Evolutionary Theory Evolves? - Survival Of The Fittest Is Likely False Study shows

reply to post by Malthus


Actually they are saying that the most "fit" is going to be present but being the most "fit" does not mean that its genotype is going to become the standard.

Let me repeat, THE MOST FIT WILL BE PRESENT IT JUST WILL NOT WIN OUT OVER THE OTHERS.

That is what the modeling is showing, it is NOT what was predicted and it is NOT in line with your understanding of survival of the fittest.

-FBB

A short living thing that has billions of offspring will always outsurvive a single organism that regenerates,or ?

As many have pointed out, the definition of 'fitness' in the study is problematic.

It seems as it they looked at all possible mutations and defined some as 'fittest' based on some pre-selected criterion that is not mentioned in the article.

Since there's no link to the original paper, it's not easy understand just what was done here. As far as I can tell, it was something like this: using a computer model, the researchers followed at all the possible routes in which a complex organic molecule might evolve, and recorded what the 'phenotypic' results would be. They found that there were some results you could arrive at by many different routes; these were the 'most frequent' results. Other results could only be arrived at through one or a few routes; these results they called 'rare'.

They then found that the results they called 'fittest' turned out to be 'rare' instead of 'common'.

But there's nothing to explain how they arrived at 'fittest'.

Astyanax
As many have pointed out, the definition of 'fitness' in the study is problematic.

It seems as it they looked at all possible mutations and defined some as 'fittest' based on some pre-selected criterion that is not mentioned in the article.

Since there's no link to the original paper, it's not easy understand just what was done here. As far as I can tell, it was something like this: using a computer model, the researchers followed at all the possible routes in which a complex organic molecule might evolve, and recorded what the 'phenotypic' results would be. They found that there were some results you could arrive at by many different routes; these were the 'most frequent' results. Other results could only be arrived at through on or a few routes; these results they called 'rare'.

They then found that the results they called 'fittest' turned out to be 'rare' instead of 'common'.

But there's nothing to explain how they arrived at 'fittest'.

Actually the link to the original paper is in the OP, right below the Q&A article . . . .

-FriedBabelBroccoli

Here is the link to the actual article;
The Arrival of the Frequent: How Bias in Genotype-Phenotype Maps Can Steer Populations to Local Optima
Steffen Schaper, Ard A. Louis
www.plosone.org...

Please check it out and let me know what you think about it.
www.plosone.org...

Abstract

Genotype-phenotype (GP) maps specify how the random mutations that change genotypes generate variation by altering phenotypes, which, in turn, can trigger selection. Many GP maps share the following general properties: 1) The total number of genotypes is much larger than the number of selectable phenotypes; 2) Neutral exploration changes the variation that is accessible to the population; 3) The distribution of phenotype frequencies , with the number of genotypes mapping onto phenotype , is highly biased: the majority of genotypes map to only a small minority of the phenotypes. Here we explore how these properties affect the evolutionary dynamics of haploid Wright-Fisher models that are coupled to a random GP map or to a more complex RNA sequence to secondary structure map. For both maps the probability of a mutation leading to a phenotype scales to first order as , although for the RNA map there are further correlations as well. By using mean-field theory, supported by computer simulations, we show that the discovery time of a phenotype similarly scales to first order as for a wide range of population sizes and mutation rates in both the monomorphic and polymorphic regimes. These differences in the rate at which variation arises can vary over many orders of magnitude. Phenotypic variation with a larger is therefore be much more likely to arise than variation with a small . We show, using the RNA model, that frequent phenotypes (with larger ) can fix in a population even when alternative, but less frequent, phenotypes with much higher fitness are potentially accessible. In other words, if the fittest never ‘arrive’ on the timescales of evolutionary change, then they can't fix. We call this highly non-ergodic effect the ‘arrival of the frequent’.

-FBB

reply to post by FriedBabelBroccoli


As well as I can tell, the abstract confirms my inference regarding the subject-matter.

I did not see, in the article itself, where the authors defined 'fitness'.

Astyanax
reply to post by FriedBabelBroccoli

 

As well as I can tell, the abstract confirms my inference regarding the subject-matter.
I did not see, in the article itself, where the authors defined 'fitness'.

Fitness has already been defined, they are operating under the standard definition and have developed the model to simulate the expression of the "fittest."

Introduction

Darwin's account of biological evolution [1] stressed the importance of natural selection: If some individuals are better adapted to their environment than their competitors, their offspring will come to dominate the population. The fittest survive and the less fit go extinct. Yet selection alone is not sufficient to drive evolution because natural selection reduces the very variation that it requires to operate. It was only recognised well after Darwin's day [2], in part through the success of the Modern Synthesis, that the fuel for selection is provided by mutations that make offspring genetically different from their parents. Crucially, mutations change genetically stored information (the genotype) while selection operates on the physical expression of this information (the phenotype). Understanding the relation between genotypes and phenotypes – the GP map – is therefore crucial to understanding evolutionary dynamics [3].

Based on other studies which you can locate links to at the bottom of the article (the study which was "not" linked to in the OP) you can see that they are modeling the behavior of the most "fit" genotypes and how those are derived through biological processes.

Yes, whatever you do, do not read the actual article in full and instead claim you were right because you made it through the abstract and didn't find what you were looking for . . . .

-FBB

reply to post by FriedBabelBroccoli

Fitness has already been defined, they are operating under the standard definition and have developed the model to simulate the expression of the "fittest."

No, it has not. The study implies a quantifiable definition of fitness. Where is that definition?

Yes, whatever you do, do not read the actual article in full and instead claim you were right because you made it through the abstract and didn't find what you were looking for

I promise I will, as long as you promise to keep misreading what I have posted.

Astyanax
reply to post by FriedBabelBroccoli

 

Yes, whatever you do, do not read the actual article in full and instead claim you were right because you made it through the abstract and didn't find what you were looking for

I promise I will, as long as you promise to keep misreading what I have posted.

By all means, in the mean time perhaps you can provide your definition of the "most fit."

-FBB

reply to post by FriedBabelBroccoli


I edited my post above while you replied it.

I am not interested in supplying a definition of fitness. I want to know that the authors' definition is.

Astyanax
As many have pointed out, the definition of 'fitness' in the study is problematic.

It seems as it they looked at all possible mutations and defined some as 'fittest' based on some pre-selected criterion that is not mentioned in the article.

Since there's no link to the original paper, it's not easy understand just what was done here . . .

How can you say their definition of 'fitness' is problematic when they are simulating the resultant genetic behavior of the 'fittest' on the gene pool.

If you are not going to provide your definition of 'fitness' which makes theirs problematic then your entire issue with the paper is essentially moot.

-FBB

reply to post by FriedBabelBroccoli

How can you say their definition of 'fitness' is problematic when they are simulating the resultant genetic behavior of the 'fittest' on the gene pool.

No, that is not what is being investigated here. As I said earlier, that is very important, and easy to misunderstand.

If you are not going to provide your definition of 'fitness' which makes theirs problematic then your entire issue with the paper is essentially moot.

What issue? I want to know what their definition of fitness is — and if they don't have one, why one isn't necessary. I am not an expert in this field; for all I know the answer is something very simple, even obvious. But it isn't in the abstract — or the paper. As far as I can see they are just using 'fitness' as an arbitrary term in a mathematical analysis, without really defining it.

FriedBabelBroccoli
That is what the modeling is showing, it is NOT what was predicted and it is NOT in line with your understanding of survival of the fittest.

-FBB

No. It's not the model. It's an overly misused descriptor. Survival of the fittest wasnt even used by Darwin. Additionally, this study failed to account for the fact that an organism who is most fit in one environment is not necessarily fit for a different environment or ecological niche. This also isn't the first time anyone has postulated that the fittest are most likely to perish. In 1866 Alpheus Hyatt proposed that lineages, like individuals, inevitably go through stages of youth, maturity, old age, and death. Towards the end of this cycle, the fittest individuals are more likely to perish than others.

Likewise orthogenesis says that certain trends, once started, kept progressing even though they become detrimental and lead to extinction. For example, it was held that Irish elks, which had enormous antlers, died out because the size increase became too much to support.

This really isn't the new amazing paradigm you seem to think let alone anything that's going to reshape evolutionary thought or research. I think punctuated equilibrium had a much bigger effect than something that's been discussed for over a century and a half.

reply to post by Astyanax

As far as I can see they are just using 'fitness' as an arbitrary term in a mathematical analysis, without really defining it.

Maybe this will help.

Ard Louis:

Darwinian evolution proceeds in two steps. Firstly, there is variation: due to mutations, different members of a population may have differences in traits. Secondly, there is selection: if the variation in a trait allows an organism to have more viable offspring, to be 'fitter', then that trait will eventually come to dominate in the population.

phys.org...

FriedBabelBroccoli
reply to post by Malthus

 

Actually they are saying that the most "fit" is going to be present but being the most "fit" does not mean that its genotype is going to become the standard.

Let me repeat, THE MOST FIT WILL BE PRESENT IT JUST WILL NOT WIN OUT OVER THE OTHERS.

That is what the modeling is showing, it is NOT what was predicted and it is NOT in line with your understanding of survival of the fittest.

-FBB

read this part of the paper and you will see that what I said was correct:

The many orders of magnitude difference in the arrival rate of
variation between phenotypes should have many important
implications for evolutionary dynamics. Consider for example
the situation where the population has equilibrated to a phenotype
q, which was the fitness peak, when subsequently the environment
changes so that a different phenotype p has a higher fitness 1+s.
In order to fix, the alternative phenotype must first be found. If the
time-scale Te on which the environment changes again is much
longer than Tp then it likely that the population will discover and
fix p. However, if Te (less than) Tp , then a new phenotype p’ may become
more fit before p has time to fix. T p can vary over many orders of
magnitude, so many potentially highly adaptive phenotypes may
satisfy Tp (greater than) Te and thus never be found.

Tp is the time required for the simulation to find/discover the phenotype

If it's not found/discovered that means the phenotype didn't come to exist in the population.

I actually found this part pretty interesting:

Finally, phenotype p2 is significantly less mutationally robust
than p1 (more frequent phenotypes are typically more robust
[13,16]), and so once discovered, produces deleterious mutants at
a higher rate, making it harder for p2 to fix at higher mutations
rates, a phenomenon known as ‘‘survival of the flattest’’ [26],
observed here for the lower ratios s 2/s 1 at higher m. Thus both the
‘‘arrival of the frequent’’ and the ‘‘survival of the flattest’’ mitigate
against the fixation of phenotypes with lower frequency F p , even if
their fitness is much higher.

So because there are fewer possibilities for neutral mutations (those that don't change the phenotype) it is more dangerous for a population to have phenotype p2 if mutation rates are high. Might be interesting to compare populations around chernobyl (because the radiation should increase mutation rates) with those outside to see if there is any evidence for this in nature.

reply to post by Phage


I understand evolution by natural selection quite well, Phage. Neither the text you quoted nor the link you attached contain any kind of answer to my question. The link is simply to the OP article, not the original study (to which the OP has kindly directed me already).

The point I am making is the same one boncho made earlier on. How did these fellows arrive at their definition of fitness? How did they decide that some phenotypes in their study are fitter than others?

Having now read the paper — not that I pretend to understand it fully, nor indeed to possess either the patience or time required to study it closely — it seems to me that 'fitness' in the model being studied is nothing but a mathematical term, one that is used as a weighting factor in the equations and is not related to any actual, physical determinants of biological fitness.

This doesn't necessarily discredit the study, but it reduces it, I think, to a somewhat sterile intellectual exercise.

reply to post by Astyanax

I understand evolution by natural selection quite well, Phage. Neither the text you quoted nor the link you attached contain any kind of answer to my question. The link is simply to the OP article, not the original study (to which the OP has kindly directed me already).

My apologies. I posted the link because it was a direct quote from one of the authors of the study. I thought that if anyone could provide the definition used by the authors of the study, it would be an author of the study.

reply to post by Phage


Sadly, they don't. Which leads one to think that perhaps they're following the standard definition.

Here's the problem I see: the experiment would then be based on a tautology. Because, if you think about it, 'survival of the fittest' is a tautology. There's some philosophical disagreement about this, but it seems clear enough to me. According to the usual definition (a version of which you posted), 'the fittest' are 'those organisms with the combination of traits best suited to survival'. But how are those traits identified? By the fact that they survive (or some combinations of them survives) best. Round we go in a circle.

Now these guys seem to be saying that the phenotypes so defined take so long to evolve that they're outbred in the meantime by others which evolve more quickly. Well, it seems to me that their failure to appear in time rules these phenotypes out of the definition of 'fittest'. The truly fittest phenotypes are the ones most widespread in the population at any given time — even if there may be a few theoretically 'fittest' phenotypes floating around in it at the same time.

Astyanax
reply to post by Phage

 

Sadly, they don't. Which leads one to think that perhaps they're following the standard definition.

Here's the problem I see: the experiment would then be based on a tautology. Because, if you think about it, 'survival of the fittest' is a tautology. There's some philosophical disagreement about this, but it seems clear enough to me. According to the usual definition (a version of which you posted), 'the fittest' are 'those organisms with the combination of traits best suited to survival'. But how are those traits identified? By the fact that they survive (or some combinations of them survives) best. Round we go in a circle.

Now these guys seem to be saying that the phenotypes so defined take so long to evolve that they're outbred in the meantime by others which evolve more quickly. Well, it seems to me that their failure to appear in time rules these phenotypes out of the definition of 'fittest'. The truly fittest phenotypes are the ones most widespread in the population at any given time — even if there may be a few theoretically 'fittest' phenotypes floating around in it at the same time.

Sooooooooo basically you agree with exactly what their models show, but you think the "most fit" is whatever is most prevalent at any given point in time . . . . . ?

I am not interested in supplying a definition of fitness.

Gee I wonder why?

This was the reason I asked you for the definition you were using as I suspected it would be something ridiculous like this.

-FBB

reply to post by FriedBabelBroccoli


How would Astyanax's definition be in any way relevant? He's not the author of the paper.

By the way, "survival of the fittest"? Haven't heard that one in about 150 years and it wasn't a valid description even back then so I don't see why you're getting so hung up on this simplistic and inaccurate description of evolution.