Wired for Culture: Origins of the Human Social Mind (11 page)

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.

Vehicles—the individual amoeba in the case we have been discussing—are just the ways that genes act on the outside world to get themselves transmitted. The tower-building amoebae each carry a copy of a gene we can call the altruism gene. That gene, by causing a disposition to build a tower, is more likely to get itself replicated than a gene for remaining solitary, because the solitary amoeba will find itself alone on the forest floor. The advantage to the tower-building gene is slight, but it is better than the solitary choice. This is true even if some or even most of the individual amoebae in which that altruism gene resides die in spite of building the tower. The key point is this: the death of these amoebae promotes copies of this same gene that reside in the other amoebae in the stalk, even though in every other respect those others are not relatives, and could even be “strangers.”

Once we understand how the amoebae’s altruism works, the problem of getting altruism to evolve seems easy to solve. But the real challenge of making altruism work lies in coming up with some way that altruists can identify and then associate with other altruists, and thereby exclude those who lack the altruistic gene. How can I possibly know whether, if I help you, you won’t take my help and run? The social amoebae solve this problem by building the shared multicellular body or vehicle, the carpet that eventually forms the tower. The mere presence of another amoeba in the carpet automatically identifies it as one that carries the altruistic disposition to build a tower. The tower is itself, then, the collection of “like-minded individuals.”

Geneticists would describe the tower-building social amoebae as related to each other at a single
locus
. This is just a technical term for saying that at a single place in their genomes these amoebae share identical versions of the altruism or tower-building gene (as a comparison, parents and their offspring are normally related at 50 percent of their many thousands of genetic loci). It is extraordinary that a single gene can produce such profound effects against the background of all the amoeba’s other genes, but it can do so because building the tower benefits not just the gene for that disposition but all of these other genes. Those genes have no reason to oppose the building of the tower, even though for most of them the fate is death, because they can do no better than try their luck in the tower. The towers align individual with group interest—the amoebae have a shared fate—and so what might seem like foolish and gullible behavior is really their best bet for getting transmitted into a future generation of amoebae.

We set out in this chapter to understand a puzzling side of our nature—our tendency to help others, even when that help might not be directly reciprocated. If this altruism extended no further than to holding doors for people or giving up seats on trains, we might be tempted to dismiss it as just a charming side of our nature, although even doing that would simply raise the question of why we have evolved minds that find helping others an attractive thing to do—don’t expect this of an orang-utan or a gorilla. But we’ve seen that our behaviors go well beyond this, including risking our health and well-being or even sometimes giving our lives in war. That surely cannot just be a charming side of our nature; or if it is, we need to know how, in a Darwinian world in which the fittest survive, people willing to give their survival away can have prospered.

But if our journey into the details of amoebae sociality has done its work, you will be able to see the answer in the reflection of our cultural survival vehicles in their towers. For at least the last 160,000 to 200,000 years humans have resided in small, close-knit cultural societies that develop strong identities, often around their common language, and restrict the flow of people, ideas, and technology. The amoebae show us that these are just the behaviors that can favor the evolution and spread of the sort of ultra-sociality that makes our species so puzzling, because they create the conditions that allow altruists to surround themselves with other altruists. Then, something of a mutual aid society arises in which dispositions toward costly acts can more than pay their way because these other altruists are just as likely to help you, as you are to help them. As a result, everyone is better off than had they tried to go it alone, just as a solitary amoeba has little chance on its own.

What form might these dispositions take in our species? Humans seem to be equipped with emotions that encourage us to treat others in our societies as if they were “honorary relatives.” This is more than just a metaphor: we seem to practice a special and limited form of nepotism in which—just like the amoebae—we target our aid toward others who might not be related to us save for the fact that they are members of the same cultural group. Our nepotism is “special” and “limited” because our helpful emotions on the one hand, and prejudicial ones on the other, might be based on being related to these other members of our societies at just a single locus among our thousands of other genes. That single locus is the helping gene, and it would have spread in our evolutionary past, just as it has in the amoebae, by identifying others who carry copies of that gene and then helping them. For instance, the gene might simply code for an emotion that disposes people to be friendly toward those they perceive to be members of their societies.

In fact, nearly everyone will have experienced the vivid and controlling emotions that get us to favor members of our own societies over members of other societies for the simple reason that they are members of our societies. Maybe it is the feeling you get at a sports event, or hearing of your country’s troops in battle, or when your country is attacked by terrorists. We call these emotions “nationalism” or “patriotism,” or when directed against people from other groups, “jingoism,” “bigotry,” “xenophobia,” or “prejudice.” Most of us probably have no idea where these feelings come from; they appear spontaneously, they are visceral in nature, and they are alarmingly easy to teach to the young. They can also direct some of our most poignant and some of our most repugnant actions, and this leads us to believe they have played significant roles in our history in promoting our cultural survival vehicles, and more to the point, ourselves.