Yes, I Spent My Saturday Night Reading About Kin Selection and Mucking About With Game Theory… So What?

There are a lot of words that can be used to describe me.

Altruistic is not one of them.

That being said, I’ve always found the concept of the altruistic individual a fascinating (if mostly unbelievable) concept. I’m cynical and tend to think, realistically, that little to no true altruism can occur- everyone is out for something, even if it’s simply the endorphin rush that accompanies helping someone else out. And yet, I still enjoy entertaining the notion of what real altruism would be like, both for the individual and en masse.

It’s not really something I’m good at- imagining another person’s emotional reaction to events. I lack a lot of the empathy that seems inherently built into other members of my gender. Still, as a mental exercise, it can be diverting to at least make the attempt.

The question of how altruism could evolve within a species, however, was never something I thought much about. I’ll grant you that this is largely because I dismiss altruism as utterly useless- it serves no real survival purpose.

Or does it?


Biology is not my strong point (insert some crude joke about biology and sex here, hur hur), scientifically speaking, though that doesn’t mean I don’t find it interesting. It just tends to take a backseat to physics and chemistry for me.


Therefore, the concept of social evolution was not one I was wholly familiar with (and, frankly, given the sheer scope of biology and evolution, I can’t say with any real conviction that I’m familiar with it now). We all know about Charles Darwin, the HMS Beagle, and evolution by natural selection. If you are not radical Christians and/or batcrap crazy, you probably accept this scientific theory as fact. The overwhelming amount of evidence supporting natural selection and evolution is quite impressive, after all.

Social evolution is another facet of evolutionary biology. One that was not covered in my public school education, though I’m almost positive I’ve run across a mention of it somewhere before… Anyway, social evolution is concerned with social behaviors that have fitness consequences for others. There are four ways to categorize these social behaviors, depending upon their fitness consequences for the donor and recipient:

I know you love it when I include a diagram for your viewing pleasure, dear galleons.

So, to get back to our original issue- altruism is one of the possible categories of social behaviors. Seems about right.

But, I have to ask: Why would any organism pursue an altruistic course when it would lead to absolutely zero benefit to them? I mean, as Darwin himself said, “he who was ready to sacrifice his life, as many a savage has been, rather than betray his comrades, would often leave no offspring to inherit his noble nature.”


Kin selection is the current prevailing theory for the prevalence of altruistic behavior among organisms, having ousted the weak group selection theory that went before. Group selection suffered from the notion that, while a tribe of altruistic individuals would indeed triumph over others, due to their cohesion and the help they provide one another, this idyll would be shattered by just one selfish mutant in their ranks. This mutant, due to the fitness advantages its selfishness would gain it, would out-produce the altruists and the village altruism would quickly become swamped by selfishness. The ease with which altruism would be banished from a tribe served as a major stumbling block for group selection, as it really didn’t help explain the evolution and prevalence of altruism.

In the late 60s/early 70s, a new theory emerged to topple group selection. This theory was kin selection.

To understand how kin selection works, let’s imagine that altruistic behavior is genetic. This altruism gene makes its bearer share food with others. Which is nice, but (as mentioned above) this puts the altruistic individual at a fitness disadvantage. While they share their food with those around them, the selfish individuals hoard theirs. The altruistic individual will have less food than everyone else, thus their fitness disadvantage. As with group selection above, this disadvantage will quickly cause the altruism gene to die out as the species evolves.

However, let us now imagine that these altruistic types, instead of just sharing with anyone, only share with those that are related to them. Suddenly, a new pattern emerges. Because relatives are genetically similar, there is a possibility that, when the altruistic individual shares food with a family member, that family member also carries the altruistic gene (but does not express it). While this behavior still lowers the altruistic individual’s fitness, it increases the fitness of relatives- relatives who have a higher-than-average chance of carrying copies of that same altruism gene. Which means there will be a high chance that the altruism gene will carry into the next generation (via the relative of the altruistic individual) and spread. Which means that altruism can, in principle, be spread through natural selection.

Because of the strange nature of altruism’s evolution, it cannot be measured through relative fitness (the amount of progeny of an individual) but by inclusive fitness (the degree to which a trait is passed from generation-to-generation, including both direct and indirect methods). There’s some math that goes along with inclusive fitness, but I really don’t feel like getting into it- not that it’s not interesting, just that I think it will send me spiraling off topic. If you are curious, look up Hamilton’s rule.


The key to the evolution of altruism is that correlation between donor and recipient. We can illustrate this with one of my favorite aspects of game theory (we might have to do a series of posts on game theory, just because I love it good)- the Prisoner’s Dilemma.

I was inordinately excited when I realized I could work this in tonight, I hope you all know…

Anyway, here’s an example of the Prisoner’s Dilemma:

Two suspects are arrested by the police. The police have insufficient evidence for a conviction, and, having separated the prisoners, visit each of them to offer the same deal. If one confesses and the other remains silent, the confessor goes free and the silent accomplice receives the full 20-year sentence. If both remain silent, both prisoners are sentenced to only one-year in jail for a minor charge. If they both confess, each receives a five-year sentence. Each prisoner must choose to confess or to remain silent. Each one is told that the other would not know about their decision before the end of the investigation. How should the prisoners act?

Because we all love diagrams, we’ll now arrange this problem in a familiar fashion:

What makes the Prisoner’s Dilemma so goddamn fascinating is how it tends to pan out. The goal of this game (as with most in game theory) is for the player to maximize their own payoff, with no concern for the other individual’s. The end result is a Pareto-suboptimal solution (in which it is impossible to make one person better off without necessarily making someone else worse off). Rational choice leads both players to confess, even though both players would reap a greater reward (only 1 year in jail) if they cooperated. For, even though both players would get a bigger payout if they remain silent, they have no way of knowing what the other player will do. Since in any individual situation confessing is more beneficial than remaining silent, all rational players will confess.

Anyway, I’m sure you are all fascinated (you should be) by this, and if you are curious, you should delve a little deeper, as the Prisoner’s Dilemma gets particularly interesting when the same players play the game multiple times.

But what does this have to do with the evolution of altruism?

Let’s substitute our altruistic/selfish individuals into our Prisoner’s Dilemma. In place of confessing, we place selfish actions. In place of remaining silent, we place altruistic ones.

We can easily see that, if the game is played rationally, selection seems to favor the selfish. This is true. The only way the altruistic benefit is if they are paired with another altruist. The only way selection can favor altruism is if there is a greater-than-random chance of altruists being paired with one another in the game.

And how can we guarantee a greater-than-random chance of pairing altruists (or those recessively carrying the altruism gene)?

You guessed it: kin selection! That is how it all works. The reason altruism can survive.

Interesting, no?


So, what have we learned today?

Being selfish is easier, has higher payouts for the individual, and doesn’t involve this messy “kin selection” bullshit.

Also, the evolution of altruism tends to hint heavily at inbreeding…

Don't make Jesus make this face, galleons.

Inbreeding is wrong.

Don’t be an altruist.

2 responses to “Yes, I Spent My Saturday Night Reading About Kin Selection and Mucking About With Game Theory… So What?

  1. Every so often, I pop into my stats to see the search terms people use to find this blog. The combinations never cease to amaze me.

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