The End of Evolution By Means of Natural Selection

Because it's already been falsified, Faith.IF we have a single bacterium, that is a single cell with a single genetic code, then we have zero diversity.Upon allowing that individual cell to multiply into a population of many individuals, variety appears via mutation. In other words, variety spontaneously appears through the process of mutation, even when you bottleneck a population tot he absolute minimum number required to continue reproduction.If you can re-establish genetic variety even after the complete and total removal of all diversity, then your assertion is completely falsified, end of story, do not pass Go, do not collect $200.And since that's exactly what we see in often-repeated experiments, you're just wrong, Faith.

Hi Faith,You've been arguing that evolutionary processes can never increase variation, only reduce it, but mutations contribute new alleles to a population, so obviously variation can increase. Rahvin described the simplest experiment yielding increasing variation, and the process this illustrates takes place at all levels of complexity.--Percy

Welcome back FaithYou are right Faith. Genetic bottlenecks do reduce the number of alleles available in a population. The most extreme form of genetic bottleneck, in sexually reproducing species, involves just one breeding pair, which means that the largest number of alleles available of each gene is 4 (not counting multiple copies of the same gene). Selective breeding is an example of this kind of bottleneck, although breeders often breed in from other lines that also have characteristics they want.Many of the species that have conservation biologists concerned today are going through a genetic bottleneck. Without human interference to reduce the selective pressures in nature they will go extinct, in fact, many species have gone extinct in the recent past. IN FACT, every species that has ever gone extinct has gone through a genetic bottleneck, unless they were all wiped out in some cataclysm. Extinction is obviously the usual outcome of genetic bottlenecks, but sometimes species do survive and eventually build up to thriving populations again.Large breeding populations will usually have a Gaussian (bell curve) distribution of the alleles for any given gene. A sub-populations will likely also have a Gaussian distribution, but the frequency for any given allele may be different from the other population.If there is a fantastic allele in the new population that confers higher survival and reproductive success, but that is in low frequency, it will still take it many, many, many generations to reach high frequency in the population and it will probably never reach 100%, because while it is increasing in frequency, new alleles are also appearing through mutation.If the new sub-population is really small and the number of alleles for the gene of the fantastic allele is reduced it may indeed come to be the only allele for that gene. The likely outcome for this population though is still extinction because there is just not enough variability to cope with all the selection pressures that nature throws at it. If this population does beat the odds and thrive, new mutations (alleles) of the fantastic gene may appear, and if they are not lethal, they will remain in the population which increases the variability of that gene.Through this whole thread you have been arguing a hypothetic scenario where you focus on the variability of one gene and what happens to it in various instances, i.e. bottlenecks, selective breeding, isolation, speciation, etc. You say this ALWAYS leads to a reduction of variability and an end to evolution, but when we look at the bewildering variety of life on this planet that is not what we see. We only see it in species that are on the brink of extinction, and I am not saying that there are not a lot of them, because in the Human era there are.You are right, in bottlenecks genetic variability is reduced and if evolution comes to a dead end the species goes extinct. The same would be true with selective breeding, especially when we only breed within the variety (Dobermans with Dobermans, etc.), but humans intervene and keep them from going extinct.Your repeated denial of the reality of mutations and that they are the source of all alleles and genetic variability is just plain silly. You have not given a single shred of evidence to support your assertions, only your own incredulity. Mutations are one of the underlying basic principals of genetics. Genes mutate it is a LAW OF GENETICS!Your repeated assertions the we do not understand your hypothesis are incorrect. We understand exactly what you are saying, but the narrow range of situations where there is reduced variability in a few alleles cannot be extrapolated to the whole genome or to all species.The phenotype of a species includes all the variation in the whole population (or sub-population) and it can be represented by a Gaussian distribution. The genotype of a species includes all the alleles for all the genes in the whole population (or sub-population) and it also can be represented by a Gaussian distribution.Enjoy

---

What if Eleanor Roosevelt had wings? -- Monty PythonYou can't build a Time Machine without Weird Optics -- S. Valley

Isn't this bordering on circular reasoning, Tanypterix, interpreting observation of the bewildering variety of life as evidence for evolution, evolution being the assumed agent of bewildering variety, given the aggregate biodiversity of species is declining?

---

BUZSAW B 4 U 2 C Y BUZ SAW.
The immeasurable present eternally extends the infinite past and infinitely consumes the eternal future.

Hi Buz, I was not saying that the bewildering variety was evidence of evolution. I was using bewildering variety as a flowery way of saying there is a really large total number of species and when we look at the majority of them we do not see evidence of the reduction of genetic variation within each individual species that Faith is claiming. Sorry that I was not clearer, I guess flowery prose is not my forte. I am not sure what this means, but if you mean that lots of species are going extinct, then I agree that that represents a decline in total biodiversity, especially within the vertebrates.At the same time, we are conducting a huge experiment by introducing non-native species around the globe, opening new habitats for them to diversify into, without the predators that normally act as forces of natural selection, but this is off topic.

---

What if Eleanor Roosevelt had wings? -- Monty PythonYou can't build a Time Machine without Weird Optics -- S. Valley

Having read your screed, I think I see the essence of your mistake.Let's try to formalize our language by labeling genes with letters and alleles with numbers, so that, for example, c1 and c2 would be two alternative alleles of gene c. OK so far?Now, you seem to be imagining the origin of species by a whittling away of alleles.For example, imagine a species which has two alleles for every gene, and twenty-six genes (twenty-six because that's how many letters of the alphabet I have to work with). So it has alleles a1, a2, b1, b2 ... z1, z2.Now, you seem, stop me if I'm wrong, to be imagining speciation happening by a process which reduces the alleles, so that a new species can be produced by a series of selection events which leaves the daughter population with only the alleles a1, b1 ... z1.But this would not actually be speciation. For a member of the daughter population would be indistinguishable from a member of the parent population such as might be produced by recombination. So we might be able to find a member of the parent population which was genetically indistinguishable from a member of the daughter population. So how could we say that two identical organisms were members of different species?(In Noah's flood, the reduction of giraffes to two would have severely depleted the genetic diversity of giraffes, but this would not mean that the two giraffes selected by Noah were somehow non-giraffes.)So when you write: ... then this is true, but it's only half the story. Because you need some production of new alleles to displace the old ones in the daughter population, otherwise what you are seeing is not speciation. There must be an increase as well as a reduction, otherwise you haven't produced a new species.Your confusion is most evident when you write: Now, that's a bad thing if your aim is to preserve the purity of a breed. But it's exactly what you need if you want to produce a new breed. If no mutation had arisen that made dogs have webbed feet, then no-one could have produced web-footed breeds of dogs.And in general, if dogs had been produced simply by selecting from the genetic material already available in wolves, then each dog would be indistinguishable from something which wolves might have produced themselves by sexual recombination. You would have to suppose that it was possible for two feral wolves to have sex and, by a lucky chance, produce a chihuahua or a dalmatian or an Old English Sheepdog because the pre-existing wolf alleles had happened to get arranged in just the right combination.Again, you write: Italics mine. Yes, enough mutations "destroy the species". And therefore, by definition, create a new one. That's what speciation means --- that the new kind of organism is a different species from the one from which it is descended.---You have made a number of minor errors in genetics and the theory of evolution, but I think that this is where your fundamental error lies.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.

Hello bluejay, thanks for the nice welcome. I have been giving oversimplified examples trying to make my point but then you all come back with the subtleties and exceptions and so on. I'm trying to talk about a trend that I think is observable if one focuses on it. When you say NS just has to smite SOME of the competition, fine, I don't want to argue about HOW MUCH of the competition has to be smitten, I just want to focus on the fact that SOME get smitten! That NS smites! It smites the competition. That's its JOB as it were. It gets drastic only at the extremes, fine, like when a snake eats up all the nonpoisonous newts in a population and the poisonous ones then multiply. They probably still have the alleles for the nonpoisonous type among them too as this isn't yet speciation, but those alleles have been "smitten" in the sense that they can't express their phenotype, right? How, I don't know, something to do with dominance and recessiveness? If the poisonous newt continues to be selected eventually it could become a species and then the alleles for the other type will finally have disappeared, no?All I meant by getting a trait "established" was that ... OK I'm thinking of a ring species. The salamanders in California that ring a desert area. Each population has a different "look" to it than each other population, its own peculiar look that identifies it. Maybe I don't have this quite right but I assume that to get this look peculiar to its population required the blending of its own collection of alleles for various traits which occur in different frequencies among them than in the original population. The original founders of the new population would have looked like the population from which they came, but due to their smaller numbers, their different proportions of alleles, perhaps even the absence of some alleles altogether, they mixed together through generations in the new setting to produce this new phenotype, this new look, this new color pattern that distinguishes them from the first population. This is what I think of as "established" -- when the whole population has this new characteristic. They had to have time for their genetics to blend together into a new phenotype characteristic of their new population. Is this what "fixed" means?They don't HAVE to completely lose alleles for this to happen, merely have them in new frequencies, but the TREND down the series of populations IS toward the loss of alleles simply because each new population starts from a small number relative to its parent population.Edited by Faith, : No reason given.Edited by Faith, : grammarEdited by Faith, : bolding

PaulK:
I don't know if increased variation in mitochondrial DNA and hypervariable minisatellite loci contribute to the genetic diversity needed by the cheetah to recover or not. It isn't the normal expected source of genetic diversity so you'd have to tell me what it means.

Phage, I still struggle to get what you are talking about, and on top of that it looks like I didn't express myself very clearly either. If I can I'll come back to your post later.

I'm trying to demonstrate what the selective/isolating processes that lead to speciation do -- they reduce genetic diversity which allows a new phenotype to become characteristic of a new subpopulation. Plenty of other things are also going on that may change that direction but the isolating-selecting processes always work in the direction of reducing genetic diversity. If all kinds of mutations and new traits are accumulating you aren't going to get to an actual new species while that is going on.

The kinds do branch, they evolve. Some creationists do have a wrong idea of fixed kinds but that's really a very old idea and it's very clear that they evolve into many different varieties. This should have been known to creationists all along too because domestic breeding is an ancient art.

This isn't GENETIC diversity you're talking about. You're talking about the proliferation of varieties or breeds. Lots and lots of those, yes. But EACH of the breeds has been able to form BECAUSE it has its own reduced complement of alleles compared to the parent population. Edited by Faith, : typo

This is a complete misreading of what I'm doing and I'm at a loss how to correct it since it keeps cropping up. I am NOT "assuming" this at all, and my argument is not "based on" it. It is an OBSERVATION that the selecting-isolating factors determine the phenotype of a new subpopulation by reducing its genetic diversity. The variation that everybody is talking about comes in at a different point in the life of the species. Oh I can't get this said in any way that you aren't going to continue to object to in the same old way so I have to find new waysto say it. The variation you keep wanting me to take into account simply does not enter into what I'm trying to get said. So go ahead and assert that I'm ignoring addition and I'll just grind my teeth again.Edited by Faith, : correct run on sentence

A distinction without a difference. The reason that poodles, greyhounds, bulldogs and so forth look more diverse than wolves is because of an underlying genetic diversity. How else? See my last post.

quote:

---

I don't know if increased variation in mitochondrial DNA and hypervariable minisatellite loci contribute to the genetic diversity needed by the cheetah to recover or not. It isn't the normal expected source of genetic diversity so you'd have to tell me what it means.

---

The reason for looking at the most variable regions is that those will show the greatest change - which is helpful for dating a relatively recent bottleneck.I have no idea what distinction you are trying to make, though. It's a clear case of mutation increasing the diversity, and there is every reason to expect increasing diversity in other genes as well. Any claim that this is not happening and cannot happen needs real evidence - not simply an assertion. Especially when that it IS happening to some genes.