Thursday, July 4, 2013

Man of Steel: Morality as an Evolutionary Advantage

"Your sense of morality is an evolutionary disadvantage...and evolution always wins"

This post will not be about monetary policy -- it will barely be about economics. But nonetheless, after seeing Man of Steel, I thought a fun essay connecting some core concepts from game theory and our notions of morality are in order.  While none of the insights are particularly new, the specific application to Man of Steel should be, and I hope you enjoy.

The core proposition was the one uttered by the evil Kryptonian woman pictured above. Between high paced punches and knocking helicopters out of the sky, Faora-Ul uttered to Superman: “Your sense of morality is an evolutionary disadvantage...and evolution always wins.” Whether evolution always wins is an issue that I will attend to perhaps on a different occasion, but I want to address the first claim. Is a sense of morality antithetical to the survival of the fittest?

With what we know about animal behavior, the answer seems to be a resounding “no”. While it is difficult, if not impossible, to impose a natural system of morality for animals, I think a natural interpretation could be the presence of behaviors that may not be beneficial to oneself. While morality surely goes beyond self-flagellation, it does serve as a useful residual for explaining altruistic actions.

One of the most commonly evoked examples of such behavior in the animal kingdom comes from ground squirrels. These squirrels make sure to loudly alarm their kin mates of the presence of dangerous predators. On the squirrel level, this is very costly behavior because it increases the risk that a predator finds and eats the squirrel. Yet if all squirrels do this, everybody is better off. This is a classic example of the difficulty of providing public goods, as every squirrel has the incentive to free-ride off of the alarm calls of others. But if nobody makes the alarm call, then they are all at a higher risk of being eaten by an eagle. Somehow, the squirrels manage to overcome this public goods problem. There’s no Coase theorem contract, no government enforcement, yet squirrels provide the public alarm nonetheless.

Why? In this case it’s simple: kin selection. Because these ground squirrels usually spend most of their lives around family, it’s in their incentive to protect their peers in order to pass on the most amount of genes to the next generation. Under the framing of Richard Dawkin, the selflessness of the individual squirrels comes from the selfishness of a gene that may encourage the alarm calls. To see this logic, suppose there exists a squirrel with a gene that induces the alarm calls. Then his offspring are also likely to have the same gene. Because the alarm behavior serves to preserve his offspring, then this alarm gene will propagate its way through the population. Therefore, this gene selfishly works to propagate itself, even at the cost of its host squirrel. Such is the power of family.

The above explanation has an interesting analogue from public economics, in particular the analysis of firm mergers in the presence of positive externalities. For example, consider the case of two stores that need to decide on their advertising budgets. Because of their proximity, the stores are complementary in the sense that more traffic in one store means more traffic in the other. Therefore in equilibrium, if there is no cooperation, these firms will choose an inefficiently low level of advertisements because they fail to take into account the positive benefits their own ads have on the other firm. But if they merge, the merged firm can capture this positive externality. While this may seem contrived, you can think of family structure as a merger between individual squirrels. By the same logic, this genetic merger allows the family to capture the positive externality from the alarm.

One of the greatest appeals of this kin selection theory is that it yields many good out of sample predictions. The original evidence was just the basic anomaly that the squirrels would take any kind of altruistic behavior. But by extending the gene logic, then it should be the case that the probability of any given squirrel to sound the alarm is positively related to the extent of familial relations between the squirrel and the group. Indeed this is the case, as the females, who tend to spend their lives around the same family, are much more likely to sound the alarm than the males, who go off to live with other squirrel groups in adulthood. These females are also more likely to sound the alarm when they are around close relatives -- further corroborating the kin selection hypothesis.

From this relatively scientific evolutionary analysis of animals I now pivot to the much more speculative and unscientific theorizing about human systems of morality. Here, I will push the claim that systems of human morality were also driven by similar evolutionary principles, and that this framing of morality helps explain some of the universality in basic morality across societies.

Again, let’s consider a concrete example. Consider the commandment “Thou shalt not covet thy neighbor’s wife”, and consider the most literal interpretation of it. Indeed, I do believe such a rejection of wife-stealing is fairly universal. Even in polygamous societies, I do not believe relations with a woman who is somebody else’s wife are encouraged. What could be a game theoretic interpretation of this? Well, suppose men indeed were encouraged to chase after the wives of others. What would the equilibrium be? If the “cheating” status of partners in a relationship were to be private information, then there could be an adverse selection spiral in which men do not believe their wives are faithful, and then wives, because they are not being treated as well, end up being open to extra-marital affairs. Therefore, society as a whole converges on the norm that a neighbor’s wife should not be coveted in order to avoid the bad adverse selection equilibrium.

I snuck in a few tricks into the past paragraph. First, what I described was more characteristic of group selection, and not kin selection as with the squirrels. Group selection is much more controversial due to its tenuous connection with the empirics and its use as a justification for genocide. Nonetheless, I do believe it provides a parsimonious framework for some of these game theoretic justifications for moral norms. Second, it should not surprise us that many observed societies do have these kinds of norms. Since societies that do not have this norm end up spiralling into some bad equilibrium, they end up erased from the historical record. As a result, we only see the societies that succeeded and, surprise, they tend to exhibit these norms that avoid bad equilibria.

Those familiar with philosophy will be able to identify my above analysis with the Kantian notion of a categorical imperative, or that ethics should be based on rules that everyone can apply. Indeed, a game theoretic interpretation of a stable equilibrium captures this notion. The stable equilibrium is the one where everyone can play the same strategy of not violating a moral code. This is why potential alternative moral rules, such as “do not covet thy neighbor’s wife except if she is very fertile and attractive” cannot hold. They cannot be held symmetrically, and therefore fail to propagate themselves through a group.

While the above analysis does not qualify as scientific (it’s quite hard to falsify), I do believe it’s a nice economic interpretation for why moral structures can be so similar across societies. Most historical codes -- I am thinking all the way back to Hammurabi’s -- have similar core ideas: don’t steal, don’t kill, etc. One would think that through the thousands of years of history, there must have existed at least one society that had very loose rules regarding murder and theft. Yet I would claim that we do not hear of these societies because the loose rules caused the society to collapse before we could find evidence for them.

As a final example, consider again the Kryptonians mentioned in Man of Steel. If the moral structure of the old Kryptonian society was governed by Faora’s preference for no regard for organisms of other species, it seems highly unlikely that they would have been able to persist for so many thousands of years. First, on a planet-level basis, would it have taken that long before military coups pulled the Kryptonian people apart? Given how easy it is for our Congress to disagree, there must have existed at least one disagreement about how to treat organisms of different species in the hundred thousand years of glorious expansion. Moreover, such a cold moral system against other organisms would have cut the Kryptonians off from the most important driver of prosperity: trade. With these weakness, it seems more likely that they would have been conquered or merged into another society that exhibited more robust morals against mass exterminations of other races.

These economic interpretations add a new spin on the design of moral structures. By grounding the development of morality in a game theoretic framework, I can derive a very natural reason why certain moral rules are so universal. So rest assured, humanity . In spite of what the villains from Man of Steel may have us think morality is an evolutionary advantage, and more evolved humans will not be forced to leave it behind.


  1. Interesting article Yichuan.

    The squirrels seem to have found an evolutionary escape from a prisoner's dilemma. The issue humanity faces when presented with the same structure of problem is our self-consciousness and therefore ego gets in the way.

    1. The terrifying implication of selection bias is that the Squirrels didn't "find" a solution in the conventional sense. It's just that those who didn't find a solution went extinct.

    2. That's true, but it somehow feels like the inherent bias in the game of not making the call should be the Nash equilibrium. So if the squirrels were thinking about things in the same rational, Homo Economicus way that you or I do (according to the theory at least, ignoring the entire body of behavioral economics) then at an individual level each squirrel would still stop. Mind-boggling!

  2. The idea that Evolution doesn't favour cooperation is ridiculously outdated. As indeed is the whole Selfish Gene nonsense.

    The scientists at the cutting edges of this are Martin Nowak (Harvard) and Denis Noble (Oxford). For popular overviews read their "Super-Cooperators" and "The Music of Life" respectively.

  3. For further research to those so interested there has been a book written on something akin to this topic already 1 century ago.

    Mutual Aid; a factor of evolution - Petr Alekseevich Kropotkin

    His thesis - that cooperation and mutual aid are the most important factors in the evolution of species and the ability to survive.