An ethos of reciprocity can pilot not just one-on-one exchanges but contributions to the public good, such as hunting animals that are too large for the hunter to eat himself, building a lighthouse that keeps everyone’s ships off the rocks, or banding together to invade neighbors or to repel their invasions. The inherent problem with public goods is captured in Aesop’s fable “Who Will Bell the Cat?” The mice in a household agree they would be better off if the cat had a bell around its neck to warn them of its approach, but no mouse will risk life and limb to attach the bell. A willingness to bell the cat—that is, to contribute to the public good—can nonetheless evolve, if it is accompanied by a willingness to reward those who shoulder the burden or to punish the cheaters who shirk it.48
The tragedy of reciprocal altruism is that sacrifices on behalf of nonrelatives cannot survive without a web of disagreeable emotions like anxiety, mistrust, guilt, shame, and anger. As the journalist Matt Ridley puts it in his survey of the evolution of cooperation:
Reciprocity hangs, like a sword of Damocles, over every human head. He’s only asking me to his party so I’ll give his book a good review. They’ve been to dinner twice and never asked us back once. After all I did for him, how could he do that to me? If you do this for me, I promise I’ll make it up later. What did I do to deserve that? You owe it to me. Obligation; debt; favour; bargain; contract; exchange; deal…. Our language and our lives are permeated with ideas of reciprocity.49
Studies of altruism by behavioral economists have thrown a spotlight on this sword of Damocles by showing that people are neither the amoral egoists of classical economic theory nor the all-for-one-and-one-for-all communalists of Utopian fantasies. In the Ultimatum Game, for example, one participant gets a large sum of money to divide between himself and another participant, and the second one can take it or leave it. If he leaves it, neither side gets anything. A selfish proposer would keep the lion’s share; a selfish respondent would accept the remaining crumbs, no matter how small, because part of a loaf is better than none. In reality the proposer tends to offer almost half of the total sum, and the respondent doesn’t settle for much less than half, even though turning down a smaller share is an act of spite that deprives both participants. The respondent seems to be driven by a sense of righteous anger and punishes a selfish proposer accordingly; the proposer anticipates this and makes an offer that is just generous enough to be accepted. We know that the proposer’s generosity is driven by the fear of a spiteful response because of the outcome of two variants of the experiment. In the Dictator game, the proposer simply divides the sum between the two players and there is nothing the respondent can do about it. With no fear of reprisal, the proposer makes a far stingier offer. The offer still tends to be more generous than it has to be, because the proposer worries about getting a reputation for stinginess that could come back to bite him in the long run. We know this because of the outcome of the Double-Blind Dictator game, where proposals from many players are sealed and neither the respondent nor the experimenter knows who offered how much. In this variant, generosity plummets; a majority of the proposers keep everything for themselves.50
And then there is the Public Good game, in which everyone makes a voluntary contribution to a common pot of money, the experimenter doubles it, and the pot is divided evenly among the participants regardless of what they contributed. The optimal strategy for each player acting individually is to be a free rider and contribute nothing, hoping that others will contribute something and he can get a share of their contribution. Of course, if every player thinks that way, the pot stays empty and no one earns a dime. The optimum for the group is for all the players to contribute everything they have so they can all double their money. When the game is played repeatedly, however, everyone tries to become a free rider, and the pot dwindles to a self-defeating zero. On the other hand, if people are allowed both to contribute to the pot and to levy fines on those who don’t contribute, conscience doth make cowards of them all, and almost everyone contributes to the common good, allowing everyone to make a profit.51 The same phenomenon has been independently documented by social psychologists, who call it “social loafing.” When people are part of a group, they pull less hard on a rope, clap less enthusiastically, and think up fewer ideas in a brainstorming session—unless they think their contributions to the group effort are being monitored.52
These experiments may be artificial, but the motives they expose played themselves out in the real-life experiments known as Utopian communities. In the nineteenth century and early decades of the twentieth, self-contained communes based on a philosophy of communal sharing sprang up throughout the United States. All of them collapsed from internal tensions, the ones guided by socialist ideology after a median of two years, the ones guided by religious ideology after a median of twenty years.53 The Israeli kibbutzim, originally galvanized by socialism and Zionism, steadily dismantled their collectivist philosophy over the decades. It was undermined by their members’ desire to live with their families, to own their own clothing, and to keep small luxuries or sums of money acquired outside the kibbutz. And the kibbutzim were dragged down by inefficiencies because of the free-rider problem—they were, in the words of one kibbutznik, a “paradise for parasites.”54
In other cultures, too, generosity is doled out according to a complex mental calculus. Remember Fiske’s ethnographic survey, which shows that the ethic of Communal Sharing arises spontaneously mainly within families (and on circumscribed occasions such as feasts). Equality Matching—that is, reciprocal altruism—is the norm for everyday interactions among more distant relatives and nonrelatives.55 A possible exception is the distribution of meat by bands of foragers, who pool the risks of hunting large game (with its big but unpredictable windfalls) by sharing their catch.56 Even here, the ethic is far from unstinting generosity, and the sharing is described as having “an edge of hostility.”57 Hunters generally have no easy way of keeping their catch from others, so they don’t so much share their catch as stand by while others confiscate it. Their hunting effort is treated as a public good, and they are punished by gossip and ostracism if they resist the confiscation, are rewarded by prestige (which earns them sexual partners) if they tolerate it, and may be entitled to payback when the tables turn. A similar psychology may be found among the last hunter-gatherers in our own culture, commercial fishermen. In The Perfect Storm, Sebastian Junger writes:
Sword[fish] boat captains help each other out on the high seas whenever they can; they lend engine parts, offer technical advice, donate food or fuel. The competition between a dozen boats rushing a perishable commodity to market fortunately doesn’t kill an inherent sense of concern for each other. This may seem terrifically noble, but it’s not—or at least not entirely. It’s also self-interested. Each captain knows that he may be the next one with the frozen injector or the leaking hydraulics.58
Beginning with Ashley Montagu in 1952, thinkers with collectivist sympathies have tried to eke out a place for unmeasured generosity by invoking group selection, a Darwinian competition among groups of organisms rather than among individual organisms.59 The hope is that groups whose members sacrifice their interests for the common good will outcompete those in which every man is for himself, and as a result generous impulses will come to prevail in the species. Williams dashed the dream in 1966 when he pointed out that unless a group is genetically fixed and hermetically sealed, mutants or immigrants constantly infiltrate it.60 A selfish infiltrator would soon take over the group with its descendants, who are more numerous because they have reaped the advantages of others’ sacrifices without making their own. This would happen long before the group could parlay its internal cohesion into victory over neighboring groups and bud off new offspring groups to repeat the process.
The term “group selection” survives in evolutionary biology, but usually with different meanings from the one Montagu had in mind. Groups were certainly part of our evolutionary environment, and our ancestors evolved tra
its, such as a concern with one’s reputation, that led them to prosper in groups. Sometimes the interests of an individual and the interests of a group can coincide; for example, both do better when the group is not exterminated by enemies. Some theorists invoke group selection to explain a willingness to punish free riders who do not contribute to the public good.61 The biologist David Sloan Wilson and the philosopher Elliot Sober recently redefined “group” as a set of mutual reciprocators, providing an alternative language in which to describe Trivers’s theory but not an alternative to the theory itself.62 But no one believes the original idea that selection among groups led to the evolution of unstinting self-sacrifice. Even putting aside the theoretical difficulties explained by Williams, we know empirically that people in all cultures do things that lead them to prosper at the expense of their group, such as lying, competing for mates, having affairs, getting jealous, and fighting for dominance.
Group selection, in any case, does not deserve its feel-good reputation. Whether or not it endowed us with generosity toward the members of our group, it would certainly have endowed us with a hatred of the members of other groups, because it favors whatever traits lead one group to prevail over its rivals. (Recall that group selection was the version of Darwinism that got twisted into Nazism.) This does not mean that group selection is incorrect, only that subscribing to a scientific theory for its apparent political palatability can backfire. As Williams put it, “To claim that [natural selection at the level of competing groups] is morally superior to natural selection at the level of competing individuals would imply, in its human application, that systematic genocide is morally superior to random murder.”63
PEOPLE DO MORE for their fellows than return favors and punish cheaters. They often perform generous acts without the slightest hope for payback, ranging from leaving a tip in a restaurant they will never visit again to throwing themselves on a live grenade to save their brothers in arms. Trivers, together with the economists Robert Frank and Jack Hirshleifer, has pointed out that pure magnanimity can evolve in an environment of people seeking to discriminate fair-weather friends from loyal allies.64 Signs of heartfelt loyalty and generosity serve as guarantors of one’s promises, reducing a partner’s worry that you will default on them. The best way to convince a skeptic that you are trustworthy and generous is to be trustworthy and generous.
Of course, such virtue cannot be the dominant mode of human interaction or else we could dispense with the gargantuan apparatus designed to keep exchanges fair—money, cash registers, banks, accounting firms, billing departments, courts—and base our economy on the honor system. At the other extreme, people also commit acts of outright treachery, including larceny, fraud, extortion, murder, and other ways of taking a benefit at someone else’s expense. Psychopaths, who lack all traces of a conscience, are the most extreme example, but social psychologists have documented what they call Machiavellian traits in many individuals who fall short of outright psychopathy.65 Most people, of course, are in the middle of the range, displaying mixtures of reciprocity, pure generosity, and greed.
Why do people range across such a wide spectrum? Perhaps all of us are capable of being saints or sinners, depending on the temptations and threats at hand. Perhaps we are set on one of these paths early in life by our upbringing or by the mores of our peer group. Perhaps we choose these paths early in life because we are endowed with a deck of conditional strategies on how to develop a personality: if you discover that you are attractive and charming, try being a manipulator; if you are large and commanding, try being a bully; if you are surrounded by generous people, be generous in kind; and so on. Perhaps we are predisposed to being nastier or nicer by our genes. Perhaps human development is a lottery, and fate assigns us a personality at random. Most likely, our differences come from several of these forces or from hybrids among them. For example, we may all develop a sense of generosity if enough of our friends and neighbors are generous, but the threshold or the multiplier of that function may differ among us genetically or at random: some people need only a few nice neighbors to grow up nice, others need a majority.
Genes are certainly a factor. Conscientiousness, agreeableness, neuroticism, psychopathy, and criminal behavior are substantially (though by no means completely) heritable, and altruism may be as well.66 But this only replaces the original question—Why do people vary in their selfishness?—with another one. Natural selection tends to make the members of a species alike in their adaptive traits, because whichever version of a trait is better than the others will be selected and the alternative versions will die out. That is why most evolutionary psychologists attribute systematic differences among people to their environments and attribute only random differences to the genes. This genetic noise can come from at least two sources. Inside the genome, rust never sleeps: random mutations constantly creep in and are only slowly and unevenly eliminated by selection.67 And selection can favor molecular variability for its own sake to keep us one step ahead of the parasites that constantly evolve to infiltrate our cells and tissues. Differences in the functioning of whole bodies and brains could be a by-product of this churning of protein sequences.68
But the theory of reciprocal altruism raises another possibility: that some of the genetic differences among people in their social emotions are systematic. One exception to the rule that selection reduces variability arises when the best strategy depends on what other organisms are doing. The child’s game of scissors-paper-rock is one analogy, and another may be found in the decision of which route to take to work. As commuters begin to avoid a congested highway and opt for a less traveled route, the new one will no longer be less traveled, so many will choose the first one, until congestion builds up there, which will induce still other commuters to choose the second route, and so on. The commuters will eventually distribute themselves in some ratio between the two roads. The same thing can happen in evolution, where it is called frequency-dependent selection.
One corollary of reciprocal altruism, shown in a number of simulations, is that frequency-dependent selection can produce temporary or permanent mixtures of strategies. For example, even if reciprocators predominate in a population, a minority of cheaters can sometimes survive, taking advantage of the generosity of the reciprocators as long as they don’t grow so numerous as to meet other cheaters too often or to be recognized and punished by the reciprocators. Whether the population ends up homogeneous or with a mixture of strategies depends on which strategies are competing, which start off more numerous, how easily they enter and leave the population, and the payoffs for cooperation and defection.69
We have an intriguing parallel. In the real world, people differ genetically in their selfish tendencies. And in models of the evolution of altruism, actors may evolve differences in their selfish tendencies. It could be a coincidence, but it probably is not. Several biologists have adduced evidence that psychopathy is a cheating strategy that evolved by frequency-dependent selection.70 Statistical analyses show that a psychopath, rather than merely falling at the end of a continuum for one or two traits, has a distinct cluster of traits (superficial charm, impulsivity, irresponsibility, callousness, guiltlessness, mendacity, and exploitiveness) that sets him off from the rest of the population.71 And many psychopaths show none of the subtle physical abnormalities produced by biological noise, suggesting that psychopathy is not always a biological mistake.72 The psychologist Linda Mealey has argued that frequency-dependent selection has produced at least two kinds of psychopaths. One kind consists of people who are genetically predisposed to psychopathy regardless of how they grow up. The other kind is made up of people who are predisposed to psychopathy only in certain circumstances, namely when they perceive themselves to be competitively disadvantaged in society and find themselves at home in a group of other antisocial peers.
The possibility that some individuals are born with a weak conscience runs squarely against the doctrine of the Noble Savage. It calls to mind the old-fashioned notions of bo
rn criminals and bad seeds, and it was blotted out by twentieth-century intellectuals and replaced with the belief that all wrongdoers are victims of poverty or bad parenting. In the late 1970s Norman Mailer received a letter from a prisoner named Jack Henry Abbott, who had spent most of his life behind bars for crimes ranging from passing bad checks to killing a fellow prisoner. Mailer was writing a book about the murderer Gary Gilmore, and Abbott offered to help him get into the mindset of a killer by sharing his prison diaries and his radical critique of the criminal justice system. Mailer was dazzled by Abbott’s prose and proclaimed him to be a brilliant new writer and thinker—”an intellectual, a radical, a potential leader, a man obsessed with a vision of more elevated human relations in a better world that revolution could forge.” He arranged for Abbott’s letters to be published in the New York Review of Books and then as a 1980 book, In the Belly of the Beast. Here is an excerpt, in which Abbott describes what it is like to stab someone to death: