To solve our existential problems and maximize human well-being, evolutionary science suggests that we need to learn to cooperate on a global scale. To understand the challenge this scale of cooperation poses, we have to appreciate the fragility of large human organizations.

Human ancestors have lived in social groups for millions of years. The unit size of bands and tribes was a very stable cooperative entity that produced evolutionary success over hundreds of thousands of generations. But around 10,000 years ago, the unit size of cooperative human groups started to grow dramatically at the expense of their stability.

Part of the problem in larger human groups is the inability to effectively enforce cooperative agreements on disruptive and selfish individuals who undermine collective endeavors. The reverse dominance hierarchies employed by hunter-gatherers that enforced strict egalitarianism and prevented any one member from dominating the tribe are most effective in smaller units. They fall apart when the groups get so large that people can’t have individual relationships with everybody in the group. This number is often speculated to be the so-called Dunbar’s number, which is around 150 individuals.

More often than not, large groups are held together through various forms of coercion, which makes them susceptible to destabilizing internal and external conflicts. This helps explain why human civilizations are estimated to last only around 340 years on average.

To address the many problems associated with human organizations, David Sloan Wilson advocates for the creation of a globe-spanning “multicellular society” that consists of a large number of smaller groups instead of a few large groups. According to Wilson, small groups are the ideal unit size for human organizations.

What makes the multicellular society significant is that it creates the positive evolutionary dynamics of between-group selection. The ensuing incentives are not only familiar to us but also highly enjoyable, because in practice, they make us feel like we are participating in a team sport. A multicellular society is like a sports league in which lots of small groups compete against each other.

As we make sense of this proposal, it’s useful to remember the three-step algorithm of evolution: variation, selection and replication. If we want to steer evolutionary forces in a particular direction, we should seek to create meaningful variation and choose wisely the qualities we are selecting for and in what unit size. Do we select the fastest, cheapest or the most durable, for example, and whether the unit of selection is the gene, the individual, the group or group of groups. If we can control these variables and the qualities are only replicated in the units we have chosen, we can manage evolutionary forces to our benefit.

When evolutionary selection is conducted at the group level instead of the individual level, the winners of these contests are selected based on their ability to cooperate instead of their capacity for selfishness. Groups that are unable to suppress disruptive and selfish individuals within the group lose the competition, and in this way, selfish behavior is weeded out and suppressed in the larger community.

When we look at plants and animals, we notice that despite the significant variation in their body size, the sizes of the cells are usually pretty uniform. So big animals don’t have bigger cells, they just have more of them. In fact, larger cells are usually a sign of a problem like cancer and the immune system tries to get rid of them. The fact that biological evolution has settled on multicellularity as the answer should make us consider how we structure human society.

As Martin Nowak points out in his SuperCooperators book, what makes small group sizes so effective is that when a disruptive individual cannot be suppressed, the others can easily abandon the group and join or form others. Lots of small groups competing against each other in their ability to cooperate also provides the meaningful variation evolutionary progress thrives on.

So, what is the ideal size for a cell? I believe it is less than 100 people. Depending on the task, 10 or 20 people seem closer to the ideal. When you calculate how many potential two-way relationships can exist in a group, the number goes up exponentially with each additional person. In a group of three, you only have three two-way relationships. In a group of 10, that number rises to 45. And in a group of 100, there are 4950 potential two-way relationships that need to be individually managed. When a cell size grows too large, the natural thing is to divide it in two.

To understand these dynamics, it’s worth looking at the small-group dynamics we find in the most durable human organization in history, the hunter-gatherer tribe. These tribes were usually strictly egalitarian and forbade economic competition. Competition for sexual partners, however, was allowed. After all, the ability to pass on one’s genes is, at least from an evolutionary perspective, the most import task an organism has.

Instead of competing for dominance, hunter-gatherers competed for prestige, which is a form of good reputation. Prestige works almost the opposite of how dominance works. In a hierarchy based on dominance you have underlings and subjects who are afraid of the powers you have, whereas in a prestige-based hierarchy you have admirers who try to emulate you.

So how then do you accumulate prestige? Having a special skill and sharing it with your community, acting heroically in dangerous situations, giving more and taking less, acting altruistically–or, to use Oliver Scott Curry’s thesis, by acting cooperatively.

Where a dominance hierarchy is like an individual sport such as tennis, in which a player tries to outcompete everybody else to get to the top, the prestige hierarchy resembles a team sport in which you compete in your ability to cooperate with your teammates against a rival team.

From the perspective of evolution or game theory, seeking prestige often depends on costly signaling. When you act altruistically and give more than you take, gaining prestige has a tangible cost. If you try to be a hero and fail, it could actually cost your life. Yet, your group greatly benefits from this behavior. Your stock rises because everybody wants to have a member like you on their team. Individuals who try to dominate others, on the other hand, can quickly be ousted from the group.

One of the thorny puzzles for the advocates of Dawkins’ Selfish Gene theory is how to explain the evolutionary logic of unselfish behavior. From the perspective of the group, altruism makes perfect sense for social animals. But to align with the theory, it also has to make sense for the altruistic organism and the genes it carries.

This is perhaps the explanation: when altruistic behavior confers you prestige in the group and a better position in the mating game, it increases your evolutionary fitness or ability to reproduce. As altruistic individuals manage to reproduce faster, it is entirely plausible that altruistic genes and thus the moral instincts they give rise to spread in the group, enabling the group to cooperate better than other groups. This increases the evolutionary fitness of all the genes that belong to the members of this group.

Amotz Zahavi’s book The Handicap Principle dissects how certain organisms provide reliable signals of their evolutionary fitness with “wasteful” or costly behavior or body morphology to attract a mate. In it he discusses the distinct “prestige-driven” behavior of a bird species called the Arabian babbler.

After establishing their internal hierarchy among siblings in their youth with fighting, hierarchies are maintained through altruistic acts, by performing guard duties and feeding others. The dominant individual feeds the individual directly below it, and by accepting the food, the lower-ranked individual acquiesces to their lower position in the hierarchy. Comparing the behavior of babbler flocks with hunter-gatherer tribes lends credence to the idea that altruistic behavior could be hard-wired in social animals and that the Selfish Gene theory might not be the last word on the subject.

As we search for the ideal way for humans to cooperate, we have hit upon a few scientifically supported solutions we can develop further. One is the ideal unit of selection, which is the small group within a multicellular society. This promotes cooperation within groups.

But what criteria or process should we use when these units are selected in a competition against each other? Prestige and good reputation are strong candidates here. This is supported by Nowak’s findings on how indirect reciprocity is able to elicit cooperative behavior in games of prisoner’s dilemma.

Our economy is the main forum in which the evolutionary algorithm of variation, selection and reproduction plays out in our society. This is where our cultural evolution happens in front of our eyes. Since we are playing with evolutionary forces, it is essential that we pay special attention to the way our economy is structured. To select for communal well-being, we need to ensure that the playing field is even and that it can incorporate our values as a selection criterion.

The central task of this book is to develop these ideas further into a coherent cooperative framework.