Randomness

[Dr.GH]

Fair enough. Ultimately, it seems to me that, in layman's terms and for practical purposes, mutations are random. Their occurance can be observed to more or less likely in certain situations but not in others. This means to me that what exists today is the result of a long chain of random mutations influenced by natural selection. Now please explain natural selection to me. But be sure to avoid expressions like: natural selection does this, that or the other thing because unless natural selection has an address and a phone number, by itself it cannot do anything. It is not a person with a purpose, I think.

OK, I want to continue being the "heavy" for a while.

First problem is that you want a layman's understanding of some rather difficult professional topics. Second problem is that you are seeking this layman's understanding on a creationist dominated internet bulletin board. You will get a lot of layman's understandings, but you should not want a layman's understanding.

Some people have tried to point out that mutations are not random, and that "random" does not mean what the "layman's understanding" represents it to mean. This still has not been made sufficiently clear, in my opinion to move on to the much more difficult issue of "selection" natural or otherwise.

First take a good long read of a professional's discussion of just what "mutations" really are.

See? Mutations are not what you thought! (Come on, really- are they)?

The next main topic should be what is a species and how do we tell one from another, and what are higher taxonomic classifications? Then we can talk about selection- negative, positive, weak, strong, and "purifying." We also will then move on to non-selected speciation that was already mentioned (genetic drift) which does regardless become a selection presure. (I am sure you see why we still need to cover some basics)?

You should have more questions about mutations.

 

[bluetrinity]

OK, I want to continue being the "heavy" for a while.

First problem is that you want a layman's understanding of some rather difficult professional topics. Second problem is that you are seeking this layman's understanding on a creationist dominated internet bulletin board. You will get a lot of layman's understandings, but you should not want a layman's understanding.

Some people have tried to point out that mutations are not random, and that "random" does not mean what the "layman's understanding" represents it to mean. This still has not been made sufficiently clear, in my opinion to move on to the much more difficult issue of "selection" natural or otherwise.

First take a good long read of a professional's discussion of just what "mutations" really are.

See? Mutations are not what you thought! (Come on, really- are they)?

The next main topic should be what is a species and how do we tell one from another, and what are higher taxonomic classifications? Then we can talk about selection- negative, positive, weak, strong, and "purifying." We also will then move on to non-selected speciation that was already mentioned (genetic drift) which does regardless become a selection presure. (I am sure you see why we still need to cover some basics)?

You should have more questions about mutations.

Being the "heavy" makes you sound somewhat pedantic bordering on the arrogant. I do not see how you have furthered the understanding regarding the source of mutations much. We had allready been through the example of flipping a coin and Poisson distributions and Loudmouth and others have made some very interesting and insightful posts in this regard. Certainly, the issue is quite complex (even professional I guess) but that doesn't mean that the essence of it cannot be reasonably summarized subsequent to arrving at a collective understanding of the issue, which is what I did. If it suits you better to regurgitate the the entire discussion each post then that is your business. I aver that this is not necessary and does not further advance the discussion. Hence, my conclusion that mutations are for all practical purposes random, i.e. we cannot predict them allthough in some instances we can observe fluctuations in the incidence rate which may or may not point to causation. The text you point to from Kimball's Biology Pages does nothing to further the aspect of randomness. It does however describe neatly what mutations are. For example, we read

Missense mutations

With a missense mutation, the new nucleotide alters the codon so as to produce an altered amino acid in the protein product.

This is intersting but does not explain how exactly the nucleotide does this and why. This, however, was the intent of the OP to get at.

PS: I resent you labelling me as "so messed up" in post 59. This sounds like inchoate musings of a peripatetic discussion about faith and reason which is a misplaced albeit interesting debate for another day.

 

[bluetrinity]

Gravity is not a person with a purpose and yet gravity moves the Earth towards the Sun. It is just a literary device for explaining concepts.

Anyway, natural selection is the second step in evolutionary two-step. The first step we have already talked about which is random mutations. The second step is the amplification of beneficial mutations. Natural selection acts as a sieve. As an analogy, random mutations are equivalent to breaking a rock into pieces. When you break a rock the pieces will fall into a random distribution of different sizes. When you pass these broken rocks through a sieve only the rocks below a certain size will pass through. What results is a non-random distribution. The same for natural selection. Only certain variations produced by random mutations are passed on through several generations. The ones that are passed on with the best success are almost always beneficial mutations. Those that don't get passed on to future generations are almost always detrimental mutations. Therefore, beneficial traits become more and more common in a population with each generation. That is how natural selection works. The viral resistance mutation in the Luria-Delbruck experiment is a perfect example.

Thank you and the others for your insightful posts.

The example of the sieve is very illustrative. I can follow your reasoning that mutations are no longer random subsequent to passing through the sieve. While this appears initially logical it seems somewhat circular also. Because, what is the sieve? The sieve is what I would call all natural laws, such as for example gravity. But what is the origin of gravity? Doesn't gravity go back to the existence, size and density of matter? So, then where does matter (in our case, for example, the sun, Earth etc) come from? And assuming the scientists are correct and everything started with a Big Bang, then we would have to ask ourselves where the Big Bang came from. If the Big Bang was a random event (i.e. not caused by (a) God), then wouldn't your sieve ultimately be just as random as the mutations themselves? In other words, one random event (a mutation) happens in the framework of a set of random natural laws. So, isn't the outcome of that also random?

 

[Loudmouth]

While this appears initially logical it seems somewhat circular also. Because, what is the sieve?

It is an analogy that I used to illustrate the actions of natural selection.

Natural selection is a consequence of two things: imperfect replicators (ie mutating organisms) and limited resources (ie natural pressures). Natural selection is unavoidable when these two criteria are met. Natural selection is as unavoidable as having a winner in a race. The fittest individuals in any population will, on average, have more offspring. If heritable traits are responsible for the fitness of the individual, then that heritable advantage will be seen in a larger and larger proportion of the population over time.

The sieve is what I would call all natural laws, such as for example gravity.

The sieve is natural selection which is caused by limited resources.

But what is the origin of gravity? Doesn't gravity go back to the existence, size and density of matter? So, then where does matter (in our case, for example, the sun, Earth etc) come from?

These questions are outside the scope of mutation and natural selection. We don't have to know the origin of matter or the natural laws in order to conclude that natural selection happens and that mutations are random with respect to fitness. While these are very important questions, they simply don't need to be addressed when studying biodiversity any more than the origin of matter needs to be discussed by car mechanics.

If the Big Bang was a random event (i.e. not caused by (a) God), then wouldn't your sieve ultimately be just as random as the mutations themselves?

You could argue that environments that create natural pressures are random in nature but yet constrained by natural laws. However, this does not get around the observation that allele frequencies are not random with respect to fitness.

In other words, one random event (a mutation) happens in the framework of a set of random natural laws. So, isn't the outcome of that also random?

I hate to answer a question with a question, but it is more rhetorical than anything. Is it a random occurence that the sickle cell allele in humans is found in higher concentrations in areas with historically endemic rates of malaria?

 

[Chalnoth]

If the Big Bang was a random event (i.e. not caused by (a) God), then wouldn't your sieve ultimately be just as random as the mutations themselves?

Yes, but the sieve wouldn't change once it started in the Big Bang. Now, consider this: if our universe began as the result of an accident, why should it have happened only once? We have a hard limit to how far we can see, after all, and as such the entirety of all existence may be vastly larger than our little pocket universe.

This is basically the idea that underlies a currently controversial theory in modern physics: the string theory landscape. The idea is that in the context of sting theory, there are an obscene number of possible physical laws that can occur (it's been calculated at 10^500). So what the people pushing the string theory landscape postulate is that the natural state of the universe is one of eternal inflation (this is a natural expectation in string theory, by the way), which basically makes the universe infinite in space and in time, but with frequent bubble universes popping up all over the place. Every once in a great while, one of these bubble universes will have properties just so, and life will arise in that universe.

This is little more than a mathematical theory right now, though, as there is as yet no connection to any observation. Some theoretical physicists really dislike the idea with a passion, others think it's a really elegant theory. I think I'm starting to like it myself, but with zero experimental support, I'm not willing to bet one cent that it's correct.

 

[bluetrinity]

It is an analogy that I used to illustrate the actions of natural selection.

Natural selection is a consequence of two things: imperfect replicators (ie mutating organisms) and limited resources (ie natural pressures). Natural selection is unavoidable when these two criteria are met. Natural selection is as unavoidable as having a winner in a race. The fittest individuals in any population will, on average, have more offspring. If heritable traits are responsible for the fitness of the individual, then that heritable advantage will be seen in a larger and larger proportion of the population over time.



The sieve is natural selection which is caused by limited resources.



These questions are outside the scope of mutation and natural selection. We don't have to know the origin of matter or the natural laws in order to conclude that natural selection happens and that mutations are random with respect to fitness. While these are very important questions, they simply don't need to be addressed when studying biodiversity any more than the origin of matter needs to be discussed by car mechanics.



You could argue that environments that create natural pressures are random in nature but yet constrained by natural laws. However, this does not get around the observation that allele frequencies are not random with respect to fitness.



I hate to answer a question with a question, but it is more rhetorical than anything. Is it a random occurence that the sickle cell allele in humans is found in higher concentrations in areas with historically endemic rates of malaria?

Let's at least agree on what natural selection is not, i.e. a process with a will of its own. Natural selection is essentially a system of contraints. It does not however decide to favor any particular mutation over another one. The only reason one mutation may be more beneficial than another is that it somehow improves its bearer's chances of survival given the environment presented. It is therefore undirected, passive and without inherent purpose. It just is.

So, if I throw a large number of random mutations into into a system of constraining laws then what comes out of that system must necessarily also be random. Kindof like taking a very large count of random numbers and running them through a supercomputer with a given set of mathematical operations that throws out a large number of different numbers. The resulting numbers will still be just as random as what I put in. Or if I take thousands dices with letters on them and throw randomly on the floor. I run the resulting recombinations of letters through a spellchecker, I will find some words that will be spelled correctly and many that are not. But the ones that are spelt correctly are logically speaking just as random as those that aren't.

As you rightly point out this matters little for the analysis and observation of biodiversity, but it matters philosphically because once I conclude that my brain is the result of random mutations whipped into shape by a system of impersonal constraints, that I must conclude that anything that my brain produces is just as random as the inputs into the system that created it in the first place.

 

[bluetrinity]

Yes, but the sieve wouldn't change once it started in the Big Bang. Now, consider this: if our universe began as the result of an accident, why should it have happened only once? We have a hard limit to how far we can see, after all, and as such the entirety of all existence may be vastly larger than our little pocket universe.

This is basically the idea that underlies a currently controversial theory in modern physics: the string theory landscape. The idea is that in the context of sting theory, there are an obscene number of possible physical laws that can occur (it's been calculated at 10^500). So what the people pushing the string theory landscape postulate is that the natural state of the universe is one of eternal inflation (this is a natural expectation in string theory, by the way), which basically makes the universe infinite in space and in time, but with frequent bubble universes popping up all over the place. Every once in a great while, one of these bubble universes will have properties just so, and life will arise in that universe.

This is little more than a mathematical theory right now, though, as there is as yet no connection to any observation. Some theoretical physicists really dislike the idea with a passion, others think it's a really elegant theory. I think I'm starting to like it myself, but with zero experimental support, I'm not willing to bet one cent that it's correct.

From my perspective this does not really matter with regard to the philosophical implications much because I am after the how and why. Also, I am not sure that eternity is a word that can be used in scientific discussions. Or, if it can, then its (eternities) existence would have to be subject to the same stringent demands for proof as the existence of deity.