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| Charles Darwin |
This right here is the Holy Grail to life. It governs all of my rational actions, most notably "tit for tat" and "defecting".
Evolutionary Stability (very loose definition): Consider a large population all of whom are playing the same strategy. The strategy is called evolutionarily stable if any small mutation playing a different strategy would die out.
Suppose that strategies or behavior in games are not chosen by reasoning people, but instead are `hard-wired' by the players' genes. Suppose further that those strategies that are relatively successful (or rather, the genes associated with those strategies and behaviors) grow while less successful strategies die out. We might want to ask what strategies will be selected by such an evolutionary process. This question has led biologists to use game theory to study animal behavior.
From: PBS Evolution Library
John Maynard Smith is best known for his use of mathematical analyses in biology. Trained as an engineer and then as a biologist, Smith applied game theory to animal behavior and found that although variation exists, natural selection tends to maintain a balance between different characteristics within a species. This balance is called the "evolutionary stable strategy."
To noted evolutionary biologist John Maynard Smith, life is essentially about information -- how information is stored, passed on, and used by organisms as they live and reproduce. "And evolutionary theory is about how that information got there in the first place," he says.
In probing evolution from this point of view, Smith has employed mathematical tools, including what is called "game theory," to explain and predict evolutionary behavior. Originally developed by John von Neumann to study poker, chess, and other games, game theory analyzes complex situations in which the best strategy of one player depends on the actions of another.
Smith's best known work incorporated game theory into the study of how natural selection acts on different kinds of behavior. The old idea had been that selection inevitably favors organisms to act aggressively. Smith showed that this isn't necessarily true, and that selection may actually favor both aggressive and non-aggressive behaviors.
As an example, imagine that two populations, one of them aggressive (hawks) and one passive (doves). Hawks will always battle their neighbors over any resource. Doves won't fight under any circumstances. A population made up entirely of doves would be unstable; that is, if a mutation caused the introduction of a single hawk, it would have an immediate advantage, and the hawkish behavior would bully the doves out of existence.
But a hawks-only population would also be unstable. A single dove introduced by mutation would have a long-term advantage. That's because the hawks' constantly aggressive behavior leads to frequent injury, while the dove, refusing to fight, escapes that risk.
Through application of game theory, Smith showed that there is a particular ratio of hawks to doves that forms what he called an "evolutionary stable strategy" for the species. Thus, selection actually works to maintain a balance of different characteristics in the population.
Evolutionary Stability Video
This video discusses evolution and game theory, and introduces the concept of evolutionary stability. We ask what kinds of strategies are evolutionarily stable.
00:00 - Chapter 1. Game Theory and Evolution: Evolutionarily Stable Strategies - Example
25:40 - Chapter 2. Game Theory and Evolution: Evolutionarily Stable Strategies - Discussion
30:42 - Chapter 3. Game Theory and Evolution: Evolutionarily Stable Strategies Are Always Nash Equilibria
42:32 - Chapter 4. Game Theory and Evolution: Nash Equilibria Are Not Always Evolutionarily Stable Strategies
01:03:00 - Chapter 5. Game Theory and Evolution: Evolutionarily Stable Strategies and Nash Equilibria - Discussion
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