The Prisoner's Dilemma dilemma

Last week's In Our Time on BBC Radio 4 was a discussion of Game Theory.  It was an interesting discussion as far as it went, but we want to talk about the evolutionary implications here. 

The Prisoner's Dilemma (PD) is a famous game theory game:

Two prisoners are accused of a crime. If one confesses and the other does not, the one who confesses will be released immediately and the other will spend 20 years in prison. If neither confesses, each will be held only a few months. If both confess, they will each be jailed 15 years. They cannot communicate with one another. Given that neither prisoner knows whether the other has confessed, it is in the self-interest of each to confess himself. Paradoxically, when each prisoner pursues his self-interest, both end up worse off than they would have been had they acted otherwise.  (Answers.com)

Both confessing can be shown mathematically to be an ESS--evolutionarily stable solution.  This is 'evolutionary' in the sense that competition for resources that involves some risk, involves similar kinds of decision-making.

Red-tailed hawk; Wikipedia

Another 'game' of evolutionary interest is called Hawk and Dove (HD), which biologist John Maynard Smith brought to prominence in the 1970's in an effort to solve the problem of how cooperation evolved.  Roughly, the idea is if there is a single resource and two competitors, each can be aggressive and try to get it all, or they each can offer to share.  You balance the expected gain by trying to out-muscle your competitor, but there is also a cost if you lose.  It's been shown that a balance can be struck in which depending on the Value and the Cost amounts, some fraction of the time--that is, with some probability--you behave aggressively, and the remaining fraction of instances, you decide to share.  That is the ESS.  The fractions depend on the Value and Cost amounts, and neither party reveals this probabilistic strategy to its opponent.

Bar-shouldered dove; Wikimedia

Both PD and HD and many other similar types of games reflect situations that are very common in human society, but also very common in Nature--ecological balances, mating competitions, competition for resources, and so on.

Game theory is immensely popular among evolutionary biologists (and others who are obsessed by the view that life is mainly about Darwinian winner-take-all competition, or who simply want to understand the balance between competition and cooperation).  There is the additional appeal that game theory usually requires sexy, sophisticated mathematics to find the right strategies, or stable ones.

If people or birds are seen to be following some strategy when they compete, it is then assumed that they probably evolved to do this.  This then whets the prurient appetites of those who want to peer into your genome to see how, despite silly illusions of free will, you're really just a genetic automaton.

So, is it realistic to assume that something so open-ended and complex as a game theory behavior could have evolved?   After all, games like PD or HD seem widespread and if birds, ants, or even humans are just complex gene machines, mustn't it be possible to pre-program them (i.e., genetically) to play the game the evolutionarily optimized way?

This is really a dilemma, because even just one game, say HD, can arise in all sorts of ways even within a given individual's lifetime.  How can genes be pre-wired to recognize all the situations and identify their similarity and then push the Play button?  After all, every brain is wired in zillions of different ways in detail.  So what kind of gene or genes could possibly produce this behavior?  Remember that genes code for proteins, and have to be regulated in specific contexts; they are not individual computer programs.

One way to answer this is by a kind of meta-evolutionary view: we may not be able to identify the wiring diagram, but the net result of evolution is a brain that can perceive the environment and evaluate costs and strategies, and figure out for itself what is best.  The selection pressure is general, and it's for evaluating conditions rather than 'for' some specific strategy.  No need whatever for any specific genes 'for' HD or PD playing!

In this view, and especially if games really are cosmically mathematical (as they must be, given how widely they are found and shown to have similar strategy properties), then a brain that is somehow good at evaluating the real world will figure this out and identify the better strategy.  The same brain is faced with multiple and diverse evaluation situations, so that all we need is overall evaluative ability to get what we see, however such ability actually can be built into neural synapses and the like.

One would certainly easily be able to relate this to probabilistic strategies like HD, because each individual is more or less guessing what to do each time, the result being an empirical probability--the observed fraction that individuals act like hawks, or doves.  Likewise, one could observe that played something like PD properly, because s/he figures out the general risk-benefit situation.  No need for specific evolution of some convoluted gene-based mechanism specific to the game (which would imply the same to evolve separately at the gene level, for every other situation-evaluating things that animals do).

This is a way in which things can be 'genetic' in a general sense, but not specifically hard-wired by selection for a specific task.  That's a big difference!

It is genetically deterministic in a sense, by not in the precise Darwinian sense so often invoked, explicitly or just under the surface, so routinely in discussions of behavioral evolution.