opposition. The parent who is too yielding gives the child nothing to come up against, no authority against which to rebel, no justification for the innate urge towards independence. No child can test out his developing strength by swimming in treacle.

The aggression coded in our genes compels the full development of the individual, a natural necessity; and the diversity of individuals all comparably coded compels competition, without which natural selection could not take place. And, finally, the competition among fellow members of a population not only brings to maturity, for worse or better, the genetic fortune of our origins, but through endless sortings evaluates unequals in terms of environmental demand.

"Human evolution is based on injustice," wrote Sir Arthur Keith a quarter of a century ago. I rarely disagree with that most admirable of anthropologists, but Keith was wrong. The evolution of men, like the evolution of meadowlarks, is based on the recognition and adequate sorting of unequals. Injustice occurs when competition is aborted. Injustice occurs when worth fails of recognition, and the unworthy go rewarded. While injustice may be regarded as a principal feature of human life, raised by human ingenuity to altitudes unknown in the world of the animal, it is not evolution. In terms of natural selection, injustice is maladaptive.

I have asserted that equality among sexually reproducing beings is a natural impossibility. I may assert with comparable force that in the history of vertebrate life, which has brought man to ascendancy, equality of opportunity is a natural law. It is opportunity suppressed not just by the totalitarian, but by the equalitarian as well.

Two major experiments have enlightened evolution throughout the past half-billion years. The first has been that of the insects and such sea-going cousins as the lobsters, all of whom have soft bodies with their hard parts on the surface. The second has concerned the vertebrates, the anatomical reverse, whose soft bodies surround hard inner backbonds. Sometimes we digressed to form hard outer armor, like the turtle and the armadillo. But in the backbone resides our strength, from earliest fish to most recent lion or monkey or bird.

While the vertebrates came to dominate the living world, their triumph is less than clean-cut. According to Simpson, of the million-odd species of successful creatures alive today, only forty thousand are vertebrate. The insects may, at some moment of future disaster, survive us all. But the experiment has tested behavioral as well as anatomical divergence. The insect, by and large, has depended for behavioral guidance on programmed instinct, the vertebrate on programmed learning. And the final returns on the success of intelligence have not yet been counted.

The insect, of course, is far from being entirely dependent on those behavioral instructions coded into its genetic beginnings. The Dutch ethologist G. P. Baerends once demonstrated the awesome capacities of the digger wasp to learn and remember. The female normally digs a hole, kills or paralyzes caterpillars, buries them and lays eggs on them. She then proceeds to dig second and third holes, where she repeats the process. In the meanwhile the eggs in the first hole have hatched and the young have been busy consuming the caterpillars. She opens each hole, restocks it.

One might interpret the mother digger-wasp's actions, at this point, as wholly instinctive. But Baerends found that she opened all three holes the first thing in the morning before proceeding on her caterpillar-catching rounds. And so before she appeared he robbed from one hole, added to another. What seemed to be demanded normally was six or seven caterpillars. And so to those holes he had robbed she brought more, to those to which he had made a contribution she brought less. Not only was she able to discriminate between the numbers demanded by her early-morning appraisal, but through as much as fifteen hours of hunting she remembered the differing demands of her differing nests.

Niko Tinbergen, Oxford's pioneer ethologist, has commented that, high though this order of learning may be, it is localized and applies only to a single, instinctive activity. We cannot say that the digger wasp has learned to count. What she has done is to complete from experience a remarkably demanding instinctive program. And this specialization of capacity may be the basis for caste in social insects.

As vertebrates have developed our societies, so insects have theirs. Since the turn of the century entomologists have revealed the wonders of social organization in the ant, the termite, the bee. Most famous of all, perhaps, has been Karl von Frisch's investigations of honeybee communication through dances. And in all such societies the member is born to his role, or succession of roles. The presence of castes has made known to us just how ancient was the evolution of the earliest societies. Recently in New Jersey a piece of amber was found and its age established as 100 million years. Within the amber, sealed as if for exhibition on Judgment Day, was a worker ant.

The evolution of living systems governed by programmed instincts finds selective advantage for social life in specialized classes of beings, not in individuals. But the evolution of living systems based on programmed learning finds a different selective advantage in the random excellence of individuals, not the destined appointments of caste. In vertebrate societies one finds two roles biologically determined, those of male and female. Otherwise the individual is on his or her own. So rare are the exceptions that they become worthy of consideration.

The ruff is a bird whose antics I described in The Territorial Imperative. In the spring aspiring males develop in all gorgeousness a shield of feathers about the neck, from which they derive their name, of such various colors that no two birds look the same. They then adjourn to what are known along the Dutch coast as hilling grounds. Here, each on his tiny hill, they strut, gyrate, display to one another, and fight. Later the hens, known as reeves, will come for copulation. But more recent observations have revealed subtleties of behavior previously unknown.

Among the males are two classes, the territorial males, true gladiators, and satellite males. The dominant, territorial class has a ruff of lighter shades of color, linked with a highly aggressive disposition. The satellite has a darker ruff, avoids conflict, and submissively stays in the vicinity of the master in a parasitic role. Tolerated by the territorial male, the satellite is occasionally permitted a copulation or two. The conclusion of the observers has been that, like blue eyes and brown, the classes are under genetic control. The linkage of coloring and behavior is brought about by polymorphism, the geneticist's term for determination of several characters by a single pair of genes or group of genes acting together. Caste in the ruff is not directly inherited. It comes about through the usual random sexual recombination, but in every generation according to a regular mathematical proportion.

If the conclusion is correct, then the ruff exhibits the only genetically determined class system within a sex that I have ever encountered in the vertebrate world. There are examples of social determination, however, reminiscent of human affairs. These occur in related species of monkey, the Japanese and the rhesus, and may occur in more.

The Japanese monkey is the social genius of the primate family, and we shall turn to him for many later illuminations. Studied constantly by a group of Japanese scientists for many years, the monkey lives in some of the largest organized societies achieved by any primate, human or subhuman, before man began to gather in towns. In these colonies, males sort themselves out in rank orders of dominance, a state of affairs common in monkeys. Uncommon, however, is a similar order among the females. And observation indicates that unless the colony becomes too large the son of a high-ranking female has a far better than normal chance of achieving high rank among the males. Kinji Imanishi, reporting on the studies, concludes that a son who has learned to get along successfully with a highly dominant mother will have the greater success cooperating with equally dominant males.

The related rhesus monkey of India is the most studied of primates in laboratories. Thirty years ago C. R. Carpenter, the pioneer student of primates in the wild, transported a large number of animals from India to tiny Santiago Island, just off the Puerto Rico coast. The colony he established still thrives, still is studied by various observers. And here has recently been recorded behavior comparable to what Imanishi watched in Japan.

The rhesus too lives in quite large organized bands within which females have orders of dominance in relation to each other. And in most bands maturing sons of dominant females succeed rapidly in outranking many elders in the male hierarchies. But the observer Carl Koford reports an odd outcome perhaps reflecting on such arrangements as unnatural. Two princelings, having achieved high rank, shortly vanished from their hierarchies and their bands to become solitaries, later to join other bands in positions of low order. "High birth permits rapid advance in the social hierarchy, apparently, but it does not insure succession to leadership."

It is a subject about which we shall know more one day. At present, however, these are the only two vertebrate species ever to come to my attention in which social discrimination takes place. And never did exceptions so prove a rule. Equality of opportunity is a vertebrate law. The castes of sex are universal, creating the simplest expression of division of labor. But within each caste the sorting of unequals takes place in a field without fences.

Animal justice was perhaps the first natural law that civilized man began systematically to violate. Advantages of birth offer no guarantee of genetic superiority. Restrictions of caste, of class, of occupation, of poverty distort or suppress the phenotypic flowering of genetic endowment in the maturing individual. But the accident of the night, in all its rich, random resource, became in man socially aborted. There have been revolutions, it is true. But human history has far more frequently witnessed the decline of empires, the vanishment of kingdoms, the disappearance of peoples genetically exhausted through order's injustice.

We shall turn to the inequalities of populations in a moment. But first we should reflect that animal justice reflects the fairness, the freeness, and the openness of the competition of unequals. Did inequality not exist, justice would have no function. And perhaps that is why the equalitarian ideal in human life, denying the nature of man, moves so easily into the tyranny of thought and power.

What in genetics looms as the Class of 1930 -- Wright, Fisher, and Haldane -- confirmed with their mathematics the general principles of Mendelian heredity. But they did more: they established the science of population genetics. Following them came a generation of new explorers of the gene -- Dobzhansky, Ernst Caspari, C. D. Darlington, Kenneth Mather, C. H. Waddington, J. M. Thoday, many others -- leading on to the molecular explosion of James D. Watson and Francis Crick. A luminous volume for the lay reader is The Language of Life, by George and Muriel Beadle. Dr. Beadle is a Nobel Prize winner in genetics, and former president of the University of Chicago. And the first sentence of their foreword reads:

In writing about genetics for non-scientists, the gap we have to bridge is not the one that is alleged to separate C. P. Snow's much-publicized two cultures, but the one that lies between people who received their formal schooling before the mid-fifties, and those whose instruction in science has occurred since then.

Respected figures in academic life, when speaking of the natural sciences, frequently sound as if they had received no schooling at all. In all compassion we must turn from such a conclusion. It is just that they went to school too soon.

Population genetics turned biology inside out. Harvard's Ernst Mayr has written that "the replacement of typological thinking by population thinking is perhaps the greatest conceptual revolution that has taken place in biology." But the revolution, like a nuclear explosion, has produced a fall-out far beyond biology's immediate neighborhood. It has affected economics, and its onetime devotion to the typical, economic man; it must affect behaviorist psychology and its reluctance to accept human variation; it must affect this chapter and our preoccupation with the accident of the night.

Population thinking denies uniformity and looks to the range of diverse individuals within a group. The range, not the average, is the reality. Yet in his classic Mankind Evolving Dobzhansky writes: "The assumption of the psychic unity, or uniformity; of mankind is probably pivotal in the working philosophy of a majority of anthropologists, psychologists, sociologists, and not a few biologists." Such a uniformity is as impossible in mankind as is identicality in the members of a Boy Scout troop. Just as population thinking accepts range as reality, it dismisses as non-existent the "average man," a being whom no one has ever met anyway.

Population genetics was a wild child of mathematics conceived in a forest of impenetrable equations. It has emerged from that forest to invade every street corner of thought as a philosophy that speaks of probability, not certainty, of horizons, not pigeonholes, that acknowledges change and rejects the immutable and accepts disorder as the foundation of order. It is a way of thinking obviously more sophisticated than our primitive, childlike devotion to the type. We may not be equal to it. Yet population thinking is indeed an imitation of nature, a philosophy in accordance not in conflict with natural processes. And that is why it is revolutionary. The supreme contribution of twentieth-century biology may only in passing concern what men know; in final assessment it concerns how men think.

The accidental consequence of sexual recombination has been a problem to nature and not just to naturalists. So uncountable are the chances of diversity, as we have seen, that sexual union, without restriction, could have launched living beings on a voyage into chaos. And so the first of the restrictions, the isolation of species, took on the burden of containing accident within reasonable bounds. Sexual union between members of separate species normally but not always results in offspring that are infertile or of declining fertility. Through "reproductive isolating mechanisms," however, the nearly total likelihood is that such sexual union will not take place.

These isolating mechanisms, ensuring that girl dog will shun boy cat, are as varied as species themselves. Some are anatomical, such as that of the red-faced stumprtailed bear macaque, Macaca arctoides, whose penis is as improbable as his name. The bear macaque, the crab-eating macaque, and the far more numerous rhesus monkey are three closely related species of the same genus frequently living in the same area. And the species problem of the bear macaque, it seems, has been how not to get hybridized out of existence by his crowd of relatives. The solution has been anatomical, and one of rare device.

All primates, including man, have in the male a penis of much the same appearance, including the blunt, helmet-shaped glans. For a long time, however, observers of such unimaginative male decor have wondered at the iconoclastic penis of the bear macaque. Its glans penis is long, slim, tapering like an aristocratic finger. Moreover, the penal bone is at least twice as long as in other macaques. (In all human regret, it should be noted that man is one of the very few primates unaccountably denied this anatomical luxury.) The question of why the male bear macaque should have such a penis has been answered only recently by intimate investigation of the female bear macaque. Across her vagina is an obstruction effectually blocking the penis of any but her slenderly built fellows. It is a chastity belt of selective advantage to bear macaques.

Konrad Lorenz has described as lock-and-key such sexually isolating devices, but they are usually less literal in design. In northern Kenya, for example, two species of zebra sometimes form mixed herds. The common zebra of the East African grasslands, with its broad stripes, is the one familiar to visitors and has the species name of burchelli. Another species, grevyi, has much narrower stripes, lives in the arid lands to the north and sometimes in drought moves south for water. It is then that they mix. Yet no known hybrid has ever been observed, nor attempted copulation between species witnessed. The differing patterns of female rumps apparently fail as sexual releasers.

Behavioral differences may in themselves isolate species. In 1963 Bristol University's John Hurrell Crook published an elegant study of weaverbirds. They are colonial creatures inhabiting a single tree. Each male weaves a globular nest which hangs neatly from a branch, so that the tree seems to bear a crop of most remarkable fruit. The yellow weaverbird, Ploceus cucullatus, has a tendency to choose a tree near houses or villages, probably to enhance protection from such predators as the genet cat and various snakes; and so at an East African lodge you will frequently find the flurry and chatter of nearby weaverbirds an entertainment for which you are not billed. But Crook studied weaverbirds in West Africa as well, where near Lagos he found the black weaverbird, P. nigerrimus, nesting in mixed colonies with the yellow in tall oil palms.

Differences of color are perhaps enough to keep the species from crossing in such close domestic arrangement. But the sharpness of behavioral difference makes one suspect that color is not enough. Unusual in bird life, the males of both species are polygamous, building several nests before acquiring female tenants, and defending the whole space as a territory. Even in this male defense, behavior differs. The yellow advances on an intruder, lunges, then, at his boundary, sings and finishes with a deep bow. The yellow intruder does the same, advancing on the boundary, singing and ending with a bow. Here, a foot apart on a branch, like the most gallant of old-time swordsmen they exchange the thrusts of their songs, the deprecations of their bows. But occasions arise when the field of honor becomes somewhat confused, and such moments come when the black is the intruder, the yellow the defender. The black has no such song and bow in his behavioral repertory. Instead he does an agitated dance. And so at the boundary we find the yellow weaverbird singing and bowing, and the black weaverbird hopping about in his dance. Yet honor, despite differences, remains accomplished.

A comparable disparity of behavior between females of the two species may account for sexual separation. At time of courtship the yellow male hangs from one of his nests below its entrance, advertising his desirability as mate and landlord by pumping his wings. A female flies through the tree, setting off an explosion in the colony which attracts more females and more violent waves of exhibition. But there is no aggression. If she enters a nest, then the issue is settled; if she passes it, the male does not argue. In the black species, however, sexual excitement is aroused by quite other means. When the female crosses a territory, the male pursues her, kindling excitement in other males, who join the chase like Roman ragazzi in pursuit of a blonde. But if the weavers have picked the wrong female, the yellow has only to pop into the nest of a bird who has not chased her. She will be with her own kind.

One last, uneasy example should be added to the range of natural ingenuity concerning reproductive isolation. The sight of snails copulating on a lawn at night is a common observation of suburbanites. And the question might well be raised: How can two snails of differing species be aware of mistaken identity, particularly in the dark? The answer has been facilitated by a piece of equipment peculiar to the sexual life of the snail. It is called spiculum amoris, or the love-dart. It is a slender, blade-like instrument made of the same limy material as the shell. In the act of copulation one plunges his love-dart into the flesh of his partner, precipitating a peak of sexual excitement. But the response may be otherwise. If members of two related snail species, Cepaea hortensis and C. nemorai attempt copulation, then problems will arise. C. nemoralis has the larger love-dart and thrusts it more powerfully. If the partner is of the weaker species, then the frightening dart will break up the affair.

Love is not so blind. Sexual discrimination has been a product of natural selection, restricting union to those animal groups called species with sufficient genetic material in common to make probable the viability of offspring. But while any two members of a species may in theory mate and breed, in fact normal choice is more limited. Evolution has encouraged a further subdivision, the population, to provide still more ordered diversity.

As our foremost authority on species, Mayr has chosen as his favorite definition that of Sewall Wright: "Species are groups within which all subdivisions interbreed successfully to form intergrading populations wherever they come in contact, but between which there is so little interbreeding that such populations are not found." In other words, Wright accepted as the true evolutionary unit the freely interbreeding population which to a degree interbreeds with adjacent populations until one comes to the species border where no further such populations are found. In his Animal Species Mayr, like Wright, looks on the relation of populations, not individuals, as the definition of species. And so we turn to the population.

Simpson has given us the favored definition: "A population is a group of organisms, similar among themselves and dissimilar from other organisms with which they live, descended from a not remote common ancestor, living in the same general region and environment, and with a continuity of many generations through time." The American psychologist John B. Calhoun has introduced another dimension: "By a population we mean any contiguously distributed grouping of a single species which is characterized by both genetic and cultural continuity over several generations." He has added the significant comment, particularly in human terms, that the population is "the major unit in which the lives of individuals find reality." We may think in our species of nations and tribes as such major units.

For the purposes of our discussion, I believe it sufficient to describe a population as a group of beings sharing a generally common environment among whom male and female have a variable but probable opportunity of meeting, mating, and breeding; where that probability drops sharply, there is the limit of the population. Consider two African tribes like the Kikuyu and the Masai living in adjoining regions in East Africa, but separated by language, by tradition, by custom, and by the differing ways of life of farming and pastoral people. A certain interbreeding has taken place as a consequence of the Masai raiding Kikuyu villages for wives. But they are distinct populations physically and psychologically, in each of which the individual finds his major unit of reality in the tribe, not the country called Kenya. The heart of the problem of independent Africa has been that the border of the population rarely corresponds with the border of the politically created nation.

In the human species, language as a rule forms the sharpest barrier between populations, and that is why the line of language forms usually the national boundary, and why, with rare exceptions, political boundaries enclosing varying language groups tend to enclose trouble as well. But even within an interbreeding population of common language, still religion, geography, allegiances of custom or occupation, economic class, even degree of education all tend to reduce to smaller groups any high probability of meeting and mating. And so the smallest unit of truly equivalent chance is known as a deme, or isolate, and Dobzhansky has suggested that among people even today isolates number hundreds, rarely thousands. A study of marriage records in France has revealed the paradox that in the mountains such isolates average about 1,100 while in Paris, where one would expect broad mixture, they are only about 900.

Within such isolates gene flow is complete. Their existence cannot, however, be explained as a human consequence of our cultural diversity, for in animal species the isolate may be of remarkably similar size. Sage grouse in Wyoming, isolated by allegiance to a single strutting ground where all copulation takes place, number about 900. Helmut Buechner's Uganda kob, which I have described elsewhere, are likewise divided by traditional stamping grounds into reproductive groups of a 1,000 or less. George Bartholomew's study of a breeding colony of Alaska fur seals on St. Paul Island gave us 800 cows and 40 bulls. Two separated wings of Tanzania's Serengeti reserve have each about 900 elephants. Since the fluctuating members of all-male parties in the western group seem familiar with one another, we may assume that it is a reproductive unit.

Wright, Simpson, and many others are agreed that the greater the subdivision of a population into such reproductive isolates, the better is the chance for survival of the entire population. Each isolate, through generations, develops its own pool of genes of similar character in which the accident of unfavorable union is reduced to a minimum, while sufficient numbers retain sufficient diversity. A chance mutation of benevolent order will have the opportunity of spreading to all members of such a restricted group. Drift -- a gradual genetic change of no specific cause -- will through the generations lend the group a special genetic character. Whatever may be the fate of the isolate, the selective advantage for the whole population is immense. We have seen that the population, despite its mosaic of breeding groups, faces a fairly uniform environment. But as no two individuals can be quite the same, so the gene pools of no two isolates can be identical. With any change of environment -- a drying up, an invasion of predators, a change of food supply, a pestilence -- chance must surely determine that some groups will be superior to others in meeting the new challenge. While the inferior may be lost, a portion should survive to restock the population with its more adaptable endowment.

Out of the concept of time -- out of the image of a population's survival not just in a given space throughout a given generation, but through changing conditions and perhaps an infinity of generations -- has come the radical departure of population thinking. The individual may die; in his contribution to the population he becomes immortal. Individuals may vary; in the range of their variation lies the resource of the population. Individuals may fail, or succeed; the sum of their successes means survival of the group. The life of the individual may be inconspicuous; but his genetic contribution to the population may with changing times be of critical value. It is the population, not the individual, that evolves.

The co-adapted gene pool -- the whole population's reservoir of genetic possibilities -- has been described by Waddington as the most advanced concept yet reached by contemporary evolutionary thought. Natural selection has gradually restricted the pool of genes to those with a fair chance of getting along together. Yet through one device or another -- through the diversity of isolates and such hidden assets as the recessive gene -- it maintains its ramparts against the unknown future.

Heterozygosity is a forbidding word, but since there exists no synonym, we must use it. Heterozygosity describes that pair of genes in which one is dominant and displays the character to which it contributes, and the other is recessive and displays nothing. You may have brown eyes. If you are homozygous -- that is, if both genes are the dominant brown -- then you can have only brown-eyed children. But if you are heterozygous, then anything can happen. Kenneth Mather demonstrated a long time ago that homozygosity governing most characters in a population better fits it for present conditions, but the hidden recessives of heterozygosity lend it better chances for the future. Natural selection has more material to work on, and in a time of stress the population, in Waddington's phrase, may be able to pull something new out of the hat.

Several geneticists, and in particular J. M. Thoday, emphasize today the startling change that has come to the old cliche "survival of the fittest." Population philosophy demands that we speak of fitness for today and tomorrow. Whether we are selecting a group of organisms, a field of ideas, or a political party, we must judge not only the compact answers for present survival but the inherent potential capacity for change to meet unknown future contingencies. Extinction has been the normal destination for species or populations bearing only one answer, as defeat is the normal lot of the general who has only one plan. Variation: the variant individual who makes little sense in today's climate, but who may save us in tomorrow's; diverse isolates, spreading the risks of total population commitment; the recessive gene, hidden here, hidden there, waiting for new environments to perform the selective alchemy of transmuting dross into shining metals. Population philosophy brings precision to the evaluation of disorder.

The new way of thought brings likewise a yardstick for populations. Since the time of Melville Herskovits and his cultural relativism it has been fashionable in anthropology to regard all cultures and all human populations as equal. The argument was persuasive. Since environments differ and each population presents its own answer to the challenge it faces, one can scarcely discriminate among answers. The most primitive tribe may, indeed, adapt more successfully than the most advanced nation to inescapable environmental demands. Yet cultural relativism rests on the concept of fitness that prevailed before population genetics. It acknowledges a single standard, the adaptability of a people to its present situation. Cultural relativism ignores the capacity of a people and its culture to evolve successfully in the face of change. "The variation within a population constitutes the raw material of evolution," wrote Haldane in 1949. This variability, in a time of rapidly increasing change, may be the population's single greatest asset.

A population must achieve a fair degree of adaptation to its environment if it is to survive in the present. And if fitness for today were the sole criterion, then cultural relativism would be theoretically sound. But adaptation can be too perfect. When selection for conformity has persisted through a sufficient number of generations, all may seem well, yet reduction of variants will have affected the population's gene pool and reduced its prospects of survival tomorrow. Either variation so wild as to render present survival dubious, or conformity so narrow as to endanger the future, becomes the character of a genetically inferior population.

We may discard what Henry Allen Moe described as the apotheosis of error, the doctrine that all men are created equal; but we must likewise discard as fallacious the proposition that all human populations, even in relation to their own environments, have equal potential.

An inquiry into human inequality cannot be regarded as concluded if it fails to enter the lethal arena of race. Yet little will come of this most fateful of entrances but the spectacle of the sciences bearing a white flag. Despite all claims, we know almost nothing. The natural sciences may properly regard the individual as a biological entity, a genetically random accident shaped and sorted by environment. The population too is a biological entity, since it possesses a common pool of genes separated from other pools by that borderline where interbreeding seldom occurs. Individuals and populations may therefore be compared in terms of disposition or indisposition to meet the challenges of an environment, either present or future. But a race comes about not by reproductive but geographical isolation. The racial confrontations of modern man could occur but rarely in a state of nature.

A race, or subspecies, is a mosaic of populations which has followed its own line of evolution through many generations separated from other such mosaics by natural barriers. During the last ice age of the Pleistocene, let us say, a species of European bird frequenting woodlands may have retreated before the advancing ice and tundra to wooded havens far apart where the species could yet survive. Divided for tens of thousands of years, facing different conditions of natural selection, the separated groups developed distinctive colors of camouflage or display, perhaps certain distinctive behaviors. Thus they became subspecies, identifiably different, yet not so disparate as to prevent interbreeding should contact be resumed. Then the ice and tundra retreated, the woodlands restored comfort to valleys and plains long forbidding. The birds returned. Contact of populations was restored and gene exchange along the margins brought hybridization to border groups. After a few thousand years one might still find a degree of racial purity in racial heartlands, but hybridized populations would link genetically the species as a whole. One would find no clear borderline.

Human races evolved in geographical separation throughout a time before wheels and boats, before sophisticated weapons and tools, before domesticated animals and crops, when barriers like water and mountains and distance itself were formidable indeed. But then, just as the withdrawal of glaciers brought the races of birds together in regrown woodlands, so cultural advances reduced natural barriers and encouraged the mixing of peoples. Probably hybrid populations had always existed along slim lines of racial contact. Now they spread.

If we briefly consider black Africa -- that portion of the continent lying below the Sahara -- we may grasp the complexity of even this most homogeneous of modern races. Migration played a part. Until about the time of Christ, the black race -- what we regard as a human subspecies -- was confined to West Africa, excepting only a branch that seems to have spread along the Sahara rim to the Upper Nile. All these peoples farmed dryland crops, chiefly millet and sorghum. Then quite suddenly a change came. Malayan and Indonesian sea trade was beginning to arrive at the East African coast, bringing such plants as bananas and yams. They were crops of superior nutrition adapted to wetter lands. A population explosion took place in West Africa, together with a freedom to move into the damper forest areas. And so, about two thousand years ago, the migrations east and south began to populate all of the sub-Saharan continent which we today call "black Africa."

And hybridization began. We know little about the pre-Negro populations of Africa. The yellow-skinned Bushman of the Kalahari Desert is a relic people, and he seems at one time to have occupied lands from East Africa to the Cape. There were probably other such primitive hunters. The migrating blacks mixed here with this people, there with that, to form what today is known as the Bantu. It is incorrect to speak of any but the West African or the tribes of the Upper Nile as Negro. Such celebrated tribes as the Zulu and Xhosa in South Africa and the Kikuyu and Baganda in East Africa are hybrid peoples with languages and physical characteristics distinct from the pure parent race. If we of the west are unfamiliar with them, it is only because our slave trade drew almost exclusively from the Negro of West Africa. Arab slavers transported the Bantu to the eastern world.

Thus the first division of the race we call black is between Negro and Bantu, and the genetic origins of the Bantu peoples may, for all we know, be as varied as they are obscure. But another migration, this from the northeast, created entirely new groups. Hamitic peoples, Caucasian in origin, had crossed from southern Arabia to spread through Somalia and Ethiopia and to hybridize in varying degrees at varying racial borders. Many were cattle people, and five or so centuries ago began drives of conquest to the south. Such are the Masai, the Watutsi, perhaps even the Herero in faraway South West Africa. Tall, proud, warriors by tradition, they formed island populations in the Bantu sea. Perhaps they derive their extraordinary stature from an early mixture with the tall, pure Negroes of the Upper Nile. Whatever their origins, no lines of racial animosity can rival the contempt with which these peoples, themselves a product of hybridization, view their longer-settled Bantu neighbors.

Yet all is black Africa. What we regard as a race is an intricate mosaic of some thousands of tribes, each an interbreeding, unit with a common history but isolated from its neighbors by language, by widely varying customs and traditions, and, as a rule, by hostility. Contemplating such African diversity, one is tempted to sympathize with the University of Michigan's Frank Livingstone, who entitled a paper "On the Non-existence of Human Races."

The population with its co-adapted gene pool has measurable reality for the scientist. The overwhelming environmental change which independence has introduced provides overwhelming disproof for the acceptances of cultural relativism. Some populations, such as the Kikuyu in Kenya and the Ibo in Nigeria, have contained superb potentiality for change. They were fit for tomorrow. (The Ibo, indeed, proved so fit that no recourse was left to their inferior neighbors other than to slaughter them.) But some populations have so far demonstrated little or no such potentiality. What can the natural scientist say of such a natural mosaic of peoples?

Tempted though we may be to dismiss races as non-existent, still we cannot. Had Livingstone come within even shouting distance of the truth, then puzzled indeed must be the spectator at the Olympic Games as he watches the representatives of no more than 7 percent of the human species staggering off the field of honor scarcely able to lift the weight of their medals. The observer must conclude that if race and genetic racial differences do not exist, then awards must in some most devious fashion have been rigged by the United Nations Assembly.

The athletic success of a very small portion of the human species (even including the white-hybridized blacks of the Americas, there are only a few more members of the race than there are citizens of the Soviet Union, and less than half as many as the inhabitants of India) recalls Fisher's comment that natural selection is a device for generating a high degree of improbability. And improbable is the word for the black. Despite all hybridization, all cultural disparity, all environmental divergence, such common traits as superb teeth and the capacity to run forever or jump over the moon or knock a baseball from San Francisco to Los Angeles must find an explanation in some dominant genetic complex inherited from common West African ancestors.

The problem of race is not that it is a fiction, but that it has never been invaded. Not even in ethology has the varying behavior of animal races received proper attention. A notable if largely forgotten exception was an experiment in 1950 by a man named Van T. Harris who was taking his doctorate at that citadel of small animals, the University of Michigan's zoology department. Harris later dropped out of the sciences, and I do not believe that his dissertation was even published. Two years later, however, his work was cited in detail by John Calhoun, and at a still later date was re-investigated. And since it is at once a remarkable story, a confirmed experiment, and a rare excursion on the part of the natural sciences into racial behavior, I suspect the study may be around for quite a long time, still puzzling the experts, still furrowing brows.

Peromyscus maniculatus, the deermouse, is a species adapted to so many differing habitats that in North America it is divided into sixty-six subspecies, somewhat outdoing Homo sapiens himself. Two of the most common races are the prairie deermouse, Peromyscus maniculatus bairdii, and the woodland race, Peromyscus maniculatus gracilis. The prairie form has a short tail and short ears, and refuses to enter wooded areas even though a grassy carpet lies beneath the trees. Gracilis has a long tail and long ears, and is as intolerantly devoted to his woodlands. Yet no physiological difference seem to dictate their environmental preferences. They interbreed freely in the laboratory, but almost never in a state of nature, where geographical attachment divides them as would a sea.

No one would suspect the deermouse of possessing much of a psychology, but Harris put it to a strange test. He had been gathering up specimens of both races through the late 1940's, breeding young ones in his laboratory, where they gained no experience of grassland or woods. Then he arranged two experimental rooms with a tunnel for free connection. In one he spread thin strips of paper crudely imitating grass; in the other he placed upright branches. Now he introduced adults which he had caught in the wild; and it was startling enough that they would find in his imitation woodland a familiar environment, in his clipped-up paper strips a semblance of the prairie, and so they would sort themselves out. What was to haunt scientists, however, was that generations born in the laboratory would make the same choice, gracilis to the branches, bairdii to the papered floor, though they had never experienced woodland or field.

Calhoun puzzled over the aesthetic problem that deermice could accept a representation of an environment; but later students at Michigan seem to have wondered if Harris had not made some mistake. And so in 1962 another man, Stanley Wecker, set out to discriminate between what was learned and what innate in the racial psychology of deermice. He found an oak-hickory woodlot sharply edging an open field, and here built a pen ten feet wide and a hundred feet long, half in the woodlot, half in the field. He divided it into ten sections, each barrier with a little stile over which his deermice could cross freely, together with an electrical recording device to keep accurate track of comings and goings. For subjects he had not only wild-caught prairie deermice and their laboratory-born young, but descendants of Van Harris' prairie race, laboratory-raised for as much as twenty generations.

The experiment confirmed that of Harris years before. The wild-caught favored the pens away from the woodlot, as did the younger generation raised in the laboratory. But it was the experiment with the descendants of the prairie race caught in the 1940's that penetrated the niceties of innate behavior.

The first experiment, with thirteen of the descendants of Harris' stock, showed no significant preference for the pens in the woods or those in the field. The conclusion seemed evident that after twenty generations of life in a laboratory innate patterns were erased. But Wecker now built two small breeding pens -- one in the woodlot, one in the field -- where he could raise new litters. The parents were chosen from the twenty-generation descendants of the prairie race who themselves exhibited no preference. When the young raised in the field were old enough to be moved to the long option pen, they unanimously voted for the field. But when the young prairie breed raised in the woodlot were tested, they remained as open-minded as their parents. They did not vote as one for the woods.

What did it mean? One must conclude, as did Wecker, that early experience reinforcing an innate pattern, though unexercised for twenty generations, is sufficient to renew the pattern with all its original force. But early experience that, as in the woodlot litters, runs contrary to the race's evolutionary history has no more than random consequence. Learning, in other words, comes more easily to those with an appropriate evolutionary background than to those for whom an environment carries no evolutionary relevance.

We cannot extrapolate from races of deermice to races of men. But we may recall a variety of comments on animal learning by our foremost evolutionists. Irenaus Eibl-Eibesfeldt, writing of innate mechanisms, has described them as "those reactions and states within the animal on which conditioning and learning depend." S. L. Washburn and David Hamburg: "Evolution, through selection, has built the biological base so that many behaviors are easily, almost inevitably, learned." Rene Dubos: "The performance of any living organism in a given situation is conditioned of course by environmental forces. But its characteristics are determined by the potentialities and the limitations which the organism has acquired and retained from its evolutionary and experiential past." Sir Julian Huxley, in Essays of a Humanist, writing of the behaviorists: "They forget that even the capacity to learn, to learn at all, to learn only at a definite stage of development, to learn one kind of thing rather than another, to learn more or less quickly, must have some genetic basis." Or we may recall the sigh of the great neurologist Karl Lashley toward the end of his career: "I sometimes feel in reviewing the evidence on the localization of the memory trace, that the necessary conclusion is that learning is just not possible."

In confronting an environment, the superiority of the individual, of the population, of the race at our stage of human history must rest in large portion on the capacity to learn. But that capacity to learn -- which we may grant in Homo sapiens as more or less equal throughout human populations -- is today founded on biological bases varying through natural selection according to the varying environments in which modern races have evolved. Selective pressures operating on tribesmen in disease-ridden tropical Africa cannot have been the same as those confronting herdsmen on the wind-swept Central Asian steppes. And not only did selection vary according to the natural environments we faced, but also -- at least for the last ten thousand years -- according to our widely varying cultural patterns which became a part of our environment. All pressures combined to favor biological bases varying slightly or broadly among the world's peoples. And no variance could have been broader or more anciently rooted than in those geographically isolated groups which we refer to as races.

We are permitted, of course, to march to the measures of intellectual fashion and dismiss biological history as having no influence on intelligence. But if we substitute for the subjective term "intelligence" the more measurable and objective phrase "capacity to learn," then we shall come closer to the realities of the human condition. The capacity, the direction, the ease an the objectives of learning must extend and supplement the genetic base evolved to promote survival within a given environment. As biological qualities must vary, so must the qualities of learning.

Throughout all of this chapter we have inquired into random inequality of individuals and populations. Inequality has rested on the accident of sexual recombination, on mutation and genetic drift in groups. The inequality of races, if it exists, must be systematic. It must rest on discernible factors in the differing natural selection placed on the hodge-podge of human mosaics to which we give the term "race." Science possesses today no such discernible factors. We possess only evidences of difference.

In the small black race -- which I much suspect, from its numbers, to be the youngest of races -- we have such evidence of superiority of anatomical endowment and neurological coordination that it must be regarded as a distinct subdivision of Homo sapiens. If racial distinction on the playing field is to be accepted, then can there exist theoretical grounds for banishing distinction in the classroom? In the United States the evidence for inferior learning capacity is as inarguable as superior performance on the baseball diamond; yet the question of intelligence remains distinctly unsettled.

In 1966 an enormous Federally financed study, Equality of Educational Opportunity, reported on the educational achievements of some 600,000 students in American schools. Referred to usually as the Coleman Report, it became instantly unavailable at bookshops and from normal distributors of scholarly literature. After some eight months of trying, I pried a copy out of the U.S. Government Printing Office. Why it had become unavailable became evident only after long exploration of its 700-plus pages of statistics. The Negro had failed in American schools -- failed catastrophically, beyond statistical doubt or sentimental apology, beyond all explanation. It was not a document to be freely circulated in Congressional areas wherein the Negro commanded the swing vote.

I say "the Negro," but let us be wary of typological thinking. A Negro student might exceed a hundred white fellows in academic accomplishment. But up and down and across the statistical tables one found approximately the same population range: curves revealed a repeated 15 percent of black students falling within the same range of academic accomplishment as the upper 50 percent of whites. It mattered a little but not much whether the student had come from a segregated or integrated school. Socio-economic level of the family brought some influence, but small. Worse still for the black was the record of the Oriental-American, subjected in American life to discrimination certainly as rigorous as the Negro, who consistently equaled and in areas excelled the records of white students.

A consequence of the Coleman Report was the hysterically received study by California's Arthur Jensen, published in early 1969 in the Harvard Educational Review, suggesting the genetical inferiority of Negro intelligence. It is a persuasive document, so persuasive that there were those who could provide no better answer than to threaten Jensen's life. But the materials must be regarded with care. Are we truly considering intelligence? or a capacity to learn according to the demands of the materialist American environment? The Coleman Report is frank in its description of the tests administered:

These tests do not measure intelligence, nor attitudes, nor qualities of character. Furthermore they are not, nor are they intended, to be "culture free." Quite the reverse: they are culture bound. What they measure are the skills which are among the most important in our society for getting a good job and moving to a better one, and for full participation in an increasingly technical world.

The Coleman Report offers small comfort for the genuine racist, since its corollary demonstrates that 15 percent of all black students are superior in achievement to one half of all white students. But in its record of Oriental-American accomplishment it offers as little comfort for those who regard black failure as a simple product of discrimination. And it offers nothing but unbounded mystification for all those, white or black, who are convinced that equality of opportunity must somehow be presented to all members of a vertebrate society. Whom it must mystify least is the baboon, whose imagination could never encompass the transportation of some millions o human beings from one continental environment in which they had been successful survivors to another offering no such guarantees.

We do not know about race; and that is the final truth today. We know that within a single interbreeding population -- let us say the Swedes, or the English, or the white Americans, or, for that matter, one must suspect, the rhesus monkeys -- the accident of the night dictates a diversity of intelligence of such order that between 3 and 3.5 percent must be termed feebleminded. There are between six and seven million mentally deficient Americans. But the occupation of a single geographical area or ecological niche by two populations of differing subspecies, rare in human life, almost unknown in nature, is a man-made situation demanding man-made answers. And until the scientist, without threat to his life, is free to explore in all candor racial differences, and to prove or disprove systematic inequalities of intelligence, an observer of the sciences has little to offer. But then, neither racist nor egalitarian has much to offer, either, beyond emotion.