• Quick note - the problem with Youtube videos not embedding on the forum appears to have been fixed, thanks to ZiprHead. If you do still see problems let me know.

What evidence is there for evolution being non-random?

mijopaalmc said:
organisms adapting to their environment in no way proves that evolution is non-random; the mean fitness of a population increasing over time only tells us that the frequency of less fit individuals is increasing and that can occur randomly.
Click to expand...
In the same way you could ask for proof that gravity isn't random "... and things falling only proves that their altitude is decreasing over time and that can occur randomly."

But they all fall in the same direction, don't they?

---

I see that most of this thread has degenerated into a bickering about the meaning of the word "random". Well, it is clear that if you told someone that "evolution is random", you'd be giving them an entirely false impression.

The line of reasoning leading to the claim that "evolution is random" would seem susceptible to a reductio ad absurdum. If evolution is "random" because the mutations on which selection acts are "random", then we must regard evolution by artificial selection as being "random" too, on the same basis. What's sauce for the goose is sauce for the fundie propaganda.
 
mijopaalmc said:
No-one to my knowledge has either explained how a process that operates on probability is non-random or directed me toward a resource that does.
Click to expand...

I know I'm not adding much to the conversation here, but I don't think this represents a clear understanding of randomness and probability, so I thought I would throw in my own example:

In gambling the house advantage is often less than 1% but always (except some hands of blackjack) greater than 50%. Between 50 and 51% of the time the house will win and between 49-50% the house will lose.

Since each hand (or dice roll, or whatever) is random and the outcomes are determined by probability, how can we predict what will happen? I'll leave it to you to learn the statistics but the result is always the same: you will eventually go bankrupt. We may not know how long it will take, but the outcome is certain.

So now to make a horrible analogy to evolution: think of the hand as mutation and the house advantage as natural selection. A random process and a probability function will determine the eventual outcome.
 
If the collisions of gas molecules against the walls of their container is random, then air pressure must be random too. So how can air pressure in your tires hold your car up off the road?

If the outcome of a pull on a slot machine is random, then the money the casino makes (or pays out) must be random too. So how can casinos predict their profit margins?

If the directions that neutrons are emitted by a nucleus undergoing radioactive decay are random, then a fission chain reaction must be random too. So how is it possible to control a nuclear reactor?

If passive diffusion of a molecule across a membrane is random, then osmosis must be random too. So how can the net flow through a membrane be precisely repeatable for a given salt concentration?

If individual variation is random, and some accidents of birth and death unrealated to genotype are random, then evolution must be random too. So how can complex inderdependent genes arise?

The answer is the same in all cases: The statistical characteristics of a large number of individually random events are not random.

Respectfully,
Myriad
 
CFLarsen said:
If selection is chaotic - unpredictable - and evolution is random, how can you correctly predict that from a gene pool of exclusively blue eyed people, you will get blue eyed children?
Click to expand...

If weather is chaotic and the wingflapping of butterflies is random, then how can you correctly protect that if a cold front is over New York and heading east, it will rain in Boston? Because chaos takes a little while to manifest itself as practical unpredictability, and because the initial randomness is small.

Dr Adequate said:
I see that most of this thread has degenerated into a bickering about the meaning of the word "random". Well, it is clear that if you told someone that "evolution is random", you'd be giving them an entirely false impression.
Click to expand...

Yes, but that doesn't mean we should go to the other extreme. I don't think it's really that much harder to explain more clearly that there's random in the sense of uncertain or non-deterministic and there's random in the sense of unordered nonsense, and that even though evolution is random in the first sense, it is extremely well-ordered randomness, in the same sense that if you flip a coin a bunch of times, you'll get heads and tails in roughly similar numbers.
 
Last edited:
CFLarsen said:
What is it you don't understand?
Click to expand...
I don't understand what your argument is meant to be at all.
I describe random fluctuations at the lower levels and explain how this can cause variation at the higher levels.

You say evolution doesn't just depend on mutation.

1) My example doesn't need the idea of mutation to work.

2) Even if it did your argument wouldn't invalidate it.
 
Dr Adequate said:
In the same way you could ask for proof that gravity isn't random "... and things falling only proves that their altitude is decreasing over time and that can occur randomly."

But they all fall in the same direction, don't they?
Click to expand...

I tried it with some Post-it notes from head height. In general yes, as to specific final locations on the floor - there seemed to a random element.

I see that most of this thread has degenerated into a bickering about the meaning of the word "random". Well, it is clear that if you told someone that "evolution is random", you'd be giving them an entirely false impression.

The line of reasoning leading to the claim that "evolution is random" would seem susceptible to a reductio ad absurdum. If evolution is "random" because the mutations on which selection acts are "random", then we must regard evolution by artificial selection as being "random" too, on the same basis. What's sauce for the goose is sauce for the fundie propaganda.
Click to expand...

Of course, if I built a big funnel to drop my Post-it notes into I'm sure I could get them to land pretty much on top of each other.
 
Dr Adequate said:
In the same way you could ask for proof that gravity isn't random "... and things falling only proves that their altitude is decreasing over time and that can occur randomly."

But they all fall in the same direction, don't they?
Click to expand...

But they don't have to with evolution, look at the article you wrote.
We have two neutral alleles present in the same ratio in the gene pool, competing for dominance.

Which one is will reach fixation? No one knows, you might as well flip a coin.

It's a clear example of randomness in evolution at the macroscopic level.
 
*Layman's ramblings follow*.

My understanding is that Mutations are random, but Evolution is predictable, and not random.

To go back to our dice analogy, let's get a large number of 6-sided dice to be our population. These aren't hypothetical perfectly random dice, equal chance of any number to roll. They're run-of-the-mill dice you'd find in the wild, some might be more disposed to rolling higher numbers, some lower, some might not be weighted at all.

We grab our pith helmet, and go off to observe these dice in their natural habitat. Las Vegas or something. And we roll the dice.

Then something interesting occurs. Some dice dissappear. Some appear. Some dice make exact copies of themselves. We roll the dice again, and again, Some vanish, some appear, some duplicate. We whip out our notebooks, and write down the following observations:

1 or 2 - Remove the Die (bad mutation)
3 or 4 - do nothing (neutral)
5 - Add a die into the population (normal reproduction)
6 - Make an exact copy of the die, such that if the die is weighted towards some numbers, then the copy will be weighted as well. (good mutation, copied during reproduction)

While there is a random element to the mutation (the rolling of the dice), you can see that the Evolution of the population is not random, as it is predictable. Based on your observations, you can predict that the population will evolve towards rolling higher numbers.

Anyway, hope that helps some and isn't just an irrelevant analogy. Now, who wants to play some craps?

Trifikas.
 
sphenisc said:
I tried it with some Post-it notes from head height. In general yes, as to specific final locations on the floor - there seemed to a random element.
Click to expand...
Are you saying that gravity is random? What?

Of course, if I built a big funnel to drop my Post-it notes into I'm sure I could get them to land pretty much on top of each other.
Click to expand...
Why would the "big funnel" be a better analogy for artificial selection than for natural selection?
 
Jekyll said:
But they don't have to with evolution, look at the article you wrote.

We have two neutral alleles present in the same ratio in the gene pool, competing for dominance.
Click to expand...
Granted. But that's a reason to say that some evolution is random, namely changes in neutral allele frequencies caused by genetic drift, not to say "evolution is random".

My analogy was between gravity and adaptation. And no, I am not claiming that every adaptive mutation will achieve fixation.

---

NB: I agree with Myriad's post, above.
 
Jekyll said:
I don't understand what your argument is meant to be at all.
I describe random fluctuations at the lower levels and explain how this can cause variation at the higher levels.

You say evolution doesn't just depend on mutation.

1) My example doesn't need the idea of mutation to work.

2) Even if it did your argument wouldn't invalidate it.
Click to expand...

The exact same discussion is going on here.
 
Myriad said:
...
The answer is the same in all cases: The statistical characteristics of a large number of individually random events are not random.

Respectfully,
Myriad
Click to expand...

This was posted by Walter Wayne in a similar thread some time ago, and it never got a satisfactory response:

Walter Wayne said:
A question for the "non-randomites". Do you think that the rise of humanity was inevitable, given the conditions when life first crawled onto land?
Click to expand...

So, those who hold that evolution is non-random: What say ye?
 
To answer the OP I'll explain it how this layperson understands it because it makes sense to me.

Mutations are random in that they can't be predicted. They aren't so random that two dogs will produce a litter of kittens though.

The environment that tests the fitness of these mutations is not random. Sure the environment is random in that we don't always know when it will rain but when it rains water falls from the sky. If it was truly random we wouldn't know what was going to fall from the sky next. (Or we might get up and find all the grass is purple instead of green. It's a good thing the environment isn't truly random.)

So, is that a good layperson's explanation? Or am I wrong somewhere? ('Cause if I'm wrong I'll fix it.)
 
Vorticity said:
This was posted by Walter Wayne in a similar thread some time ago, and it never got a satisfactory response:

A question for the "non-randomites". Do you think that the rise of humanity was inevitable, given the conditions when life first crawled onto land?
Click to expand...

So, those who hold that evolution is non-random: What say ye?
Click to expand...
That depends on how deterministic the universe is. But if we take mutations to be "random", then in such a model the outcome is not totally determined by the preconditions.

Which does not mean that the outcome is "random".
 
Dr Adequate said:
Granted. But that's a reason to say that some evolution is random, namely changes in neutral allele frequencies caused by genetic drift, not to say "evolution is random".

My analogy was between gravity and adaptation. And no, I am not claiming that every adaptive mutation will achieve fixation.

---

NB: I agree with Myriad's post, above.
Click to expand...

Ok, cool. I agree with you and Myriad that by the law of large numbers we have a guarantee that the population will converge on local optima.

I just think that which local optima it tends to is up for grabs, and highly dependent upon which mutations happen first, the happenstance of which genes turn up mixed together first, arbitrary environmental interactions and genetic drift.

In fact, the instability of the evolutionary process seems to me to be the only explanation for the variety of life. If it was very stable all life would have evolved together as one homogeneous species, instead of branching and diversifying.
 
Jekyll said:
I just think that which local optima it tends to is up for grabs, and highly dependent upon which mutations happen first, the happenstance of which genes turn up mixed together first, arbitrary environmental interactions and genetic drift.
Click to expand...

Given that each organism "evolves" independently, I suspect that it's not as "up for grabs" as you seem to think.

If there are two or more local optima, the usual outcome of evolution is to tend to both of them.

At once.

We call this "speciation."
 
You must log in or register to reply here.

Back
Top Bottom