Evolutionarily Stable Strategies ft. Richard Dawkins
What are evolutionarily stable strategies?
In many cases, it is kind of clear what is the best thing for an individual to do, the best thing it can do to increase its survival with deduction. But there are times when what is the best thing to do depends on what other individuals in the population are doing, what, in particular, the majority of individuals in the population are doing. A hypothetical example we could call fishers and pirates. And I am talking now about some kind of birds where there are two ways of getting fish. These are sea birds. Either you can fish for fish. You either dive in a sea of catfish or you hang about waiting for a bird that has caught a fish and steal it. Those are pirates. And these are two ways of making a living.
Now what is the best thing to be? A fisher or a pirate? And the answer is that it is not obvious because it depends on what the rest of the population are doing. If the whole population is fishing, then it could very well be that an individual could mutate and become a pirate because there are plenty of fishing going on. And it is easy to steal a fish. So then you might say: Well, natural selection then favors piracy, the gene for being a pirate spreads through the population. In a few generations, now everybody is a pirate. And there is no fish. So piracy is not stable. It is an unstable... it is evolutionary unstable.
Fishing might also be unstable because if the whole population is fishing, then a mutant pirate invades, so a stable strategy is a strategy such that when all the population is doing it, no mutant individual could arise which would do better. So neither fisher nor pirate in my hypothetical sort of game is evolutionarily stable. What might be evolutionarily stable is some kind of ratio. It might be 80 percent fishers and 20 percent pirates, something of that sort. And the definition of stability in this case is when they are doing equally well.
A well-known example is the sex ratio where any departure from the stable sex ratio is penalized by natural selection. If there are too many males, an individual is better off having daughters. And if there are too many females in a population, an individual is better off having sons. And so the stable ratio is 50-50, or, strictly speaking, it is 50 percent investment, economic investment in sons and economic investment in daughters. So an evolutionarily stable strategy is a strategy which cannot be bettered by any other strategy provided that everybody else in the population is doing it.
You know, two years ago when this channel reached half a million subscribers, you guys asked me who would I like to meet. And I answered: Bill Nye, Neil DeGrasse Tyson, Richard Dawkins. And since then, Bill Nye has taught me how to tie a bow tie. I got to interview Richard Dawkins and on August 22nd and 23rd, I will be hosting Neil DeGrasse Tyson in Sydney and Canberra. Link in the description. And I really want to thank you guys because I think it is your support that has made this all happen.
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