It’s valuable to model the development of phenomena like altruism and spite (harming someone else at a cost to oneself) by combining game theory with evolutionary theory. The results should be seen as predictions to be tested against empirical evidence about actual organisms. My question is what this combination tells us about our situation as human beings in historical time.

The basic assumptions are:

1. Organisms interact with each other so that each one can win or lose. For instance, a parent feeds its child, a predator eats its prey, a mite hitches a ride on an insect. These interactions can be modeled as games in which each player makes a choice (e.g., kill or don’t kill), and positive or negative outcomes result for each as a joint result of their decisions. (“Choice” is a metaphor, because completely non-sentient organisms can be modeled as players in a game. For instance, a plant can release a chemical or not.)
2. Changes in how organisms interact in game-like situations arise more or less randomly. As a result of a genetic mutation, an organism may begin to mimic another species. Or, as a result of a change in climate, an organism’s prey may become scarce.
3. If playing a game in a particular way increases the odds that a species will reproduce, that behavior will become more common. For instance, if mimicking works, it will spread.
4. This means that the payoffs that matter from game-like interactions among organisms are best measured in terms of evolutionary fitness. Whatever an organism may want or think or feel, what matters is whether its chances of reproducing increase or decrease.
5. Given the first four assumptions, under certain conditions, behaviors that we might consider proto-moral, such as helping offspring, helping others outside the family lineage, or even sacrificing oneself to punish another for violating a norm, predictably arise. By being altruistic (or punitive) in game-like interactions, an organism may gain evolutionary fitness.
6. Thus we can explain proto-moral behavior through a combination of game theory and evolutionary theory. The behavior is a consequence of background conditions. This form of explanation applies to homo sapiens, who have cognitive capacities and instinctive drives for things like fairness and punishment because of the conditions that pertained before historical time when we evolved into our current form.

Game theory is part of my own toolkit. I believe it clarifies many situations that confront human beings as we interact with each other and helps us to devise solutions to collective problems. I also acknowledge that we are a biological species that evolved with certain capacities and drives, and that inheritance must be taken into consideration as we diagnose and try to address our problems as a species. However, I tend to believe that Darwinian evolution gave us certain capacities that now fundamentally change the premises described above (points 1-6):

7. We can design games. The original Prisoner’s Dilemma, for example, is a situation intentionally created by a prosecutor within a legal system. The prosecutor could change the game, or he could be required to change it by a legal reform. A shared pasture is a very different game from a Prisoner’s Dilemma, but it’s also intentionally designed.
8. We can choose goals. If natural selection determines change in a whole population, then it doesn’t matter what each organism wants; it matters what promotes survival and reproduction. But human beings can choose what we want in specific interactions. Sometimes we want things that reduce our chances to survive and reproduce, but we compensate with other strategies.
9. We can change our identities. If a person’s main identity is a parent, his impact on his own offspring is central. But he could instead choose to identify primarily with a church, a community, a nation, or other grouping.
10. We can design and change the groups within which our interactions occur. As an example, the size of a group influences how organisms interact. But we human beings can merge small groups to form vast nations, decentralize governance to small groups, nest communities within states, or place people in multiple overlapping groups. We can intentionally vary not only the size of groups but also their internal diversity, spatial extension, equality of influence, and cost of entry and exit.
11. We can influence individuals’ predilections to play games in various ways, e.g., to be altruistic, trusting, selfish, spiteful, or punitive. We can influence children in lasting ways by raising and educating them to have certain character traits. We can also influence behavior in local and temporary ways by changing messages and contexts to encourage desired behaviors.
12. We are influenced in all the above choices by norms, but we disagree about the best ones, and the available norms are the results of deliberate human creativity. In short, we invent and choose norms.

Game theory remains relevant–in fact, it is an especially useful toolkit for a creature that is capable of designing and redesigning its own interactions. I am less sure that evolutionary theory is relevant, except insofar as it explains certain proto-moral tendencies and limitations that now contribute to our challenges.

Notes: Points 1-6 are guided by my Tufts colleague Patrick Farber and specifically his excellent paper “Reciprocal Spite” (with Rory Smead). Points 7-12 are heavily influenced by Elinor Ostrom, who emphasized the diverse outcomes that result when people face collective action problems and the importance of their intentional choices about groups, rules, and norms.