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?

[ST88]

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 think you have the relationship between natural selection and mutation backwards. The term "natural selection" is merely a description of the overall process, much of which happens through mutation. A mutation can happen via many different mechanisms, all of which are random chance. The DNA isn't aware of its own survival, and doesn't particularly care if it does survive. There are other organelles & enzymes in a cell that take care of that sort of thing, and they're just doing a job. Similarly, one cell isn't particularly concerned with any of the other surrounding cells surviving, as long as it gets its food and water (it can't do anything about it anyway if it doesn't). Any given cell will (generally) survive in a petri dish given the right conditions.

Because mutations are random chance, there is no specific direction to the process other than the directions in which previous mutations have been pointing.

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.

In some sense this is true, but not really. It's an interesting way of looking at it, though. We are "hosts" to many different types of materials: organs, blood, skin, connective tissue, etc. But stop and think about that for a moment, without any of these materials (including DNA), we would not be human. For that matter, DNA is only an agglomeration of smaller substances which you could say the same thing about if you wanted to think about it in that way. But just like there is no way to separate A, G, C, T from DNA, there is no way to separate the DNA in our cells and our humanity.

I'm not sure what you mean by "relevance" though.

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.

DNA "survives" only as a code, not as a living organism. It requires a transcriptionist to replicate, so by itself it is useless.

What is being selected for survival and why?

Organisms aren't "selected for survival", they survive because they contain traits cruicial for survival. "Selection" is such a poor word choice for this process because it implies some sort of active preference, when it's really more of a passive process.

Natural selection says the strongest will survive, not those who are lucky

Actually, these two ideas, strength and luck amount to the same thing in this case. Those lucky enough to be "strong" (another misnomer) will survive. "Strength" in this case means "ability to survive". I would guess that because early biologists observed stronger predators eliminate and exile weaker ones, they came up with the idea of Strength as a property required for survival.

[Furrowed Brow]

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.

I was about to answer this and say something similar to Juliod then thought again. Natural selection has no target. It is blind. However the phenotype interacting with its environment is where success and failure is worked out. I’d say that the phenotype could be any of those things you mentioned. So there could be selection processes going on at multiple levels.

However gene seems to be the self replicating and mutating unit. Maybe culture has memes. And maybe there are other kinds of units.

OK. I’m gonna ramble now. Just thinking through the implications. I’m not so sure there could be natural selection if there were not

1/ patterns of molecules
2/ those patterns are self replicating
3/ replication is imperfect.
4/ changing environments.

So without self replication there could not be natural selection. (The gene being the oft studied self replicating unit of nature.) If the last point is right then it would be circular reasoning to say natural selection selected for self replication. Hmm.

Abiogenesis? A spontaneous coming togther of the right mix of molecules. I don't think so. So how and why self replication at all then? The standard evolutionary explanation above the level of gene is a climbing mount improbable type argument where nature takes small, nay imperceptible, incremental steps. Can the same argument work here? Surely you’ve either got self replication or you have not? Does it even make sense to say you have a partial self replicating molecule. Well yes it does. DNA though very good, is not a perfect self replicator. If it were perfect it would be useless for natural selection.

If we give DNA a figure of 99.99% replication efficiency, what kind of molecules would be 50%, 5% and 0.5% efficient? Hmm. Let say there is or was such a thing as a 0.5% efficient replicator. We would not really be able to say what such a molecule looked like because it its progeny would not look very much like the original at all. It would probable under most reasoanble analysis look 100% like any old chemical interaction, and well 99.5% like anything but self replication.

So lets say there are a class of molecules which are all very inefficient self replicators. However from time to time one throws up a 0.6% efficient progeny. If resources are finite, and that pool of primordial goo is only so big, before long (a few million years say) then that 0.6% trait will dominate a population of only 0.5% efficient. And so on etc etc etc.

So as I mull over these points I find myself moving away from any theory reliant on a spontaneous creation of self replicating life. I think natural selection is a truism. But it requires self replication. But if it is a truism then so must be self replication. So even if you have very very poor self replication there can be natural selection, and some molecule you would not consider to be a self replicating unit, can be classed as a self replicating unit - just a very very poor one.

I think arguments that point to the information storage capacity of say RNA or some similar molecule, and cite a minimum level of complexity is required for there to be self replication, have not really absorbed the lesson of climbing mount improbable.

Perhaps I should stop thinking out loud.

[juliod]

I was about to answer this and say something similar to Juliod then thought again.

Of course, I was using "target" in the metaphorical sense of "locus of action".

Surely you’ve either got self replication or you have not?

No. Imagine a pre-biotic mixed environment. You might not have self-replication. But there maybe chemicals that by accumulation create an environment that is favorable for the synthesis of that chemical.

For example, lipids can create micelles and liposomes. In a natural environment, these liposomes will be created, fuse, rupture, bud off, etc. But to a certain extent, the membrane of the liposome protects the inside (lumen) from changes in the environment. It's not hard to imagine that the lumen environment might be favorable for the creation of more lipid, compared to the outside. So the liposomes might be creating an environment that favors the creation of more lipid, which can make more liposomes. Not self-replication, but something that is approaching self-replication.

DanZ

[Confused]

I was about to answer this and say something similar to Juliod then thought again.

Of course, I was using "target" in the metaphorical sense of "locus of action".

Surely you’ve either got self replication or you have not?

No. Imagine a pre-biotic mixed environment. You might not have self-replication. But there maybe chemicals that by accumulation create an environment that is favorable for the synthesis of that chemical.

For example, lipids can create micelles and liposomes. In a natural environment, these liposomes will be created, fuse, rupture, bud off, etc. But to a certain extent, the membrane of the liposome protects the inside (lumen) from changes in the environment. It's not hard to imagine that the lumen environment might be favorable for the creation of more lipid, compared to the outside. So the liposomes might be creating an environment that favors the creation of more lipid, which can make more liposomes. Not self-replication, but something that is approaching self-replication.

DanZ

But what sets off the sequence of events for the lipid molecules to create micelles and liposomes? They don't do it spontaneously. Something has to spark a need for the change otherwise survival wouldn't be dependent on it. If we consider survival dependent on the ability to adapt, then natural selection will weed out those less likely to adapt and those who can adapt will do so. If there exists no need to adapt, then we have no need for the "self replication" sequence to occur. We assume that it is usually environmental factors that induce change. Less food supply, less water, etc.... Those who can adapt to the new environment will survive.



Since liposomes are very selective in their permeability, would not any environment they create actually be countercoducive to life? If we consider one of the most essential elements for life being water, then liposomes would actually negate this.

[Confused]

ST88:

Confused wrote:
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 think you have the relationship between natural selection and mutation backwards. The term "natural selection" is merely a description of the overall process, much of which happens through mutation.

You are correct, I was mingling my terms. Using DNA wasn't the best of examples either, sorry about that.
ST88:

Because mutations are random chance, there is no specific direction to the process other than the directions in which previous mutations have been pointing.

Mutations don't necessarily have to be random chance. They can be a reaction to change in an effort to increase the ability for an organism to survive. We usually assume that environmental factors are the leading cause of change.
But what if internal factors are the actual causation of the change? For example, when man became primarily meat eaters, the need for the appendix was made moot. The change would have been environmental, but the actual target of the change is now the phasing out of the appendix. The less need for something, the more efficient it is to phase it out, correct. Rather than carry excess baggage that leads to things like appendicitis, etc... So here it isn't the entire organism being targeted for adaptation, but instead, it is a primary organ, or cells, etc... that are being targeted for survival of the fittest. The smaller the appendix becomes, the less likely it is to become inflamed, burst and lead to peritonitis and death. A person can survive with an appendix providing it doesn't become infected/inflammed. However, the organ has no functioning purpose any longer, so would not a species that phased it out be more likely to survive.

ST88:

DNA "survives" only as a code, not as a living organism. It requires a transcriptionist to replicate, so by itself it is useless. Organisms aren't "selected for survival", they survive because they contain traits cruicial for survival. "Selection" is such a poor word choice for this process because it implies some sort of active preference, when it's really more of a passive process.

Not in all cases. Viruses use reverse transcriptase. HIV is a retrovirus and requires antiretroviral medications for suppression of them. By iteself, it may be useless, but in has more than one mechanism to replicate. Why did the body develop more than one enzyme capable of carrying out the transciption process? By a random mutation without purpose? I see very few things in life as random. In hindsite, we can look at history and find few things that had no specific purpose. Instead we see a seeemingly inconsequential event lead to a chain of reactions. Sort of like Babel (if you could make it through the movie without falling asleep). On minor event set into motion events that affected a series of individuals across the world. So what may be seen as a random mutation today, could very well dictate the survival of a species in the future.

[Cephus]

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

Natural selection makes the best of what random events give it to work with. If there is an earthquake that changes the local biosphere, then natural selection can only work with the new environmental conditions. Chance, at least on the local level, has a major effect on what lifeforms end up evolving because chance has a lot to do with the local conditions to which lifeforms must adapt.

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?

There is no 'target' for natural selection. You're trying to impose meaning and purpose on a purely natural phenomenon. Natural selection has no intelligence, it has no purpose, it has no goals. Mankind was never planned, we just happened. We're not special and I think that's what most theists have a problem understanding.

[Cathar1950]

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

Natural selection makes the best of what random events give it to work with. If there is an earthquake that changes the local biosphere, then natural selection can only work with the new environmental conditions. Chance, at least on the local level, has a major effect on what lifeforms end up evolving because chance has a lot to do with the local conditions to which lifeforms must adapt.

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?

There is no 'target' for natural selection. You're trying to impose meaning and purpose on a purely natural phenomenon. Natural selection has no intelligence, it has no purpose, it has no goals. Mankind was never planned, we just happened. We're not special and I think that's what most theists have a problem understanding.

I agree but we are special at least to our selves. Maybe everything is special to God?
Except the ones that disagree, they are lower then grass.
It seems to me that Natural selection is simply the process of organisms living and reproducing and therefore is selected naturally. But some can be selected for or against for all matter or reasons or accidents.

[Cephus]

I agree but we are special at least to our selves. Maybe everything is special to God?

Well, we are certainly egotistical, but special? Is a human inherently better than a cow, for instance? Is a human better than a vastly superior alien species? As far as the universe is concerned, we're all equally pointless, but most people seem to have a problem accepting the very real fact that they are utterly meaningless in the grand scheme of things and in 100 years, at least for the majority of us, no one will ever remember or care that we were alive.

[ST88]

Because mutations are random chance, there is no specific direction to the process other than the directions in which previous mutations have been pointing.

Mutations don't necessarily have to be random chance. They can be a reaction to change in an effort to increase the ability for an organism to survive. We usually assume that environmental factors are the leading cause of change.
But what if internal factors are the actual causation of the change? For example, when man became primarily meat eaters, the need for the appendix was made moot. The change would have been environmental, but the actual target of the change is now the phasing out of the appendix. The less need for something, the more efficient it is to phase it out, correct. Rather than carry excess baggage that leads to things like appendicitis, etc... So here it isn't the entire organism being targeted for adaptation, but instead, it is a primary organ, or cells, etc... that are being targeted for survival of the fittest. The smaller the appendix becomes, the less likely it is to become inflamed, burst and lead to peritonitis and death. A person can survive with an appendix providing it doesn't become infected/inflammed. However, the organ has no functioning purpose any longer, so would not a species that phased it out be more likely to survive.

No. The appendix rarely causes problems. It just sort of sits there. It gets inflamed and bursts in less than 1% of the population, so there is no selective pressure against it. That's why it's lasted as long as it has in the population. The things that are selected against are those that keep the species from reproducing. Often the appendix causes problems in later life, long after reproduction is an issue. This is also why older people have more problems than younger people. Long about 38, say, nature says, "OK, we're done with you, you can go off and disintegrate." So anything that happens after that creates no selection pressure.

And correct me if I'm wrong here, the appendix occurs in most primates, so it survived the transition from ape to man. Is it currently getting smaller all over the world?

But irrespective of the appendix, the larger point is that it is still mutation that will get rid of it. Just because we don't need it doesn't mean it will go away. There has to be some kind of valid reproductive advantage to not having it.

ST88:

DNA "survives" only as a code, not as a living organism. It requires a transcriptionist to replicate, so by itself it is useless. Organisms aren't "selected for survival", they survive because they contain traits cruicial for survival. "Selection" is such a poor word choice for this process because it implies some sort of active preference, when it's really more of a passive process.

Not in all cases. Viruses use reverse transcriptase. HIV is a retrovirus and requires antiretroviral medications for suppression of them. By iteself, it may be useless, but in has more than one mechanism to replicate. Why did the body develop more than one enzyme capable of carrying out the transciption process? By a random mutation without purpose? I see very few things in life as random. In hindsite, we can look at history and find few things that had no specific purpose. Instead we see a seeemingly inconsequential event lead to a chain of reactions. Sort of like Babel (if you could make it through the movie without falling asleep). On minor event set into motion events that affected a series of individuals across the world. So what may be seen as a random mutation today, could very well dictate the survival of a species in the future.

I think you proved my point. DNA without a transcriptionist will not be able to do anything, and since it can't transcribe itself, by itself it is, indeed useless if it's just sitting there on a log by the bog. And not to be picky (or tacky) but viruses have RNA, not DNA.

[Cathar1950]

I agree but we are special at least to our selves. Maybe everything is special to God?

Well, we are certainly egotistical, but special? Is a human inherently better than a cow, for instance? Is a human better than a vastly superior alien species? As far as the universe is concerned, we're all equally pointless, but most people seem to have a problem accepting the very real fact that they are utterly meaningless in the grand scheme of things and in 100 years, at least for the majority of us, no one will ever remember or care that we were alive.

\

My kids friends and loved ones are special and yes it is egotistical. A little bit goes a long waays.
I would eat a cow but not my children.
I love my house plants and they like me(they grow and flurish) when I neglect them.
But we are not that special that it makes it special that we think about it and show awareness. It is nice to see it in other creatures as well.
Life has its own purpose and beauty.
It is works for now.
I don't mean to be mushy either.