Why Evolution Gave Us Happiness
One Friday morning in 2007, commuters on the Washington, DC, Metro got a once-in-a-lifetime opportunity. As a study in human psychology, the Washington Post arranged for Joshua Bell, one of the world’s great violinists, to busk in a downtown Metro station. For nearly forty-five minutes, Bell played classical music on his Stradivarius, during which time more than a thousand commuters entered the doorway directly in front of him. The Post had made elaborate plans in case the crowd got out of hand, but its preparations proved unnecessary. Only seven people stopped to listen to Bell for more than a minute.
What these commuters didn’t know was that thousands of people pay a small fortune to hear Bell play in symphonies all over the world, at which point they have to dress up in their finest, struggle to find parking, and sit at a great distance from the master. Much has been made of this demonstration and its outcome. How could the same man be so sought after yet so readily ignored? As the Washington Post explained, Bell was “art without a frame”—in the context of a Metro station, people didn’t know what to make of his music and were unable to appreciate it. No doubt there is some truth to this interpretation, as the price of a painting goes through the roof when we discover it’s a Picasso and drops through the floor when we discover it’s not, even though the painting itself hasn’t changed an iota. But there is more to this story than context. Intentionally or not, when it set up this event, the Post tapped into a deeply ingrained feature of the human psyche.
By way of explanation, consider a classic psychology experiment from the early 1970s. John Darley and Dan Batson of Princeton University were pondering the story of the Good Samaritan, and wondering why so many people fail to help the unfortunate soul who has been beaten and robbed. Jesus tells this parable to highlight that everyone is our neighbor, and even the lowliest member of society can play an important role. (Samaritans were a disliked group at the time.) Darley and Batson took away a different lesson, wondering if perhaps the Samaritan was the only one to help because there was nowhere else he had to be. The Levite and the priest were more important than the Samaritan, and the fact that they walked by the man in need raised the possibility that they had other demands on their time. So, Darley and Batson set out to test whether being in a rush might predict who helps and who doesn’t. The two researchers are both incredibly nice people, but to drive home their point, they designed a study with a particularly sadistic streak.
In their experiment, Darley and Batson asked seminary students to give a brief talk about what can be learned from the parable of the Good Samaritan. The students were told one of three things: (1) they had plenty of time to go to the office where their speech would be recorded, (2) they had just enough time to get there, or (3) they would need to hurry because they were behind schedule. The students then headed off to give their talk, and on their way, they encountered a person in need of help.
Darley and Batson had paid an actor to lie on the ground moaning, positioned so the seminary students almost needed to step over him on their way to explain how important it is to help people in need. The critical question was how many of them would heed the advice they were about to give. Consistent with Darley and Batson’s predictions, the students were much less likely to help if they were behind schedule than if they had plenty of time. But perhaps the most remarkable finding of all is that across the three conditions, only 53 percent of the seminary students stopped even to ask the man if he was all right.
The extraordinary failure of these students to help the needy individual gives us a clue about why commuters on the Washington Metro failed to stop when they walked past Joshua Bell: in both cases, people were focused on the future. I suspect that many of the seminary students didn’t really notice the person in need of help. They clearly saw him, as some of them stepped right over him, but they were so busy thinking about how they could persuade other people to be helpful that they probably paid him almost no attention. In the same manner, the commuters in the Washington Metro probably barely heard Joshua Bell through the buzz of their own thoughts, as they focused on how to deal with their difficult boss or their coworker who keeps stealing their lunch from the office fridge.
As I discuss in chapter 6, this capacity to travel in time mentally and make complex plans for the future has given us an enormous selective advantage. Unfortunately, that advantage comes at a cost, given that the time we spend living in the future distracts us from the present. As a consequence, people often fail to appreciate the pleasures (or demands) of the moment because they pay so little attention to the here and now. In my own case, I can’t tell you how many times I’ve barely tasted a delicious snack because my mind was on an upcoming lecture, our next vacation, or how I was going to explain yet another speeding ticket to my wife.
Our proclivity to live in the future and ignore the present is not an easy problem to solve, although the varied approaches to mindfulness around the globe reflect the fact that many people try. Most meditation practices teach people to live in the moment. This is a laudable goal, but it’s incredibly difficult to achieve because it’s at odds with an evolved skill that has served us so well over the last million-plus years. We have a great deal of difficulty shutting down thoughts of the future unless the demands or pleasures of the moment are so substantial that they drag us back to the here and now.
My dogs, in contrast, show no signs of this inner struggle. They live in the moment because they are incapable of casting their minds forward. Every treat I give them is devoured with gusto, regardless of whether it means we just finished dinner or are off to the vet. Of course, planning for tomorrow isn’t their strong suit, and thus their lives are under my control rather than the other way around. As in so many other ways, evolution gives with one hand but takes with the other. And this, in turn, brings us to what may be the most important question of all . . .
Why Aren’t We Always Happy?
I’ve often wondered what it would be like to win the lottery and suddenly have more money than I could ever reasonably spend. I won’t win because I don’t play, but of course most people’s lottery dreams never come true. This is not such a bad thing. As hard as it is to believe, lottery winners are usually no happier than they were before they won, and a fair few of them are a lot less happy. Not the day after they win—that’s a pretty good day—but by a year or two later, most people have adapted to their new normal, and their happiness has returned to where it was before they drew the winning ticket. They may be driving a nicer car, but their mind is focused on the fact that they’re still sitting in traffic.
Worse yet, some of them are focused on all the problems that their windfall has brought them, as friends and family come out of the woodwork expecting them to share their good fortune. As Sandra Hayes put it after winning the $224 million Missouri lottery in 2006, “I had to endure the greed and the need that people have. . . . These are people who you’ve loved, and they’re turning into vampires trying to suck the life out of me.”
The sad truth is that all of us have dreams, but even when our dreams come true, we rarely end up happier than we were before. New successes bring new challenges. The German folk saying Vorfreude ist die schönste Freude (“Anticipated joy is the greatest joy”) is much more accurate than Disney’s “happily ever after.”
Why did evolution play this dirty trick on us, giving us dreams of achievements that will provide lifelong happiness but then failing to deliver the emotional goods when we achieve our goals? Some have blamed our modern world and the many discrepancies between our current lives and how we used to live (more on this later), but there is more to it than that. The advent of agriculture has led to major changes, many of which are disruptive for happiness, but our hunter-gatherer ancestors were also incapable of achieving lasting happiness.
The more important answer to this question lies in the fact that evolution doesn’t care if we’re happy, so long as we’re reproductively successful. Happiness is a tool that evolution uses to incentivize us to do what is in our genes’ best interest. If we were capable of experiencing lasting happiness, evolution would lose one of its best tools.
By way of example, consider two hypothetical ancestors, Thag and Crag. Both of them are sitting in a cave during the Pleistocene, eating lizard tails and dreaming of killing a mastodon. It’s a pretty big ask to slog across the freezing glacier only to face such a dangerous animal, but in our hypothetical scenario, both of them live the dream and single-handedly kill the beast—actually, that’s too unlikely; let’s put them in charge of the hunt. As expected, both are incredibly happy and are the toast of their respective clans.
Imagine what would happen if Thag stayed incredibly happy forever while Crag dropped back to baseline within a week or so. Thag no longer feels the need to go out and kill anything, as he is content to relax in the cave and relive the exploits of his hunt. Crag, on the other hand, is motivationally hungry again, with a need to achieve. His continued ambition will get him off his duff and back out on the ice. This will result in further successes, which will attract a mate and the respect of his clan, and maybe his appreciative friends will see to it that he gets to sleep a little closer to the fire.
But our happy hippie Thag will soon be of little interest to the group by virtue of his lack of productivity. No one will want to hear his story about the mastodon anymore, and people will start asking the age-old question, “What have you done for me lately?” He won’t particularly care—he is, after all, permanently happy—but he’ll suffer the social and reproductive consequences regardless, and there will be fewer baby Thags in the next generation. As is evident in this epic tale of Thag and Crag, our inability to achieve lasting happiness pushed our ancestors to reach for further goals, which in turn meant that they left more offspring in the next generation.
We see a similar pattern today when we examine the motivational effects of happiness over time. Really happy people are rarely high achievers because they simply don’t need to be. As Ted Turner put it, “You’ll hardly ever find a super-achiever anywhere who isn’t motivated at least partially by a sense of insecurity.” The data agree with Ted. Consider the relationship between prior happiness and future earnings documented by Shigehiro Oishi of the University of Virginia and his colleagues in Figure 9.1.
On the far left of the graph we see that people who were unhappy in the mid-1980s (charted on the x-axis) go on to earn less money in the early 2000s (charted on the y-axis) than their happier compatriots. No surprise here: happy people are more energetic and compelling than sad people, and being energetic and compelling helps them earn more money.
Figure 9.1. The relationship between earlier happiness and later income. (Adapted from Oishi et al., 2007)
More important for the current point, the moderately happy folks who sit in the middle right of this graph went on to earn the most money fifteen years later, while the earnings of the very happy folks on the far right look a lot like those of the unhappy ones. Some joy is clearly good for success in life, but too much happiness is a financial disaster. This is why evolution designed us to be reasonably happy, with occasional moments of giddiness that soon fade as we return to our individual baseline level of happiness. Numerous self-help professionals would have us believe that attaining maximal or permanent happiness should be our goal, but an evolutionary perspective clarifies that such a goal is neither achievable nor desirable.
Happiness evolved for a reason—it gets us out there killing mastodons. But happiness is more than just a motivator; it also plays a critical role in the connection between mind and body. So, before turning to the question of exactly what makes us happy, let’s spend a little time figuring out why happiness is important even for the unrepentant curmudgeons among us.
Happiness and Health
Late one evening about a decade ago, I received an unexpected call on my cell phone. The caller was from overseas, and the connection was poor, so I missed his name but caught something about his being in an anthropology department at what sounded like Rutgers University. I didn’t ask him to repeat himself, as I figured that most people don’t call at that hour and it would soon become clear who he was and what he wanted. After a bit of idle chitchat, the caller told me that he had been invited to take a sabbatical in Berlin the following year, and he wanted me to join him. I have nothing against sabbaticals or Berlin—in fact, I’m a big fan of both—but I have my own commitments, so I was politely excusing myself from this unusual request when it dawned on me that I was talking to Robert Trivers.
I’d had the good fortune of meeting him at a small conference about five years prior to that phone call, and although I’d spoken with him only a few times in the intervening years, he has a distinct, gravelly voice that I eventually recognized over the poor telephone line. If it was Trivers who was inviting me on sabbatical, then that changed everything, so I told him to hold on for a moment while I covered the mouthpiece and asked my wife how she felt about a sabbatical in Berlin. She thought that sounded like fun, so I told him to count me in.
We arrived at the wonderful Wissenschaftskolleg in Berlin in October 2008. The plan was for me to spend the next six months working with Trivers to help develop his theory of self-deception (discussed in chapter 5). Trivers is legendary not just for his brilliance, but also for his mercurial temperament—you don’t need to take my word for it; just get a copy of his autobiography, Wild Life—and at that point I didn’t know him well. So, I was a little concerned about how our collaboration would proceed. It turned out that we got along famously, but that first week, we definitely got off to a rocky start.
In one of our first meetings, Trivers suggested that our immune system can serve as a bank—I had no idea what he meant by that, but I nodded thoughtfully—and that we evolved to orient ourselves toward positive thoughts as we aged in an effort to enhance our immune functioning. (I wasn’t sure what he meant by that, either.) I was aware that older adults tend to remember positive things in life better than negative things, whereas younger adults remember the positive and negative equally well. The predominant theory in psychology to explain this effect is that older adults are aware that they have a limited time left on this planet, so they prioritize positive emotional experiences (much as students do when they are about to graduate and leave their friends behind). I had always found this theory convincing, and felt that with his alternative theory, Trivers was barking up the wrong tree. I was also aware that evolution has a much stronger impact on people before they reproduce than after, so an evolutionary basis for the increase in positivity with age seemed unlikely to me.
After a fair bit of arguing (and a fair bit of explaining), Bob eventually convinced me that this was an idea worth testing. As I discuss in the prologue, in our premedical past, grandparents played an important role in the survival of their grandchildren (more on this later), which suggests that their longevity is important to their grandchildren. Indeed, humans show several adaptations that enhance functioning late in life, such as changes in our genetic makeup that protect us against Alzheimer’s and other forms of neurological decline that impact only older adults. These findings raise the possibility that evolution might also shape older adults’ motivational system to keep them alive as long as possible. But what did Trivers mean with his talk of the immune system as a bank, why would older adults capitalize on it, and what does any of this have to do with the importance of happiness and its relationship to health? Let me answer these questions one at a time.
When we consider the costs of development and maintenance, our brain is our most expensive organ. It demands 20 percent of our metabolic energy at all times, whether we are solving math problems or watching reruns. Due to its constant energy requirement, there is no way to borrow energy from the brain when our need for energy exceeds the available supply. In contrast, our muscles use way more energy when they are active than when they are at rest, so in principle, we could borrow energy from our muscles by sitting down and relaxing. The problem with this strategy is that most of the energy-demanding emergencies our ancestors faced required a muscular response. There was no way to borrow energy from our muscles during an emergency because sitting down when a mastodon showed up was not an effective option.
This brings us to our immune system, which also hums along at great metabolic cost, but largely in the service of future needs rather than current ones. At any one moment, we have an enormous number of immune cells coursing through our body, so we can afford a momentary break from production if the demands on our metabolic energy supply become pressing. When our body is in need of more energy than it has, one of the first things it sacrifices is immune function.
When did our ancestors face pressing energy demands? Running from hungry saber-toothed tigers and thwacking enemies with a club would be prime examples. When you can feel a tiger’s hot breath on your neck as you cover the last few yards to the nearest tree, you don’t really need to waste energy making more immune cells to fight off tomorrow’s cold. What you do need is to shift all available resources to your legs, with the hope that you’ll live to see another cough or sneeze. Because fighting and running for our lives are not happy times, evolution took advantage of this fact to link our bodily systems to our psychological states.
As a result, our immune system evolved to hum along at peak capacity when we’re happy but to slow down dramatically when we’re not. This is why long-term unhappiness can literally kill you through its immune-suppressing effects, and why loneliness in late adulthood is deadlier than smoking. Indeed, once you’re over sixty-five, you’re better off smoking, drinking, or overeating with your friends than you are sitting at home alone.
With this background in mind, Trivers hypothesized that older adults evolved a strategy of turning this relationship on its head, becoming more focused on the positive things in life in an effort to enhance their immune functioning. Such a strategy would be more sensible for older than younger adults for two reasons. First, older adults have a weaker immune system than younger adults, and face greater threats from tumors and pathogens. Second, older adults know much more about the world than younger adults do, so they don’t need to pay as much attention to what’s going on around them. For example, when older adults interact with a surly bank employee or a harried flight attendant, they have a library of related experiences to draw upon and can respond to the situation effectively without giving it much thought. As a result, they can afford to gloss over some of the unpleasant things in life.
When I returned from Berlin to my lab at the University of Queensland, I raised this hypothesis with my collaborator Julie Henry, and with Trivers on board we asked my student Elise Kalokerinos if she would like to take the lead in testing the idea for her PhD. Elise thought it sounded like fun, so she set about finding a way to test it. Over the course of the next year, she brought young and old adults into the laboratory and showed them photographs of nice things, such as baskets of puppies, and photographs of nasty things, such as plane crashes, and then tested their memory for the pictures. Sure enough, our participants who were over sixty-five tended to remember the puppies better than the plane crashes (which suggests that they were paying more attention to the positive), while our younger participants remembered both equally well.
Elise then asked our older participants to return to the lab one and two years later so we could draw blood to assess their immune functioning. The immune system is vast, but in this initial study, we decided to focus on a class of white blood cells known as CD4+s. These cells facilitate immune functioning by triggering other white blood cells (known as B cells) to produce antibodies. Elise found that better memory for positive but not negative pictures was associated with higher CD4+ counts and lower CD4+ activation* one and two years later.
Higher CD4+ counts usually indicate a greater preparedness to fight off illness. In contrast, higher activation of CD4+s indicates that the person is busy fighting infection, and thus is in poor health. In other words, the more positive their memories were today, the healthier they were next year and the year after. This relationship between positivity in memory and CD4+s raises the possibility that by focusing on the positive aspects of life, we enhance our own immune functioning.
These findings are not a good fit with the theory that positivity with age is caused by older adults’ awareness of their limited time on this planet; but they are consistent with other research showing that happiness plays an important role in health and longevity. For example, when researchers intentionally expose people to cold viruses, they find that people who are happy and have good social support are less likely to catch a cold than unhappy people and those with poor social support. Happy and well-supported people also heal more quickly when intentionally wounded in the name of science.
This effect holds for our primate cousins as well. Wild monkeys in the mountains of Morocco who have stronger friendship ties show a decreased physiological stress response (i.e., reduced steroid hormones in their feces) to cold weather and aggression from other monkeys. Notice that the key issues for monkeys and for us are friendship and social support. Satisfying relationships play an important role in proper immune functioning.
My favorite experiment on this effect is by Jan Kiecolt-Glaser at Ohio State University and her colleagues. In their study, they brought couples into the lab on two different occasions to create blisters on the inside of their forearms by attaching small vacuum suction devices. After they had suctioned up eight blisters on the participants’ arms, they then snipped the skin off the top of the blisters and put little plastic tubs over them. (I know this sounds horrific, but apparently, it’s not as bad as it seems.) These tubs were now artificial blister chambers that the researchers could use to collect blister goo to examine cellular immune responses throughout the experiment.
On the first visit to the lab the researchers asked the couples to discuss their relationship history, and on the second visit they asked them to discuss areas of ongoing conflict (such as money or in-laws). The researchers made themselves scarce while these conversations took place, but recorded them for later analysis. Despite the semi-public nature of the setting, couples were quite willing to speak their minds (e.g., “You’re only being nice so I’ll have sex with you tonight,” “You were being mean on purpose”).
This experiment yielded several interesting findings. First, the blisters took one more day to heal after the conflict discussions than after the more positive initial conversations. Second, the blisters took an extra two days to heal among couples who were hostile to each other during their conflict discussions compared to the couples who were not. Third, the cellular immune activity inside the blisters mirrored what was going on with the healing. There were large increases in inflammation following hostile conflict discussions but almost no increase in inflammation following non-hostile conflict discussions.
These inflammatory responses are implicated in cardiovascular disease, diabetes, and other illnesses, which is precisely why happy marriages help us live longer and why unhappy marriages (and loneliness) shorten our lives. These findings also clarify why even people who enjoy living alone need regular human contact, a group that matters to them, and meaningful friendships. People differ in how many friends they need and how often they need to see them, but everyone requires social connections to maintain health and happiness.
So, what is the purpose of happiness? As you can see, there is no single answer to this question. Happiness motivates us to do things that help us survive and reproduce, but happiness is not an end in and of itself. Evolution often sacrifices our happiness in the service of other goals; those who cannot feel pain and despair are severely constrained in their ability to learn to avoid bad people, situations, and ideas. Indeed, negative emotions are just as important as positive ones (perhaps even more so), as the costs of plans gone awry can far outweigh the benefits of success.
We saw in chapter 5 that happiness is readily apparent to others and its signaling value is not lost on people who are trying to size you up as a potential partner, ally, or enemy. In this sense, happiness is also a critically important social emotion. Happiness serves as a signal to our own bodies as well, by communicating that now would be a good time to expend energy on repair and illness prevention.