The Rational Animal: How Evolution Made Us Smarter Than We Think

by Kenrick, Douglas T.

  Hundreds of findings across the animal kingdom support this principle. Ground squirrels are more likely to risk their lives by giving a loud alarm signal to warn of a predator if doing so will save their brothers and sisters, as compared to their second cousins. White-fronted bee-eaters are more likely to share food with full siblings than with half siblings. And aid within human families tends to run along genetic lines as well. Of the inheritance money left in people’s wills, 92.3 percent goes to family and only 7.7 percent to nonfamily. And of the money left to genetic relatives, 84 percent goes to those sharing 50 percent of the benefactor’s genes, 14 percent to those sharing 25 percent, and less than 2 percent to those sharing 12.5 percent or fewer genes.

  The power of shared genes shows up in bold relief if you compare the way parents treat children who are related to them by blood as compared to by marriage. In the classic fairytale, Cinderella’s nasty stepmother treats her like a lowly servant, all the while showering rewards and affection on her two evil daughters. Sadly, the real world resembles the cruel fairytale. Parents are 5.5 times less likely to help pay college costs for stepchildren versus biological children. And while they are shut out of many rewards, stepchildren are often dealt more than their share of punishments. Children living with a stepparent are forty times more likely to suffer physical abuse than those living with two genetic parents, with much of the abuse coming from the stepparent. Even more shocking are the data on homicides. Although murders of small children are rare, children living with a stepparent are forty to one hundred times more likely to be killed! Is this because stepchildren live in poorer families, or because of some other confounding variable? No. Even for parents who have both biological children and stepchildren living with them in the same house (for whom all the possible confounding variables are equated), stepchildren are nine times more likely to be abused than biological children living under the same roof.

  Nancy Segal, the twins researcher, wondered whether the principle of inclusive fitness would apply to the extreme case in which siblings share more than the usual number of common genes. To explore this question, she compared identical (or monozygotic) twins with fraternal (or dizygotic) twins. While both types of twins tend to be born into the same family at the same time, they differ in the proportion of genes they share. Fraternal twins share the usual brotherly 50 percent, while identical twins share 100 percent of their genes. Identical twins are in fact clones.

  In her research, Segal repeatedly finds that identical twins have closer and more cooperative relationships than fraternal twins. Identical twins feel closer to one another’s children than fraternal twins. And when a member of a pair of identical twins dies, the surviving twin feels a more intense and longer sense of mourning than that felt by the surviving member of a pair of fraternal twins.

  In one study, Segal and her colleague Scott Hershberger had twins play a prisoner’s dilemma game. To be consistent with the economic rules of the game, the researchers gave the twins instructions designed to encourage self-interested play, explaining that each person’s goal should be to win as much money for him- or herself as possible and not worry about what happens to the other player. Yet even when spurred to think about maximizing their own self-interest—rational economist style—the twins had a hard time defecting on one another. Instead, they spontaneously chose to cooperate much of the time.

  The most interesting finding was the difference in cooperation between twins who shared half versus all of their genes. Compared to fraternal twins, identical twins were 27 percent more likely to cooperate. We’re not suggesting that twins were making relatedness calculations in their head before they decided to cooperate. Identical twins simply feel more cooperative toward one another than fraternal twins, in the same way that most of us feel more willing to lend money to a sibling (who shares 50 percent of our genes) than to Cousin Myrtle (who shares only 12.5 percent).

  The twin study shows not only that blood is thicker than water but that the blood of genetically closer kin is thicker than that of less closely related kin. Our preference for those who share our genes is not simply due to the fact that we have spent more time with our closer relatives. Even after being raised separately and then reunited, identical twins regularly become closer to one another than do reunited fraternal twins.

  HOME ECONOMICS VERSUS CORPORATE ECONOMICS

  Let’s go back to the Disney example and consider the two different pairs of men who ran the company. The founding brothers, Walt and Roy O., had many disagreements and fierce negotiations, but they found a way to cooperate and stuck together through a lifetime of ups and downs. Roy E. and Michael Eisner, however, were unwilling to see eye to eye; instead, they aired their dirty laundry in public and let the company and its image flounder.

  Each of these conflicts can be analyzed using game theory. Let’s say that Eisner and Roy E. are playing the prisoner’s dilemma in the laboratory and can win up to $100. The situation is a zero-sum game: If Eisner receives $100, that’s $100 that Roy won’t get. If Roy gets a larger payout, on the other hand, Eisner will have to take less money. The rules of rational economics predict that when interests conflict, the best strategy for each player is to defect—to avoid being the sucker. Roy E. and Eisner followed the rules of the game perfectly, playing with pure self-interest and generating a relatively dismal outcome.

  But now consider the case of two brothers, like Walt and Roy O., playing the same game. Unlike Eisner and Roy E., the two brothers share 50 percent of their genes. This is important because, from an evolutionary perspective, if your brother benefits, so do you. Anything that contributes to your brother’s survival and reproduction gets tallied in your own evolutionary success ledger. This makes the dilemma a positive-sum game: a $100 benefit for your brother is a $50 benefit for you. Indeed, sometimes a family member can still win by losing.

  When one of the authors of this book, Doug, and colleagues Federico Sanabria, Jill Sundie, and Peter Killeen joined to recalculate the prisoner’s dilemma in these terms, they found that the dilemma often disappeared if two brothers were playing. Under most conditions, the deeply rational strategy was no longer to defect but to cooperate. Thinking about this makes it easier to understand why Roy O. was able to tolerate his brother Walt’s financial eccentricities in a way that Roy E. could not for Michael Eisner, who was connected to the Disney clan only through dollar signs and not genes.

  The fact that siblings are genetically related doesn’t mean they will always get along. Brothers and sisters often fight bitterly, and even lifelong business partners Walt and Roy spent a long period avoiding one another and communicating through intermediaries. Eminent evolutionary biologist Robert Trivers has noted that some degree of sibling rivalry is to be expected from an evolutionary perspective. Except in the rare case of identical twins, siblings share only half their genes. From your genes’ selfish perspective, every dollar mom and dad invest in you is perfectly well spent, but the same buck invested in your brother wastes fifty cents (on those unshared genes).

  Despite the fact that siblings are not completely cooperative with one another, however, they cooperate more with one another than with nonrelatives. Conflict between family members is hardly impossible; it’s just less vicious than conflict between nonrelatives. All else being equal, Roy Disney prefers a dollar spent on Roy Disney. A dollar spent on a member of the Eisner clan, on the other hand, is worth nothing. The same dollar spent on brother Walt is at least worth fifty cents.

  THE RULES OF THE GAME (THEORY) FOR DIFFERENT SUBSELVES

  When it comes to game theory, then, there are at least two different games in town—one based on Wall Street market pricing and another based on kinship bonds. But are there more? As it turns out, each of the different subselves we met earlier has its own set of rules for how to play the game. Because our evolutionary interests align differently when it comes to corporations, blood relatives, friends, bosses, dating partners, and spouses, each subself negotiates according to its own se
t of rules. And whether a particular subself comes out to play depends on who else is on the playground.

  TEAM PAYOFFS: THE AFFILIATION GAME

  Friendships can be quite rewarding. Your buddies can provide a shoulder when you need one to cry on and an extra pair of arms and legs when you need to move a large piece of furniture. And if you read the cast of characters in any individual’s financial success story, you will usually find a few friends playing key supporting roles. Take the case of the person listed in the Guinness Book of World Records as “the most successful musician and composer in popular music history.” This individual has had sixty separate records go gold (selling more than a half million copies), and a single one of this person’s songs has been covered by over two thousand other artists. That song, “Yesterday,” helped make its author (a fellow named Paul McCartney) one of Britain’s wealthiest men, with a net worth of approximately $741 million in 2010.

  But none of this would have happened if not for a powerful friendship McCartney formed as a mere lad of fifteen years, when he went to hear a local skiffle band called The Quarrymen. The lead singer of The Quarrymen, a cocky seventeen-year-old named John Lennon, invited McCartney to join the band, and the two later formed a songwriting partnership in which they agreed to take equal credit for any of the tunes they wrote. They cowrote approximately 180 songs during their decades-long friendship, most of them recorded by their band, whose name they later changed from The Quarrymen to The Beatles.

  Lennon and McCartney’s share-and-share-alike arrangement is common among friends. A couple of decades later, when Steve Wozniak and his young buddy Steve Jobs started Apple Computer, Inc., they had a precisely equal share in the company’s stocks. The two friends agreed on a fifty-fifty split, even though Wozniak’s father thought it grossly unfair since his son had designed the Apple I computer with little or no technical help from Jobs.

  Alan Fiske, an anthropologist at the University of California, Los Angeles (UCLA), believes that the human mind has separate systems for calculating exchanges between different types of people. Fiske’s theory grew out of his anthropological fieldwork in West Africa. Living among the Mossi people of Burkina Faso, he observed that the villagers switched between very different modes of exchange, depending on whom they were dealing with. Fiske was struck by the fact that he had observed the same patterns of exchange growing up in the United States and later uncovered them in other cultures he visited in his roles as a Peace Corps volunteer and field anthropologist.

  We have already met two of Fiske’s models. The first, market pricing, is the cold-blooded monetary system that rational economists presume people use for most of their decisions. But Fiske detailed several other systems that he observed humans regularly using across the globe. Fiske’s second model, communal sharing, is that used between close relatives, like Walt and Roy O. Disney or the twins in the prisoner’s dilemma. This set of kinship rules involves giving what you can, taking what you need, and not keeping track of individual contributions. Communal sharing is the model used by the kin-care subself we met earlier.

  Fiske’s third model, equality matching, describes exchanges between peers or friends, such as Lennon and McCartney or Jobs and Wozniak. The affiliation subself typically uses this set of rules. When the mind is running this program, it feels fair when everyone gets the same amount and has an equal turn. Friendly kids on the playground use this system, as do teenagers on athletic teams, adults in carpools, and members of babysitting cooperatives. Between friends, strict mathematical calculation isn’t necessary. If I invite you over to dinner or pay for lunch, next time you’ll take your turn. As turn-taking friends, we don’t worry about the fact that you’re a studied chef who lays out a five-star presentation to highlight your special steak tartare, whereas I have to stretch my capacities to fry up a humble repast of breaded chicken and home fries.

  Fiske contrasts this buddy system with the rational economist’s market-pricing system, in which people pay for commodities in proportion to what they receive, carefully calculating market value, with everyone bargaining to get the best deal for themselves and allowing those with more capital to get a larger share of the goodies. To appreciate the contrast between the rational economic model and the model used between friends, imagine finishing a dinner at a friend’s house and receiving a bill that calculated the difference between the value of the fine wine, steak, and selected mushrooms they’d served against the estimated value of the beer, chicken, and potatoes you’d served the week before, with an extra 50 percent surcharge added in for the additional preparation time and culinary skills your friend had brought to bear. This is more or less exactly what gets calculated into the bill when you go to a fine restaurant. The rational economic model applies to how goods are exchanged on the open market, but it would be highly inappropriate, indeed positively insulting, between friends. Friends take their turns, and both are satisfied with the deal.

  One study found that people cluster the rewards other folks provide into several distinct categories. Sometimes other people provide you with love; other times they give you status; and still other times they give you money or goods. The researchers asked participants to imagine that they had given one of those rewards to another person, for example, love (“You convey to a person that you feel affection for him and enjoy being with him”), status (“You convey to a person your respect and esteem for his talents”), or goods (“You give a person certain objects that you possess”). They then asked what participants would prefer to get back in each case. If you gave someone love, for example, would you prefer that the other person give back affection, merchandise, money, or a willingness to run an errand for you?

  In contrast to what one might expect from the rational economist’s perspective, the researchers found that money was the last thing their subjects wanted back from other people, unless they had given them money in the first place. Money and love were even viewed as negatively linked to one another. Not only can’t money buy me love, as The Beatles put it, but an offer of cash in exchange for your girlfriend saying she loves you may buy you a ticket to ride—one-way, back to your bachelor pad.

  The focus on balance in friendly relationships has a negative side. When friends start to feel a gross imbalance, they may feel resentful and respond with spiteful tit-for-tat exchanges of negativity. This happened when Lennon and McCartney split up The Beatles, and the former moptops starting singing a much less harmonious tune. They began wailing about exactly which one of them should get credit for which lyrics and melodies in which particular songs, and insulting one another in public (Lennon wrote a nasty tune called “How Do You Sleep?” with lines like “the only thing you done was ‘Yesterday’”).

  The originators of Apple avoided such an acrimonious split, but Wozniak was bothered for years after learning that Steve Jobs had deceptively neglected to share a few dollars of bonus money Jobs had earned when Wozniak helped him with a programming project at Atari during their younger years. “I wish he had just been honest. If he had told me he needed the money, he should have known I would have just given it to him. He was a friend. You help your friends.”

  The equality-matching rulebook, used by our affiliation subself, is very different from the one used by our kin-care subself. Next we turn to our status subself, which has its own specialized instructions for navigating social hierarchies.

  PYRAMID PLAY: THE STATUS GAME

  It’s good to be king, right? Kings, presidents, and CEOs of major corporations have access to palatial dwellings, personal airplanes, and servants to prepare their food, clean up after them, and deliver their purple robes to the dry cleaners. As CEO of the Disney corporation, Michael Eisner earned a cool $40 million in 1987 alone. But Eisner was a mere peasant compared to Bhupinder Singh, Seventh Maharajah of the state of Patiala in India, who lorded over immense areas of land, collected Rolls-Royces, and had hordes of wives and concubines waiting in line to please him. Even down in the humbler towns and villages where most of
us mortals live, our fellow townies with higher status get larger paychecks, better parking spaces, offices with views, personal secretaries, and houses on the right side of the tracks.

  And yet, not everyone wants to be a leader. Steve Wozniak insisted on remaining an engineer and refused to take a managerial position when he and Steve Jobs started Apple. In many universities, most faculty eligible to chair a department run from the opportunity for a big raise, a secretary, and a corner office. When an opening for a new chair arises, many faculty take the same position as famous Civil War general William Tecumseh Sherman did when he was being considered as a candidate for president: “I will not run for the office, and if elected, I will not serve.” People’s ambivalence about climbing the ladder stems from the fact that the higher rungs bring not only boosted benefits but also elevated expectations.

  Alan Fiske, the UCLA anthropologist, points out that leaders and followers use rules of exchange that are very different from those that guide brothers and sisters, friends, or consumers and shopkeepers. Fiske calls this hierarchical system authority ranking. In this mode of exchange—the one used by our status subself—people receive different benefits and pay different costs depending on their position in a status hierarchy, and nobody gets by for free. The underlings bestow loyalty and special privileges on the higher-ups, but in turn they expect leaders to provide resources, money, protection, and direction. For example, the US president gets to live in the White House, fly on Air Force One, and speak on television whenever he feels the impulse, but his constituents expect him to reduce unemployment, increase everyone’s paychecks, provide a first-rate education for their kids, stand up to military threats all around the world, and reduce taxes along the way.