[Maayan]

A simple introduction:

Environments are variable over all spatial and temporal scales. Driven either by natural stochastic forces or by anthropogenic disturbance, much of this environmental variation is unpredictable. A trait that contributes to high relative fitness in one generation might be inappropriate in the next. Changes in the selective environment through time will not necessarily favour a phenotype that simply maximizes average fitness over generations (this is because fitness is determined by a multiplicative process across generations). Rather, so-called "bet-hedging" traits are expected to evolve.

Bet-hedging traits are defined as those that maximize long-term (geometric mean) fitness over generations, yet do not maximize expected within-generation fitness. Such traits are also known as "risk aversion" or "risk-spreading" traits. (
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)


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. Unfortunately, the math makes me want to run into the arms of the Jonas Brothers.

It's cool. I want more detail -- in terms that I can understand. Please, how does it work?

[Jinxu]

	Originally Posted by Maayan To view links or images in this forum your post count must be 2 or greater. You currently have 0 posts.
	It's cool. I want more detail -- in terms that I can understand. Please, how does it work?

I don't have the time to read the whole thing. But it sounds a lot like natural selection. The environment change. Natural disaster happens. Traits that help you to survive in a tropical environment may not be so useful if that environment turn into a desert. Sometimes, a meteor crash into the planet and if you're a big dinosaur you wouldn't be able to survive while the burrowing underground animals would, like some mammals and reptiles for example. I think the author is speaking about traits that are flexible and adaptable to a changing environment that survive over time.

You might want to read these thread too:

Evolution - Proteins Found to Regulate Evolution

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Evolutionary developments to ensure the continual survival of human beings?

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[Rudy]

Okay, that was really interesting; I've read through the first two chapters of that book, and I'll try to give a straightforward explanation of the concept of bet hedging as it relates to natural selection. Forgive me if I say anything obvious to you.

Bet hedging is, in general, sacrificing expected gain in order to minimize risk. A simple example of this is in the stock market. People often will diversify what stocks that they have invested in. By doing so, they lower their change of making a large profit, but they also lower their chance of significant failure.

Now, how does this apply to natural selection? Imagine that there are two annual desert plants, the tortoise plant and the hare plant. (Those names might be foreshadowing *hint* *hint*)

The hare plant is concerned amount maximizing within generation fecundity. It wants to produce as many offspring as possible, as quickly as possible, so that they can get right to having their own offspring. In order to do this, the hare plant expands all its resources on creating as many offspring as it can during the brief desert rainy season. All of its offspring germinate during the next heavy rain, and get down to their own business.

The tortoise plant, on the other hand, is a little slower at getting things done. It produces the same number off offspring, but puts chemicals around some of the seeds that slow the germination. Thus, rather than having all of its offspring germinate immediately, some of them will germinate immediately, some the season after that, some the season after that, etc.

On average, the hare plant will have a much better within-generation fitness, because it is producing more germinating plants in a generation. Just as sticking with a single, strong stock is generally much more profitable than widely diversifying under normal conditions.

What happens, though, when things go wrong? Well, with the stock, if your chosen company tanks, you are screwed. In the desert environment, the comparable analogy is drought. What happens if there is a year with no good rain. The hare plant is likewise screwed. All hare plants, and all of their descendants, could die out at once, because they are all trying to germinate with insufficient water.

Meanwhile, some of the tortoise seeds try to germinate. These will fail, and die, just like the hare plants. However! The tortoise plant still has seeds waiting, patiently for the next season, and the season after that.

Hedge betting of this sort seems to be found most commonly in very volatile environments, where the conditions can change a lot from year to year. In summary, a species allows its rate of reproduction to be reduced, in order to increase its multi-generation odds of surviving the worst conditions.

Let me know if that clears things up at all.

[blueback]

That was a very good explanation.

I'd like to expand on it.

You can think of all organisms as investors. They accumulate resources and invest them with the goal of maximum return at minimum risk.

Just like in financial investment, an organism cannot maximize its returns if it takes no risk; neither can it maximize its returns if it takes too much risk. There is a certain amount of risk at which the organism/investor gets maximum return.

This principle expresses itself in the capital world when investors diversify their portfolios. They put some of their resources into sure things with minimal but acceptable returns, and some into long-shots with maximum but acceptable risk. It expresses itself in the organic world when organisms diversify their genetic stock. Some resources go to things that always work, but only because they don't have any chance of working really well. Some resources go into things that rarely work, but when they work they hit a home-run. The successful investors/organisms are the ones who can best express the precise balance between risk and return (and who don't get caught in a natural disaster).

Another example, which you might not have much experience with, is advantage play. In Blackjack the player can erase, and even reverse, the house edge by memorizing strategy tables and learning to count cards. However, if the casino makes any changes to the rules it usually renders these advantages moot. For example, an excellent advantage player can potentially gain a 0.5-1.0% advantage over the house. But, if the house changes one rule, say not allowing them to split their hand or limiting Blackjack payoffs to 1:1, the advantage disappears. It turns out a significant percentage of the money Blackjack players win is a direct result of the one or two times they get a chance to make more than even money. If you reduce all payoffs to even money the casino gets something like a 10% edge, which can't be overcome no matter how good you are. It is knowing when to bet large, so that one can take advantage of the larger payoffs, that nets a Blackjack player all their winnings.

So, in a sense, it is the same thing. It only makes sense to play Blackjack if you are allowed to "diversify" your betting in that way, with mostly 1:1 payoffs but also a few 1.5:1 and 2:1 payoffs. If you can't diversify your bets you are limited to only the "works every time but not very well" type of thing, which significantly reduces your returns. It would be like not allowing the seeds in RudyHenkel's example to dely their germination and forcing them all to germinate right away. An investor which cannot diversify might as well not bother, because the very first turn of bad luck will erase all their appreciation.

[Rudy]

Originally Posted by blueback To view links or images in this forum your post count must be 2 or greater. You currently have 0 posts.

So, in a sense, it is the same thing. It only makes sense to play Blackjack if you are allowed to "diversify" your betting in that way, with mostly 1:1 payoffs but also a few 1.5:1 and 2:1 payoffs. If you can't diversify your bets you are limited to only the "works every time but not very well" type of thing, which significantly reduces your returns. It would be like not allowing the seeds in RudyHenkel's example to dely their germination and forcing them all to germinate right away. An investor which cannot diversify might as well not bother, because the very first turn of bad luck will erase all their appreciation.

Not quite. What you're describing is an important phenomenon, but it's not quite the same as hedge betting. Hedge betting is not about acting on immediate knowledge, it's about making decisions to minimize your risk before you have any real knowledge of the outcome.

When you describe the situation of betting more when the odds favor you, the desert plant analogy would be a plant waiting for a heavy rainfall before releasing its seeds to germinate. The presence of the rain gives them the knowledge that their chances are better if they place their bets (i.e. germinate,) now. This is something that does occur, so it is an important principle, just not the same thing as hedge betting. I'm actually trying to think what the proper term for it is...