Altruism can also evolve when organisms trade favors. One helps another by grooming, feeding, protecting, or backing him, and is helped in turn when the needs reverse. This is called reciprocal altruism, and it can evolve when the parties recognize each other, interact repeatedly, can confer a large benefit on others at small cost to themselves, keep a memory for favors offered or denied, and are impelled to reciprocate accordingly. Reciprocal altruism can evolve because cooperators do better than hermits or misanthropes. They enjoy the gains of trading their surpluses, pulling ticks out of one another’s hair, saving each other from drowning or starvation, and baby-sitting each other’s children. Reciprocators can also do better over the long run than the cheaters who take favors without returning them, because the reciprocators will come to recognize the cheaters and shun or punish them.
The demands of reciprocal altruism can explain why the social and moralistic emotions evolved. Sympathy and trust prompt people to extend the first favor. Gratitude and loyalty prompt them to repay favors. Guilt and shame deter them from hurting or failing to repay others. Anger and contempt prompt them to avoid or punish cheaters. And among humans, any tendency of an individual to reciprocate or cheat does not have to be witnessed firsthand but can be recounted by language. This leads to an interest in the reputation of others, transmitted by gossip and public approval or condemnation, and a concern with one’s own reputation. Partnerships, friendships, alliances, and communities can emerge, cemented by these emotions and concerns.
Many people start to get nervous at this point, but the discomfort is not from the tragedies that Trivers explained. It comes instead from two misconceptions, each of which we have encountered before. First, all this talk about genes that influence behavior does not mean that we are cuckoo clocks or player pianos, mindlessly executing the dictates of DNA. The genes in question are those that endow us with the neural systems for conscience, deliberation, and will, and when we talk about the selection of such genes, we are talking about the various ways those faculties could have evolved. The error comes from the Blank Slate and the Ghost in the Machine: if one starts off thinking that our higher mental faculties are stamped in by society or inhere in a soul, then when biologists mention genetic influence the first alternatives that come to mind are puppet strings or trolley tracks. But if higher faculties, including learning, reason, and choice, are products of a nonrandom organization of the brain, there have to be genes that help do the organizing, and that raises the question of how those genes would have been selected in the course of human evolution.
The second misconception is to imagine that talk about costs and benefits implies that people are Machiavellian cynics, coldly calculating the genetic advantages of befriending and marrying. To fret over this picture, or denounce it because it is ugly, is to confuse proximate and ultimate causation. People don’t care about their genes; they care about happiness, love, power, respect, and other passions. The cost-benefit calculations are a metaphorical way of describing the selection of alternative genes over millennia, not a literal description of what takes place in a human brain in real time. Nothing prevents the amoral process of natural selection from evolving a brain with genuine big-hearted emotions. It is said that those who appreciate legislation and sausages should not see them being made. The same is true for human emotions.
So if love and conscience can evolve, where’s the tragedy? Trivers noticed that the confluence of genetic interests that gave rise to the social emotions is only partial. Because we are not clones, or even social insects (who can share up to three-quarters of their genes), what ultimately is best for one person is not identical to what ultimately is best for another. Thus every human relationship, even the most devoted and intimate, carries the seeds of conflict. In the movie AntZ, an ant with the voice of Woody Allen complains to his psychoanalyst:
It’s this whole gung-ho superorganism thing that I just cant get. I try, but I just don’t get it. What is it, I’m supposed to do everything for the colony and… what about my needs?
The humor comes from the clash between ant psychology, which originates in a genetic system that makes workers more closely related to one another than they would be to their offspring, and human psychology, in which our genetic distinctness leads us to ask, “What about my needs?” Trivers, following on the work of William Hamilton and George Williams, did some algebra that predicts the extent to which people should ask themselves that question.4
The rest of this chapter is about that deceptively simple algebra and how its implications overturn many conceptions of human nature. It discredits the Blank Slate, which predicts that people’s regard for their fellows is determined by their “role,” as if it were a part assigned arbitrarily to an actor. But it also discredits some naïve views of evolution that are common among people who don’t believe in the Blank Slate. Most people have intuitions about the natural state of affairs. They may believe that if we acted as nature “wants” us to, families would function as harmonious units, or individuals would act for the good of the species, or people would show the true selves beneath their social masks, or, as Newt Gingrich said in 1995, the male of our species would hunt giraffes and wallow in ditches like little piglets.5 Understanding the patterns of genetic overlap that bind and divide us can replace simplistic views of all kinds with a more subtle understanding of the human condition. Indeed, it can illuminate the human condition in ways that complement the insights of artists and philosophers through the millennia.
THE MOST OBVIOUS human tragedy comes from the difference between our feelings toward kin and our feelings toward non-kin, one of the deepest divides in the living world. When it comes to love and solidarity among people, the relative viscosity of blood and water is evident in everything from the clans and dynasties of traditional societies to the clogging of airports during holidays with people traveling across the world to be with their families.6 It has also been borne out by quantitative studies. In traditional foraging societies, genetic relatives are more likely to live together, work in each other’s gardens, protect each other, and adopt each other’s needy or orphaned children, and are less likely to attack, feud with, and kill each other.7 Even in modern societies, which tend to sunder ties of kinship, the more closely two people are genetically related, the more inclined they are to come to one another’s aid, especially in life-or-death situations.8
But love and solidarity are relative. To say that people are more caring toward their relatives is to say that they are more callous toward their nonrelatives. The epigraph to Robert Wright’s book on evolutionary psychology is an excerpt from Graham Greene’s The Power and the Glory in which the protagonist broods about his daughter: “He said, ‘Oh god, help her. Damn me, I deserve it, but let her live forever.’ This was the love he should have felt for every soul in the world: all the fear and the wish to save concentrated unjustly on the one child. He began to weep…. He thought: This is what I should feel all the time for everyone.”
Family love indeed subverts the ideal of what we should feel for every soul in the world. Moral philosophers play with a hypothetical dilemma in which people can run through the left door of a burning building to save some number of children or through the right door to save their own child.9 If you are a parent, ponder this question: Is there any number of children that would lead you to pick the left door? Indeed, all of us reveal our preference with our pocketbooks when we spend money on trifles for our own children (a bicycle, orthodontics, an education at a private school or university) instead of saving the lives of unrelated children in the developing world by donating the money to charity. Similarly, the practice of parents bequeathing their wealth to their children is one of the steepest impediments to an economically egalitarian society. Yet few people would allow the government to confiscate 100 percent of their estate, because most people see their children as an extension of themselves and thus as the proper beneficiaries of their lifelong striving.
Nepotism is a universal human bent a
nd a universal scourge of large organizations. It is notorious for sapping countries led by hereditary dynasties and for bogging down governments and businesses in the Third World. A recurring historic solution was to give positions of local power to people who had no family ties, such as eunuchs, celibates, slaves, or people a long way from home.10 A more recent solution is to outlaw or regulate nepotism, though the regulations always come with tradeoffs and exceptions. Small businesses—or, as they are often called, “family businesses” or “Mom-and-Pop businesses”—are highly nepotistic, and thereby can conflict with principles of equal opportunity and earn the resentment of the surrounding community.
B. F. Skinner, ever the Maoist, wrote in the 1970s that people should be rewarded for eating in large communal dining halls rather than at home with their families, because large pots have a lower ratio of surface area to volume than small pots and hence are more energy efficient. The logic is impeccable, but this mindset collided with human nature many times in the twentieth century—horrifically in the forced collectivizations in the Soviet Union and China, and benignly in the Israeli kibbutzim, which quickly abandoned their policy of rearing children separately from their parents. A character in a novel by the Israeli writer Batya Gur captures the kind of sentiment that led to this change: “I want to tuck in my children at night myself… and when they have a nightmare I want them to come to my bed, not to some intercom, and not to make them go out at night in the dark looking for our room, stumbling over stones, thinking that every shadow is a monster, and in the end standing in front of a closed door or being dragged back to the children’s house.”11
It is not just recent dreams of collectivism that are subverted by kin solidarity. The journalist Ferdinand Mount has documented that the family has been a subversive institution throughout history. Family ties cut across the bonds connecting comrades and brethren and thus are a nuisance to governments, cults, gangs, revolutionary movements, and established religions. But even a thinker as sympathetic to human nature as Noam Chomsky does not acknowledge that people feel differently about their children from how they feel about acquaintances and strangers. Here is an excerpt of an interview with the lead guitarist of the rap metal group Rage Against the Machine:
RAGE: Another unquestionable idea is that people are naturally competitive, and that therefore, capitalism is the only proper way to organize society. Do you agree?
CHOMSKY: Look around you. In a family for example, if the parents are hungry do they steal food from the children? They would if they were competitive. In most social groupings that are even semi-sane people support each other and are sympathetic and helpful and care about other people and so on. Those are normal human emotions. It takes plenty of training to drive those feelings out of people’s heads, and they show up all over the place.12
Unless people treat other members of society the way they treat their own children, the answer is a non sequitur: people could care deeply about their children but feel differently about the millions of other people who make up society. The very framing of the question and answer assumes that humans are competitive or sympathetic across the board, rather than having different emotions toward people with whom they have different genetic relationships.
Chomsky implies that people are born with fraternal feelings toward their social groups and that the feelings are driven out of their heads by training. But it seems to be the other way around. Throughout history, when leaders have tried to unite a social group they have trained their members to think of it as a family and to redirect their familial emotions inside it.13 The names used by groups that strive for solidarity—brethren, brotherhoods, fraternal organizations, sisterhood, sororities, crime families, the family of man—concede in their metaphors that kinship is the paradigm to which they aspire. (No society tries to strengthen the family by likening it to a trade union, political party, or church group.) The tactic is provably effective. Several experiments have shown that people are more convinced by a political speech if the speaker appeals to their hearts and minds with kinship metaphors.14
Verbal metaphors are one way to nudge people to treat acquaintances like family, but usually stronger tactics are needed. In his ethnographic survey, Alan Fiske showed that the ethos of Communal Sharing (one of his four universal social relations) arises spontaneously among the members of a family but is extended to other groups only with the help of elaborate customs and ideologies.15 Unrelated people who want to share like a family create mythologies about a common flesh and blood, a shared ancestry, and a mystical bond to a territory (tellingly called a natal land, fatherland, motherland, or mother country). They reinforce the myths with sacramental meals, blood sacrifices, and repetitive rituals, which submerge the self into the group and create an impression of a single organism rather than a federation of individuals. Their religions speak of possession by spirits and other kinds of mind melds, which, according to Fiske, “suggest that people may often want to have more intense or pure Communal Sharing relationships than they are able to realize with ordinary human beings.”16 The dark side of this cohesion is groupthink, a cult mentality, and myths of racial purity—the sense that outsiders are contaminants who pollute the sanctity of the group.
None of this means that nonrelatives are ruthlessly competitive toward one another, only that they are not as spontaneously cooperative as kin. And ironically, for all this talk of solidarity and sympathy and common blood, we shall soon see that families are not such harmonious units either.
TOLSTOY’S FAMOUS REMARK that happy families are all alike but every unhappy family is unhappy in its own way is not true at the level of ultimate (evolutionary) causation. Trivers showed how the seeds of unhappiness in every family have the same underlying source.17 Though relatives have common interests because of their common genes, the degree of overlap is not identical within all the permutations and combinations of family members. Parents are related to all of their offspring by an equal factor, 50 percent, but each child is related to himself or herself by a factor of 100 percent. And that has a subtle but profound implication for the currency of family life, parents’ investment in their children.
Parental investment is a limited resource. A day has only twenty-four hours, short-term memory can hold only four chunks of information, and, as many a frazzled mother has pointed out, “I only have two hands!” At one end of the lifespan, children learn that a mother cannot pump out an unlimited stream of milk; at the other, they learn that parents do not leave behind infinite inheritances.
To the extent that emotions among people reflect their typical genetic relatedness, Trivers argued, the members of a family should disagree on how parental investment should be divvied up. Parents should want to split their investment equitably among the children—if not in absolutely equal parts, then according to each child’s ability to prosper from the investment. But each child should want the parent to dole out twice as much of the investment to himself or herself as to a sibling, because children share half their genes with each full sibling but share all their genes with themselves. Given a family with two children and one pie, each child should want to split it in a ratio of two-thirds to one-third, while parents should want it to be split fifty-fifty. The result is that no distribution will make everyone happy. Of course, it’s not that parents and children literally fight over pie or milk or inheritances (though they may), and they certainly don’t fight over genes. In our evolutionary history, parental investment affected a child’s survival, which affected the probability that the genes for various familial emotions in parents and in children would have been passed on to us today. The prediction is that family members’ expectations of one another are not perfectly in sync.
Parent-offspring conflict and its obverse, sibling-sibling conflict, can be seen throughout the animal kingdom.18 Littermates or nestmates fight among themselves, sometimes lethally, and fight with their mothers over access to milk, food, and care. (As Woody Allen’s character in AntZ pointed out, “When you’re th
e middle child in a family of five million, you don’t get much attention.”) The conflict also plays out in the physiology of prenatal human development. Fetuses tap their mothers’ bloodstreams to mine the most nutrients possible from her body, while the mother’s body resists to keep it in good shape for future children.19 And it continues to play itself out after birth. Until recently, in most cultures, mothers who had poor prospects for sustaining a newborn to maturity cut their losses and abandoned it to die.20 The fat cheeks and precocious responsiveness in a baby’s face may be an advertisement of health designed to tilt the decision in its favor.21
But the most interesting conflicts are the psychological ones, played out in family dramas. Trivers touted the liberatory nature of sociobiology by invoking an “underlying symmetry in our social relationships” and “submerged actors in the social world.”22 He was referring to women, as we will see in the chapter on gender, and to children. The theory of parent-offspring conflict says that families do not contain all-powerful, all-knowing parents and their passive, grateful children. Natural selection should have equipped children with psychological tactics allowing them to hold their own in a struggle with their parents, with neither party having a permanent upper hand. Parents have a short-lived advantage in sheer brawn, but children can fight back by being cute, whining, throwing tantrums, pulling guilt trips, tormenting their siblings, getting between their parents, and holding themselves hostage with the threat of self-destructive behavior.23 As they say, insanity is hereditary: you get it from your children.
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