by Mark Pagel
We take this cooperation for granted in our modern world, but it rests on a psychology and social behaviors new to evolution, and unique to our species because no other animal has confronted the crisis of visual theft. Consider that even the simplest acts of exchange among unrelated people wobble on an unstable tightrope, because now my instincts to take advantage of you will not be held back by the usual bonds of family ties. This is because when I help a relative I help a little genetic bit of myself, and so natural selection favors my nepotism so long as the help I provide to them is not too costly. It also means I have less incentive to cheat that relative, or for them to cheat me. When we watch a streaming mass of ants mount a suicidal charge out of their nest to take on some foe, we admire their unflinching courage, but we recognize these ants are dying to save their brothers and sisters, and especially their queen. She is the source of additional copies of their shared genes, produced in the form of more brothers and sisters. The same logic of what evolutionary biologists call kin selection tells us why your skin cells are happy to die to protect you from the penetrating and deadly rays of the sun. These skin cells are all genetic clones of each other, only too happy to die if this makes it more likely the body they inhabit will reproduce one day.
But the hallmark of modern human tribal societies was that they were not limited to relatives, and this meant that evolution had to confront the problem of having a potentially unruly mob of individuals on its hands, each looking out for their own well-being. The difference is everything. Now anything I do for you might benefit you and your genes, but at my expense. In fact, once people started living together in groups, natural selection would have favored a raft of selfish psychological ploys for taking advantage of others’ good nature, because there would have been a continual conflict between what was best for you and what was best for your group. I might take more than my share from the dwindling grain store when you are not looking, or attempt to convince you that I am hungrier than you when food is scarce. I may “forget” in future to return a favor, I may try to escape your attentions, I might return less of a favor, or plead poverty. I might lag behind out of harm’s way in battle, or I might get angry if you try the same, and spread rumors that you are not to be trusted.
Left unchecked, these ploys would have caused our societies to collapse before they got off the ground. To make our societies work, then, we had to acquire the social and psychological systems that could somehow overcome and tame selfish instincts born of millions of years of evolution by natural selection to cheat, exploit, dupe, and even murder one’s rivals. The solution was simple in principle but profound in its effects: natural selection found ways that made it possible for individuals to align their interests with those of their group. If the benefits of the cooperation that might flow from this alignment could exceed the returns from acting on pure self-interest, cooperation, even with non-relatives, begins to make sense. Maybe you show great courage in battle and this makes it far more likely your group triumphs over an aggressive foe. If as a consequence you are also more likely to survive, this apparent altruism is a good strategy for you. Or maybe by virtue of having some skill that you share with other members of your group, like being good at making spears or at navigating on the open seas, you acquire a value to the group or a reputation that makes people treat you more charitably. If the collective action you inspire, or the benefits you can bring to the group, can return more to you than behaving selfishly, then your apparent altruism is really a case of enlightened self-interest, and the usual conflict of interest between what is best for you and what is best for the group can vanish.
In fact, the monumental and even sometimes terrifying achievement of human culture has been to discover how to get groups to act together in a coordinated way. It is monumental because by unlocking the psychological means to pool our efforts and skills, it granted our societies a formidable degree of shared purpose that could be put to use in solving the problems of survival. At the same time, aligning individuals’ interests with those of their groups could be terrifying in making our cultural survival vehicles formidable competitors against other groups that might be competing for the same territories. Now, someone could forage while another hunted, someone could mend sails while another plotted a course, two could stand guard with sharpened spears while a third steals a competing tribe’s animals, and my army could cross the valley and attack yours, or repulse it when you attack me.
As I mentioned in the Introduction, the distinctive and salient feature of much of our social existence is the sense of belonging to a cultural group toward which we feel an allegiance that we often do not easily extend to others outside of that group. That sense is the emotion natural selection has kindled in us to get us to behave as a group with a shared purpose. The unusual psychology it brings us can even extend to getting us to engage in costly altruistic acts that rival those of the social insects—the ants, bees, wasps, and termites. Who, for example, can forget images of Japan’s fabled World War II Kamikaze pilots, or the warriors in World War I streaming out of the trenches “over the top” to die in battle? You will take this cooperative psychology entirely for granted because it has been wired deep into your DNA, but no other animal does anything like this. You will never see a group of horses or a group of chimpanzees streaming out “over the top” to die for each other. No lion or zebra holds doors for one another, no ape ever politely stood in line; they don’t look after the elderly or help those in distress. It is true, elephants are sometimes described as “grieving” for a dead member of their group, but this behavior is normally directed at relatives.
If the social insects are sometimes described as eusocial, or truly social, humans have uniquely among the animals achieved a hyper- or ultra-sociality. This label acknowledges that our altruism has broken free of acts aimed merely at helping relatives. In this chapter we will even see how our evolved cooperative psychology can admit a disposition toward suicidal self-sacrifice. Surprisingly, confusingly, and seemingly paradoxically, it will be shown to be in an individual’s self-interest to have this disposition. At the same time, a troubling feature of the way this disposition evolves is that it can cause us to treat people from other societies, and sometimes from even our own, crudely and violently. That is the fragile nature of our sociality and psychology, and it arises because our cultures are cooperative vehicles for the survival of unrelated people, and their genes.
VEHICLES AND THE DISCOVERY OF COOPERATION
THE ORIGINS of human cooperation can be traced to developments in the earliest replicators that populated the Earth beginning perhaps 3.8 billion years ago. The earliest replicators were probably RNA molecules or ribose nucleic acids, a simpler form of the DNA molecule or deoxyribose nucleic acids, whose twin strands elegantly intertwine in a twisting helical shape. Nearly 4 billion years ago, the biotic world of the very young Earth may have comprised little more than naked replicating segments of RNA floating in a warm primordial soup. Molecular biologists call this the RNA-world, and RNA may be the ultimate or ur-ancestors (meaning the original or earliest form) of all life on Earth.
One of the more remarkable discoveries during the early years of molecular biology in the 1960s was that strands of RNA all on their own can have distinctive shapes or what biologists call phenotypes. Whereas all DNA molecules have more or less the same shape, strands of RNA that differ in their chemical makeup of nucleic acids fold and twist into different forms. This discovery about RNA gave molecular geneticists a mechanism for the early evolution of life on Earth. It turns out that the different shapes can influence the survival of one strand in competition with others. Some shapes are, for example, more resistant to being pulled apart by water. An RNA strand with the right chemical makeup to adopt one of these shapes will live longer and therefore tend to accumulate in competition with RNA strands more easily pulled apart. The RNA strand itself becomes a kind of phenotype, and its own survival vehicle.
The early biotic world was probably one of compe
ting strands of these simple replicators of RNA, and whichever strand was lucky enough to escape the forces of nature and find enough chemicals to replicate itself would have dominated. But there would have been only so many different shapes. At some point, two strands of RNA—competitors for the same chemical resources—might have discovered they could physically combine to make a new kind of shape. This transition would have produced the first vehicle comprised of more than one replicator, and it would have increased the complexity of life. But the question is why would this new cooperative venture work? On their own, each of these strands could replicate whenever it wished, but together they would have to give up some of this freedom. Why, for example, should I join forces with you to pick apples when I can pick them on my own, or better yet steal from you?
One of the great insights of evolutionary biology has been to understand how entities that would otherwise compete can be tamed or domesticated to form alliances that serve both. John Maynard Smith and Eörs Szathmáry have called these the “major transitions” in our evolution, and two RNA strands joining together might have been the first of these major transitions. Perhaps the two strands of RNA could help each other to duplicate or copy themselves, or perhaps they could better avoid being pulled apart by water. Living longer would have given this new joint vehicle more chances to replicate itself. We can see from this a reason to give up some of your freedom and to cooperate with a former competitor: your joint enterprise can work if the payoffs more than offset the loss of the freedom to act alone. I should join forces with you in picking apples if we get more than twice as many together as we do separately. Even so, why shouldn’t I wait until we have accumulated a large number of apples and then run off with them?
The first of the evolutionary transitions unfurled the first partnership, and the world of evolution never looked back. Once two or more replicators can combine to produce a vehicle that gives them better returns than they would get from competing, their fates become linked, and it is this linkage that can tame their instincts to compete with or exploit each other. Now the answer to why I should not run off is clear: to give up on the partnership is to give up some of its riches from future returns. Once fates are linked, replicators acquire a new incentive: to become better and better at what they do because now they have less reason to fear betrayal. They can specialize in ways that promote the partnership even more. Maybe if we join forces to pick apples and you are stronger than me, I should specialize in standing on your shoulders and you should specialize in supporting me.
Later on in the course of evolution, partnerships of genes moved beyond shapes to devise even better ways to influence their survival. Collections of genes joined forces in cells that housed the genes and protected them from hot or cold or acids or salt, or from other predatory bits of RNA that might pull them apart chemically. Eventually, collections of individual cells came together in the big multicellular bodies such as our own that are very good at surviving, often living for many years. These large bodies were partnerships of billions, maybe trillions of cells, all clones of each other and specialized into different roles as hearts or muscles or kidneys, livers or brains. These large cooperative vehicles were a success because, on their own, nearly all of the individual cells would have died. The incentive for these cells to join forces is clear: all they had to achieve out of their partnership in forming a body was to improve on their stark individual fates.
A new kind of evolutionary transition occurred when the genes residing in separate individuals learned to contribute to a shared vehicle that acts something like a large body itself. The Australian compass termites are famous for building tall, monolithic, skyscraperlike structures that can be taller than an adult human. Areas in which they are prevalent resemble a sort of haphazardly laid out graveyard with a collection of unusual tombstones. But far from marking graves, these mounds provide a safe and warm environment for thousands, maybe millions, of individual termites—brothers and sisters who cooperate to construct and maintain the mounds and who rarely if ever reproduce themselves. Instead, their collective actions are really not so different from the collective actions of the cells in your body; they are simply more loosely organized. Like the cells in your body, the vehicles these termites produce serve their reproductive interests by promoting the queen’s—their mother’s—reproduction. The same is true of the other social insects—the ants, bees, and wasps. In fact, in each of these societies the queen plays a role not different from the special cells in our bodies we call our germ line—the source of our eggs and sperm. Her immense reproductive output more than pays for her offsprings’ sacrifices for her. On their own, their chances of survival are nearly zero.
SLIME MOLDS, SUICIDE, AND TRIBAL MINDS
THE LAST of the great evolutionary transitions was the transition to human societies. Now groups of human individuals acquired the abilities—some learned, some no doubt cast in our genes—to construct a shared cooperative vehicle. But unlike beehives, ants’ nests, and termite mounds, human societies are constructed around unrelated people, all of whom are seeking to further their own reproductive interests, not those of a single mother or queen they all have in common. The old rules of nepotism that natural selection had so skillfully exploited to make the shared vehicles of the social insects would have to be thrown out the window. Now any help you might provide to your cooperative group could benefit someone else. How, then, did we manage to construct the systems of cooperation that would allow us to form these shared survival vehicles we call our cultures or societies?
There is an organism that can provide some clues, and its solution to this same problem has profound implications for understanding its nature and ours. The slime molds or social amoebae are a species of single-celled creatures that live on the forest floor. Most of the time they lead a solitary existence resembling tiny drops of jelly. But when they suffer from starvation, something wondrous occurs. One after another sends out a chemical alarm summoning them to unite. From all around, the amoebae converge, eventually forming into a streaming multicellular saffron-colored carpet. This society of strangers then oozes across the ground. At a suitably sunny point the carpet stops and then the amoebae cooperate to build a physical tower or stalk. It is composed of their individual bodies and it rises from the forest floor as they climb up over each other, in effect standing on each other’s shoulders. Some climb to the very top of this tower, where a fortunate group makes its way into a bulbous cluster. This cluster acts as a launching pad for spores that will be carried on the wind or the backs of passing animals to better lands, where they will become the progenitors of the next generation of amoebae. The rest will die, having quietly given their lives for other amoebae they did not know and had probably never seen.
The social amoebae have long been a puzzle. Why do so many give their lives for so few in a supreme act of altruistic self-sacrifice? Were the amoebae relatives, as is true of the ants, wasps, termites, or skin cells in our bodies, we would have a ready answer—that they were dying to promote copies of their genes residing in those relatives. But the amoebae are not all relatives, and so the puzzle of their sociality is how natural selection could ever favor the cooperative individuals over selfish ones who never give their lives, given that an altruist runs the risk of helping others who have no intention to repay the kindness. We can begin to see a solution to this puzzle in two choices that confront an amoeba. One is to join in the building of the tower and risk helping others; the other is to remain solitary. Joining the tower gives an amoeba at least some chance to reproduce because it might just find itself getting into the launch pad cluster at the top. Remaining solitary on the forest floor takes away even this small chance. This means that the cost to the amoeba of joining the tower is negligible or even zero, because there is nothing else it could use its time and energy to do that would improve its chances of reproducing—remember, it is starving.
Natural selection has favored the altruistic disposition to build a tower, then, despite
the risks of helping others, because over long periods of evolutionary time amoebae with this disposition will, on average, have left more offspring than those who acted alone. It might seem odd, but this statement is true even though the most likely outcome to any one amoeba that helps to build the tower is to die, and to die “childless.” The strategy works because building the tower at least holds out the chance, even if a small one, of entering the sought-after cluster of cells at the top, and sending your spores wafting off into the breeze. When that happens, some other amoeba will have given its life for you.
For the amoebae, the choice to behave altruistically is a stark and lonely one because the rewards are so rare. But the amoebae’s actions and the societies they produce, even if temporary, illustrate the fundamental ingredient needed to get altruism to evolve. It is that altruism can thrive if altruists can surround themselves with other altruists. This ensures that selfish cheats are excluded from enjoying the benefits of altruistic acts, and means that any given altruist is just as likely as any other to be helped. It also means that in the long run altruists receive more benefits than they would by acting alone. A collection of “like-minded” individuals can even produce more benefits than simply adding up everyone’s individual help. In the case of building a tower, more individuals acting together means a taller tower, and taller towers are better at dispersing spores.
Without perhaps realizing it, we have discovered something fundamental about the amoeba’s disposition that will prove relevant to trying to understand humans. It is that the amoeba’s altruism is not one of “expecting” a return from some other particular amoeba it has helped. Rather, it is a disposition merely to grant assistance, to club together to form a “mutual aid society.” An important and surprising aspect of this kind of altruism is that individuals can acquire tendencies to behave in ways that are costly or even deadly (remember that most amoebae die), and yet those tendencies can, paradoxically, evolve. The paradox is resolved when we realize that natural selection promotes replicators, not the temporary vehicles such as you and me or an amoeba that merely carry them. It is something that you might find peculiar, especially in this context, but read on.
