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.

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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).

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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 advance an interesting alternate theory involving bacteria as one of the driving forces in systemic evolution.

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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).

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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 and read. Everything you never wanted to know about the issue, geared specifically toward interested layman.

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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?

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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.

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

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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.

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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?

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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.

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What exactly is the definition of a species, anyway?

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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.

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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.

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

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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).

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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]

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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.


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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]

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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.


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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.

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

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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.

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