Question about the Theory of Natural Selection and Theory of Evolution

OK, first of all, I haven't studied this stuff. I'd also prefer that this doesn't turn into an Evolution vs. Creationism debate, either (please).

A good friend emphatically stated that "The Theory of Evolution is as scientifically certain as the mathematical truth that 2+2=4." I expressed some doubt and he persisted (he has not studied it either, though). So I am asking the scientists/biologists on this forum to please help shed some light on the matter.

I understand the Theory of Natural Selection. That theory has been proven, right? My question has to do with the Theory of Evolution. Has the Theory of Evolution ever been *proven*? And has its effect ever been completely simulated in a laboratory setting, e.g., with bacteria or fruit flies?

Maybe this question should be posed after first asking, "What exactly is the definition of the Theory of Evolution?"

Fruit flies can be bred quickly and repeatedly over successive generations in laboratories, and those successive generations of flies can show certain specific trait enhancements in experiments designed to test such things. BUT...has such an experiment ever continued to the point where a truly new species was produced? If not, why hasn't such an experiment ever been successfully performed?

What exactly is the definition of a species, anyway?

Faster or bigger fruit flies, or flies with different coloration patterns, can be bred...but the newer genetic lines can still mate and reproduce with the older genetic lines, right? They aren't a new species, just a different model of the same species--perhaps like various breeds of dogs.

It seems quite plausible that truly distinct new species can be, and have been, developed through evolution. Yet of course we hear some people claiming otherwise, or claiming that the missing link between apes and man has never really been found. Some others might claim that there is no definitive "missing link" anyway--it's all a matter of degree. But assuming humans evolved from apes: at some point humans and apes became incapable of producing offspring via mating with each other. Without knowing the scientific definition of "species", that divide seems to me as good a demarcation point as any for what constitutes distinct "species" (also assuming the offspring are not sterile, such as are some hybrids like mules).

So to recap:

1. Is my friend right that the Theory of Evolution is scientifically considered to be as sound as the statement that 2+2=4? Or as scientifically sound as, say, the laws of thermodynamics?

2. Definition of Theory of Evolution?

3. Definition of a Species?

4. Has the Theory of Evolution ever been *proven*

5. Have new distinct species ever been bred, through (simulated) evolutionary conditions, in a controlled laboratory setting?


Thanks.

[diebitter]

1. Is wrong. A scientific proof must be possible to refute BY DEFINITIION. It cannot be a certainty to remain scientific. That's not to say it isn't truth, but the point is you cannot be sure it is absolute truth. To assert so is dogma, not science. The mathematical 'truth' is a definition, so is therefore truth by definition, within its own framework.

2. There are several "Theories of Evolution". If you mean Darwinian evolution by natural selection - it's defined all over the place. Google it.

3. Off the top of my head, it's a grouping that can breed to produce fertile offspring (ie the offspring can breed) that have the same chromosome count as the parents (or very close to this count).

4. Not really, but there are enourmous quantities of evidence supporting it, and very, very, very little refuting it - if any. But be aware, no scientific theory is 'proven'. The essence of science is that theories need to be refutable. If they are taken as 'proven' absolutely, it ain't science, it's dogma.

5. don't think so, but look at dogs, cats, etc. Look at something like a Shitzu lapdog - you think that's a naturally-occuring breed of dog? Give it a few thousand generations, you'll have something that won't be able to breed with other breeds of dogs.

[ QUOTE ]
1. Is wrong. A scientific proof must be possible to refute BY DEFINITIION. It cannot be a certainty to remain scientific. That's not to say it isn't truth, but the point is you cannot be sure it is absolute truth. To assert so is dogma, not science. The mathematical 'truth' is a definition, so is therefore truth by definition, within its own framework.

2. There are several "Theories of Evolution". If you mean Darwinian evolution by natural selection - it's defined all over the place. Google it.

3. Off the top of my head, it's a grouping that can breed to produce fertile offspring (ie the offspring can breed) that have the same chromosome count as the parents (or very close to this count).

[/ QUOTE ]


Hi diebitter,

Thanks, and I think I modified my post a bit before your response was posted.

Your answers are pretty close to what I was thinking. I modified the comparison my friend made to include a comparison (hopefully more apt) with the laws of thermodynamics. I'm still wondering if new species have ever been "evolved" in a controlled laboratory setting, in some sort of simulated application of Darwin's Theory of Evolution via Natural Selection.

[diebitter]

Like I said, I'm not aware of a new species created by enforced 'natural selection'. Plenty of races of species created by artifical selection though (dogs,cats, sheep, cows,pigs).

[Kurn, son of Mogh]

Actually, its doubt that natural selection is the prime mover behind evolution that's driving some of the doubt as to how accurate Darwin's theory on how evolution happened.

In the simplest view, "survival of the fit" is a tautology.

Microbiologists have had no success experimentally re-creating any evidence of macro-evolution, which runs counter to the fossil evidence.

Margulis & Sagan (http://www.context.org/ICLIB/IC34/Margulis.htm) advance an interesting alternate theory involving bacteria as one of the driving forces in systemic evolution.

[ QUOTE ]
Like I said, I'm not aware of a new species created by enforced 'natural selection'. Plenty of races of species created by artifical selection though (dogs,cats, sheep, cows,pigs).

[/ QUOTE ]

Well, OK...have any of those lines created by artificial selection, become a new species incapable of reproducing viable offspring with the old? (Wolves with dogs can viably reproduce, for instance, even though one is lupus and the other is canis. I'm not positive that dogs were bred from wolves, though).

[Borodog]

6M,

First, go here (http://talkorigins.org/) and read. Everything you never wanted to know about the issue, geared specifically toward interested layman.

[ QUOTE ]
OK, first of all, I haven't studied this stuff. I'd also prefer that this doesn't turn into an Evolution vs. Creationism debate, either (please).

A good friend emphatically stated that "The Theory of Evolution is as scientifically certain as the mathematical truth that 2+2=4." I expressed some doubt and he persisted (he has not studied it either, though). So I am asking the scientists/biologists on this forum to please help shed some light on the matter.

I understand the Theory of Natural Selection. That theory has been proven, right? My question has to do with the Theory of Evolution. Has the Theory of Evolution ever been *proven*? And has its effect ever been completely simulated in a laboratory setting, e.g., with bacteria or fruit flies?

[/ QUOTE ]

That depends on what you call a laboratory, and what you call "simulated". Can chihuahuas interbreed with mastiffs? I would say not, simply for mechanical reasons. Chihuahuas and mastiffs were both bred from the same ancestral stock and can nolonger interbreed. By a defensible argument, you might classify them as distinct species. By a more genetically based argument, you would not. But, is there any doubt that, if given long enough, the lines descending from mastiffs and the lines descending from chihuahuas will be so genetically distinct that you couldn't even get them to hybridize in a petry dish? I don't believe there is. If you do, by what magic mechanism is it accomplished?

I don't find it the least bit incredible that "dogs" will eventually be bred to the size of bears or horses, while other lines are bred to the size of mice.

[ QUOTE ]
Maybe this question should be posed after first asking, "What exactly is the definition of the Theory of Evolution?"

[/ QUOTE ]

This is off the top of my head, so it may be inadequate or incomplete, but the theory of evlution is a collection of hypotheses and logical arguments for explaining the similarities and dissimilarities of all living organisms. There is much evidence to be explained, the fossil record, the genetic, structural, behavioral, geographic distributions of living things, just to name a few.

[ QUOTE ]
Fruit flies can be bred quickly and repeatedly over successive generations in laboratories, and those successive generations of flies can show certain specific trait enhancements in experiments designed to test such things. BUT...has such an experiment ever continued to the point where a truly new species was produced? If not, why hasn't such an experiment ever been successfully performed?

[/ QUOTE ]

I believe they hve been. I.e. descendent populations of fruit flies have been bred that can interbreed with each other but not with their ancestral population.

[ QUOTE ]
What exactly is the definition of a species, anyway?

[/ QUOTE ]

There's the rub, isn't it? The best definition I know of is that two populations, which can interbreed with their own population but not the other, are distinct species. However, life is more complex. We know that different animal species (even with different numbers of chromosomes) can interbreed, horses and donkeys make mules, lions and tigers make ligers, dolphins and whales make wolphins, etc. Also, there are the so-called "ring species", where members on opposite side of the "ring" cannot interbreed with each other, yet interbreeding occurs all the way round the ring (picture snakes living around a tall mountain; snakes interbreed with their neighbors anywhere around the mountain, but the snakes on opposite sides could not interbreed). Life is tricky.

[ QUOTE ]

Faster or bigger fruit flies, or flies with different coloration patterns, can be bred...but the newer genetic lines can still mate and reproduce with the older genetic lines, right? They aren't a new species, just a different model of the same species--perhaps like various breeds of dogs.

[/ QUOTE ]

Eventually the genetic changes will add up, and they will not be able to interbreed. As I said, what mechanism prevents it?

[ QUOTE ]
It seems quite plausible that truly distinct new species can be, and have been, developed through evolution. Yet of course we hear some people claiming otherwise, or claiming that the missing link between apes and man has never really been found. Some others might claim that there is no definitive "missing link" anyway--it's all a matter of degree. But assuming humans evolved from apes: at some point humans and apes became incapable of producing offspring via mating with each other. Without knowing the scientific definition of "species", that divide seems to me as good a demarcation point as any for what constitutes distinct "species" (also assuming they are not sterile, such as some hybrids like mules).

[/ QUOTE ]

Picture humans and, for example, chimpanzees as members of a ring species, with the ring cut, of course. But it isn't a ring in space around a mountain, it is a ring in time. Modern humans can interbreed with humans from 1000 years ago, I think we would all agree. Modern humans could certainly interbreed with humans from 10,000 years ago. It is almost certain that modern humans could interbreed with humans from 100,000 years ago. But . . . could they interbreed with humans from 1,000,000 years ago? Perhaps. Perhaps not. Could modern humans interbreed with the other side of the ring, the modern chimpanzee? It seems extremely unlikely . . . until you remember the wolphin, who parents are separated by a similar genetic and temporal rift.

The thing that will really convince you, of course, is to start with some basic assumptions that you can agree on, use a little logical deduction, and see what the result is.

Given that:

1. The phenotype of living organisms depends to any extent on their genome,
2. The reproductive success of living organisms depends to any extent on their phenotype, and
3. The reproduction of the genome is to any extent fallible,

Evolution must occur.

Edit: diebitter's definition of species is much better; it's not just interbreeding, it's interbreeding that produces fertile offspring. That takes care of the mules, liger, wolphins, and humanzees.

[morphball]

[ QUOTE ]
Could modern humans interbreed with the other side of the ring, the modern chimpanzee? It seems extremely unlikely . . . until you remember the wolphin, who parents are separated by a similar genetic and temporal rift.


[/ QUOTE ]

This could be one the coolest expiraments ever! We should try artificially inseminating a chimp with human sperm, or go to a zoophile site and find a volunteer.

[Borodog]

[ QUOTE ]
[ QUOTE ]
Could modern humans interbreed with the other side of the ring, the modern chimpanzee? It seems extremely unlikely . . . until you remember the wolphin, who parents are separated by a similar genetic and temporal rift.


[/ QUOTE ]

This could be one the coolest expiraments ever! We should try artificially inseminating a chimp with human sperm, or go to a zoophile site and find a volunteer.

[/ QUOTE ]

Do not google on "dolphin vagina". It only leads to pain (and asterisks).

[ QUOTE ]
[ QUOTE ]
Could modern humans interbreed with the other side of the ring, the modern chimpanzee? It seems extremely unlikely . . . until you remember the wolphin, who parents are separated by a similar genetic and temporal rift.


[/ QUOTE ]

This could be one the coolest expiraments ever! We should try artificially inseminating a chimp with human sperm, or go to a zoophile site and find a volunteer.

[/ QUOTE ]

I'm pretty sure this has been tried already (one way or another /images/graemlins/tongue.gif )

[diebitter]

I remember something about the Chinese trying to cross-breed chimps and humans. It was however in a British tabloid, so the chances are there's the tiniest smidgeon of untruth in it.

[ QUOTE ]
I remember something about the Chinese trying to cross-breed chimps and humans. It was however in a British tabloid, so the chances are there's the tiniest smidgeon of untruth in it.

[/ QUOTE ]

At the market yesterday, I saw a photo of a flying saucer that had been shot down by rednecks. One of the rednecks resembled Don Knotts, holding a rifle with a gigantic scope attached.

[hmkpoker]

[ QUOTE ]
humanzees

[/ QUOTE ]

WHAT!?

[morphball]

[ QUOTE ]
[ QUOTE ]
humanzees

[/ QUOTE ]

WHAT!?

[/ QUOTE ] http://www.federalpost.ru/issue.img/20376_Untitled1.jpg

[diebitter]

[ QUOTE ]
[ QUOTE ]
humanzees

[/ QUOTE ]

WHAT!?

[/ QUOTE ]

My exact thoughts when wolphins came up.

[Borodog]

[ QUOTE ]
[ QUOTE ]
humanzees

[/ QUOTE ]

WHAT!?

[/ QUOTE ]

Oliver, the hamanzee (http://en.wikipedia.org/wiki/Oliver_the_humanzee):

http://i27.photobucket.com/albums/c153/Borodog/Humanzee-smaller.jpg

He walks bipedaly, too.

But alas, genetically, he's just a chimp.

[Borodog]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
humanzees

[/ QUOTE ]

WHAT!?

[/ QUOTE ]

My exact thoughts when wolphins came up.

[/ QUOTE ]

Wolphins (http://en.wikipedia.org/wiki/Wolphins).

Bred for its skills in magic.

[Lestat]

Nothing is ever "proven" in science. Science at best, makes predictions. The more accurate the predictions, the stronger the theory.

There are still many gaps and/or questions about evolution to be sure. However, it is still a very strong theory. Theories are constantly being refined. That's ok. Newton's theories needed some refinements and we're still looking for apparent large gaps in our understanding of gravity.

In short, scientific theories are often refined and there's little doubt evolution will be refined as we learn more. But almost NEVER is a scientific theory proven entirely wrong! So to this extent, I think it's pretty safe to say that the theory of evolution is on very solid ground. It is correct. We just don't know everything there is to know yet.

[CallMeIshmael]

[ QUOTE ]
[ QUOTE ]
humanzees

[/ QUOTE ]

WHAT!?

[/ QUOTE ]

http://www.derok.net/derok/images/classics/planet%20simpsons%20monkeys.jpg

[Aardvark]

One problem: Defining species as populations that cannot interbreed ignores the many species that reproduce asexually. It makes no sense to apply this definition to bacteria for example -- in cases such as these, the breaks between species are much less clear-cut and subjective, based on physiology and genetic similarity. There is no complete catch-all definition for a species; life is much more squishy than mathematics.

Taking the "unable to interbreed" definition: Yes, new species have been created in laboratories, and it is not as uncommon or difficult as you may think. It is relatively simple to induce plants to produce offspring with twice as many chromosomes as the parents. When a normal parent with two sets of chromosomes (diploid) produces a child with 4 sets of chromosomes (tetroid), the offspring and its lineage would produce infertile triploid offspring when mated with diploids. This by definition is a new species. This is how we get seedless fruit -- they are triploid. This process happens in nature as well, a very simple method of speciation. This happens in animals too. http://en.wikipedia.org/wiki/Polyploidy

Additionally, the species of fruitfly that is used in genetic studies is Drosophila melanogaster. The laboratory strains are descendant from flies caught in the 1800's. Since then, a strain of wild Drosophila melanogaster (P strain) has diverged enough to greatly diminish the ability for the wild and lab strains to interbreed: Evidence of speciation.

[pilliwinks]

Aardvark, I think most people are interested in speciation that does not involve polyploidy - there's no doubt it works, but there's also no doubt that it does not explain the difference between most diverged animal species.

On the topic of flies, I think it is correct to say that the experiment has been attempted on varying scales and with varying selections about 10 times. They got mild reproductive isolation in a couple of these. Nothing like speciation. But then, there shouldn't have been, given the number of generations, strength of selection and population size. The problem is, nature tells us that it takes about 1My minimum to get a speciation event in Drosophila. And that's in populations of who knows what size. In the lab you can speed things along by harsh selection, but the bottom line is, you expect nothing to happen for a very very long time unless your starting population was very lucky or very huge.

So to answer the OP on #5: No. It hasn't been done for any multicellular animal.

On #4, it depends on what you accept as proof. Mathematical proof, no. But 'proven' used to mean (and probably still should mean) 'tested'. As in 'proving grounds'. And the theory of evolution has been very heavily tested and is exceptionally successful (after heavy modification).

[Rduke55]

[ QUOTE ]
In the simplest view, "survival of the fit" is a tautology.

[/ QUOTE ]

I always have a problem when people say this. "Survival of the fittest" is an oversimplified phrase that people seem to latch onto. We're talking about traits here.

Here's what Wiki has to say on it

[ QUOTE ]
The phrase "survival of the fittest" is sometimes claimed to be a tautology (i.e. it is a statement which is true by its own definition, and is therefore intrinsically uninformative). Unfortunately, although in evolutionary biology the word "fitness" has nothing to do with being "fit" since it quantifies potential or realized reproductive success (as in "realized fitness"), the noun's etymological connection with the adjective "fit" leads many to charge the phrase "survival of the fittest" is equivalent to saying "those who survive best are those who survive best" or "those who reproduce most are those who reproduce most", i.e., that it is a tautology. The reasoning is that if we take the word "fit" to mean "fitness" then "survival of the fittest" means "highest fitness of those with highest fitness".

However, Darwin and Spencer used "survival" as a proxy for "fitness" in the modern sense and "fittest" to refer to those individuals that are functionally most capable to tackle life challenges, i.e. to individuals endowed with phenotypic characteristics which improve most strongly one's probability of survival and reproduction. Therefore "survival of the fittest" intends to be a short version of the statement "those who are best at surviving and reproducing will have higher fitness" and this is not a circular statement since the sentence indicates that fitness is the consequence of one's ability to tackle life challenges.

The full cause-and-effect picture of how natural selection generates fitness differences is that those individuals which end up reproducing more do it because they differed from others in biologically relevant traits that affected their probability of surviving and/or reaching reproduction in better condition.

For instance, a gazelle that for some biomechanical reason runs faster than average will be more likely to escape predators and will therefore be more likely to produce more offspring than slower ones since the latter would get to reproduce during fewer breeding seasons. The faster gazelle would therefore be "selected", i.e., it would have higher relative fitness than slower ones, etc, but not "because it is selected" but rather because it can run faster and thus can escape better from predators so that ultimately it will go through more breeding seasons than average gazelles and thus will reproduce more (will have higher fitness).

In the gazelle example, "survival of the fittest" would simply mean that faster gazelles have highest fitness because they are more "fit" at escaping predators. Saying the latter is fully explicit about the causation of fitness differences and is highly informative since this tells us what the selection regime is asking from the gazelles in functional terms.

In the causality chain that leads from functional differences to higher absolute or realized fitness nothing is tautological, since fitness is simply a measurement of the result of selection, a result that is determined by one's biological functionality.

[/ QUOTE ]

[Borodog]

Evolution in some sense is a numbers game. As a (very) crude and simplistic model, imagine a population of 100 animals, each of which manage to have 1 offspring (on average). Now imagine that an individual of a new variation arises, due to some random mutation, that can reproduce 1.01 offspring on average. Eventually, inevitably, the population will come to be dominated by this new variant, simply by mathematics.

http://i27.photobucket.com/albums/c153/Borodog/EvolutionGraph.png

[Rduke55]

People seem to overlook that some aspects of evolution are mathematical inevitablilities.

[Borodog]

[ QUOTE ]
People seem to overlook that some aspects of evolution are mathematical inevitablilities.

[/ QUOTE ]

Exactly; both logical and mathematical.

[pilliwinks]

Maths is great. Shame it never works that way in real life.

Typically that variant that can produce 1.01 offspring looks kooky, the chicks dig the other guys, and the mutation's gone in a puff of hormones. Or a tree falls on him.

The race is not always to the swift, as a wise man once said.

[Borodog]

[ QUOTE ]
Maths is great. Shame it never works that way in real life.

Typically that variant that can produce 1.01 offspring looks kooky, the chicks dig the other guys, and the mutation's gone in a puff of hormones. Or a tree falls on him.

The race is not always to the swift, as a wise man once said.

[/ QUOTE ]

You have missed the point entirely.

And the last time I checked, math actually does work in the real world.

[Rduke55]

[ QUOTE ]
Maths is great. Shame it never works that way in real life.

Typically that variant that can produce 1.01 offspring looks kooky, the chicks dig the other guys, and the mutation's gone in a puff of hormones. Or a tree falls on him.

The race is not always to the swift, as a wise man once said.

[/ QUOTE ]

Wait, I thought you're a scientist.

[pilliwinks]

Yes. Real scientists know that the real world is lumpy. We can dream up schemes that describe it to some approximation, and some of those schemes are mathematical. But to suggest that nature is obliged to adhere rigidly to our formulae is to make the tail wag the dog.

If you find a highly fecund variant, it does not always dominate the population, despite Borodog's impressive graph. There are massive numbers of variables that affect gene frequencies in populations. Sometimes fecundity is rate-limiting, usually not. Just think of trees.

More often it is rate of predation, food finding or mate selection that drive gene frequencies.

And the graph does not include drift, which in any normal population would have a fair chance of taking out a 1.01 reproductive advantage early on.

Note that I absolutely do think that selection for advantageous traits regularly fixes new variants in a population. Just not as a mathematical certainty.

[madnak]

The "lumpiness" is just variance. You're being results-oriented. I think Boro's implication was that all things being equal, a greater ability to produce viable offspring is advantageous.

[Borodog]

[ QUOTE ]
Yes. Real scientists know that the real world is lumpy. We can dream up schemes that describe it to some approximation, and some of those schemes are mathematical. But to suggest that nature is obliged to adhere rigidly to our formulae is to make the tail wag the dog.

If you find a highly fecund variant, it does not always dominate the population, despite Borodog's impressive graph. There are massive numbers of variables that affect gene frequencies in populations. Sometimes fecundity is rate-limiting, usually not. Just think of trees.

More often it is rate of predation, food finding or mate selection that drive gene frequencies.

And the graph does not include drift, which in any normal population would have a fair chance of taking out a 1.01 reproductive advantage early on.



[/ QUOTE ]

You are missing the forest for the trees. The figure of 1.01 vs 1.00 is the result of all the factors you name. It does not reflect simple "fecundity".

And the fact that a variant that would have achieved higher reproductive success is wiped out by chance is immaterial. The doesn't stop other advantage traits from spreading.

[ QUOTE ]
Note that I absolutely do think that selection for advantageous traits regularly fixes new variants in a population. Just not as a mathematical certainty.

[/ QUOTE ]

While any individual variant might be wiped out by chance, it is a mathematical certainty that advantageous traits do in fact come to dominate populations.

[gumpzilla]

[ QUOTE ]

You are missing the forest for the trees. The figure of 1.01 vs 1.00 is the result of all the factors you name. It does not reflect simple "fecundity".

[/ QUOTE ]

If we try and figure out what the only possibly interesting argument could be against those curves, I would say the assumption that the new variant continues to be 1% more efficient in reproducing over hundreds of generations is the weak link. How successful it is is going to be a function of its environment, and one aspect of that environment is the relative population of different variants.

[pilliwinks]

I apologise, Boro. I thought you were trying to say that if there is a particular trait that gives more progeny, it will dominate. Which I believe is a mistake for the reasons I mentioned.

Now it seems you were saying that inevitably, the traits that survive are advantageous ones.

I have no objection to that. Nor could I have, as it is a tautology. Since survival is an advantage, of course advantageous traits will survive - whatever you end up with is advantageous by definition.

Science is not particularly interested in tautologies, however. If you are claiming that whatever survives has a proliferative advantage, there is good evidence that you are mistaken. If you are claiming that whatever survives has a survival advantage, you are right by definition, and the graph is unnecessary as well as inaccurate.

[Rduke55]

[ QUOTE ]
I thought you were trying to say that if there is a particular trait that gives more progeny, it will dominate. Which I believe is a mistake for the reasons I mentioned.

[/ QUOTE ]

As Boro said, predation, finding food, and mate selection are traits that influence progeny and therefore are involved in selection.

[ QUOTE ]
I have no objection to that. Nor could I have, as it is a tautology. Since survival is an advantage, of course advantageous traits will survive - whatever you end up with is advantageous by definition.

[/ QUOTE ]

You're missing the point I made earlier. We're talking about traits' influence on selection - not organism-organism on each side of the phrase "Survival of the Fittest" so it isn't a tautology. Look at the Wiki article on Survival of the Fittest I excerpted from. Or if you want non-Wiki souorces look at Mayr's explanation in "What Evolution Is" (or the Wiki references).

[pilliwinks]

I'm not sure how to make this any clearer. I know that there are a bunch of traits that can be selected for. Traits that are selected for tend to increase their gene frequency in the population. That is the non-tautological meaning of the theory of natural selection.

To suggest that any one trait (that is being selected for) will inevitably dominate the population, is false.

To suggest that "it is a mathematical certainty that advantageous traits do in fact come to dominate populations" is also false, unless you define 'advantageous traits' as those that are dominant in populations.

I can cite any number of deleterious traits that dominate populations. I can cite any number of advantageous traits that are at very low frequency in populations and have been that way for ages.

Some people may think that natural selection implies that all organisms are optimised, but this is far from being the case

I don't think I'm being controversial here. As far as I can tell this is straightforward population genetics 101. Population genetics is mathematical, but it is very like economics. It deals with trends, not certainties, and it is often a poor model of reality (apologies to the economists).

[Borodog]

[ QUOTE ]
I can cite any number of deleterious traits that dominate populations.

[/ QUOTE ]

Go for it.

[ QUOTE ]
I can cite any number of advantageous traits that are at very low frequency in populations and have been that way for ages.

[/ QUOTE ]

Again, go for it.

[ QUOTE ]
Some people may think that natural selection implies that all organisms are optimised, but this is far from being the case

[/ QUOTE ]

Luckily, being "optimized" doesn't apply to anything brought up in the thread.

[ QUOTE ]
I don't think I'm being controversial here. As far as I can tell this is straightforward population genetics 101. Population genetics is mathematical, but it is very like economics. It deals with trends, not certainties

[/ QUOTE ]

Which is not at odds with anything Rduke55 or I have stated.

[ QUOTE ]
, and it is often a poor model of reality

[/ QUOTE ]

This doesn't follow.

[pilliwinks]

OK. Let's start with the well known ones.

Sickle cell anaemia is a deleterious trait by most people's definitions. It inevitably leads to a large fraction of the population suffering a debilitating illness. It is also found at greater than 50% in some human populations. The usual explanation is that malaria is even worse, and sickle cell trait gives you some protection in som eplaces. So is the trait an advantage? Well that depends on your point of view. For the majority of African Americans it is absolutely not.

Or we could bring up the hoary old example of the appendix, which is of no obvious advantage and of a very obvious disadvantage. Yet we all seem to have one.

I can go on and on. Most species have at least a few traits which they have been bequeathed that are far from ideal in their current environment.

In terms of advantageous traits, how about fecundity? This is generally regarded as an advantage in evolutionary terms. But you usually find that there are only a few organisms in a species that are exceptionally fecund, most have a more moderate output. Why is that? The usual explanation is that many organisms are better off having a few offspring that they can devote great care to, than hundreds that all die. That is, no one trait is advantageous in itself, only in combination with all the others (ie food finding, mate availability etc etc).

Selection does not drive all advantageous traits to fixation. It deals with a complex changing world, and the outcome is not always predictable in terms of the apparent value or otherwise of individual traits.

I agree that dealing with trends does not necessarily lead to being a poor model. In this case it happens to be that way. Reality has too many variables.

[fluorescenthippo]

[ QUOTE ]
5. Have new distinct species ever been bred, through (simulated) evolutionary conditions, in a controlled laboratory setting?

[/ QUOTE ]

i think so. this was mentioned in a class i took last semester. forgot most of it though /images/graemlins/frown.gif

[Copernicus]

We usually agree on most things but a couple here I think are off the mark :

[ QUOTE ]
OK. Let's start with the well known ones.

Sickle cell anaemia is a deleterious trait by most people's definitions. It inevitably leads to a large fraction of the population suffering a debilitating illness. It is also found at greater than 50% in some human populations. The usual explanation is that malaria is even worse, and sickle cell trait gives you some protection in som eplaces. So is the trait an advantage? Well that depends on your point of view. For the majority of African Americans it is absolutely not. In the region where the trait evolved it was an advantageous trait. When the affected population became less isolated and exposed to malaria it no longer had its advantages. Populations that no longer have that exposure will evolve away from that trait. That isnt "point of view", thats evolution.

Or we could bring up the hoary old example of the appendix, which is of no obvious advantage and of a very obvious disadvantage. Yet we all seem to have one.

Im surprised this keeps coming up. The appendix is no longer thought to be a useless appendage during fetal development and early infancy. Even if it is, that doesnt make it a disadvantageous trait. Similar to the sickle cell scenario above, it was advantageous at one time. The gene sequence that produces it is still there, even though it serves no function. That doesnt render it disadvantageous.

I can go on and on. Most species have at least a few traits which they have been bequeathed that are far from ideal in their current environment. In general disadvantageous traits are either so seroius the individual doesnt survive or so minor that they are considered anomalies, rather than evolved traits. Eg. webbed feet or hands in humans. They are clearly disadvantageous (especially hands), genetic, but easily correctable, so they will not be selected against.

In terms of advantageous traits, how about fecundity? This is generally regarded as an advantage in evolutionary terms. But you usually find that there are only a few organisms in a species that are exceptionally fecund, most have a more moderate output. Why is that? The usual explanation is that many organisms are better off having a few offspring that they can devote great care to, than hundreds that all die. That is, no one trait is advantageous in itself, only in combination with all the others (ie food finding, mate availability etc etc). I dont think moderation of fecundity is an advantageous trait in and of itself. It is a byproduct of the complexity and the reproductive capababilities of the species. Eg the relatively low fecundity of the human isnt to allow for the care of the infant, since a woman can conceive shortly after birth. Rather, 3/4+ of a year is spent in gestation because of the complexity of the human and multiple births are difficult and traumatic to both the mother and offspring and would have been selected against. If a species is physcially capable of frequent reproductive cycles, it spits them out, and health of the offspring be damned. Eg. rodents. They have short gestation periods and multiple births, but relatively low survival rates of the offspring in the wild. If moderation of fecundity were an evolutionary "goal" rodents would probably benefit from more time with the protection of a parent. I think a better example of an advantageous trait that is related, and isnt just a byproduct of other factors is "love" and "bonding". That is the trait that I think is more directly ascribed to the need for long term nurturing of the offspring. For the younger of you, there was (still is?) a phenomena euphemistically called the "Seven Year Itch", 7 years being the threshold for men to start to desire other mates. Like many "jokes" it has a basis in reality, imo, in that an infant becomes more self-reliant at around 6-7 years old, and a single mother more able to cope with being single. That frees the male to be less focused on the current offspring and able to seek out other "diversions", and that pheremones and other chemical generators of "love" and "lust" would begin to fade at that point is not coincidence.

Selection does not drive all advantageous traits to fixation. It deals with a complex changing world, and the outcome is not always predictable in terms of the apparent value or otherwise of individual traits. Agreed..I think your distinction between "advantageous" and "disadvantgeous" is somewaht contradictory to this

I agree that dealing with trends does not necessarily lead to being a poor model. In this case it happens to be that way. Reality has too many variables.

[/ QUOTE ]

[Borodog]

[ QUOTE ]
OK. Let's start with the well known ones.

Sickle cell anaemia is a deleterious trait by most people's definitions. It inevitably leads to a large fraction of the population suffering a debilitating illness. It is also found at greater than 50% in some human populations. The usual explanation is that malaria is even worse, and sickle cell trait gives you some protection in som eplaces. So is the trait an advantage? Well that depends on your point of view. For the majority of African Americans it is absolutely not.

[/ QUOTE ]

I thought this is where you would go. Traits that are deleterious do not come to dominate populations over advantageous variants. If the environment that a population exists in changes and a formerly advantageous trait is now deleterious, this does not imply that deleterious variants can come to dominate populations. In fact, given long enough, the now deleterious trait will wane, given that there are other variants that are now differentially more successful due to the change in environment.

[ QUOTE ]
Or we could bring up the hoary old example of the appendix, which is of no obvious advantage and of a very obvious disadvantage. Yet we all seem to have one.

[/ QUOTE ]

Our species did not develop deleterious appendices from their total absence. Presumably, they used to be useful for something, and now that they seem to be a disadvantage, they are being selected against.

[ QUOTE ]
I can go on and on. Most species have at least a few traits which they have been bequeathed that are far from ideal in their current environment.

[/ QUOTE ]

Again, irrelevent. What is relevent is that if there are variants that have differential reproductive success, the more successful variants will gain numbers relative to the less successful variants. That the environment might change, and hence change the direction of differential reproductive success doesn't change anything about the mathematical inevitability of the process itself.

[ QUOTE ]
In terms of advantageous traits, how about fecundity? This is generally regarded as an advantage in evolutionary terms. But you usually find that there are only a few organisms in a species that are exceptionally fecund, most have a more moderate output. Why is that? The usual explanation is that many organisms are better off having a few offspring that they can devote great care to, than hundreds that all die. That is, no one trait is advantageous in itself, only in combination with all the others (ie food finding, mate availability etc etc).

[/ QUOTE ]

So?

[ QUOTE ]
Selection does not drive all advantageous traits to fixation. It deals with a complex changing world, and the outcome is not always predictable in terms of the apparent value or otherwise of individual traits.

[/ QUOTE ]

Which does not change the fact that mathematics still works, and that if one variant manages on average to leave 1.01 viable offspring in the next generation to the 1.00 viable offspring of aother variant, the numbers of the first variant will grow in comparison to the second.

[ QUOTE ]
I agree that dealing with trends does not necessarily lead to being a poor model. In this case it happens to be that way. Reality has too many variables.

[/ QUOTE ]

Luckily, nothing I have said depends on knowing any variables at all. Nor is there any "model" involved. Variants that leave more viable offspring in the next generation than other variants will see their numbers increase relative to those other variants. It cannot be oherwise.

[pilliwinks]

Can we just clear up what I'm not trying to say here?

I am not trying to suggest that evolution does not occur. I am not trying to say that organisms with many advantages and few disadvantages fail to dominate over those with the reverse.

What I am trying, quite unsuccessfully it seems, to get across, is that for any single solitary individual trait, you cannot conclude from its effect on number of progeny whether or not it will come to dominate the population.

For example, you cannot conclude from the fact that a trait kills a quarter of your progeny that it will be removed, (because it may be saving two quarters from malaria). Nor can you conclude that a trait that makes you bear 10% more young will come to dominate for all sorts of reasons including those you mention.

These examples were not brought up to show that evolution does not work, nor to suggest that bad is good and good bad. I am just trying to show that there are lots of factors out there that make assessment of whether a trait is advantageous or not extremely tricky.

So tricky in fact, that many people give up, and say 'well whatever we've ended up with must be good'. This Panglossian view of evolution is mistaken. We have lots of detritus, enough in fact to make 'intelligent design' laughable.

The main point, however was: just because good things tend to spread and bad things be removed (in total), this does not mean that for any individual trait, that will be its fate.

My original quote is still the most accurate statement of what happens: the race is not always to the swift, nor the battle to the strong, but time and chance affect all.

Of course you should still bet on the swift and the strong /images/graemlins/grin.gif

[pilliwinks]

[ QUOTE ]
[ QUOTE ]
Sickle cell anaemia is a deleterious trait ...

[/ QUOTE ]

Traits that are deleterious do not come to dominate populations over advantageous variants...

[/ QUOTE ]

They do if circumstances change. What I'm trying to point out is that the same allele can be good or bad depending on where you live and what diseases are going about. Consequently you are rash to assume that a particular variant is going to dominate or be removed: things change.

[ QUOTE ]
What is relevent is that if there are variants that have differential reproductive success, the more successful variants will gain numbers relative to the less successful variants. That the environment might change, and hence change the direction of differential reproductive success doesn't change anything about the mathematical inevitability of the process itself.

[/ QUOTE ]

As I have mentioned several times, I am not disputing that natural selection works. Can you see that if the direction of selection changes that a different allele will start to gain ground? That the one you graphed might take a nose-dive as an alternative starts to work better? The process is not mathematically inevitable for any single trait. Overall the organisms move toward fitting their environment, but individual traits have no inevitability at all in the process. Unless you believe in intelligent design.

[ QUOTE ]
[ QUOTE ]
.. no one trait is advantageous in itself, only in combination with all the others (ie food finding, mate availability etc etc).

[/ QUOTE ]

So?

[/ QUOTE ]

So individual traits do not inevitably move toward fixation, regardless of their apparent fitness.

[ QUOTE ]
Which does not change the fact that mathematics still works, and that if one variant manages on average to leave 1.01 viable offspring in the next generation to the 1.00 viable offspring of aother variant, the numbers of the first variant will grow in comparison to the second.

[/ QUOTE ]

Or not. If you are looking at the past, you can see whether or not that happened, and it may look inevitable. If you look now and see 1.01 progeny compared to 1.00, you would be extremely unwise to bet on that variant going to fixation.


[ QUOTE ]
Variants that leave more viable offspring in the next generation than other variants will see their numbers increase relative to those other variants. It cannot be oherwise.

[/ QUOTE ]

Well I'm glad you're sure of that. I assure that it can be and is otherwise. I think you're mushing together anything that works and saying 'these are growing' rather than looking at the fate of any one solution. Gene X may be handy today, but it may kill you next generation. At which point gene Y takes over. You may be saying that "X or Y (or Z or something) will always grow', but what I am saying is that if you look at X, it may be gone tomorrow.

[Zeno]

Two book suggestions:

Evolutionary Tome Stephen Gould (http://www.amazon.com/gp/product/0674006135/qid=1148874708/sr=1-1/ref=sr_1_1/102-0985612-7406554?s=books&v=glance&n=283155)


Not so heavy Richard Dawkins (http://www.amazon.com/gp/product/0618005838/qid=1148874972/sr=2-1/ref=pd_bbs_b_2_1/102-0985612-7406554?s=books&v=glance&n=283155)


Gould's book, which I have glanced through in a bookstore, is technical and will cause a hernia in most people when packing it out to the car. Dawkin's book is more compact and more of what you are looking for I think. I haven't read it but it is a reasonable assumption that it would be worth reading if want to know more about evolution. I’m sure there are other equally good books to chose from.


As a side note, most have trouble with evolution because they lack the proper perspective of time. To humans, one hundred years is a long time. Five thousand years is a very long time and one hundred thousand years is beyond comprehension. We have no frame of reference for comparison. Our reference to time is usually just a few generations; this is paltry when dealing with evolution. This is only one of the stumbling blocks that many have difficulty with.

-Zeno, Still Evolving.

[Copernicus]

[ QUOTE ]
Can we just clear up what I'm not trying to say here?

I am not trying to suggest that evolution does not occur. I am not trying to say that organisms with many advantages and few disadvantages fail to dominate over those with the reverse.

What I am trying, quite unsuccessfully it seems, to get across, is that for any single solitary individual trait, you cannot conclude from its effect on number of progeny whether or not it will come to dominate the population.

For example, you cannot conclude from the fact that a trait kills a quarter of your progeny that it will be removed, (because it may be saving two quarters from malaria). Nor can you conclude that a trait that makes you bear 10% more young will come to dominate for all sorts of reasons including those you mention.

These examples were not brought up to show that evolution does not work, nor to suggest that bad is good and good bad. I am just trying to show that there are lots of factors out there that make assessment of whether a trait is advantageous or not extremely tricky.

So tricky in fact, that many people give up, and say 'well whatever we've ended up with must be good'. This Panglossian view of evolution is mistaken. We have lots of detritus, enough in fact to make 'intelligent design' laughable.

The main point, however was: just because good things tend to spread and bad things be removed (in total), this does not mean that for any individual trait, that will be its fate.

My original quote is still the most accurate statement of what happens: the race is not always to the swift, nor the battle to the strong, but time and chance affect all.

Of course you should still bet on the swift and the strong /images/graemlins/grin.gif

[/ QUOTE ]

I think you are missing the point of the graph/math. The only point being made was that if, after all of the effects that you mention are netted out, a certain trait still retains a 1% selection advantage, it will come to dominate in short order.

[pilliwinks]

That was one of the points. The other was that this process is inevitable.

I'm not sure which version of inevitability Boro was thinking of, but it might have been the 'in a perfect world where everything works in a unvarying manner' kind. My comment was that the world is lumpy. That is, even if you can find a trait which will always give you a reproductive advantage over your peers (which is not possible by any means I can think of), even then, you run the risk of being hit by an evolutionary truck. Even without a truck there is drift (which you cannot 'net' out) and which often makes low frequency alleles disappear despite their advantages.

There is no inevitability. Statisticians know this. Mathematicians often fail to notice.

[Borodog]

Your comment was that math does not work in the real world.

My comment was that no matter how "lumpy" the world is, math still works. And those variants that leave more viable offspring in the next generation than other variants will see their frequency in the population increase relative to those others. Regardless of what change of circumstances switches advantageous for deleterious and vice versa, advantageous gains relative to deleterious.

I'm not sure how many more ways to say the same simple concept.

[pilliwinks]

The concept is simple in the HL Mencken way: "For every complex problem there is a solution that is simple, neat, and wrong".

You can only judge with certainty what was advantageous after the event. If you are watching the process, you cannot easily determine what is, or will be advantageous.

You have now switched to saying "those variants" rather than "a variant", so I hope that means you agree that for an individual variant, there is no inevitable process.

The only thing that is inevitable is the 'benfit of hindsight' tautology that I mentioned before: if you define advantageous in terms of what has succeeded, you always find that it has succeeded. Amazingly.

The non-tautologous non-inevitable formulation is: things that give a reproductive advantage today, are likely to do so tomorrow, and in the long term may well come to dominate the population. If they are lucky.

You say that advantageous always gains relative to deleterious. But how can you tell which is which? Only by which is gaining? Let's say you have alleles A and B. Follow the population for five generations and observe A disappear. Was it deleterious? Or just unlucky?

[Borodog]

None of the arguments you keep coming up with are in any way in disagreement with anything that I've said, except that math doesn't work in the real world and that natural selection is tautological. I give up trying to make my point. I content myself that several others seem to understand what I've been saying.

[pilliwinks]

Well, I'm sorry that I can't point out more clearly what the difference in our opinions is. It is very clear to me.

You think that advantageous traits inevitably dominate. I think that this is a naive fudge that doesn't come to grips with real individual traits, which may or may not come to dominate for reasons that may not even be connected with their fitness.

[pilliwinks]

No wait! I have one more explanation to try out.

How about this one: Does the best football team in the country always win the superbowl?

I know some people who would say yes. For them, winning the superbowl makes them the best team, so if you win you are the best. It is inevitable, and happens every year.

Others would say no. There are loads of stats these days about every aspect of play, and they may clearly indicate which team has the best chance, week on week, of beating any other. A team may lose no matches all through the playoffs. They may have all the very best players in each position. And still lose the superbowl. Does that make them not the best team? The bookies, who really know about this stuff, would have given you worse odds on them than any other team, and for good reason. Any objective measure other than 'winning the superbowl' makes them the best.

This is like natural selection. There are lots of measures of 'advantageous' that you can use to put odds on a trait dominating. But there is no guarantee. Unless you define 'advantagous' as 'having already survived', which like 'having won the superbowl', you can only determine in retrospect.

[noseeds99]

im from Kansas, what's evolution?

[siegfriedandroy]

stopped reading when you said, 'he has not studied it either'...perhaps read further than i should've....but S*IT HAD A GOOD IDEA BUT TOOO DRUNK TO STATE IT

[siegfriedandroy]

SH*T THIS TIME I STOPPED AT FRUIT FLIES...SERIOUS. MIDGE WILL EXPLAIN WHATEVER HE DOES...(BELIEVES IRREVELANTLY AND UNACCEPTABLY) SO JADED- ANYWAY....TOO DRUNK TO EXPLIAIN IT ALL U AND EVERYONE HERE AT 2 PLUS TWO IS DESTROYED THAT IS WHY I BEAT U ALL HU WHATEVER JK TRUE BUT JK ANWAY, LUV U ALL EVEN MIDGE PEASE

[MidGe]

Thanks siegfriedandroy for the peace wishes etc... Don't know where it is coming from. I didn't contribute to this topic!? Hope it was a good and enjoyable drop though.

MidGe

[Kurn, son of Mogh]

Darwin and Spencer used "survival" as a proxy for "fitness"

Exactly my point. Survival of the fittest just means survival of the survivors. By focusing on a catchphrase, we gloss over the complexity of evolution.

But focusing on that one sentence missed the point of my post. To many secular scientists, Darwin is a sacred cow. Question Darwin and you *must* be a creationist.

[CallMeIshmael]

siegfriedandroy,

Please stop posting.

ty,

-CMI

[pilliwinks]

Kurn, I think it's a little unfair to say Darwin uses survival as a proxy for fittest, since he is at pains to point out all of the actual traits under selection, and in any case was not the originator of the phrase.

Your points are still valid, though - there are many who find it convenient to ignore the complexity, and criticisms of their simplifications do tend to get you labelled a creationist or at least anti-scientific. Particularly if you happen to be a Christian.

Facts are facts, though. Here's a quote from someone else who feels uncomfortable with this particular simplification:

[ QUOTE ]
The idea that what is important is a gene's average effect on the reproductive successes of its bearers, generation after generation, falls into the difficulty that evolution could not proceed by taking each gene, one at a time, whilst holding constant the effects of all the other supposedly selfish 99,999 genes which make up a typical 100,000 genes' worth of contribution to an advanced primate phenotype. Were this to be done for each gene in turn, there would not be enough time since the cooling of the earth, to have evolved what we know has evolved

[/ QUOTE ]

Note particularly the last sentence - Gabriel Dover is a Professor of Genetics, and no creationist! Nonetheless he spends several books and articles attempting to refute the popular idea that individual genes are selected and come to dominate on the basis of their individual effect on reproduction.

[chrisnice]

[ QUOTE ]
Nonetheless he spends several books and articles attempting to refute the popular idea that individual genes are selected and come to dominate on the basis of their individual effect on reproduction.

[/ QUOTE ]

Nowhere in this thread did anyone ever assert that an individual advantageous trait will inevitably come to dominate. Your fighting a strawman. What was stated that a group with a reproductive advantage (as a result of many traits and other factors) will inevitably overtake a group with less successful repoductive abilities (as a result of many traits and other factors). Yes a meteor could strike the more advantageous group, but the chance of that happening to the less advantageous group is the same so its a mathematical wash.

[pilliwinks]

[ QUOTE ]
Nowhere in this thread did anyone ever assert that an individual advantageous trait will inevitably come to dominate. Your fighting a strawman.

[/ QUOTE ]

Oh really? Allow me to refresh your memory:

[ QUOTE ]
Evolution in some sense is a numbers game. As a (very) crude and simplistic model, imagine a population of 100 animals, each of which manage to have 1 offspring (on average). Now imagine that an individual of a new variation arises, due to some random mutation, that can reproduce 1.01 offspring on average. Eventually, inevitably, the population will come to be dominated by this new variant, simply by mathematics.

[/ QUOTE ]

Of course you could say 'he didn't mean that. Actually he meant that a group of animals with a total set of traits that are best adapted will gain ground each generation and sometimes this leads to traits being fixed', but I think you would be misrepresenting his opinion.

[ QUOTE ]
What was stated that a group with a reproductive advantage (as a result of many traits and other factors) will inevitably overtake a group with less successful repoductive abilities (as a result of many traits and other factors). Yes a meteor could strike the more advantageous group, but the chance of that happening to the less advantageous group is the same so its a mathematical wash.

[/ QUOTE ]

I'm sorry, but it looks like you also have Borodog's opinion, which is different to mine. Even though you accept that lots of traits inevitably get factored in (which is a step in the right direction), you are missing the issue of varying selection pressures (and drift and drive, but let that pass).

I'm not saying a meteor is the only way the superathletes can lose to the couch potatoes. If you change the rules to include a two week starvation period during the race, the couch potatoes win comfortably. This clearly happens in nature: change is the only constant. There is nothing inevitable about victory for the well-adapted, because today's superathlete is tomorrow's starving wreck.

Yes, you can say 'well the couch potatoes are now adapted, they are the inevitable victors', but you see the problem. As the rules change, the group or set of genes that are adaptive, also change, and you can't predict which will do best in the long run, ahead of time.

To say 'it is inevitable that the best adapted will dominate in the end' has no predictive value, because you are defining 'best adapted' as whatever comes out on top after the event. You are just saying that the winner always wins, not that the fastest runner always wins (which would be non-tautological, and false).

The problem that most people have with this concept is that they are more comfortable with abstractions (ie a group with superior reproduction), than with realities (a set of individuals with particular genes giving a particular reproductive outcome). Consequently they see no problem with their abstraction remaining constant over time (the group with superior reproduction remains, though the individuals may change). The reality may be that the original group is dead. A different group, with no genetic similarity to the first, is currently doing OK, but they may be dead tomorrow too. This changes your opinion about inevitability.

[Cerril]

It's all pretty well covered, so I'll only add the comparison I tend to make when explaining the ID conflict to people.

It's worth knowing that evolution is a theory (i.e. 'proven' by support and examples/counter-examples), but when you talk about our certainty that it's working in some form rather than saying that it's as certain as 2+2=4, you can say that we can be as sure that it's working as we are that the earth will continue to orbit the sun or that we aren't going to fly off the earth. i.e. gravity is a theory as well (one, oddly, plagued with similar issues in completeness but less commonly attacked).

[siegfriedandroy]

yeah, hopefully you guys can come up with something better than gould and dawkins. if that is the best you can come up with, then you have a lot more evolving still left to do!! jk

[The Dude]

MMMMMMM,

There is no theory of evolution. Only a list of species Chuck Norris has allowed to live.

[Chips_]

The original post here contains some excellent questions. If more people thought like this, we would make more progress toward a better understanding of the origin of life and evolution.
This is one of our big problems today :
1. Is my friend right that the Theory of Evolution is scientifically considered to be as sound as the statement that 2+2=4? Or as scientifically sound as, say, the laws of thermodynamics?

No your friend is not right.The dominant theory of evolution is the so called "Neo-Darwinian" model. In a nutshell it says that random mutations and natural selection have produced all the variation of life on the earth. Your fruit fly question is right on the money. The reference that I usually use is microorganisms though.

We believe that man and ape share a common ancester about 2 million years ago. Thats about 100,000 generations and a population size in the 100's of millions (only billions recently) . We can get that number of generations in microorganisms in a year. We can get the population size. We can control the mutation rate. We can control the environment. The mathematical side of this is much easier with microorganisms - their gentic code is many orders of magnitude shorter than in humans. If it really is the case that evolution is caused by random mutation and selection in the environment then why not show it with an experiment in the lab ? This is a very good question. I personally think there is a Nobel Prize waiting for someone who comes up with such an experiment. It may be out there. It may also turn out that evolution doesnt happen quite the way we think it does. I really think there is some discovery out there waiting to be found. Because to me the math - the numbers - the lack of experimental evidence - something is missing. Dawkins does not answer these questions at all although he tries to get at some of this. Now there are some pretty good counter arguments as to why experiemnts like the one I talked about - and the fruit flies - are not as easy as they seem. All I can say is from my experience talking with people about this the counter agruments are just not all that convincing to me.

So here is your answer about theories - a good theory has a model. The model has some math behind it. The model is used to predict experimental results. The experiments are repeatable and demonstrate simple ideas within the theory.
Evolution really doesnt have that on its side right now. Ahh people can argue this point - the diehards will contest this, but there really must be more out there folks. And people can argue all day over what a "species" is. And we can make observations in nature that certainly support the idea of evolution - the general idea, not really the "neo-darwinian" model. But repeatable experiments that demonstrate this model - not there in my opinion.

So its a good theory yes, but more people need to think about how to prove it without getting sidetracked into religious arguments. This includes the notion that it is impossible to conclude from science that there was any design in life - one of the worst statements nowadays in terms of scientific logic and in terms of the pursuit of truth. You can't prove a theory if alternatives are dismissed like that. Saying it is just like 2+2=4, as some in our educational system do, amounts to the stifling of good scientific reasoning that may lead to better understanding in the future.

Sometimes the path to a better understanding of something is clearly and honestly laying out what we know about something and what we dont know. Observations and experiements that are designed to demonstrate principles of a theory - or to uncover that the models are inadequate - are critical in the path of scientific advancement.

This is kind of an outsider's view. I taught College Physics, but I am not a biologist. I think that learning how to ask the right questions is very important and that is what caught my eye on the original post.

[Borodog]

[ QUOTE ]
We believe that man and ape share a common ancester about 2 million years ago.

[/ QUOTE ]

This is too low by over a factor of 3.

[ChrisV]

[ QUOTE ]
1. Is my friend right that the Theory of Evolution is scientifically considered to be as sound as the statement that 2+2=4? Or as scientifically sound as, say, the laws of thermodynamics?

4. Has the Theory of Evolution ever been *proven*

[/ QUOTE ]

Neither of those are theories. 2+2=4 is a statement of fact given the axioms of mathematics. The laws of thermodynamics are laws.

[ QUOTE ]
In scientific usage, a theory does not mean an unsubstantiated guess or hunch, as it often does in other contexts. A theory is a logically self-consistent model or framework for describing the behavior of a related set of natural or social phenomena. It originates from and/or is supported by experimental evidence (see scientific method). In this sense, a theory is a systematic and formalized expression of all previous observations that is predictive, logical and testable. In principle, scientific theories are always tentative, and subject to corrections or inclusion in a yet wider theory. Commonly, a large number of more specific hypotheses may be logically bound together by just one or two theories. As a general rule for use of the term, theories tend to deal with much broader sets of universals than do hypotheses, which ordinarily deal with much more specific sets of phenomena or specific applications of a theory.

If enough experiments and observations are made by many researchers, such a theory may become sufficiently verified to be considered so thoroughly confirmed that its premises may after that stage be termed laws.

[/ QUOTE ]

One of the properties of laws is that they are extremely concise statements, so the theory of evolution will never become a law. Nor will, say, the theory of quantum mechanics.

EDIT: Just wanted to say a bit more about laws, since the above quote makes them sounds like they're just highly confirmed theories. The first law of thermodynamics is "Energy is neither created nor destroyed". This was discovered in the same way as any other scientific truth, by hypothesis, experiment and theory. The reason it can be made a law is that it is a very basic statement and one that is either true or false. It admits no wiggle room. By contrast, a theory like relativity might be basically correct (ie the idea of 4-dimensional spacetime with different frames of reference is correct) but have some fine detail wrong, like say gravitational waves don't occur because of some unforseen effect. The theory of relativity would be altered, but not considered disproven because the basic concepts are intact. So relativity can never become a law, although a simpler statement like "E = mc^2" could.

I would say that evolution is as well regarded a theory as relativity. No scientific theory is ever proven.

[ QUOTE ]
2. Definition of Theory of Evolution?

[/ QUOTE ]

It's the same as the theory of natural selection. It encompasses both basic survival of the fittest concepts and speciation.

The difficulty you are having is that the hypotheses are different, but they are bound up under the one theory.

[ QUOTE ]
3. Definition of a Species?

5. Have new distinct species ever been bred, through (simulated) evolutionary conditions, in a controlled laboratory setting?

[/ QUOTE ]

This is what you're really after, I think. Speciation has been observed in laboratories, yes. But that isn't even necessary since it has been observed in the wild too.

Observed Instances of Speciation (http://www.talkorigins.org/faqs/faq-speciation.html)

Some More Observed Speciation Events (http://www.talkorigins.org/faqs/speciation.html)

That first link also has discussion on the definition of a species. Some of it's heavy going, but worth reading.

The different characteristics of the newly formed species may seem trivial (or in some cases basically nonexistent). The idea isn't that a completely different organism suddenly springs into existence, but that populations of organisms stop interbreeding and then natural selection pressures exert themselves on the two populations in different ways.

[aeest400]

Observed Instances of Speciation (http://www.talkorigins.org/faqs/faq-speciation.html)

Some More Observed Speciation Events (http://www.talkorigins.org/faqs/speciation.html)

That first link also has discussion on the definition of a species. Some of it's heavy going, but worth reading.

The different characteristics of the newly formed species may seem trivial (or in some cases basically nonexistent). The idea isn't that a completely different organism suddenly springs into existence, but that populations of organisms stop interbreeding and then natural selection pressures exert themselves on the two populations in different ways.

[/ QUOTE ]

It isn't really fair to provide this kind of evidence. It could interfere with some folk's beliefs. [Just kidding, I don't think there is any danger in that happening.]

[godBoy]

How can the grim-reaper and mutations that more-often-than-not produce a non-beneficial change produce a constant positive gradual change as described in the theory?

I actually want to know, please don't take this question the wrong way.

[tolbiny]

[ QUOTE ]
How can the grim-reaper and mutations that more-often-than-not produce a non-beneficial change produce a constant positive gradual change as described in the theory?

I actually want to know, please don't take this question the wrong way.

[/ QUOTE ]

A positive mutation can effect many generations down the line, while a negative mutations will have less of an effect. For example a mutation that is 100% fatal would kill 1 individual whenever it popped up. While a mutation that is midly beneficial (say it allows for a 1% advantage in reproduction over the average) will build and increase its frequency in every generation.

[tolbiny]

[ QUOTE ]
MMMMMMM,

There is no theory of evolution. Only a list of species Chuck Norris has allowed to live.

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Observation 1: Chuck Norris is the fittest human being ever.
Obsrevation 2: Whenever a fight breaks out Chuck Norris inevitably survives.
Logical deduction: Survival of the fittest.

[godBoy]

that's a good point, however i'd still expect to see a lot of crippled organisms walking around from all the negative mutations. Why is that we only really see the good fruits of evolution and not more of the bad fruits if negative mutations are more common?

[bunny]

I think its because the bad fruits die (often before being born) and the good fruits live. So there is an inherent bias in the changes that we observe.

[MidGe]

[ QUOTE ]

that's a good point, however i'd still expect to see a lot of crippled organisms walking around from all the negative mutations. Why is that we only really see the good fruits of evolution and not more of the bad fruits if negative mutations are more common?

[/ QUOTE ]

Go and spend some time in the maternity ward of a large gynelogocal hospital. I think the number of unliveable monsters being born will help with your blindness or lack of sight.

[pilliwinks]

I wouldn't get too carried away with that list of observed speciation events. None of them show more than a modest level of reproductive isolation as far as I am aware.

If someone does do an experiment in which they claom to have shown clear speciation, I would examine it very carefully indeed, since the numbers of individuals and generations you would expect to require (if nature is any guide), is prohibitively large for multicellular organisms.

Don't get me wrong, every step in the process of speciation, from mild sexual preferences through to complete incompatibility, can be observed. Just not in the lab, and not from start to finish. My recommendation is not to provide more ammunition for the nay-sayers by over-interpreting results.

[tolbiny]

[ QUOTE ]
that's a good point, however i'd still expect to see a lot of crippled organisms walking around from all the negative mutations. Why is that we only really see the good fruits of evolution and not more of the bad fruits if negative mutations are more common?

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1. There are more bad mutations than good mutations, but there are far more Non-mutations than either (or both put together)
2. Animals that reproduce sexually get 2 copies of each gene, if you get a bad copy fairly often the good copy can take over.
3. Hemophelia, siemese twins, tay sach's, albinos- there are tons of humans born with mutations all the time, mutations which would mark them for death in the animal kingdom but you may be able to survive with for years (or even a regular lifetie) as a human.

[tolbiny]

[ QUOTE ]
[ QUOTE ]
that's a good point, however i'd still expect to see a lot of crippled organisms walking around from all the negative mutations. Why is that we only really see the good fruits of evolution and not more of the bad fruits if negative mutations are more common?

[/ QUOTE ]

1. There are more bad mutations than good mutations, but there are far more Non-mutations than either (or both put together)
2. Animals that reproduce sexually get 2 copies of each gene, if you get a bad copy fairly often the good copy can take over.
3. Hemophelia, siemese twins, tay sach's, albinos- there are tons of humans born with mutations all the time, mutations which would mark them for death in the animal kingdom but you may be able to survive with for years (or even a regular lifetie) as a human.

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I need to fire in a few edits.
1. there are also "neutral" mutations- those which neither provide a benefit nor a detriment under current conditions.
3. I don't know the genetivc basis (if there is one) for siemese twins, just an example of reproduction gone wrong that clearly wouldn't survive outside of humans.

Extra stuff- any major mutation that effects either a sperms abilty to fertilize an egg (or an eggs to be fertilized) or will cause a miscarige will never be seen.

[godBoy]

ok i'm pretty satisfied with those answers tolbiny, just one more..

[ QUOTE ]
Animals that reproduce sexually get 2 copies of each gene, if you get a bad copy fairly often the good copy can take over.

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If this is true, then it explains how an organism with defective genes can reproduce and not pass them on, the other parent would pass on it's uneffected gene.
Has this been witnessed? - how does the child aquire the good gene 'fairly often'.. more often than not?

[tolbiny]

[ QUOTE ]
If this is true, then it explains how an organism with defective genes can reproduce and not pass them on, the other parent would pass on it's uneffected gene.
Has this been witnessed? - how does the child aquire the good gene 'fairly often'.. more often than not?


[/ QUOTE ]

You have 2 copies of every gene, one you got from your mother and one from your father. Each of your children will get one of those two copies at random, and thier other copy will come from thier mother (assuming your male)- so if you have 1 defective copy out of your two genes then each of your children have a 50/50 shot at inheriting that particular copy.