Darwinism?

[DannyM]

Danny,

grading exams right now and will provide some ideas of merit (hopefully without typos and on topic).

There have been multiple studies showing the possibilities of genetic variation within a population. Of mutations, there are plenty of examples of mutations, most harmful, plenty neutral, and some beneficial depending on the environment. For instance, the mutation that causes sickle cell anemia is beneficial in those areas with malaria. Cystic fibrosis is another possible mutation that provides some resistance in some environmental areas.

These sorts of examples, however, rarely would lead to speciation in themselves.

Speciation occurs in two main pathways: allopatric speciation and sympatric speciation. In allopatric speciation, two groups of the same species are geographically isolated and thus reproductive isolation occurs automatically. The idea then is that because these two sub-populations cannot interbreed, each group is accumulating different variations and mutations. Conceivably, then, if the two populations were to come together at some point, they would be sufficiently different that they cannot interbreed and produce fertile offspring (the hallmark of biological speciation). This can happen several potential ways (perhaps mate choice plays a significant role, perhaps the sperm and eggs cells no longer recognize each other, perhaps the timing of mating is off, or mating behaviors).

For allopatric speication, the best evidence lies on ring species, where a population, around geographic barrier, changes in subtle ways and the two ends of the "ring" around the barrier no longer interbreeds (mind you, this doesn't necessarily mean that they can't, just that they won't). In this instance, the two ends represent the best evidence of reproductive isolation and speciation. Now...the big issue, however, is that these difference are still relatively miniscule in the grand idea of evolution. In the case of salamanders, notice that the differences lie in the coloration and the recognition of the genders.



The other main method is called sympatric, where something happens to one group within the same geographic area that causes that subset to be reproductively isolated, either the genome of the cells has doubled, mating choice, mating behaviors, or some other factor where the two populations cannot interbreed.

Best examples of these cases involve those factors above or plants that have gone polyploid, with several sets of their genomes, that prevents them from pollinating a flower of the previous genome.

//www.google.com/imgres?imgurl=//evolutio ... s%3Disch:1

Anyhoo, just some thoughts to generate more conversation....

Thanks Zoe. From the link: "In the summer of 1995, at least 15 iguanas survived Hurricane Marilyn on a raft of uprooted trees. They rode the high seas for a month before colonizing the Caribbean island, Anguilla. These few individuals were perhaps the first of their species, Iguana iguana, to reach the island. If there were other intrepid Iguana iguana colonizers of Anguilla, they died out before humans could record their presence.

"Evolutionary biologists would love to know what happens next: will the colonizing iguanas die out, will they survive and change only slightly, or will they become reproductively isolated from other Iguana iguana and become a new species? We could be watching the first steps of an allopatric speciation event, but in such a short time we can't be sure. "

What actual evidence is there to suggest these Iguana might become a new species if they are reproductively isolated from other Iguana? The link says "we have several plausible models of how speciation occurs - but of course, it's hard for us to get an eye-witness account of a natural speciation event since most of these events happened in the distant past. We can figure out that speciation events happened and often when they happened, but it's more difficult to figure out how they happened. However, we can use our models of speciation to make predictions and then check these predictions against our observations of the natural world and the outcomes of experiments. As an example, we'll examine some evidence relevant to the allopatric speciation model. Scientists have found a lot of evidence that is consistent with allopatric speciation being a common way that new species form:

"Geographic patterns: If allopatric speciation happens, we'd predict that populations of the same species in different geographic locations would be genetically different. There are abundant observations suggesting that this is often true. For example, many species exhibit regional “varieties” that are slightly different genetically and in appearance, as in the case of the Northern Spotted Owl and the Mexican Spotted Owl. Also, ring species are convincing examples of how genetic differences may arise through reduced gene flow and geographic distance."

Now the pictures of the Northern Spotted and Mexican Spotted Owls are just different looking Owls. I'm asuming these 'differences' are simply 'adaptive' differences and have nothing whatsoever to do with a full transition from a species to another. If these subtle differences are the 'start of something bigger' then what, roughly, is this 'bigger' something? When does the Owl become a new species, Zoe?

"Experimental results: The first steps of speciation have been produced in several laboratory experiments involving “geographic” isolation. For example, Diane Dodd took fruit flies from a single population and divided them into separate populations living in different cages to simulate geographic isolation. Half of the populations lived on maltose-based food, and the other populations lived on starch-based foods. After many generations, the flies were tested to see which flies they preferred to mate with. Dodd found that some reproductive isolation had occurred as a result of the geographic isolation and selection in the different environments: “maltose flies” preferred other “maltose flies,” and “starch flies” preferred other “starch flies.” Although, we can't be sure, these preference differences probably existed because selection for using different food sources also affected certain genes involved in reproductive behavior. This is the sort of result we'd expect, if allopatric speciation were a typical mode of speciation."

Reproductive isolation seems rather inevitable given the separation and dietry changes involved in the experiment, but what has ruled out these sub-populations of same species from 'inter' breeding, Zoe, in case I missed it? Allopatric speciation appears a mere theoretical stepping stone on the path to spec iation.

Dan

[zoegirl]

Danny,

grading exams right now and will provide some ideas of merit (hopefully without typos and on topic).

There have been multiple studies showing the possibilities of genetic variation within a population. Of mutations, there are plenty of examples of mutations, most harmful, plenty neutral, and some beneficial depending on the environment. For instance, the mutation that causes sickle cell anemia is beneficial in those areas with malaria. Cystic fibrosis is another possible mutation that provides some resistance in some environmental areas.

These sorts of examples, however, rarely would lead to speciation in themselves.

Speciation occurs in two main pathways: allopatric speciation and sympatric speciation. In allopatric speciation, two groups of the same species are geographically isolated and thus reproductive isolation occurs automatically. The idea then is that because these two sub-populations cannot interbreed, each group is accumulating different variations and mutations. Conceivably, then, if the two populations were to come together at some point, they would be sufficiently different that they cannot interbreed and produce fertile offspring (the hallmark of biological speciation). This can happen several potential ways (perhaps mate choice plays a significant role, perhaps the sperm and eggs cells no longer recognize each other, perhaps the timing of mating is off, or mating behaviors).

For allopatric speication, the best evidence lies on ring species, where a population, around geographic barrier, changes in subtle ways and the two ends of the "ring" around the barrier no longer interbreeds (mind you, this doesn't necessarily mean that they can't, just that they won't). In this instance, the two ends represent the best evidence of reproductive isolation and speciation. Now...the big issue, however, is that these difference are still relatively miniscule in the grand idea of evolution. In the case of salamanders, notice that the differences lie in the coloration and the recognition of the genders.

The other main method is called sympatric, where something happens to one group within the same geographic area that causes that subset to be reproductively isolated, either the genome of the cells has doubled, mating choice, mating behaviors, or some other factor where the two populations cannot interbreed.

Best examples of these cases involve those factors above or plants that have gone polyploid, with several sets of their genomes, that prevents them from pollinating a flower of the previous genome.

http://www.google.com/imgres?imgurl=htt ... s%3Disch:1

Anyhoo, just some thoughts to generate more conversation....

Thanks Zoe. From the link: "In the summer of 1995, at least 15 iguanas survived Hurricane Marilyn on a raft of uprooted trees. They rode the high seas for a month before colonizing the Caribbean island, Anguilla. These few individuals were perhaps the first of their species, Iguana iguana, to reach the island. If there were other intrepid Iguana iguana colonizers of Anguilla, they died out before humans could record their presence.

"Evolutionary biologists would love to know what happens next: will the colonizing iguanas die out, will they survive and change only slightly, or will they become reproductively isolated from other Iguana iguana and become a new species? We could be watching the first steps of an allopatric speciation event, but in such a short time we can't be sure. "

What actual evidence is there to suggest these Iguana might become a new species if they are reproductively isolated from other Iguana? The link says "we have several plausible models of how speciation occurs - but of course, it's hard for us to get an eye-witness account of a natural speciation event since most of these events happened in the distant past. We can figure out that speciation events happened and often when they happened, but it's more difficult to figure out how they happened. However, we can use our models of speciation to make predictions and then check these predictions against our observations of the natural world and the outcomes of experiments. As an example, we'll examine some evidence relevant to the allopatric speciation model. Scientists have found a lot of evidence that is consistent with allopatric speciation being a common way that new species form:

"Geographic patterns: If allopatric speciation happens, we'd predict that populations of the same species in different geographic locations would be genetically different. There are abundant observations suggesting that this is often true. For example, many species exhibit regional “varieties” that are slightly different genetically and in appearance, as in the case of the Northern Spotted Owl and the Mexican Spotted Owl. Also, ring species are convincing examples of how genetic differences may arise through reduced gene flow and geographic distance."

Now the pictures of the Northern Spotted and Mexican Spotted Owls are just different looking Owls. I'm asuming these 'differences' are simply 'adaptive' differences and have nothing whatsoever to do with a full transition from a species to another. If these subtle differences are the 'start of something bigger' then what, roughly, is this 'bigger' something? When does the Owl become a new species, Zoe?

By definition (at least with the biological definition of species), as soon as they cannot interbreed and produce fertile offspring. If the owls *can* interbreed but often choose not to because of mate choice, this would be, in their eyes, the potential start of speciation....because as soon as they *don't* mate, the different populations accumulate different mutations, which could lead to them not being able to mate and produce fertile offspring.

"Experimental results: The first steps of speciation have been produced in several laboratory experiments involving “geographic” isolation. For example, Diane Dodd took fruit flies from a single population and divided them into separate populations living in different cages to simulate geographic isolation. Half of the populations lived on maltose-based food, and the other populations lived on starch-based foods. After many generations, the flies were tested to see which flies they preferred to mate with. Dodd found that some reproductive isolation had occurred as a result of the geographic isolation and selection in the different environments: “maltose flies” preferred other “maltose flies,” and “starch flies” preferred other “starch flies.” Although, we can't be sure, these preference differences probably existed because selection for using different food sources also affected certain genes involved in reproductive behavior. This is the sort of result we'd expect, if allopatric speciation were a typical mode of speciation."

Reproductive isolation seems rather inevitable given the separation and dietry changes involved in the experiment, but what has ruled out these sub-populations of same species from 'inter' breeding, Zoe, in case I missed it? Allopatric speciation appears a mere theoretical stepping stone on the path to spec iation.

Dan

yes, you are right, and even in their first paragraph they admit that real-time evidence is hard to accumulate because this would happen over many many generations. Some of the sub-species can interbreed. What is interesting is that the hybrids they produce often have trouble mating with either parent population, reinforcing the isolation (because of coloration or size or mating bahvior the mates don't choose them).

I don't have an issue with some level of speciation. It remains to be seen if these limited examples provide the basis for the variation generated to produce large scale changes.

[jlay]

Cystic fibrosis is another possible mutation that provides some resistance in some environmental areas.

These sorts of examples, however, rarely would lead to speciation in themselves.

Rarely? That means it has happened although, not often. So you have documented cases. Please share.

I have a dear friend with children who suffer from CS. And let me assure you, they suffer. Beneficial? Good grief.

[zoegirl]

Cystic fibrosis is another possible mutation that provides some resistance in some environmental areas.

These sorts of examples, however, rarely would lead to speciation in themselves.

Rarely? That means it has happened although, not often. So you have documented cases. Please share.

I have a dear friend with children who suffer from CS. And let me assure you, they suffer. Beneficial? Good grief.

First, I am of course, very sorry for anyone to have CF. It is very brutal to those that have it. That being said, I didn't imply that CF in itself is beneficial, I said that the mutation potentially is beneficial in some areas. There is a big difference in the frequency of CF in different areas of the world and in different populations. In European countries, it is as common as 1 in 25 people, whereas in African and Asian countries and populations, the frequency is much lower.

CF is the most common fatal genetic disease among European populations. It is unusually common for a genetic disease that is so severe, suggesting that there has been some advantage to the allele else it would have been markedly reduced in the population.

Heterozygote advantage, the idea that carriers of an allele have only some traits of the disease, would prevent the decrease in the frequency of the allele. This happens with sickle cell anemia....those with both alleles will suffer from sickle cell, those with both normal alleles will suffer from malaria, those that are heterozygous have a resistance to malaria and yet have enough normal functioning hemoglobin for good oxygen saturation. There are several ideas about the CF allele:

* Cholera: With the discovery that cholera toxin requires normal host CFTR proteins to function properly, it was hypothesized that carriers of mutant CFTR genes benefited from resistance to cholera and other causes of diarrhea.[94] Further studies have not confirmed this hypothesis.[95][96]
* Typhoid: Normal CFTR proteins are also essential for the entry of Salmonella typhi into cells,[97] suggesting that carriers of mutant CFTR genes might be resistant to typhoid fever. No in vivo study has yet confirmed this. In both cases, the low level of cystic fibrosis outside of Europe, in places where both cholera and typhoid fever are endemic, is not immediately explicable.
* Diarrhea: It has also been hypothesized that the prevalence of CF in Europe might be connected with the development of cattle domestication. In this hypothesis, carriers of a single mutant CFTR chromosome had some protection from diarrhoea caused by lactose intolerance, prior to the appearance of the mutations that created lactose tolerance.[98]
* Tuberculosis: Another possible explanation is that carriers of the gene could have some resistance to TB.[99][100]

In many of these cases, you can see that in those areas affected by cholera or typhoid, which would be immediately deadly, those that carried the gene could have survived the outbreaks of the disease and did not suffer much because they only had one allele for CF.

You can imagine it would be tough to test for this other than by using animal models and genetic correlation studies. But it is compelling.

And I said rarely because in these instances, the homozygous condition leads to fatality. So these examples would not be a good cause for speciation.

[jlay]

Can you site any tested and observed cases of mutations directly leading to speciation?


I guess we could say tape worms are beneficial to weight loss.

[zoegirl]

Jlay, reread my posts....

I have already said at length that they have not. Danny asked for their evidence, I provided some of their evidence. I even went through and explained the LIMITS of their evidence.

This is what is know:

1) There is an abundance of variation
2) Much of this variation leads to changes in frequency of alleles
3) Mutations happen; most are harmful, some are neutral (affecting color, behavior)....some that are harmful, in some instances, can provide a benefit in other environmental situations
4) there are several examples of sympatric speciation with plants where the polyploid plant cannot reproduce with the parent plant, there are several intriguing instances of reproductive isolation where two populations choose to avoid mating with the other (can they still interbreed, yes)
5) there are several instances of changes that suggest the beginnings of allopatric speciation. Has it happened yet? No, (I never said it had), but it certainly bears watching.

Should we examine this, absolutely, should we be fearful of this? No...

I guess we could say tape worms are beneficial to weight loss.

not the same thing by a *long* shot. this isn't even an appropriate example

Are you denying the relationship between sickle cell allele and resistance to malaria?? Basic fact that those that are heterozygous for the sickle cell allele are able to live better and survive malaria. Is this not beneficial in this environmental pressure?

[jlay]

Here is the context of what you said, and what I am addressing.

There have been multiple studies showing the possibilities of genetic variation within a population. Of mutations, there are plenty of examples of mutations, most harmful, plenty neutral, and some beneficial depending on the environment. For instance, the mutation that causes sickle cell anemia is beneficial in those areas with malaria. Cystic fibrosis is another possible mutation that provides some resistance in some environmental areas.

These sorts of examples, however, rarely would lead to speciation in themselves.

Did I miss something?

Not trying to be argumentative here Zoe. Just trying to make sure I understood what you said. The way I am understanding what you said, leads me to indicate you didn't understand what you said.

I never argued that mutations didn't exist, and that most, overwhelmingly, are harmful. I am simply pointing out that you stated something, at least as I am reading it, that is not true. That these examples (mutations) rarely lead to speciation. Do they rarely lead to speciation or not? And if they rarely do, where is the evidence?
If I am reading your statement right, then it is very apparent that you were forcing your Darwininst leanings on to the evidence. Another example. "Has it happened yet " Very clearly an assumption, based on your Darwinist's worldview.

Is this not beneficial in this environmental pressure?

that is not my beef. If you have even the slightest evidence that such things even remotely lead to speciation, then please share.

[zoegirl]

There have been multiple studies showing the possibilities of genetic variation within a population. Of mutations, there are plenty of examples of mutations, most harmful, plenty neutral, and some beneficial depending on the environment. For instance, the mutation that causes sickle cell anemia is beneficial in those areas with malaria. Cystic fibrosis is another possible mutation that provides some resistance in some environmental areas.

These sorts of examples, however, rarely would lead to speciation in themselves.

In the context of the *theory*, lethal mutations would rarely lead to speciation, yes. I never that they we have seen examples, I have only worked on the current theories. In the current model, mutations that lead to shorter lifespans would mean a population in trouble. In the examples I gave, those mutations exist in the populations because they allow a certain set of the population to survive in a certain set of conditions. In those conditions, those mutations (in the sickle cell its shown, in the CF allele it's still a hypothesis) provide some benefit to those individuals and allow them to live longer. Simple logic there.

As a theory, selection leading to speciation is pretty compelling, IF, mind you, IF, the mutations happened the way they liked them. In that regard I have nothing against the theory. It is perfectly logical...the phenotypes that match the environment, the different reproductive fitness, would lead to changes in the populations.

It comes down to the question of whether those mutations occur at the rate that would support changes in a population.

[DannyM]

By definition (at least with the biological definition of species), as soon as they cannot interbreed and produce fertile offspring. If the owls *can* interbreed but often choose not to because of mate choice, this would be, in their eyes, the potential start of speciation....because as soon as they *don't* mate, the different populations accumulate different mutations, which could lead to them not being able to mate and produce fertile offspring.

This is what we can call 'theoretically plausible' in the Darwinist's eye, right? Would you see any objection, Zoe, to my saying that it is no more unreasonable and no less rational for me to say to the Darwinist that the theoretically plausible just doesn't cut it when debating the issue? The Darwinist or neo-Darwinist is prone to use the theoretical as though it were inevitable given (an unspecified!) long period of time. Why do you think the dissenter from neo-Darwinism is so often treated to scorn for merely pointing out that something 'theoretically plausible' does not constitute the leap from this 'plausibility' to some wild notion of inevitability?

yes, you are right, and even in their first paragraph they admit that real-time evidence is hard to accumulate because this would happen over many many generations. Some of the sub-species can interbreed. What is interesting is that the hybrids they produce often have trouble mating with either parent population, reinforcing the isolation (because of coloration or size or mating bahvior the mates don't choose them).

I don't have an issue with some level of speciation. It remains to be seen if these limited examples provide the basis for the variation generated to produce large scale changes.

It seems to me that, apart from it being a good idea to experiment with these things, to call any of this "speciation" is to imply that a species is literally changing or on its way to changing into another species, when in reality we are merely witnessing changes of the species, adaptation to certain changes whether imposed naturally or in a controlled environment. There are no species to species changes occuring here, there are simply changes within the species... Unless we once again appeal to that wonderfully accommodating term 'theoretically plausible'...

[zoegirl]

By definition (at least with the biological definition of species), as soon as they cannot interbreed and produce fertile offspring. If the owls *can* interbreed but often choose not to because of mate choice, this would be, in their eyes, the potential start of speciation....because as soon as they *don't* mate, the different populations accumulate different mutations, which could lead to them not being able to mate and produce fertile offspring.

This is what we can call 'theoretically plausible' in the Darwinist's eye, right? Would you see any objection, Zoe, to my saying that it is no more unreasonable and no less rational for me to say to the Darwinist that the theoretically plausible just doesn't cut it when debating the issue? The Darwinist or neo-Darwinist is prone to use the theoretical as though it were inevitable given (an unspecified!) long period of time. Why do you think the dissenter from neo-Darwinism is so often treated to scorn for merely pointing out that something 'theoretically plausible' does not constitute the leap from this 'plausibility' to some wild notion of inevitability?

Well, for them, there is historical evidence that is compelling. While we hesitate about using that evidence, they argue that it fits. DNA homologies that suggest that African cichlid fish divided over the last tens of thousands of years provide them with a record that shows the divergence. http://horizon.documentation.ird.fr/exl ... /26389.pdf Couple that we what we see with regards to microevolution over years and they connect the dots.


There are those for whom it is an absolute necessity to support evolution because of their atheism, but there are many scientists who are Christian who do not have this requirement and yet still support the evidence.

yes, you are right, and even in their first paragraph they admit that real-time evidence is hard to accumulate because this would happen over many many generations. Some of the sub-species can interbreed. What is interesting is that the hybrids they produce often have trouble mating with either parent population, reinforcing the isolation (because of coloration or size or mating bahvior the mates don't choose them).

I don't have an issue with some level of speciation. It remains to be seen if these limited examples provide the basis for the variation generated to produce large scale changes.

It seems to me that, apart from it being a good idea to experiment with these things, to call any of this "speciation" is to imply that a species is literally changing or on its way to changing into another species, when in reality we are merely witnessing changes of the species, adaptation to certain changes whether imposed naturally or in a controlled environment. There are no species to species changes occuring here, there are simply changes within the species... Unless we once again appeal to that wonderfully accommodating term 'theoretically plausible'...[/quote]

But that is the basis for experimentation....it *is* plausible until it's falsified. So for them to say that it is potentially happening, that is technically true, as long as that is the language used. Problem is, that might take over hundred years to see the results....

[JordanRHughes]

I believe the secrets will be reveled when we find the missing link. Once that becomes obvious that will explain the science of things. If you find that out you'll be remembered forever.

Darwinism is where it's at until the missing link...

[lupham]

Majoring in Science I believed in evolution. The question is "if we came through evoulution...why has evolution stopped?" Our human bodies are far from perfect...evolution supports changes in our enviornment....and now i believe in creation.

[Kristoffer]

But did what science? Biology? Botany? or whatt and why "believed"

Majoring in Science I believed in evolution.

Has it stopped? Natural Selection doesn't stop, nor does Artificial Selection(something we have been doing for centuries) there are tiny chuwowa dogs and big danes, that shows how much change can happen to a genepool even in a short space of time

The question is "if we came through evoulution...why has evolution stopped?"

They are far from perfect because Evolution works with trade offs, birds for instance could sacrifice some stability to gain in manœuvrability , actually I would think it is the other way round, changes in the environment would trigger changes in species, although looking at human beings...it can happen because we can change the environment, I do not know about creation, but in the sense of Artificial Selection "Intelligent design" is real.

Our human bodies are far from perfect...evolution supports changes in our enviornment....and now i believe in creation.

[cslewislover]

I prefer the british accent....but I have no idea of your question...it is so painful that I don't watch it....but I usually feel so left out of the conversations at school that I succumb every once in awhile....

Sorry Zoe, but I thought you were saying that the Brits had "tiny buts"... Blame RickD !! You'd hate my accent Zoe, but I know I'd love yours...

Lol, I hadn't been keeping up with this thread earlier, so I just saw this. Why would Zoe not like your accent? I know the accents vary a lot, depending on the area, and while I love some accents there, others I don't so much. Have you seen that XBOX game Fable? A lot of the accents on there are not very pleasant. You can marry someone in that game, and I picked the same person out twice! I wasn't trying to (her face is hidden), but the accent she has (um . . . you play a guy) is very nice, I guess it would be considered upper class. She says kind-of snooty things sometimes too, LOL. Anyway, you would like our accent?

[Kristoffer]

What actual evidence is there to suggest these Iguana might become a new species if they are reproductively isolated from other Iguana?

Well if they are isolated from the parent species then the genetic compatibility will drift apart. It would be speciation, however the generation for an iguana is about 2 years, so people could always "sabotage" the evolution just to prove a Point. It is worth pointing out that Species are abstract constructs and not actually a real thing.