Questions of Natural selection

[Confused]

At the end of Why Darwin Matters: A case against intelligent design, the author, Shermer, raises some interesting issues with Natural Selection. These will naturally be the issues for debate:

1) If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?

2) What is the target of Natural Selection: the individual organism; or the lower levels of genes, chromosomes, organelles, and cells; or the higher level of groups, species, etc.. Why?

[micatala]

At the end of Why Darwin Matters: A case against intelligent design, the author, Shermer, raises some interesting issues with Natural Selection. These will naturally be the issues for debate:

1) If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?

Well, chance would play a role via mutations for one. Which molecule or gene is affected by a particular mutation event does happen randomly, at least as I understand it.

Also, the environment also presents random events. FOr example, if an asteroid had not impacted near what is now Yucatan 65 million years ago, causing the extinction of the dinosaurs, would mammals have developed? Would we even be here now?

2) What is the target of Natural Selection: the individual organism; or the lower levels of genes, chromosomes, organelles, and cells; or the higher level of groups, species, etc.. Why?

I am not sure about this one. I think it might depend on exactly how natural selection is acting with respect to a particular organism.

[juliod]

1) If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?

It is natural selection that mediates the effect of chance.

For example, imagine a mutation that slightly increases resistance to one disease, but reduces it for another (as in malaria/sickle-cell). Whether this mutation is selected for or selected against will depend on which disease becomes more severe or more prevalent within the population. Chance plays a role in evolution, but the effect of chance events and chance mutations can only be understood in terms of how they influence selection.

2) What is the target of Natural Selection: the individual organism; or the lower levels of genes, chromosomes, organelles, and cells; or the higher level of groups, species, etc.. Why?

It's all of those, and more. Many people see evolutionary principles operating in society and politics. Others see it in chemicals and geophysics. I think we can view selection as a general principle that operates at any level where change is possible. Things that are stable, self-promoting, self-reproducing, useful, or attractive tend to accumulate, while things that are unstable or harmful tend to be eradicated. Whether this selection is natural or artificial is a matter of perspective.

DanZ

[Cathar1950]

As I almost understand it, natural selection amounts to a live or die selection. If it lives it has been naturally selected to live and if it dies it has been natural selected to die. It seems to be factors of chance, environment, mutations and copy errors.
It is just change that happens for all kinds of reasons and the natural selection is a mater of what lives and what doesn't. You can't pass on changes if you don't reproduce.

[Confused]

But what is natural selection targeting for the change. Is it altering the DNA via mutations etc in order for the overall organism to survive or for that particular DNA's survival. Though many may say it doesn't really matter, I think it does. Because if it is targeting the DNA alone, then humans may not be relevant at all. In retrospect, humans could be nothing more than a host for DNA evolving into a separate and independent entity. We know nothing of our beginnings, but our DNA does. We have no present ability to survive after death or to know what happens after death or before conception metaphysically, yet DNA can survive for decades after its host is dead and reduced to bone. Yes, sci-fi, but valid. What is being selected for survival and why?

In regards to natural selection and chance. Chance negates the purpose natural selection doesn't it? Natural selection says the strongest will survive, not those who are lucky. So chance shouldn't even be relevant. Shouldn't every mutation be a calculated mutation, sort of like DNA doing its own experimentation. If a mutation occurs that isn't relevant, it may be a stepping stone for future mutations that will become relevant and beneficial. If the DNA creates a mutuation that is detrimental, it learns and doesn't repeat it by making any future combinations of genetic codes that will lead to that and those who have that sequence will eventually fade out of the population.

Am I making sense here? You all know I am horrible at putting on paper what is running through my mind. Add the flu to that and a disaster is in the makings.

[juliod]

But what is natural selection targeting for the change. Is it altering the DNA via mutations etc in order for the overall organism to survive or for that particular DNA's survival.

I would say that natural selection is not targetting anything. It's a process of change first, then selection. To a first approximation, the two processes are not related.

Though many may say it doesn't really matter, I think it does. Because if it is targeting the DNA alone, then humans may not be relevant at all. In retrospect, humans could be nothing more than a host for DNA evolving into a separate and independent entity.

Yes, many people take this view. Humans are just "bags for carrying genomes to the next generation". There's probably a lot of truth to that view.

We know nothing of our beginnings, but our DNA does. We have no present ability to survive after death or to know what happens after death or before conception metaphysically, yet DNA can survive for decades after its host is dead and reduced to bone. Yes, sci-fi, but valid.

Too metaphysical for my perspective. Keep in mind that human DNA generally can't be transmitted from a dead human to a living human (at least not without modern technology). But in the bacterial world, living organisms do often take up foreign DNA and use it. Plasmids seem to be an "intentional" user of this system.

In regards to natural selection and chance. Chance negates the purpose natural selection doesn't it? Natural selection says the strongest will survive, not those who are lucky. So chance shouldn't even be relevant.

No. Chance is what happens "out there". A cosmic ray hits your DNA and makes a mutation. Pure "chance" in that it can't be predicted. Does the mutation help or hurt? That's where selection comes in.

Bacteria are living in a puddle. Suddenly a gust of wind drops a bunch of fungi into the puddle. These fungi produce spectinomycin. Some of the bacteria are killed, others are resistant. The resistance gene for the drug may have been harmful to those that carried it until that chance event carried the fungi into the puddle. Natural selection again.

Shouldn't every mutation be a calculated mutation, sort of like DNA doing its own experimentation.

It isn't like that. Most mutations are caused by the DNA repair mechanism. When DNA is damaged it is sometimes not repaired correctly. This all happens at the level of chemicals, and there is no concept of intent or purpose.

Am I making sense here?

Yes, of course.

DanZ

[juliod]

natural selection amounts to a live or die selection.

It's more of a reproduce or don't selection.

DanZ

[Goat]

But what is natural selection targeting for the change. Is it altering the DNA via mutations etc in order for the overall organism to survive or for that particular DNA's survival. Though many may say it doesn't really matter, I think it does. Because if it is targeting the DNA alone, then humans may not be relevant at all. In retrospect, humans could be nothing more than a host for DNA evolving into a separate and independent entity. We know nothing of our beginnings, but our DNA does. We have no present ability to survive after death or to know what happens after death or before conception metaphysically, yet DNA can survive for decades after its host is dead and reduced to bone. Yes, sci-fi, but valid. What is being selected for survival and why?

In regards to natural selection and chance. Chance negates the purpose natural selection doesn't it? Natural selection says the strongest will survive, not those who are lucky. So chance shouldn't even be relevant. Shouldn't every mutation be a calculated mutation, sort of like DNA doing its own experimentation. If a mutation occurs that isn't relevant, it may be a stepping stone for future mutations that will become relevant and beneficial. If the DNA creates a mutuation that is detrimental, it learns and doesn't repeat it by making any future combinations of genetic codes that will lead to that and those who have that sequence will eventually fade out of the population.

Am I making sense here? You all know I am horrible at putting on paper what is running through my mind. Add the flu to that and a disaster is in the makings.

It isn't altering anything. What happens is that there is variation for some reason (mutation is just one reason for a varation), and often, the environment will either
"select for" or "against' that variation. Many times, the variation will be totally neutral, and not be either seleted FOR or against (until the environment changes)

These variations can have a much more profound effect in small , isolated populations. It isn't that it 'learns and is beneficial'. It is just that a certain percentage of random mutations are beneficial, or detrimetnal, and those are put through the 'filter' of having successful offspring.

[QED]

1) If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?

It supplies the novelty. Something has to come up with "new ideas" to be tried out when stasis is not an option for survival. Mention of survival sometimes makes peoples eyes roll so it could be thought of instead as persistence, or continued existence - at any level. Natural sources of novelty in this respect are plentiful at the atomic level where molecules go about their daily business.

There's nothing significant about randomness as source of novelty though. I dare say that combinatorial changes (e.g. those that could count through all possible permutations of base-pairs) would supply an exhaustive set of new ideas and, in principle, supply natural selection with equally usable material -- but such "counts" are very rare (if ever to be found) in nature.

Taking a wider view, I would say that we should recognize the fact that there will be places where pure chance is to be thanked for some remarkable outcomes. This is because there are things that only need to happen once, perhaps as was the case with the first successful molecular candidate for the natural selection of a self-replicator. If such flukes had to recur for every "generation" we should be alarmed. In these instances, we can only be satisfied with our "luck" if the Anthropic Principle can account for the fluke. For example, on the early Earth, there was a vast potential for interesting chemistry -- in the same way that the Galaxy has a vast potential for Earth-like planets. There may only have been one self-replicating candidate and only one Earth-like planet -- but that is irrelevant as one instance is all it takes for us to arrive on the scene.

2) What is the target of Natural Selection: the individual organism; or the lower levels of genes, chromosomes, organelles, and cells; or the higher level of groups, species, etc.. Why?

I think that's a bit like asking what was the target of the 1961 Lincoln: Was it to produce a four-door convertible that surprised people with its intriguing door-opening arrangement? Was it to provide a means of transporting people around Texas? Was it to make a profit for the Ford Motor Co? Was it to make an opportunity for a sniper? All those things and more might be the answer.

Really though, the way you put your question suggests that there is some objective behind life. If we look at the question as "being what can atoms do?" we can see that, in particular circumstances, they can self-assemble into complicated structures that are kept in check by the physics of gravity, thermodynamics etc. and, by no means less importantly, by each other. These factors shape and influence what structures are possible and what aren't, within boundaries of which some are static and some dynamic.

[Confused]

1) If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?

It supplies the novelty. Something has to come up with "new ideas" to be tried out when stasis is not an option for survival. Mention of survival sometimes makes peoples eyes roll so it could be thought of instead as persistence, or continued existence - at any level. Natural sources of novelty in this respect are plentiful at the atomic level where molecules go about their daily business.

There's nothing significant about randomness as source of novelty though. I dare say that combinatorial changes (e.g. those that could count through all possible permutations of base-pairs) would supply an exhaustive set of new ideas and, in principle, supply natural selection with equally usable material -- but such "counts" are very rare (if ever to be found) in nature.

Taking a wider view, I would say that we should recognize the fact that there will be places where pure chance is to be thanked for some remarkable outcomes. This is because there are things that only need to happen once, perhaps as was the case with the first successful molecular candidate for the natural selection of a self-replicator. If such flukes had to recur for every "generation" we should be alarmed. In these instances, we can only be satisfied with our "luck" if the Anthropic Principle can account for the fluke. For example, on the early Earth, there was a vast potential for interesting chemistry -- in the same way that the Galaxy has a vast potential for Earth-like planets. There may only have been one self-replicating candidate and only one Earth-like planet -- but that is irrelevant as one instance is all it takes for us to arrive on the scene.

2) What is the target of Natural Selection: the individual organism; or the lower levels of genes, chromosomes, organelles, and cells; or the higher level of groups, species, etc.. Why?

I think that's a bit like asking what was the target of the 1961 Lincoln: Was it to produce a four-door convertible that surprised people with its intriguing door-opening arrangement? Was it to provide a means of transporting people around Texas? Was it to make a profit for the Ford Motor Co? Was it to make an opportunity for a sniper? All those things and more might be the answer.

Really though, the way you put your question suggests that there is some objective behind life. If we look at the question as "being what can atoms do?" we can see that, in particular circumstances, they can self-assemble into complicated structures that are kept in check by the physics of gravity, thermodynamics etc. and, by no means less importantly, by each other. These factors shape and influence what structures are possible and what aren't, within boundaries of which some are static and some dynamic.

Only you make me get reference books to understand you responses. You kill me. Good and valid points though (after reading it 3 times )