Evolutionary Stable Strategies

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Evolutionary Stable Strategies

Postby hyksos on February 5th, 2019, 6:03 pm 

(Outside of having a geeky fascination in biology as a science,) the concept of ESS or "evolutionary stable strategies" hides philosophical ramifications that exceed biology. Further, once ESS is understood, it can be seen as a whole new way of thinking about the world around us, and might even exceed the scope of science.

There are many examples in nature of Evolutionary Stable Strategies, and the basic gist here is that over a very long period of thousands and millions of generations, various rules-of-thumb will appear as they arise from statistical and probabilistic truisms.

Sampling Error
One example of a truism in regards to biology is genetic drift resulting from sampling error. So say that there are 173,422 moths in a heavy industrial section of India. This species of moth has white and grey variants. Say

Code: Select all
Moth population breakdown

154,062  white
19,360  grey 

At this snapshot in the present moment, the ratio of white to grey moths is 0.125663694 . Say that some unusual event happens in the area like a flood with an intensity to damage property and flood regions normally used by the moths for breeding. Only 1000 of the moths in the region escape to a safer place, and the rest die off.

To a high probability it is very unlikely that the number of escaping greys and whites will exactly match the ratio 0.125663694 In fact, even if it matched it by a sheer stroke of luck , the exact ratio would actually be 0.12600000 . The number must change because 1000 is less granular than 173422. In general, accidents and natural randomness of events will cause additional changes to this ratio. The lesson is, if a large portion of a population is decimated, the remaining survivors will not exhibit the original ratios among their traits.

Thus without a creator, without a designer, and without complex evolutionary processes, sampling error alone will give rise to genetic drift.


Males and Females
We may notice that for any given sexually-reproducing species, the probability of producing male offspring is always 0.50 And in general the number of males to females in many mammals is 50/50. For reasons that have nothing to do with genetics, nothing to do with DNA, nothing to do with offspring, and nothing to do with evolutionary dynamics --- the 50/50 female-to-male ratio is an Evolutionary Stable Strategy.

(as documented in other parts of this forum) I have written and deployed ecosystem simulations on a computer. I did give my simulated organisms the ability to alter their probability of giving birth to a male. However, I did notice that even when given the ability to evolve this parameter, they still continued to have a perfect 50/50 split between males and females. I noticed this at the time, found it odd, and never gave it any deeper thought. I may have even believed there was a bug in my code.

Only years later did I discover that all reproducing populations will trend asymptotically towards a 50/50 female/male ratio. The reason for such a tendency is entirely numerical. It is (, as I like to often say) a mathematical truism.

Suppose more females are present than males because of lopsided genetically-inherited tendency to give birth to more females. Then each male in the population will have a higher chance of finding a mate. If any organisms have an unusually high change of producing males, they will (statistically speaking) tend to have more grandchildren. Over time, those with the 'make-more-males' gene will come to dominate the population, and the population as a whole will trend away slowly from the lopsided tendency to have female offspring. Once balance is achieved among the sexes , the advantage afforded to such male producing parents goes away.

Either way this pendulum is swung, it will trend slowly back to the 50/50 middle line. It is an E-S-S. It has nothing to do with 50/50 being better for some extraneous reason having to do with sex differences such as hunting, nesting, raising young, and etc. It is true because it is mathematically true.

Creationism thinking
The worldview held by many creationists would perhaps have them suppose that the ratio of human females to males remains 50/50 worldwide due to the design decisions of a creator. Or they might think it must be set up that way to maximally ensure that humans must face tough ethical challenges in our morally-staged life. On the other hand, a zealous young atheist attending the Reason Rally might believe the ratio was simply handed down by precursors and was originally evolved for a situation in which our furry ancestral species was "in the trees".

Both of these are wrong. The balanced ratio between sexes is due to simple statistics. It is faithfully reproduced in simulation. These are mathematical truisms. It can't be subverted anymore than 1+1=2 could be "subverted". Populations will trend towards this ratio for the same sorts of reasons that in a casino the House has an advantage over the gamblers. While not obvious at any one time, averaged over many trials, the slight advantage comes to bear on the outcome. The same statistical outcomes determine the very makeup of our biology.
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Re: Evolutionary Stable Strategies

Postby hyksos on February 5th, 2019, 6:05 pm 

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Re: Evolutionary Stable Strategies

Postby A_Seagull on February 5th, 2019, 11:37 pm 

hyksos » February 6th, 2019, 10:03 am wrote:(the concept of ESS or "evolutionary stable strategies" hides philosophical ramifications that exceed biology. Further, once ESS is understood, it can be seen as a whole new way of thinking about the world around us, and might even exceed the scope of science.

.


What philosophical ramifications?
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Re: Evolutionary Stable Strategies

Postby hyksos on April 19th, 2019, 2:16 pm 

What philosophical ramifications?

The 50/50 split between males and females is not due to design decisions by a creator.

It is not due to an intentional differentiation by a Fodorian Mind-Selector.

Nor is it due to an "accident of mutation" that happened millions of years ago and was passed down by inheritance.

The ratio is due to math.
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Re: Evolutionary Stable Strategies

Postby A_Seagull on April 19th, 2019, 5:31 pm 

hyksos » April 20th, 2019, 6:16 am wrote:
What philosophical ramifications?

The 50/50 split between males and females is not due to design decisions by a creator.

It is not due to an intentional differentiation by a Fodorian Mind-Selector.

Nor is it due to an "accident of mutation" that happened millions of years ago and was passed down by inheritance.

The ratio is due to math.


Well I suppose that could be of philosophical interest for creationists.

But I don't consider creationists to be philosophical.
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