The monogamous tendencies documented by our Cro-Magnon anthropologist, by contrast, are unusual for higher primates. They have never been observed, except in hominids, in species where the sexes mix in large groups without territorial boundaries. This sexual organization had several important implications. Females evolved to become sexually active throughout their menstrual cycles. Males and females could maintain exclusive sexual interest in each other. For example, in a survey of world cultures, monogamy was recognized as official policy in only 16 percent of 853 societies sampled, but sexual monogamy was the most common sexual pattern. Males evolved to know who their offspring were and to provide resources and care to them.
Our Cro-Magnon anthropologist, then, would conclude that the social environment of the EEA would be defined by an acute tendency to care, by highly coordinated, face-to-face social exchanges, by the need to reconcile and the flattening of social hierarchies, by perpetually negotiated conflicts of interests, and by the emergence of the tendency toward sexual monogamy. It is these properties of our early social existence that gave rise to the moral emotions, of interest to Darwin but long ignored by the science of emotion that he inspired. Compassion, embarrassment, awe, love, and gratitude emerged in the recurring social interactions of early hominid social life: the attending to vulnerable offspring, the playful exchanges between kith and kin, the status moves and negotiations, the courtships and flirtations between current and potential sexual partners. These emotions were wired into the body and our social life through processes of natural and sexual selection. They evolved into the language of human social life, the species-characteristic patterns of parent-offspring relations, relations between mates and allies, dominant and subordinate members of hierarchies, and in mating relationships. These emotions became our ethical guides to help us fold into stable, cooperative communities. They operated according to three general principles, revealed in a tournament that pitted the brightest mathematicians and computer hacks against one another in an attempt to discover what strategies prevail in the survival of the fittest.
THE WISDOM OF TIT-FOR-TAT AND THE GREAT SHIFT
In The Evolution of Cooperation Robert Axelrod asks the following question: How might cooperation emerge in competitive environments governed by the ruthless pursuit of self-interest? How might compassion, awe, love, and gratitude, powerfully oriented toward enhancing the welfare of others, take hold within social communities governed by the pursuit of self-interest, in such a fashion that they would become favored by natural selection and encoded into our genes and nervous system?
Axelrod himself was taken aback by striking acts of cooperation that confound assumptions about self-preservation and self-interest. In the trenches of World War I, for example, British and French soldiers were separated from their enemies, the Germans, by a few hundred yards of burned-out, treeless, muddy no-man’s-land. Brutal assaults by one side were typically met with equally fierce, lethal attacks by the other. And, yet, in these nightmarish patches of annihilation, cooperation emerged. The two sides flew certain special flags, signaling nonconfrontation. They made verbal agreements not to shoot at each other. They evolved patterns of firing their weapons in purely symbolic, harmless ways, to signal nonlethal intent. All of these cooperative strategies allowed the soldiers to eat meals peacefully and to enjoy long periods of nonengagement. On special occasions, the warring sides even fraternized with one another. In fact, cooperation became so pervasive that commanding generals had to intervene, demanding a return to deadly combat.
From historical anecdote Axelrod turned to the prisoner’s dilemma game (see table below) to answer his question about the evolution of cooperation. He conducted a tournament in which players—cold war strategists, psychologists, prize-winning mathematicians, computer specialists, and other aficionados of the game—were invited to submit computer programs that specified what choice to make on a certain round of the prisoner’s dilemma game, given what had happened in previous rounds. In Axelrod’s first tournament, fourteen different strategies were submitted. Each was subsequently pitted against the others for 200 rounds. Here the game really mirrors human social life. Individuals with different strategic approaches went toe-to-toe with one another, much as bullies and altruists do on the grammar-school playground, Machiavellians and kindhearted colleagues do at work, hawks and doves do in foreign policy debate, and presumably our hominid predecessors—genetically prone, through random mutation, to cooperate or compete—did. Who prevailed?
THE PRISONER’S DILEMMA GAME (PDG)
PARTNER’S ACTION
COOPERATE
COMPETE
YOUR ACTION
COOPERATE
5,5
0,8
COMPETE
8,0
2,2
In the PDG, participants are required to make a simple choice: to cooperate or compete with one another. If both participants cooperate, they do well (in our example, they each receive $5). If one competes while the other cooperates, the competitor thrives at the expense of the cooperator (in our example receiving $8 to the cooperator’s zilch). If both compete, they each get $2. From the perspective of maximizing self-interest, the rational thing to do is to compete. The rub, though, is that, as in arms races, the use of shared resources, intimate life, and business partnerships, the mutual pursuit of self-interest leads to worse joint outcomes.
A tit-for-tat strategy was submitted by Anatol Rapaport. It is disarmingly simple: It cooperates on the first round with every opponent. Then it reciprocates whatever the opponent did in the previous round. An opponent’s cooperation is rewarded with immediate cooperation. The tit-for-tat was not blindly cooperative, however: it met an opponent’s competition with competition. Defection was punished with immediate defection.
Axelrod held a second tournament that attracted the eager submission of sixty-two strategies. All of the entrants knew the results of the first round—namely, that tit-for-tat had won. All had the opportunity to return to their blackboard, to adjust their mathematical algorithms and carry out further computer simulations, and to devise a strategy that could unseat the tit-for-tat. In this second tournament, once again the tit-for-tat prevailed. The tit-for-tat did not prevail, it is important to note, against all strategies. For example, your more sinister mind might have anticipated that a strategy that starts out competitively and always competes will have the upper hand against the tit-for-tat, because it establishes an advantage in the first round (of course, this strategy scores few points, and suffers profoundly, against other purely competitive strategies). Overall, however, tit-for-tat, so simple and cooperative in its jen-like design, achieved the highest outcomes against the society of different strategies in the tournament.