Author Topic: Why evolution is not just chance.  (Read 70 times)

Tank

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Why evolution is not just chance.
« on: March 18, 2017, 04:43:57 AM »
Why evolution is not just chance.

Some people think evolution is impossible because it is based on chance, that is pure chance where a whole organism has to appear complete in one go. Well that would be true if there was not another factor in the mix. That factor is selection.

You can see this yourself with a few dice. Take the dice, 6 or more is good, but you can do this with a pair of dice. Throw all the dice at once again and again until all show a six in one go. If you have six dice the probability of this happening in one go is 1/6 x 1/6 x 1/6 x 1/6 x 1/6 x 1/6 or 1/46,656. So while you could throw six sixes at the first throw or throw six sixes many times the mathematical probability of throwing six sixes all at once is 1/46,656. At 5 seconds a throw it would take you 2.7 days to complete the task and even then there is no guarantee you’d throw six sixes. Probability is a bastard like that. And many, possibly most, people do not understand probability. So it looks like ‘chance’ does put an end to evolution. How could something as complex as a cell possibly evolve?

So now consider your six dice again. This time throw all of them. With six dice what is the probability (not certainty) of one of those dice showing a six? Well with six dice the probability is that one dice will show a six. Now this is where selection comes in. If you throw one six put it aside and throw the remaining five dice. You have to throw twice this time before another six shows. So you’ve now thrown three times but have two sixes. You take the remaining four dice and say have to throw those four dice four more time to get a six. You have now thrown 7 times and have three sixes. Take the three dice and throw them three times to get a six. We now have thrown 10 times and have 4 sixes. Take the last two dice and it takes 8 throws (bugger!) to get a six. We now have 18 throws and 5 sixes. Take the last dice and throw it. It’s a six! So we now have six sixes in 19 throws. A lot quicker than the 2.7 days it would take by pure change.

If you consider the dice as genes and the environment as the selector you have a much better understanding of how chance works in evolution.

In addition one has to bear in mind that we considered 19 throws. In reality each ‘throw’ is a reproductive event. Consider the billions upon billions of reproductive events that occur each day across all the organisms on Earth. Then consider that those reproductive events have been happening for about 3,875,000,000 years. How many trillions upon trillions upon trillions of ‘throws’ have happened over that time period?

This is a very basic analogy of how evolution is driven by reproduction (dice throws) and selection (natural selection).
« Last Edit: March 18, 2017, 05:55:22 AM by Tank »
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No one

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Re: Why evolution is not just chance.
« Reply #1 on: March 18, 2017, 05:03:52 AM »
So then, we are the result of a universe playing craps?

Tank

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Re: Why evolution is not just chance.
« Reply #2 on: March 18, 2017, 05:11:12 AM »
So then, we are the result of a universe playing craps?
That would be a good analogy if the universe had a concept of winning. As the universe isn't sentient that analogy fails. Good joke though  :)
If religions were TV channels atheism is turning the TV off.
“Religion is a culture of faith; science is a culture of doubt.” ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett

hermes2015

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Re: Why evolution is not just chance.
« Reply #3 on: March 18, 2017, 05:46:40 AM »
Thank you Tank, that is a great post: very clear and well explained. Another stats-related concept that most people get wrong is entropy. It would be nice if you could give us an equally clear introduction to entropy.

Tank

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Re: Why evolution is not just chance.
« Reply #4 on: March 18, 2017, 05:51:27 AM »
Thank you Tank, that is a great post: very clear and well explained. Another stats-related concept that most people get wrong is entropy. It would be nice if you could give us an equally clear introduction to entropy.
Now that's something I would love to see too. My understanding of entropy is not what it should be.
If religions were TV channels atheism is turning the TV off.
“Religion is a culture of faith; science is a culture of doubt.” ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett

Gloucester

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Re: Why evolution is not just chance.
« Reply #5 on: March 18, 2017, 06:53:09 AM »
Good one, Tank.

Made me think about a practical, nechanical evolution demonstrator - then I thought it could probably be done on a computer by someone clever.

Back in the old days, 198x-ish, there was a game of very simple sprites that one could configure (within size and type (species) limits) and let loose to compete with each other. It was purely random as to who ate or "mated"  who but I found it fascinating. Populations could grow or die, species could consume or be consumed. But the environment remained constant.

Change it round a little; again within simple rules on, say, five factors, let the sprites configure themselves and have the ability to mutate one of their factors at random. Then set the enviromental factors, temp increase/decrease, available food type changes etc analogs to vary over time. Then see which mutations survive the changes.

The random bit comes into play, as I understand it, in the natural genetic mutations. If the random mutation was positive for an environnental change then that mutation will be selected, naturally, over a negative one.

There is probably something like this already modelled for academic purposes, very complex and needing a super computer, but I have never seen anything sold as a "game" for home/school use on simpler machines.
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hermes2015

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Re: Why evolution is not just chance.
« Reply #6 on: March 18, 2017, 06:58:05 AM »
Thank you Tank, that is a great post: very clear and well explained. Another stats-related concept that most people get wrong is entropy. It would be nice if you could give us an equally clear introduction to entropy.
Now that's something I would love to see too. My understanding of entropy is not what it should be.

I saw a beautiful statistical explanation of entropy somewhere and will try to find it again and post it here. It talked about the statistical distribution of the possible states of a system, not in terms of the popular view of a tendency towards increasing disorder.

No one

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Re: Why evolution is not just chance.
« Reply #7 on: March 18, 2017, 07:11:28 AM »
no one:
So then, we are the result of a universe playing craps?

Tank:
That would be a good analogy if the universe had a concept of winning. As the universe isn't sentient that analogy fails.


Eh...I took a gamble.

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Re: Why evolution is not just chance.
« Reply #8 on: March 18, 2017, 10:33:16 AM »
This would be good to tell my Father because he just flat out denies evolution. He dropped out of high school so I don't blame him, it's not like he ever got the chance to study statistics or therein probability. I tried explaining evolution to him once but he never said anything. It was a good explanation​ too. If I remember it, I will put it here.
But, uh...well there it is.