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Nice Genes

The Altruism Equation: Seven Scientists Search for the Origin of Goodness

By Lee Alan Dugatkin

(Princeton University Press, 188 pp., $24.95)


The saga of man's quest to crack the mystery of altruism is a weird, uplifting, and sometimes tragic affair. Its heroes include a bearded Russian anarchist prince who thought mankind needed to learn a lesson from the animals; a bushy-browed loner who asked to be laid out in the Brazilian rainforest so that his body could be buried and then eaten by beetles; and the enigmatic suicide in a dingy London apartment of an atheist-chemist turned religious evolutionarymathematician. The tale invites to the stage spitting tadpoles and "free-riding" cuckoo birds, naked blind mole rats, and some over-abused stepchildren of man. It spans the globe from the Siberian tundra to the South American tropics to the African plains, and gallops in time from Aristotle and Aquinas, through Hume and Adam Smith, to the "last man to know all there is to know," and then all the way to economists, anthropologists, and brain imagers today.

In his slim book, the biologist Lee Alan Dugatkin skillfully presents the fabulous tale of modern biology's wrestling with the problem of altruism. After Darwin found "altruism" in nature, a debate broke out between his "bulldog" Thomas Huxley and Pyotr Kropotkin about whether competition or cooperation is the norm in the living world. After all, cooperation was an anomaly in a Darwinian world that was all about struggle and survival. But since it was nonetheless observed in nature, people tried to explain how what seemed like acts of kindness could have arisen over evolutionary time. For a while the answer was that "friendly" groups will have a leg up on groups with selfish fellows, a solution that Darwin himself seemed to arrive at years before. But in the 1960s Bill Hamilton punched a great big hole in this feel-good "togetherness" story. Formalizing a quip made by J.B.S. Haldane, he explained "altruism" by looking at the world from an entirely surprising angle: benevolence could arise in nature precisely because selfish genes were running the show.

This is where Dugatkin's story ends, but we must take it somewhat further. We must ask ourselves what we mean by "altruism," a question that challenges the pretension of science to explain all the wonders of the human condition. The Altruism Equation pits the individual against the group and the gene against the individual, true goodness against masquerading self-interest, heartless biological necessity against the transcendence of the spirit. Dugatkin is wonderful on the science, but he forgets to deal with its implications, ending his book too abruptly. This is a tale not only about the majesty of science, but also about the hubris of scientism. One of the greatest projects of modernity is to explain to the public where science does and does not matter, and altruism is a valuable example.

Darwin was dumbfounded by the ants. Many an ant species, he knew, was divided into fast, unbreachable castes. The honeypot ant of the American deserts has workers whose sole job is to hang upside down, motionless, like great big pots of sugared water, so that they may be tapped when the queen and her brood are thirsty. Members of another caste in the same species have gigantic heads with which, Cerberus-like, they block the nest entrance before intruders. The leaf-cutter ants of South America sport castes that differ in weight up to three hundredfold, from miniature serene fungus gardeners to giant ferocious soldiers. In the ant world, some tend to the queen, others tend to the nest, others to food, others to battle--each to his caste and each to his fate. What Darwin found amazing was the fact that, besides the queen and a few lucky males, all the rest of the ants are effectively neuters. They have no offspring of their own, but instead perform duties that benefit the young of the queen: after all, she is the only female doing any procreating, the sole mother.

For Darwin, the mystery lay in trying to explain how such different behavior and morphology arose in a single species, for since all the workers had no offspring, natural selection could hardly be fashioning their traits through their own progeny. What this meant was that the queen and her mate were somehow passing on to the next generation traits--such as massive heads and gardening- scissor teeth--that they themselves did not possess, an obscurity that Darwin found "by far the most serious special difficulty, which my theory has encountered." (To be fair, he did have a number of such "by far the most..." difficulties.) This was a problem of heredity: how could traits perform such Houdini acts in their journey from generation to generation?

To solve the mystery, Darwin asked a simple question: who benefits from this situation? The answer, he thought, was the family. It makes sense for sterile ants (and bees and wasps and termites) to devote themselves selflessly to others while forsaking their own procreation and even sometimes sacrificing their own lives, if their close kin benefit from such assistance. This was quite an idea, for the very essence of Darwin's theory of evolution, as he declared in The Origin of Species, was that "every complex structure and instinct" should be "useful to the possessor." Natural selection could "never produce in a being anything injurious to itself, for natural selection acts solely by and for the good of each." But now Darwin was allowing kamikaze stinging bees and sugar-filled, childless hanging ants to broaden the spectrum of selection: it could fashion the good of the group as well as the good of the individual.

In truth, this was not a solution to the problem, and the mysteries of heredity would linger years into the future, well after Darwin's day. What he did accomplish, however, by way of failing to solve what amounts to a developmental conundrum, was to bring the logic of evolution to bear on a problem that had been the province of philosophers and moralists. Why is it that beings sometimes put the interests of others above their own? Following many other commentators, Dugatkin thinks that "greater-goodism" was Darwin's solution to the problem of selfless behavior in a competitive world, and in a way it was. But again, Darwin was most perturbed by an altogether different riddle; selflessness did not seem like much of an anomaly to him once life became a social rather than a solitary affair. So the roots of the attempts to find a biological explanation for kindness lay in the great man's ignorance of how organisms develop, and how the instructions for development are passed on. Scientifically speaking, the problem of altruism was stumbled upon too soon.


It was probably in a dank Victorian library in Harrow, on the outskirts of London, that Prince Kropotkin first laid eyes in 1888 on an essay by Thomas Henry Huxley titled "The Struggle for Existence." Kropotkin was the son of a distinguished aristocratic general who claimed descent from the Rurik family, the rulers of Russia before the Romanovs. He grew up in the style of a country gentleman, courted and fed by more than a thousand serfs, and, at the age of eight, costumed as a Persian page at a palace ball, he was noticed and marked for greatness by Czar Nicholas I himself. At fifteen he was sent to Russia's elite military academy, the Corps of Pages, and, graduating at the top of his class, was assigned to be the private page of the new czar, Alexander II. Although he took a personal liking to his liege, the young prince began to view authority as the greatest impediment to human cooperation, and, taken now by nature, he used his station to duly arrange a surprising outpost in the Amur region, the "outback of outbacks" of the Siberian steppes. This would be his version of the voyage of the Beagle, and it would give birth to a theory very different from Darwin's, for Kropotkin had already read The Origin of Species and had taken the "struggle for existence" to be entirely wrong.

Years later, in exile in Harrow, Kropotkin was enraged by the words of Darwin's self-appointed bulldog. "Life was a continual free fight," Huxley wrote, "and beyond the limited and temporary relations of the family, the Hobbesian war of each against all was the normal state of existence.... The history of civilization ... is the record of the attempts which the human race has made to escape from this position." Treading the path laid by Malthus, Hobbes, Machiavelli, and Augustine all the way back to the Sophist philosophers, Huxley believed that human nature was fundamentally selfish, and needed the refinement of culture to lift it above the animal fray. After all, how could nature's "war of each against all"--what Darwin called "the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms"--lead to anything other than the survival of the self-interested strong? There was no place in nature for magnanimity, aside from the rare provision of kindness between kin. For the hardened progressivist Huxley, "the ethical progress of society depends, not on imitating the cosmic process [evolution], still less in running away from it, but in combating it."

This "atrocious article" seemed to Kropotkin a distorted mistranslation of rugged British individualism and cut-throat laissez-faire economics into a natural world which was nothing of the kind. Wherever Kropotkin had looked in Siberia, he saw animals struggling together against the elements by sacrificing for each other and building societies of mutual aid. Wolves hunting in packs, horses forming defensive rings against predators, kittens huddling together to stay warm, selfless (and usually solitary) beetles coming together to bury the corpse of a small animal so that some of their kind might live off its decaying organic matter and lay their eggs within--all these made plain to Kropotkin what had escaped Malthus and Huxley and even Darwin himself: cooperation, not competition, was the rule of nature. The "infidels" who had "raised the pitiless struggle for personal advantages to the height of a biological principle" had distorted Darwin's theory. It was Godwin and Rousseau who had it right, not Hobbes: selfishness was not an animal legacy. Cooperation and benevolence were humankind's evolutionary heritage; and if people would only hark back to nature, altruism would flourish and "full liberty of initiative and action" would once again be restored.

Returning to Moscow from the steppes, Kropotkin began a double life as palace aristocrat and peasant agitator, assuming the pseudonym Borodin and moving with subversive alacrity between Winter Palace dining halls and underground anti-czarist meetings, where he published such materials as "The Scientific Bases of Anarchy." His cover was eventually blown, leading to two very lonely and scurvy-ridden years at the Peter and Paul prison, which in turn led to a dramatic escape and finally to self-enforced exile in London's dreary outskirts. Desperate to counter the cutthroat Victorian interpretation of Darwin's natural world, the anarchist prince produced a book, Mutual Aid, that quickly became a classic. He went to his grave believing that goodness had been hardwired by evolution into animals as well as into humans, and that if only government were banished and mankind returned to the ways of the wild, altruism and kindness could raise their heads once more.

After Mutual Aid was published in 1902, biologists increasingly embraced the theory of "greater-goodism," widening its Darwinian scope from the ants and the bees to a general principle of nature. At Harvard, the entomologist Morton Wheeler spoke of the community as a single individual, rendering "altruism" little more than a specialization of function: sterile workers toiling for the nest made as much sense as a heart pumping for the good of the body. In the 1920s in Chicago, a group of ecologists led by A.C. Allee and Alfred Emerson followed Kropotkin by emphasizing the struggle of organisms against their environments rather than against each other--the kind of battles that Darwin himself had visualized as "a plant on the edge of the desert" struggling against the drought. Darwin had expressly stated that what he meant by the struggle for existence included this more metaphorical kind of battle alongside "nature bloody in tooth and claw," but in practice he tended to discount the former in favor of Tennyson's more bellicose depiction. ("Red in tooth and claw" appeared in Tennyson's poem nine years before the publication of Darwin's book.) By focusing on the more metaphorical kind of struggle, the ecologists from Chicago saw cooperation in nature rather than competition, discovering such surprises as "friendly" starfish and "loyal" sea urchins. Allee was a Quaker who sought to provide the scientific rationale for pacifism that Quakerism invited but lacked. He even contributed a number of articles to The New Republic, arguing that spontaneous aggregations of starfish protecting one another in the absence of grassy cover proved that when humans went to war, they were acting against their cooperative nature.

If life is a competitive struggle, how can cooperation ever arise? How can self-seeking beings ever graduate into selflessness if chivalry is punished and egoism extolled? In the vein of Kropotkin and the Chicago School, an influential Scottish bird expert thought he had the answer. V.C. Wynne-Edwards observed that when food becomes scarce, animals tend to reproduce less, as if consciously regulating their numbers. This could not be explained by classical Darwinism. Why would an individual check his own reproduction, the only true measure of earthly success? Wynne-Edwards offered that if groups that regulated their dispersal did better on the whole than groups that did not, then natural selection would tend to favor them over their rivals, and self-regulating behavior would evolve. So the unit of natural selection was the group rather than the individual, for clearly the collective benefit of the crowd could trump the self-seeking interest of the greedy singleton.

Except that Wynne-Edwards and "greater-goodism" had one little problem. They could think of no convincing natural mechanism to explain their feel-good theory, a fact that had been all too obvious to an inebriated genius crouched over his beer in a London pub. He was J.B.S. Haldane. In the 1920s and 1930s, the Cambridge biochemist and mathematical geneticist's popular essays and books were widely read, and his Periclean speeches--to the Royal Society, to Cambridge's iconoclastic Heretics Society, and in Hyde Park--were famous. He was a scientist, a philosopher, a writer, and a political speaker. "Ce n'est pas un homme," a scientific colleague said of him, "c'est une force de la nature!" Others simply said of Haldane that he was "the last man to know all there is to know." So perhaps it is not all that surprising that, slouched over his beer, Haldane made an offhand remark that was to lead to the apparent solution of the problem of altruism. "I'd jump into the river to save two brothers and eight cousins," he is said to have slurred. Here was the core idea: altruism was a function of genetic relatedness.

But it would not be Haldane who would work it out. That was left to Bill Hamilton, a bushy-browed loner born in 1936 in Oaklea, Kent, just a four-mile walk from Darwin's old Down House. In his youth, Hamilton read the classic tome of R.A. Fisher, another of the great population biologists of the 1930s, and his restless mind became animated with genes and mathematics. Spending lonely nights huddled on the benches of Waterloo Station scribbling equations, Hamilton desperately sought to solve nature's mystery of kindness. His perplexed and increasingly angry supervisors (he was enrolled simultaneously in doctoral programs in anthropology and genetics in two separate universities) did not understand what his anguish was all about: after all, "greater-goodism" instructed that "altruism" protected a species from extinction--case closed. But Hamilton did not believe it. Would not one of Wynne-Edwards's birds, who perceived his friends' communal forfeit in times of strife, stand to gain immeasurably by defecting? Surely such a bird would sire a greater proportion of the next generation, and if his "defecting" nature was passed on through his genes, "cooperators" would be reproductively stamped out of the population. This was a notion that a colorful former student of Haldane's, John Maynard Smith, had also been bruiting about at the time.

So group selection is not evolutionarily stable, and individual selection fails to explain altruistic behavior. Perhaps, then, selection was operating on a completely different level. This had been Haldane's drunken insight: if genes were the entities vying to get to the next generation, then it made sense for individuals to incur a cost at their own expense if at the same time they conferred a benefit on relatives who carried the same genes. From the point of view of the gene, it would not really matter. That is why jumping into a river to rescue two brothers, whose relatedness co-efficient is one-half, or eight cousins, whose relatedness co-efficient is one-eighth, would make sense even if the savior lost his life in the process. Nothing would be lost; the very same genes that would die in the altruist's sinking body would thrive in the bodies of those he had gallantly saved, and could be passed on to their children. Organisms, in this view, were simply the gene's way of getting itself into the next generation.

Trudging through the math, Hamilton finally came up with an elegant equation. r x b > c was the mathematical formulation of the idea that if the cost (c) of acting altruistically (measured in numbers of offspring the altruist loses by conferring help on another) was lower than the benefit (b) to the recipient of the altruistic act (again, measured in numbers of offspring) times the co- efficient of relatedness (r) of the two players (the probability that the two individuals both possess the gene in question), then genes for altruistic behavior could evolve. Suddenly the mystery of the ants vanished into thin air: since, due to a quirk of their genetics, female workers are more related to their sisters than to their daughters, it actually makes good genetic sense for them to invest in helping their sister, the queen, to procreate like mad. In this way more of their own genes would make it through to the next generation than if they procreated themselves. Incredibly, what became known as Hamilton's Rule seemed to make it possible to predict just how much altruism should be expected as a function of the degree of genetic relatedness: the lower the r, the lesser the degree of "good-heartedness"; the greater the r, the more "chivalry" rises to the fore. Hamilton and Maynard-Smith published these ideas at around the same time in the 1960s, and the face of biology was changed. The gene had emerged as the star actor in the modern production of "Why goodness?"

Meanwhile, in America, a disaffected former chemist turned science writer was breaking up with his religious wife. With the insurance money from a botched thyroid operation, George Price bought a ticket on the Queen Elizabeth and sailed to England. There, he decided, he was going to help crack the problem of altruism. Never mind that he had no statistical or biological education, nor institutional affiliation, nor any connections. Noting on his resume that the years 1967-1968 would be devoted to "reading and writing in London on evolutionary biology, while living on savings," Price went straight to work. Soon a daunting realization struck him: not only was Hamilton's mathematics sound, but in fact it could be generalized further to explain not only altruism but also the evolution of spiteful behavior. The logic of the gene seemed unassailable: beings were good to each other, or bad, because their genes were running the show.

Price grew increasingly disturbed. If genes were our masters, then--contrary to our intuition--no true goodness could ever exist. It was all a farce: self- interested genes masquerading in "altruistic" bodies, Nature's grotesque joke on her sole conscientious creation. Once a passionate atheist, Price now discovered God. As if trying to fight nature's cruel inheritance, he began giving away his possessions to the destitute among whom he lived, desperately seeking to find a genuine goodness within. In the end, hopeless, broke, and alone, he slit his throat and was found dead by the police on the linoleum floor of his decrepit London squat. The funeral, on a cold, rainy day in January 1975, was attended by eight people: Hamilton, Maynard-Smith, and a handful of red-nosed drunks who had been Price's last companions.


Hamilton's Rule was good for the family, but what about altruism between non-kin? Dugatkin stops here, but this, after all, has been the moralist's concern throughout the ages, sacrifice among relations being intuitively less of a riddle. Recognizing the problem, the Jewish and Christian traditions exhorted their followers to "love thy neighbor as thyself," but Aristotle was more hard- boiled. "The friendly feelings that we bear for another," he wrote in the Nichomachean Ethics, "have arisen from the friendly feelings that we bear for ourselves." Pagan thought was not the only hardened philosophy on the moralism block: Aquinas took a surprisingly utilitarian position, arguing in the Summa Theologica that we should love ourselves more than our neighbors. His interpretation of the Pauline phrase was that we should seek the common good more than the private good, since the common good is a more desirable good for the individual. Hume, in A Treatise of Human Nature, spelled out what the medieval theologian was thinking: "I learn to do service to another, without bearing him any real kindness: because I foresee, that he will return my service, in expectation of another of the same kind, and in order to maintain the same correspondence of good offices with me or others." In 1776, the year of Hume's death, his Edinburgh neighbor, the economist Adam Smith, put it even more directly in The Wealth of Nations: "It is not from the benevolence of the butcher, the brewer, or the baker, that we expect our dinner, but from their regard to their own interest. We address ourselves not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages. Nobody but a beggar chooses to depend chiefly on the benevolence of his fellow citizens." And most succinct of all was Bernard de Mandeville's couplet, from 1714: "Thus every Part was full of Vice/Yet the whole Mass a Paradise."

And so, when a precocious son of Lithuanian Jewish immigrants started his education at Harvard in the early 1960s, he had quite a philosophical tradition to build on. But Robert Trivers was not interested in biology; he wanted to be a lawyer, and it would take a tragic breakdown (a mania that took the form of staying up all night, night after night, reading Wittgenstein and finally collapsing) to bring him closer to the animal world. While recovering, Trivers (who, strangely, does not appear in Dugatkin's book) took a course in illustrating, and was hired to draw animals for a biology textbook. His mentor was Bill Drury, an ornithologist whom the young Trivers learned to love and revere. "Bill and I were walking in the woods one day," Trivers once told a reporter, "and I told him that my first breakdown had been so painful that I had resolved that if I ever felt another one coming on, I would kill myself. Lately, however, I had changed my mind, and drawn up a list of ten people I would kill first in that event. I wanted to know if this was going forwards or backwards. He thought for a while, then he said, 'Can I add three names to that list?' That was his only comment." With Drury's encouragement, Trivers signed up for a doctorate in zoology armed with a plan to study monkeys. But his adviser was a herpetologist, and pointed Trivers to Jamaica and lizards instead. "When we flew to Jamaica," Trivers remembers, "I took one look at the women and one look at the island and decided to become a lizard man if that's what it took to go back there." Thus was born the career of the man who would pretend to explain altruism.

Like Hamilton and Maynard-Smith, and indeed Darwin before them, Trivers thought that behavior was as much a product of evolution as were eyes and ears and feathers and tails. And with the help of solid Darwinian and game- theoretical logic, he came to see, like Aquinas and Hume and Adam Smith, that self-sacrifice could serve one's interest if the chance was better than decent that the good deed would someday be repaid. This depended on the rewards of cooperation outweighing the costs of conflict, on coming into regular contact with one's neighbors, and on being able to remember just how friendly or selfish they had been in previous encounters. The theory of "reciprocal altruism" was modeled as the famous Prisoner's Dilemma, and Trivers and others were able to show that repeated encounters between "players" would produce cooperative behavior, since in the long run this provided more gain. Literally and logically, benevolence can be born of self-seeking: under the right circumstances, cooperation actually pays.

Game-theoretical logic combined with the all-powerful point of view of what Richard Dawkins called "the selfish gene" to make a revolution in the study of the natural world. Whether animals aid their kin (ants and wolves who help their sisters breed) or nonrelatives (generous vampire bats who share blood, mouth to mouth, at the end of the night with members of the troop who were less successful); whether animals abandon their children (many species of birds do so when the going goes rough) or sacrifice themselves for the next generation (male praying mantids serve their heads during coitus to their avaricious ladies); whether they help the group (Kropotkin's Siberian steeds forming rings against predators) or themselves at the expense of others (from common colds to cancer)--no matter how they appear to serve others, all living things are acting in the interest of their true masters: a cabal of genes whose sole imperative is their own replication. In the body, in the family, in the outside world: countless iterated games and events of selection had fashioned genes that do whatever it takes to survive.

This perspective could sometimes lead to wacky notions. Here is Dawkins:

Consider a pride of lions gnawing at a kill. An individual who eats less than her physiological requirement is in effect behaving altruistically towards others who get more as a result. If these others were close kin, such restraint might be favored by kin selection. But the kind of mutation that could lead to such altruistic restraint could be ludicrously simple. A genetic propensity to bad teeth might slow down the rate at which an individual could chew at the meat. The gene for bad teeth would be, in the full sense of the technical term, a gene for altruism, and it might indeed be favored by kin selection.

"Tooth decay as altruism?" the biologist and philosopher Helena Cronin asked, in her book The Ant and the Peacock. "That's hardly how saintly self-sacrifice was originally envisaged! And yet," she added, "the logic is unassailable."

The concept that genes, unrelated to our own notions of kindness, could be responsible for behaviors that we choose to so define was quite a strange notion. But a specific insight of Trivers's that was even more jarring, for it came closer to traditional notions of what kindness really means. Benevolence, Trivers reasoned, requires a strong sense of justice. This is because a sense of justice is necessary in order to appreciate dishonesty, and what better way to police a system of reciprocal good faith than to be able to detect deceit? Over evolutionary time, beginning with the animals, a genuine instinct of fairness had been born from the need to distinguish trusty campers from party-pooping cheats. Our sense of right and wrong, after all that could possibly be said and thought about it, is actually in our genes.

Darwin, in fact, had the original intuition, only without the accompanying game-theoretical logic and the gene's-eye point of view. In The Descent of Man, in 1871, he wrote:

Mr J.S. Mill speaks, in his celebrated work, "Utilitarianism," of the social feelings as a "powerful natural sentiment" and as "the natural basis of sentiment for utilitarian morality."... But ... he also remarks, "... the moral feelings are not innate, but acquired...." It is with hesitation that I venture to differ at all from so profound a thinker, but it can hardly be disputed that the social feelings are instinctive or innate in the lower animals; and why should they not be so in man? [Several thinkers] believe that the moral sense is acquired by each individual during his lifetime. On the general theory of evolution this is at least extremely improbable. The ignoring of all transmitted mental qualities will, as it seems to me, be hereafter judged as a most serious blemish in the works of Mr. Mill.

In private, rhetorical deference could duly be abandoned: "He who understands baboon," Darwin wrote in his personal notebook, "would do more towards metaphysics than Locke." The mind had been crafted by millions of years of evolution. Life in small, socially stable units produced in Nature something entirely, spectacularly new: the biological adaptation of morality.


So where do we stand today? Haldane's drunken insight and Hamilton's resulting rule have actually held up incredibly well. From the African naked mole rats--the mammalian equivalent of termites--who forsake procreation in order to help their chosen monarch, to the carnivorous spadefoot toad tadpole who can actually "taste" relatedness and therefore spits out cousins and brothers--but not strangers--who find themselves ominously in his mouth, relatedness has proved a robust predictor of altruistic behavior. Even cuckoo birds have figured out this metric: they take advantage of other birds' familial instincts by laying their eggs in complete strangers' nests, allowing the tricked parents to shoulder the burden of parenthood. The biologist Stephen Emlen and his group of ecologists and evolutionary modelers at Cornell University have in the past three decades used Hamiltonian logic to make sense of many family dramas of love and deception in the animal world, and the general rule seems to hold: the closer the kin, the greater the benevolence. The fact that stepchildren are much more likely to be abused by their parents than biological children has been used by some to argue that the genetic logic of relatedness has left its fingerprint, real and tragically unforgiving, on unsuspecting but culpable humankind: man and tadpole might not be as distant as we imagine.

But reciprocal altruism between non-kin in nature has proved more difficult to establish. For one thing, helpers might actually be related more often than Trivers and others suspected, rendering "reciprocal altruism" nothing but a looser version of Hamiltonian kin selection. (This now seems to be the case, for example, with blood-sharing bats.) Another problem seems to be that behaviors once interpreted as selfless assistance (baboons grooming each other's backs for fleas) may actually just be a form of mutualism (the baboons gain valuable nourishment from eating their friends' pests). Yet another thorn in the side of the you-scratch-my-back-I'll-scratch-yours theory comes courtesy of Oscar Wilde. "I can resist everything but temptation," he is said to have quipped, and most animals, experiments show, are not all that different. Immediate gratification is the custom of even the most intelligent and social of mammals, and it is hardly the best path to establish the courtly conventions that serve as requisites for reciprocal restraint. Finally, a competing theory called the "handicap principle," espoused by the Israeli zoologist Amotz Zahavi, argues that animals who perform ostensible acts of sacrifice are actually advertising the fact that they can afford to do so--a sign of their strength and endurance. Thus, when a gazelle spots a lion lurking in the grass and begins to jump up and down six feet into the air, what may seem like a selfless warning to her friends is actually a signal to the lion that he should focus his pursuit on a member of the troop less athletic and therefore more likely to end up in his palate. A male peacock sporting a gigantic colorful tail, or a bull elk showing off its large rack of antlers, may be signaling to potential mates not to look any further, that they are stronger precisely because they carry a hindrance that would handicap a lesser fellow. Yet recent studies have called some of the data supporting the handicap principle into question, and "reciprocal altruism," where it exists, seems to be circumscribed to just a few highly social mammals. If kindness exists in nature, it is almost certain to be bestowed on kin.

Not so in humans. As if we really needed them to do so, clever scientists at respectable institutions now use $20 bills and "donating experiments" to teach us that many people cooperate with others even when it is absolutely clear that they have nothing to gain. This may not be all that surprising if one considers how valuable regard, and its more subtle sibling self-regard, may be to human beings. But why should this be so? The economist Robert Frank proposed that it all comes down to trust: to do well in life, our simian and hunter-gatherer ancestors needed to forsake the short-term temptation of self-interest, since they lived in small, mutually dependent groups. Emotions, or what used to be called moral sentiments, helped to solve such conflicts by establishing commitment ("I love you, and won't leave you") and eliciting reciprocity ("I love you, love me back!"). Life is finally a game in which one seeks trusted partners to play with, so altruistic acts are the price we pay--our "handicap"--for having what amount to self-interested emotions. According to this view, we have the capacity for goodness for no other reason than that it helps us join hands with other virtuous sorts to everyone's mutual advantage.

This may help to explain why we are so good at detecting cheaters. A number of clever experiments suggest that this is in fact a cognitive bias: we are better at solving logical riddles that have to do with exposing swindlers in real-life situations than we are at solving the very same riddles when they remain abstract. So perhaps a sense of fairness really is a part of our biology. Reciprocal good faith seems to require policing, which may in the end, be the source of our capacity for justice. A recent study by Ernst Fehr shows how the size of the group in which reciprocal altruism becomes possible can be increased if cheaters are punished. (The problem this helps to solve is that the larger the group, the easier it is for cheaters to slip through the cracks.) The group can grow larger still if not only cheaters are punished, but also people who do not punish cheaters, and so forth. So as the group size of monkeys and then humans grew from tens to hundreds and then to thousands, mechanisms evolved to safeguard cohesion. Today, scientists tell us, we choose to call such mechanisms morality, justice, conscience--august ascriptions that are really just culture's words for biological instincts.

A recent study takes this kind of argument one step further. The neuroscientists Jorge Moll and Jordan Grafman placed volunteers in a functional MRI unit and asked them to imagine either donating a sum of money to charity or keeping it for themselves. They found that thoughts of generosity activated a primitive part of the brain that lights up with reference to food and sex--a result interpreted by them to mean that altruism is as hard-wired into our brains as our most primitive and basic functions. The psychologist Marc Hauser claims that his research proves that all over the world people process ethical dilemmas in very similar ways, suggesting that the capacity for moral judgment, like language, should be thought of as intrinsic to our brain, rather than a product of our culture. All this kind of science, much of it still woefully "soft" but nonetheless suggestive, is a far cry from the moral transcendence that Thomas Huxley had in mind when he spoke of mankind's need for "combating" the "cosmic process." One can only wonder what Darwin would have made of it.

But how strong a grip should the biological approach to morality have on our own imaginations? To begin with, we can agree that Kropotkin got it backward by searching for reciprocity in nature in order to urge it upon civilization. Reciprocal relations define the human condition, and real charity may in fact be a uniquely human invention. Hobbes was right that we are out for ourselves, but Rousseau was not wrong that harmony and progress are possible without government. Self-seeking can produce genuine and true benevolence, and, it would seem, there are compelling reasons from evolution to believe that this all began in nature. So Kropotkin and Huxley both held a piece of the truth.

As for Hamiltonian kin-selection logic, it is often attacked on the grounds that it implies genetic determinism. The notion that genes are running the show does not comport well with our self-important conscience--nor, in truth, with our healthy intuitions about reality. But this is not the best way to safeguard human free will from the threat of biological necessity, for two very important reasons. First, when Hamilton spoke of genes for altruism, he was really using a shorthand for genes that increase the probability that their bearers will behave altruistically. So long as such behaviors have a genetic component, Hamilton's theory applies. Despite the incautious remarks of scientists (and, more often, science writers), this does not imply that a behavior is determined, and it is entirely compatible with culture and education playing a central, even exclusive role. There may be no behavior in humans that, strictly speaking, has no genetic component, but this is a world away from saying that our genes determine who we are and what we choose. Natural selection based on cultural variation has produced behaviors that have nothing directly to do with genes.

The second reason is that many human behaviors clearly have absolutely nothing to do with natural selection in the narrow biological sense. For the biologist, the consequences of an action for reproductive fitness are what determine whether the action counts as altruistic, not the intentions with which the action is performed. Psychological, or "true," altruism is independent from the kind of altruism that confers fitness on its bearer. Helping an elderly lady across the street can hardly affect her fitness, while selfishly snubbing her grandson could lead--who knows?--to his decision to have children who will exact revenge on you someday. Selfishness and altruism in human affairs has nothing to do with tadpoles spitting and mole rats digging and cuckoo birds sneaking eggs into strangers' nests. Kindness is kindness only if it is meant to be so.

We have known this truth for many years. In The Theory of Moral Sentiments, Adam Smith wrote that "man possesses the capacities which interest him in the fortune of others, and render their happiness necessary to him, though he derives nothing from it, except the pleasure of seeing it"--and there is no arguing that he was right. So perhaps a more useful way to think of things is to consider that evolution has blessed us with many gifts. What we do with them is our challenge, for together with kindness we were given also the capacities for cruelty, malice, and just pure boredom. If our genetic endowments provide the foundation for both ethical action and unethical action, then our moral life is up to us. There can be no doubt that social life in nature put into place the substrates that would one day allow the birth in humans of something we call our moral sense: the policing against cheaters, the mechanism for conflict resolution, and the capacities for empathy, reciprocity, jealousy, and rage are all way stations on this wondrous evolutionary journey.

This same journey also saw the laying down of the basic needs and compulsions of our species: the desire to be a part of the group, the dependence of young on care, the striving for status, the desire for sex, the motherly instinct, and of course the survival instinct itself. These basic compulsions and necessities are not infinitely pliable, nor should our moral sense ignore them. The fact that goodness may have natural origins--"the so- called moral sense is aboriginally derived from the social instincts," Darwin declared--can, in the wrong hands, be made to be confusing and coarsening, for it tends to produce a mentality that discounts what is not utilitarian in the biological sense. We must resist such scientistic "originalism." Sure, natural disposition plays a part in our decision-making process, but it is hardly our most interesting or our most distinguishing feature--nor can it ever lead directly to the moral imperatives that help define our lives.

Bill Hamilton, in an article in a Japanese insect magazine, asked that, when he died, his body be laid out beneath the canopy of the Brazilian rain forest so that the giant copropheanaeus beetle could join hands with its friends to bury him, allowing some, but not all, of the toilers to live off the remains and lay their eggs within his corpse. I guess there was something in Hamilton that wanted to live forever through his beloved "altruistic" beetles. He died tragically in 2000 from malaria contracted during an unfortunate trip to the Congo, which he understood to prove that AIDS was the result of a botched polio vaccination program in the 1950s by avaricious drug companies. In the end, however, he had a conventional burial in Wytham Village. His family wanted him close by.

OREN HARMAN is an assistant professor in the Interdisciplinary Program on Science Technology and Society at Bar Ilan University. He is the author of The Man Who Invented the Chromosome (Harvard University Press, 2004) and the co-editor of Rebels, Mavericks and Heretics in Biology (Yale University Press, 2008).

By Oren Harman