On Human Nature and the biology of our species
The most consequential and most controversial step Edward O. Wilson ever took was to turn the lens of sociobiology upon his own species. Having built, in Sociobiology, a general science of social behavior spanning the animal kingdom, he devoted its notorious final chapter, and then an entire subsequent book, to the proposition that human beings are no exception — that Homo sapiens, like every other species, possesses a nature shaped by evolution, and that human social behavior can and must be studied as a biological phenomenon. That book, On Human Nature, published in 1978 and awarded the Pulitzer Prize, is the fullest statement of Wilson's vision of humanity, and it is the primary subject of this chapter. In it Wilson confronted directly the questions his sociobiology had raised about our own species: whether there is such a thing as human nature, what evolution has written into it, and what it means for our sense of freedom, morality, and meaning to learn that we are, at bottom, biological beings like any other. The general theory of sociobiology and the firestorm it provoked are treated in Chapter 6; here the subject is what that theory says about us.
The provocation at the root of the whole enterprise was stated baldly at the opening of Sociobiology itself, where Wilson proposed that ethics, emotion, and social behavior — the very phenomena that humanists had always regarded as the special province of the human spirit — could all be understood as products of the genes, shaped by natural selection like any other biological trait. To extend this claim to humanity was to insist that Homo sapiens is as subject to evolutionary analysis as any other species, that there is no magic circle around the human that exempts our behavior from the biology that governs the rest of life. Wilson made this extension deliberately and unapologetically, in the conviction that the refusal to apply biology to ourselves was not humility but evasion, a failure of intellectual nerve that left the study of humanity fractured and unscientific. The final chapter of Sociobiology, and then the whole of On Human Nature, were his attempt to make good on this conviction — to show, concretely and in detail, that the methods which had illuminated the societies of ants and the behavior of animals could illuminate the human animal as well, and that we had nothing to fear and much to gain from turning the biological gaze upon ourselves.
Wilson opened On Human Nature not with an answer but with a dilemma — the profound predicament that a scientific account of human nature seems to create. If human nature is truly a product of evolution, shaped by natural selection to promote the survival and reproduction of our ancestors' genes, then our deepest values, our sense of purpose, and our belief in our own freedom may have no foundation beyond biological survival — no transcendent grounding, no meaning beyond the blind imperatives of the genes. This was the central dilemma of the book, and Wilson did not flinch from it: he acknowledged that the biological view of humanity threatens to dissolve the comforting certainties by which people have always lived, to reveal our loftiest aspirations as the workings of evolved machinery. He identified two grave spiritual difficulties in particular that the scientific account creates — the loss of religious certainty, as the supernatural explanations of traditional faith give way before biology, and the apparent absence of any purpose beyond survival and reproduction. Rather than evade these difficulties, Wilson made confronting them the organizing task of his book, asking whether humanity could find a way to live meaningfully in the light of what science had revealed about its own nature.
The two spiritual difficulties Wilson identified deserve to be drawn out, for they framed the whole book and much of his later thought. The first was the loss of religious certainty: as the empirical explanations of science steadily displaced the supernatural explanations of traditional faith, humanity risked losing the cosmic framework of meaning that religion had always supplied, the assurance of a purposeful universe and a place within it ordained by a higher power. The second was subtler and in some ways more troubling: even granting the scientific account, human beings seemed left without any purpose beyond the biological imperatives of survival and reproduction, their loftiest strivings revealed as the machinery of gene propagation, their sense of transcendent meaning exposed as an evolved illusion. Together these difficulties constituted what Wilson saw as the spiritual crisis of a scientific age — the danger that in gaining a true account of our origins we might lose the sense of significance by which human beings have always lived. Wilson refused both the retreat into denial, which rejects the science to preserve the meaning, and the surrender to nihilism, which accepts the science and abandons the meaning; his whole effort was to find a third way, in which the scientific truth about human nature could itself become a source of meaning rather than its destroyer.
Before that question could be addressed, however, Wilson had to establish the claim on which everything else depended: that there is such a thing as human nature at all. Against the then-dominant view in the social sciences — that human behavior is almost infinitely malleable, a blank slate shaped entirely by culture and environment — Wilson insisted that a species-typical human nature genuinely exists, a set of evolved predispositions shared across all human cultures and grounded in our common genetic inheritance. He marshaled several lines of evidence for this claim. There were the human universals: behaviors and institutions that recur across virtually all known societies — incest avoidance, kinship classification, division of labor, status-seeking, and many more — whose ubiquity across otherwise diverse cultures suggested a common biological root rather than independent invention. There was the evidence from studies of twins and adoption, indicating that heredity influences not merely physical traits but personality and temperament. And there was the comparative approach, the comparison of human behavior with that of other primates and social mammals, which helped identify the traits humanity shares with its evolutionary relatives and thus likely inherited from common ancestors.
The comparative method was, for Wilson, more than a source of evidence; it was a way of locating humanity honestly within the order of nature. By setting human behavior alongside that of chimpanzees, baboons, and other social primates and mammals, he could identify which of our traits are the shared inheritance of our lineage and which are distinctively our own, and thereby resist both the temptation to exaggerate human uniqueness and the opposite error of denying it. Humans emerged from this comparison as recognizably primate in much of their social behavior — in the hierarchies, the alliances, the kin bonds, the sexual and parental patterns we share with our relatives — yet also as genuinely exceptional in the degree of our cooperation, the sophistication of our language, and the reach of our culture. Wilson's aim was never to reduce humanity to 'just another animal,' a phrase he would have rejected, but to understand precisely how the human animal both resembles and differs from its kin, and to ground that understanding in the comparative evidence rather than in prior assumptions about human dignity or human degradation.
Wilson was careful, too, to insist that a shared human nature does not imply human uniformity, and he addressed directly how development produces both the common features of the species and the rich individual variation among its members. The epigenetic rules and predispositions that constitute human nature are shared, but they interact with genes that vary from person to person and with environments that differ enormously, so that the outcome is a species united by a common nature yet composed of irreducibly distinct individuals. Human nature, in Wilson's account, is the shared foundation on which individuality is built, not a mold that stamps out identical copies; it sets the range of the humanly possible while leaving vast scope for the particular. This attention to individual variation was part of Wilson's defense against the charge that his biology flattened human difference or licensed crude generalizations about types of people. The very developmental processes that give us our common humanity, he argued, also guarantee our individuality, for no two human beings, not even identical twins, are shaped by exactly the same interaction of genes and experience.
The genetic basis of human nature, Wilson argued, is therefore substantial and real — a hereditary component shaped over millions of years of evolution and shared across all human cultures, setting the deep parameters within which the variety of human life unfolds. But he was careful, from the first, to specify precisely what this claim did and did not mean, for he knew that the charge of genetic determinism would be leveled against him, and he regarded that charge as a misunderstanding. Genes, he insisted, prescribe tendencies and capacities, not fixed and inevitable behaviors; they bias the odds without dictating the outcome. Human nature does not consist of rigid instincts that compel particular actions, but of predispositions — inclinations to develop in certain directions, to learn certain things more readily than others, to feel certain emotions in certain circumstances — that leave enormous room for individual variation and for the shaping power of culture. To say that human nature has a genetic basis was to say that we are born with a structured set of biases and potentials, not that our behavior is genetically foreordained. This careful distinction between predisposition and determination was central to Wilson's whole argument, and its repeated misreading was the source of much of the controversy that dogged him.
This insistence on the reality of human nature was, in its intellectual context, a genuinely radical claim, and Wilson pressed it against a powerful current of opinion that denied any fixed human nature at all. Against those who held that human beings are wholly the creatures of their culture, indefinitely reshapeable by social arrangement, Wilson maintained that a species-typical nature genuinely exists — that beneath the vast diversity of human cultures runs a common human substrate, recognizable in every society, that sets real limits and real tendencies. To deny this, he argued, was not enlightened but blind, a refusal to see the obvious continuities of human behavior across all times and places, and a doctrine with its own dangers, for a species that believes itself infinitely malleable may imagine it can be reshaped by force into any desired form. He argued, further, that a proper understanding of human development, grounded in biology, must inform any credible social theory — that the social sciences could not hope to succeed while ignoring the biological nature of the beings they studied, and that a realistic account of human possibility had to begin from a realistic account of human nature. This was the constructive core of his challenge to the social sciences: not to abolish them, but to ground them, to give the study of human society the biological foundation without which, he believed, it could never become a mature science.
At the foundation of human nature, in Wilson's account, lie the emotions — and here his biological analysis reached its most provocative. Human emotional responses, he argued, are seated in the evolved centers of the brain, shaped by natural selection because they guided our ancestors toward choices that promoted survival and reproduction; and it is these evolved emotions that underlie our moral and social behavior. In a famous and much-quoted passage from Sociobiology, Wilson had suggested that the deepest questions of philosophy and ethics may ultimately be rooted in the emotional centers of the brain, in the hypothalamus and limbic system, themselves the products of evolution. This was among the most radical implications of his whole program: that our sense of right and wrong, our loftiest moral intuitions, are not deliverances of reason or revelation but the felt output of neural machinery built by natural selection. The human brain itself he described as an organ shaped by selection to promote survival and reproduction — not a general-purpose reasoning device standing outside nature, but an evolved organ like any other, its very structure bearing the marks of the adaptive problems our ancestors faced.
This evolved character of the brain had far-reaching implications for how Wilson understood human reason itself. The mind, he argued, did not evolve toward pure logic or disinterested truth-seeking; it evolved as a survival device, an instrument for solving the practical problems of staying alive and reproducing in the ancestral environment. Its very biases and shortcuts — the recurrent patterns of human cognition and emotion that psychologists catalog — are best understood as adaptations that guided ancestral decision-making, rules of thumb that served our forebears well even when they lead us astray in the utterly different world we now inhabit. Wilson stressed, too, that reason and emotion are not separate faculties, one noble and one base, but integrated in the evolved brain, so that human rationality is always suffused with feeling and human judgment always shaped by the emotional coloring that evolution has given our perceptions. There is no cool, dispassionate reason standing apart from the passions; there is only the evolved mind, in which thought and feeling are woven together, both bearing the imprint of the adaptive past.
That adaptive past was, for Wilson, the key to understanding the human present, and he returned often to the fact that human nature was shaped during the long prehistory of hunter-gatherer life. For the overwhelming majority of our existence as a species, human beings lived in small bands of foragers, and it was the demands of that way of life — cooperation within the group, competition between groups, the management of kinship and reciprocity and status — that selected the emotions and predispositions we still carry. Modern civilization is a recent veneer over this ancient inheritance; we are, in Wilson's memorable framing, creatures whose instincts were forged in the Paleolithic but who now find themselves in a world of cities, technologies, and institutions utterly unlike the one to which they are adapted. This mismatch between our evolved nature and our created circumstances he took to be one of the fundamental facts of the human condition, the source of much of our difficulty and much of our danger, and a reason that self-understanding grounded in evolutionary history was not a luxury but a necessity.
From these foundations Wilson proceeded to analyze the specific domains of human behavior, and none drew more attention than aggression. Here Wilson's conclusions were more nuanced than either his critics or his popularizers often allowed. He explicitly rejected the notion, popular in his day, that human beings are driven by an innate bloodlust — the killer-ape myth that portrayed humanity as instinctively murderous. Humans are not born with a drive toward violence, Wilson argued; aggression is not a unitary instinct demanding release but a conditional capacity, a family of distinct behaviors — territorial, defensive, predatory, and more — that evolution has equipped us to deploy under particular circumstances. The evolutionary roots of human hostility he traced to ancestral competition over resources, mates, and territory, and he took seriously the human tendency toward in-group loyalty and hostility to outsiders — xenophobia — as an evolved disposition with deep roots. But because aggression is conditional rather than compulsory, its specific forms are heavily shaped by learning and culture, and culture and institutions can either amplify or curb it. Human beings are not doomed by their nature to violence; they are equipped with a capacity for it that circumstances may evoke or restrain.
Human sexuality Wilson analyzed in a similarly biological but non-reductive spirit, emphasizing above all its social dimensions. In humans, he argued, sex serves social bonding far more than mere reproduction, for the great majority of human sexual activity has nothing to do with conception and everything to do with cementing the pair bond between partners. This human tendency toward enduring pair bonds he interpreted as an adaptation supporting the unusually prolonged dependency of human children, who require years of care from more than one adult. He examined the evolved differences between the sexes in behavior and disposition, tracing them to the divergent reproductive strategies of males and females over evolutionary history, while addressing directly the fraught social implications of such claims — arguing that to acknowledge biological differences is not to endorse inequality, and that recognizing our nature need not dictate our social arrangements. Human sexuality, he stressed, is saturated with emotion; love, jealousy, and desire are the felt expressions of evolved bonding mechanisms. And while the biological foundations of sexuality are universal, the customs and taboos that surround it vary enormously across cultures — biology providing the substrate, culture the endlessly variable forms.
Wilson did not shy from the most socially charged implications of this analysis, though he handled them with care. On the question of sex differences, he argued that acknowledging evolved differences in the average dispositions of males and females need not, and should not, translate into any endorsement of social inequality — that a biological difference is not a moral warrant, and that a just society could recognize the facts of human nature while insisting on equal rights and opportunities. His discussion of homosexuality was similarly framed in the sociobiological terms of his day: he offered the tentative suggestion that homosexuality might have persisted in human populations because it conferred some indirect advantage, perhaps through the support that non-reproducing individuals could give to their relatives and thus to the propagation of shared genes. Whatever the merits of such specific hypotheses, which remained speculative, Wilson's larger point was methodological: that the full range of human behavior, including its most intimate and contested dimensions, falls within the scope of biological understanding, and that to bring these matters under the light of evolutionary analysis is not to judge them but to seek to comprehend them. The customs and taboos that different cultures have erected around sexuality he treated as the variable cultural expressions of a universal biological substrate.
The deepest puzzle Wilson confronted in human nature was the one that had launched sociobiology in the first place: altruism, the willingness of individuals to sacrifice their own interests for others. In human beings this puzzle takes a particularly rich form, and Wilson drew a famous distinction between two kinds of human altruism. Hard-core altruism is unconditional, directed chiefly toward close kin, demanding nothing in return — the fierce, unreasoning devotion of a parent to a child, rooted in kin selection and the propagation of shared genes. Soft-core altruism, by contrast, is ultimately self-serving, extended toward non-relatives in the expectation, conscious or not, of eventual return — the reciprocal altruism that underlies so much human cooperation, in which acts of kindness are exchanged over time to mutual benefit. Much human cooperation among non-relatives, Wilson argued, rests on this reciprocity, the trading of favors that allows unrelated individuals to build the elaborate webs of mutual obligation that structure human societies. The distinction mattered to Wilson because it bore directly on human morality and its prospects: hard-core altruism, being parochial and kin-directed, is in a sense the enemy of a truly universal ethics, while soft-core altruism, being flexible and calculating, is more malleable but also less reliable.
This distinction carried, for Wilson, a sobering implication about the prospects for human morality. If our deepest and most reliable altruism is hard-core — unconditional but narrow, directed by kin selection toward those who share our genes — then the universal benevolence preached by the great ethical and religious traditions runs against the grain of our strongest evolved dispositions, and must be built, precariously, upon the weaker and more calculating foundation of soft-core reciprocity. Human beings are, on this account, most fiercely good to their own and only conditionally good to strangers, and the moral project of extending genuine concern to all humanity is therefore an uphill struggle against our nature rather than a simple flowering of it. Wilson did not draw a cynical conclusion from this; he did not hold that universal ethics is impossible, only that it is difficult, that it requires working with a full and honest knowledge of the evolved dispositions it must channel and restrain. The tension between the parochial and the universal in human moral life, rooted in the two kinds of altruism, he regarded as one of the permanent features of the human condition, and one that any realistic ethics would have to confront rather than wish away (the evolutionary analysis of altruism is developed further in Chapter 5, and its ethical implications in Chapter 22).
This analysis opened onto Wilson's treatment of morality itself, which he insisted must be grounded in biology. The moral emotions — guilt, gratitude, indignation, sympathy, shame — he interpreted as evolved mechanisms, the felt machinery of a conscience shaped by natural selection to regulate our dealings with others in the intensely social world of our ancestors. Any adequate account of human ethics, he argued, must be grounded in an understanding of these evolved moral emotions rather than treating morality as a wholly autonomous realm of pure reason or divine command. Wilson located a deep tension at the heart of human morality: the conflict between the parochial pull of kin-directed altruism, which binds us fiercely to our own, and the universalist aspirations of ethical philosophy and the great religions, which call us to extend our concern to all humanity. Much of moral life, he suggested, consists in the struggle between these two forces — between the narrow loyalties evolution has built into us and the wider circle of moral concern to which our reason and our ideals aspire. He proposed that recognizing the biological roots of our moral sentiments could help humanity construct a more honest and effective ethics, one that works with the grain of human nature rather than against it (the ethical program is developed further in Chapter 22).
Religion posed a special case for Wilson's biological analysis, and he approached it with a mixture of scientific detachment and genuine respect for its power. Human beings, he argued, carry an evolved predisposition to religious belief — a readiness to accept supernatural explanations and to bind themselves into communities of shared faith — that is among the most universal and powerful of human traits. Religion, on this view, is not a cultural accident or a mere error to be dispelled by reason, but a deep expression of human nature, one that answers profound evolved emotional needs and that has served, throughout human history, to bind groups together and to give meaning to individual lives. Wilson framed a fundamental tension between the mythic explanations offered by religion and the empirical explanations offered by science, each competing to account for humanity's place in the cosmos — a tension he did not think could be simply resolved in religion's favor. Yet he also concluded that religion would not simply vanish before the advance of science, precisely because it answers evolved emotional needs that a purely rational worldview struggles to meet. The persistence and power of religion were, for Wilson, among the most important facts about human nature, to be explained rather than explained away (his fuller treatment of religion appears in Chapter 23).
Beneath all these particular analyses ran the great question with which the book had begun: if human nature is the product of evolution, what becomes of human freedom, dignity, and meaning? Wilson raised the difficult question of free will directly, considering how a biologically shaped and partly determined nature could be reconciled with the sense of free choice that is so central to human self-understanding. He did not offer a tidy resolution, but he resisted the fatalistic conclusion that biology abolishes freedom, arguing that the sheer complexity of the human brain, and the vast range of behavior its predispositions permit, leave ample room for something worth calling choice. More fundamentally, he confronted the fear that biological explanation drains human life of meaning, and rejected it: to understand the evolutionary origins of our emotions and values, he insisted, does not make them less real or less precious, any more than understanding the physics of light diminishes the beauty of a sunset. The reductionist understanding of human nature, in Wilson's view, need not be a source of despair; it could instead be the foundation of a clearer and more honest self-knowledge, and even of a kind of reverence for the long evolutionary drama that had produced a creature capable of contemplating itself.
The emergence of the human mind itself Wilson regarded as the deepest and most remarkable problem his biology confronted. The higher properties of the mind, he argued, emerge from the biological substrate of the brain — consciousness and self-awareness arising, through the immense complexity of neural organization, from the physical organ that natural selection had built. This was a bridge his science aspired to cross but could not yet fully traverse: the passage from neurons to consciousness, from the material brain to the felt experience of being a self. Wilson considered the emergence of consciousness and self-awareness as evolutionary developments, capacities that conferred enormous adaptive advantage by allowing our ancestors to model themselves and others, to anticipate and plan and deceive. Yet he acknowledged, especially in his later writing, the genuine limits of our present ability to explain consciousness, the hard residue of mystery that remains even after all the neural correlates have been mapped. The mind was, for Wilson, at once wholly natural — a product of the evolved brain, continuous with the rest of biology — and the site of the deepest unsolved problem in all of science, the place where the ascent from matter to meaning still awaited its full explanation.
Out of this confrontation Wilson sought to build something constructive, which he called a biological humanism — an outline of how humanity might ground its values and find its purpose in evolutionary understanding rather than in the fading certainties of traditional religion. If the old sources of meaning were failing before the advance of science, Wilson proposed, then perhaps a new source might be found in the scientific epic itself — in the grand story of evolution, of life's long struggle and humanity's emergence from it, which he came to regard as potentially the most powerful and unifying of all human narratives. This biological humanism would preserve human dignity and aspiration while grounding them honestly in what science had discovered about human nature; it would find meaning not in a supernatural order but in humanity's real place in the natural one, and in the responsibilities that flow from being the one species able to understand its own origins. Wilson did not claim to have completed this project in On Human Nature; he offered it as a sketch, a direction, a hope. But it expressed his fundamental conviction that the scientific understanding of human nature, rightly grasped, need not leave us in a meaningless universe but could furnish the materials for a mature and honest vision of the human condition.
The centerpiece of this constructive vision was what Wilson called the evolutionary epic — the grand scientific story of the cosmos and of life, from the origin of the universe through the emergence of life and mind to the appearance of a species capable of comprehending the whole sweep. This epic, Wilson proposed, might serve as a kind of mythology in the deepest sense: not a falsehood, but a true and shared narrative capable of giving human beings a sense of their place in the order of things, of connecting the individual life to something vast and meaningful. Where traditional religious myths located humanity in a supernatural drama of creation and redemption, the evolutionary epic located us in a natural drama no less grand — the four-billion-year adventure of life on Earth, of which we are the momentary and self-aware culmination. Wilson believed that this story, rightly told, could satisfy something of the human hunger for meaning and transcendence that religion had always addressed, offering a source of awe and belonging grounded not in revelation but in the discovered facts of our real origins. The evolutionary epic was his candidate for the unifying narrative a scientific civilization would need, the myth that is also true.
In his later works, and especially in The Meaning of Human Existence, Wilson deepened and darkened this account of human nature, dwelling on the tensions and dangers built into our evolved constitution. The human condition, he came to argue, is the product of a long series of evolutionary accidents, a nature cobbled together by natural selection for ancestral circumstances and now carried, unaltered in its essentials, into a world it was never designed for. At the center of this nature he placed the instinct of tribalism — the deep human tendency to form groups, to bind fiercely to the in-group, and to regard outsiders with suspicion or hostility. Tribalism, Wilson argued, is among the most powerful of human instincts, the wellspring of solidarity and loyalty and much of what is best in human social life, but also the root of religion's divisive force, of war, of the countless conflicts between groups that have scarred human history. He saw in this instinct a fundamental ambivalence: the same disposition that makes possible the deepest human bonds also makes possible the deepest human cruelties, and much of the tragedy of the human condition flows from this single evolved trait. To understand tribalism, and to find ways of managing it, Wilson came to regard as among the most urgent tasks that self-knowledge sets us.
Yet Wilson's late reflections on human nature were not finally pessimistic, for he coupled his darkening view of our evolved instincts with a heightened sense of human significance and human possibility. The very fact that we are the product of a long chain of evolutionary accidents, he argued, makes our existence precious rather than meaningless: we are not the intended culmination of any cosmic plan, but we are the one species, so far as we know, that has achieved the capacity to understand its own origins, to reflect on its own nature, and to choose, within the limits of that nature, what to become. This capacity for self-knowledge Wilson regarded as humanity's distinction and its opportunity — the possibility that a species might, for the first time in the history of life, come to comprehend the forces that made it and thereby gain some measure of mastery over its own future. The meaning of human existence, in his mature view, lay precisely here: not in a purpose handed down from above, but in the responsibility that falls to a creature able to understand itself and its world, and to act, however imperfectly, on that understanding. To know our nature truly, including its dangers, was for Wilson the beginning of any wisdom about how we might live.
The reception of Wilson's human sociobiology was, as he had anticipated, ferociously divided, and it is impossible to understand On Human Nature apart from the storm that surrounded it. To apply evolutionary biology to human behavior was, in the intellectual climate of the 1970s, to touch the most sensitive of nerves, for it seemed to many to threaten the foundations of the social sciences, to revive the discredited biological determinisms of the past, and to lend comfort to those who would justify existing inequalities as natural and inevitable. Wilson found himself accused of these things and worse, and he spent much of the rest of his career defending his position against misreadings he regarded as willful (the controversy is treated in Chapter 6). His defense rested always on the same distinction: that to identify a biological component in human behavior is not to endorse it, not to declare it unchangeable, and not to justify any particular social arrangement. Understanding our nature, he argued, is the precondition for improving our condition, not an excuse for accepting it as it is; and a clear-eyed reckoning with what evolution has made us is more likely to advance human freedom and dignity than the comforting fiction that we are infinitely malleable.
There is a deep continuity between Wilson's human sociobiology and the naturalism that ran through the whole of his thought, and it is worth making explicit. Wilson approached the human species exactly as he had approached the ant: as a biological phenomenon to be understood through the methods of evolutionary science, without exemption or special pleading. This was, for him, not a diminishment of humanity but an act of intellectual honesty and even of a kind of reverence — a refusal to place human beings outside the nature they had emerged from, and an insistence that we can only understand ourselves by understanding our place in the living world. The human mind, with all its powers of consciousness and self-awareness, he regarded as a natural product of the evolved brain, emerging from its biological substrate as the colony's order emerges from its ants; the higher properties of mind bridging, in a continuous ascent, from neurons to consciousness. To study human nature scientifically was to complete the Darwinian revolution, to bring the one species that had imagined itself exempt from nature back within its fold, and to see in humanity not a fallen angel or a special creation but the most remarkable achievement, so far, of the same evolutionary process that had produced everything else alive.
On Human Nature endures as the central document of Wilson's vision of humanity, the place where his science confronts most directly the questions that matter most to human beings. Its argument can be stated simply, though its implications are vast: that human nature is real, that it is a product of evolution, that it is written in our emotions and our predispositions rather than in rigid instincts, and that to understand it is not to be diminished but to be enlightened. Wilson asked his readers to accept a difficult truth — that we are biological beings, shaped by the same forces that shaped all life — and he tried to show that this truth, far from being a counsel of despair, could be the foundation of a more honest and more hopeful understanding of ourselves. Whether he succeeded in dissolving the dilemma with which he began, whether biological humanism can truly furnish the meaning that traditional sources once supplied, remains an open question, one he would continue to grapple with in the books of his later years (see Chapter 17, The Social Conquest of Earth, and Chapter 18, The Psychology of Human Nature). But in posing the question so honestly, and in insisting that humanity look squarely at its own evolved nature, Wilson performed one of the essential intellectual services of his age: he held up to our species the mirror of biology, and asked us to recognize ourselves in what we saw.