Is Evolution Universal?

[Dak]

Sorry, but evolution does NOT apply to the formation of life itself. That is chemistry. Once you get life, then you can look to see IF that life is such as to be able to evolve and be the object of natural selection.

 

that's not entirely true.

 

at some point, evolution starts having an effect, and it's not proven required that this point be after life has formed.

 

viruses are one example of non-life that clearly evolves. it's hypothetically possible that, given enough time, viruses could evolve into something that qualifies properly as life.

 

so, evolution could well play a (non-exclusive) role in the formation of life from non-life. in fact, i believe a large thrust of abiogenesis theory is trying to figure out how evolution could apply to non-life, is it not?

 

 

In the RNA world, you could envision a self-replicating molecule but it could not evolve. This ribozyme would be such that one and ONLY one base sequence could synthesize an identical base sequence. Any variation would destroy the ability to self-replicate. In that situation, you would have a self-replicating molecule (what you call "life"), but it could not evolve by natural selection because there could be no competition.

 

if the RNA molecules degraded, then there would be evolutionary forses increasing the frequency of stable RNA molecules in your example, as the more stable ones would exist for longer, and thus replicate more, than the other RNA molecules. any variation that increases stability without lowering the rate of copying would find itself gradually increasing in frequency with time.

 

either way, it's definately true that the modern synthesis (i.e., the current theory of evolution) doesn't apply to non-life --> life.

[lucaspa]

that's not entirely true.

 

at some point, evolution starts having an effect, and it's not proven required that this point be after life has formed.

 

We have two different ideas going here, Dak. "Effect" in getting life from non-life or "effect" on that life.

 

Viruses are not a good example because they are not going from non-life to life. Instead, they are going from independent living organisms to as simple a parasite as you can get. IOW, the ancestors of viruses are NOT non-life, but rather living cells that gave up independence for parasitism.

 

So, your statement " given enough time, viruses could evolve into something that qualifies properly as life" is backwards. Viruses started out as "something" that already qualified as "alive" and has evolved toward parasitism so far that they no longer have independent metabolism.

 

in fact, i believe a large thrust of abiogenesis theory is trying to figure out how evolution could apply to non-life, is it not?

 

Not really. The focus is trying to figure out how to get directed protein synthesis. And, for that, evolution by natural selection would play a role. Unfortunately, there is a tendency to confuse the two concepts: life and directed protein synthesis. You can have one without the other.

 

if the RNA molecules degraded, then there would be evolutionary forses increasing the frequency of stable RNA molecules in your example, as the more stable ones would exist for longer,

 

I'm sorry, but you misunderstood what I was saying. Let me try again. I am not talking about "degrading". Instead, I am talking about variations of the self-replicating RNA molecule. What if there is one and ONLY one base sequence that allows replication? That means that any change in base sequence (variation introduced by reproduction) means a non-functional RNA molecule -- a molecule that can't self-replicate. So we would have only 2 possibilities: a base sequence that can self-replicate and all other base sequences that can't. There is no possible evolution because there is no variation in the base sequence. Do you follow now?

 

What we are saying is that there must be several different base sequences that ALL self-replicate. Then a variation that was "longer-lived" (= more stable) would indeed predominate in the population because it would produce more offspring. And the characteristics of the population would shift to that variation. We might then find other variations (base sequences) that could bind to proteins or lipids and still continue to self-replicate.

 

But all that presumes that there are many base sequences all of which self-replicate, in which case there can be selection based on what they ALSO do in addition to self-replicate.

[Dak]

Viruses are not a good example because they are not going from non-life to life. Instead, they are going from independent living organisms to as simple a parasite as you can get. IOW, the ancestors of viruses are NOT non-life, but rather living cells that gave up independence for parasitism.

 

So, your statement " given enough time, viruses could evolve into something that qualifies properly as life" is backwards. Viruses started out as "something" that already qualified as "alive" and has evolved toward parasitism so far that they no longer have independent metabolism.

 

that's irrelevent. all that matters is that:

 

a/ they're not alive, yet are evolving (so, evolution can work on non-life), and

 

b/ they may eventually become life (again?).

 

replace viruses with my RNA example above, if you want, or with genetic programming, which is unquestionably non-living.

 

the point is that evolution (as in, not neccesarily biological evolution described by the modern synthesys, but the basic phenomena of evolution) can effect non-life and increase it's complexity, potentially forming life from non-life. wether that happened or not, and exactly how it would work, is not currently known, but evolution was possably/probably involved at some point prior to it becoming 'life' and at least partially drove the transition from 'non-life' to 'life'.

 

so i'd say that "we don't know how/if/to what extent evolutionary forses can turn non-life --> life" is correcter than "evolution does not turn non-life --> life".

 

I'm sorry, but you misunderstood what I was saying.

 

yes, sorry: i didn't realise you were giving a specific hypothetical example of something that could tentatively be considered alive, yet does not evolve.

[lucaspa]

that's irrelevent. all that matters is that:

 

a/ they're not alive, yet are evolving (so, evolution can work on non-life), and

 

b/ they may eventually become life (again?).

 

Remember the original claims. This is what you said:

 

viruses are one example of non-life that clearly evolves. it's hypothetically possible that, given enough time, viruses could evolve into something that qualifies properly as life.

 

Viruses are not a good example because they are not a clear example of "non-life". In order to be that for this discussion, viruses' recent ancestors must have been non-living chemicals. But they aren't. The ancestors of viruses are living cells. So viruses cannot provide an example for evolution to participate in non-life to life.

 

Now, what makes you think viruses can evolve into fully independent cells again? How do they compete with already existing fully independent cells? They are at a severe selection disadvantage. It's the same reason a chimp won't evolve to a human -- there are already humans occupying that ecological niche!

 

replace viruses with my RNA example above, if you want, or with genetic programming, which is unquestionably non-living. ... the point is that evolution (as in, not neccesarily biological evolution described by the modern synthesys, but the basic phenomena of evolution) can effect non-life and increase it's complexity, potentially forming life from non-life.

 

That's the disconnect. What you are talking about is natural selection, not evolution. Natural selection is a mechanism of evolution. I would even go so far as to call it the overwhelmingly important mechanism. However, it is not the "basic phenomena of evolution". The "basic phenomena" of evolution is "descent with modification". Natural selection is the major means to get that modification.

 

Yes, natural selection happens in ANY system that meets the requirements of 1) a population of non-identical individuals, 2) selection, 3) inheritance. The disconnect is whether natural selection can create the system to begin with! I say "no". Genetic programming was not created by genetic programming -- it was created by humans. Even if you turn genetic programming loose on chips or programs to make "synthlife", did genetic programming make the first chip or the first program? NO. They were created by other processes.

 

Even looking at your self-replicating RNA molecule, can natural selection create the RNA molecule to begin with? NO! The first RNA molecule that can self-replicate has to arise by chemistry. Once that RNA molecule exists, then (perhaps) you have a molecule that meets the requirements for natural selection.

 

This is one reason why the protocell data is so great: you go from non-life to living cell in 2 simple steps using simple chemical reactions! The increase in complexity comes directly from chemistry and you end up with a system that has the requirements for natural selection.

 

wether that happened or not, and exactly how it would work, is not currently known, but evolution was possably/probably involved at some point prior to it becoming 'life' and at least partially drove the transition from 'non-life' to 'life'.

 

This presumes that we have never seen life come from non-life. I dispute that premise. Yes, we have seen life come from non-life and it involved chemistry, not natural selection. Once that life existed, then yes it met the system requirements for natural selection to work.

 

And no, what you call "evolution" was not involved at some point prior to its becoming "life". Because natural selection cannot create an entity with the requirements for natural selection to work. Natural selection only works once an entity has those properties -- from some other source.

 

yes, sorry: i didn't realise you were giving a specific hypothetical example of something that could tentatively be considered alive, yet does not evolve.

 

I would not consider a self-replicating RNA by itself to be "alive". Instead, it is something that can reproduce but can't evolve. Why? Because it is missing one of the essential components of the system of natural selection: variation.

[Dak]

That's the disconnect. What you are talking about is natural selection, not evolution.

 

no i'm not.

 

to calrify, as 'evolution' can mean so many things: i'm talking about a natural process whereby information can generally become more complex over time without the need for an intelligent agent.

 

biological evolution is an example of evolution. genetic programs are another. there are no doubt countless systems, each of which utilise the underlying mechanisms of 'raw' evolution, which is what i'm talking about.

 

Yes, natural selection happens in ANY system that meets the requirements of 1) a population of non-identical individuals, 2) selection, 3) inheritance. The disconnect is whether natural selection can create the system to begin with! I say "no". Genetic programming was not created by genetic programming -- it was created by humans. Even if you turn genetic programming loose on chips or programs to make "synthlife", did genetic programming make the first chip or the first program? NO. They were created by other processes.

 

 

Even looking at your self-replicating RNA molecule, can natural selection create the RNA molecule to begin with? NO! The first RNA molecule that can self-replicate has to arise by chemistry. Once that RNA molecule exists, then (perhaps) you have a molecule that meets the requirements for natural selection.

 

that's true. an evolving system cannot evolve from a non-evolving system. however -- correct me if i'm wrong -- you seem to be defining 'alive' as 'can evolve', which makes your statement a tautology.

 

I would not consider a self-replicating RNA by itself to be "alive". Instead, it is something that can reproduce but can't evolve. Why? Because it is missing one of the essential components of the system of natural selection: variation.

 

my example of self-replicating RNA could evolve, and i'd personally still not call it alive. hence, a non-living thing that can evolve.

 

you're correct in that the RNA would have to be generated aevolutionarily, but incorrect to claim that evolution cannot drive non-life to life.

 

once you have an evolution-capable non-life, evolution could drive it to become life (somewhat obviously). equally obviously, you'd need a non-evolutionary system to generate that first evolution-capable non-life.

[CDarwin]

You wouldn't have a population! If all the members of the population are sterile, then they die and there is no population.

 

In order to have a population -- as opposed to a single generation (which is what you are proposing) -- then you have to have reproduction.

 

In fact, since the definition of "life" mandates the ability to reproduce, you could argue that your coral or bryozoan colony has ceased to be "alive".

 

I didn't say all members of the population were sterile. I said those that differ functionally from the ancestrula would be unable to bud.

 

Completely aside and not to reopen that discussion: There really are upright petrified trees. They occur a lot in coal deposits. Here is the Talk Origins page explaining them. I made a mistake on my response to, though. Corals with algae can't live more than 90m down. I am somewhat gratified that we seemed to make similar points. I take that to mean I can at least look like I sort of know what I'm talking about.

[immortal]

I know its hard to say that evolution is universal unless we find life elsewhere. But if evolution is not universal then how the organisms would look like do they have wheels instead of legs or are we going to see the same stuffs again?

[Sayonara]

I know its hard to say that evolution is universal unless we find life elsewhere. But if evolution is not universal then how the organisms would look like do they have wheels instead of legs or are we going to see the same stuffs again?

 

I think what most people are trying to say is that if living systems do not have the capacity to evolve in some way, they die out. So yes, any other living system we encounter is likely to be subject to evolutionary forces.

 

Assuming exploration across the galaxy, we could reasonably expect to encounter a large number of common problems solved in evolutionarily similar ways, and a relatively small number of rare problems solved in wildly different ways (although this does not mean that organisms sharing common solutions to survival problems will look similar in any way).

 

For example leg systems like the ones we see on Earth are probably going to be common not just across the galaxy, but the universe - conditions like gravity might change from planet to planet but legs are basically just levers, which only have a couple of governing principles. There are two basic leg designs; one is a pair of sticks with rubber bands on the outside (e.g. in mammals) or the inside (e.g. in crabs), and the other is a hydraulic tube with a flexible cuff (e.g. in spiders).

 

However primary senses might be solved in any number of weird ways. In fact even on this one planet there are half a dozen systems I can think of just off the top of my head.

 

So it can get complicated, but the thing to remember is that many problems for living systems very often have so few basic principles behind them that the most effective solutions crop up again and again in completely unrelated species. So while we wouldn't expect see the same organisms on different planets, we would expect to see different species solving similar problems in similar ways.

[JohnF]

Without evolution how could you get life any more complex than that which can be formed by random interaction of chemicals?

[Sayonara]

Dunno, but I am not going to make an argument from incredulity out of it

[bombus]

In the RNA world, you could envision a self-replicating molecule but it could not evolve. This ribozyme would be such that one and ONLY one base sequence could synthesize an identical base sequence. Any variation would destroy the ability to self-replicate. In that situation, you would have a self-replicating molecule (what you call "life"), but it could not evolve by natural selection because there could be no competition.

 

What about mutation?

 

For natural selection you need:

1. Functional variations among individuals.

2. Selection by a competition for scarce resources.

3. Inheritance.

 

No. 2 is not always required. The challenges of the abiotic environment is just as good.

[bombus]

Sorry, but evolution does NOT apply to the formation of life itself. That is chemistry. Once you get life, then you can look to see IF that life is such as to be able to evolve and be the object of natural selection.

 

As an example, look at this discussion of protocells:

 

"The ease with which such protocell units arise under possible primitive Earth conditions has been abundantly documented, especially in the elegant experiments of Sidney Fox and his collaborators on the proteinoid microspheres. .. For our purposes it is sufficient to note that preformed primitive polypeptides (proteinoids) have properties enabling them to aggregate spontaneously to form remarkably uniform spherical units of bacterial dimensions which contain complex internal morphology including a double wall, exchange materials with the ambient medium, grow, cleave in two, fuse, exhibit weak catalytic activiity, and move when ATP is added to the medium. Protocells containing both proteinoid and polynucleotide have been shown to carry on a primitive kind of protocoding activity (27,29) The proteinoid microsphere is a compelling model for the high-probability prebiotic origin of discrete individual units of evolving organic mattter which could conceivably compete with one another and thus provide the basis for a primitive selection process." Dean H. Kenyon, Prefigured ordering and protoselection in the origin of life. In The Origins of Life and Evolutionary Biochemistry, ed. Dose, Fox, Deborin, and Pavlovskaya, 1974, pg 211.

 

I think you should read the above again:

 

The proteinoid microsphere is a compelling model for the high-probability prebiotic origin of discrete individual units of evolving organic mattter which could conceivably compete with one another and thus provide the basis for a primitive selection process.

[lucaspa]

What about mutation?

 

Look what I said: "This ribozyme would be such that one and ONLY one base sequence could synthesize an identical base sequence. Any variation would destroy the ability to self-replicate. "

 

The postulate is that the mutation (variation) could only destroy the ability of the ribozyme to replicate.

No. 2 is not always required. The challenges of the abiotic environment is just as good.

 

And what exactly do you see as the difference between "challenges of the abiotic environment" and "competition for scarce resources"?

 

You are taking too narrow a view of "competition" as being only directly between individual living organisms. I suggest you review Darwin in Origin of Species in the chapter "Struggle for Existence"

http://darwin-online.org.uk/content/frameset?itemID=F391&viewtype=text&pageseq=1

[lucaspa]

I think you should read the above again:

 

The part you looked at has Dean Kenyon stating that the protocells were not alive. However, look above where Kenyon lists the abilities of the protocells: "exchange materials with the ambient medium, grow, cleave in two, fuse, exhibit weak catalytic activiity, and move when ATP is added to the medium. " This covers the 4 essential criteria for being alive. So Kenyon says the protocells are alive, then refers to them as "prebiotic". Oops on his part.

 

Bombus, you have to read what is actually there by the data, not focus in on key phrases that you mindlessly repeat. Kenyon was wrong on that point. The protocells are fully alive.

 

Life from chemistry, and then that life is subject to evolution.