Evolution Requires Reduction in Genetic Diversity

I want to try to put together a spin-off from The Origin of Novelty thread because Bolder-dash is pursuing a different objective from mine there and it's getting too confusing to try to keep the arguments separate.I'll try to pick out the posts from that thread I think best define where this thread should go:I started my argument there with this brief statement in Message 235: In Message 323 I said In Message 356 I was responding to a post herebedragons made to Bolder but it was partly about my own posts: The topic then took a turn as PaulK wanted me to account for the effect of mutations: To which I responded in Messages 369 and 376: Message 380 in answer to PaulK PaulK answer to above Message 384 Taq answer to my last message387 saying the same thing PaulK was saying: This is pretty unwieldy I guess but I'm going to post it as is and will probably come back to try to improve it.(For reference as the thread proceeds, I want to keep the link to the Introduction to Genetics thread available. It was started but never finished though there was some good discussion there.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : TO ELIMINATE SNARKY SENTENCEEdited by Faith, : Add link to Intro to Genetics thread

Can this get promoted?

I did want to have the whole basic argument on the table at least which i guess you are saying is possible. And I'm amazed that you agree with that much of it, even, since I don't recall that ever happening when I argued it many times before. But best not to look a gift horse in the mouth.Yes that part can just be left as is and I'll go cut out that offending line if you want {ABE: Just did so}. I do think you stated my view pretty well, so the topic to be pursued at the moment is the questions about mutations raised by PaulK and Taq.So I'm happy if you're willing to promote as is. Edited by Faith, : No reason given.Edited by Faith, : No reason given.

Odd then that it has never before been expressed to me. While I'm quite willing to keep the focus at least at first on the questions raised about mutations, I do have to say that nobody in my recollection in discussing this subject before has ever acknowledged that i am right about my claim that evolution in ANY context whatever leads to reduced genetic diversity.You are carefully defining the context here in terms of "one route to speciation" through a subpopulation, which is fine because it's true, so I appreciate that much acknowledgment, but I particularly appreciate what herebedragons said, which I include in the OP, which had me wanting to frame it and hang it on my wall BECAUSE even that much had never been acknowledged before.Your description of the idea of course reserves the implicit claim that other routes do not encounter this problem of reduced genetic diversity. Since my argument is that there are no other routes I will at some point have to try to prove it. But we don't have to start there.Edited by Faith, : No reason given.

The theory I've been pursuing for years is that it does, and I realize it's my job to prove it. There is no argument with this basic notion except perhaps to suggest that it is overemphasized in the range of actual occurrences in nature. For my purposes it doesn't matter which context you choose, including nature's own "selections" by the fairly frequent and often accidental occurrences that bring about reproductive isolation of separated portions of a population, leading to new phenotypes by reduced genetic diversity there as in all other cases.But this is all just by way of preliminary statement that can be discussed as we go along.I want to officially start this thread by answering the last two posts I include in the OP, about mutations.Edited by Faith, : No reason given.

Well, as a matter of fact it is, but I've been too tired all day to get back to this yet. I hope I'm up to answering the mutation statements now. Fine, that is true, but again nobody ever acknowledged that fact before, a fact I've hammered away at on more than one thread here, many times trying to keep the subject as oversimplified as you have put it here but still no acknowledgement until now. Nevertheless I do appreciate the acknowledgement even though hyou don't think you are doing anything of the sort.But you overdefine the situation. The subpopulations can be created by anything that reproductively isolates one from the larger group and that doesn't have to be distinct geographical regions, and believe it or not "differing environments" is NOT what creates the new phenotypes. The genetic situation itself is what creates the new phenotypes, the fact that a new mix of alleles forms the gene pool of the new population compared to the old. That's ALL it takes to produce a new phenotype or variety or breed, or in other words "change in gene frequency." There are a lot of details that need to be discussed about all this and I hope it's going to be possible to get to them before the thread gets swamped in side issues. What you haven't yet grasped is that SELECTION always inevitably reduces genetic diversity. That is the substance of my argument very oversimplified. You can have mutations galore within a population but once you have selection of whatever mix of mutations -- or alleles however formed -- selection reduces genetic diversity in the new population. Selection brings a certain allele mix to expression in the phenotype BY ELIMINATING COMPETING ALLELES from the gene pool. Yes it will take some time to work through this argument. Actually they would evolve according to the particular mix of alleles in their gene pool, which may adapt to peculiarities in their environment certainly, but the environmental factor is not necessarily the driving factor. If you get a finch with a beak that crushes nuts those nuts don't have to be peculiar to the particular environment, it's just that that finch prefers them to the bugs that other finches with slender beaks prefer because they can get at them more easily than the nut-crunching finches can. Well, yes, this is another way you can get reproductive isolation -- within the population itself -- so that it can evolve over time just as the populations in the other situations can. Not into a completely new species however, just the usual subspecies or variety, because it will be by the same processes that involve the bringing forward of a phenotype along with the reduction of alleles for other phenotypes, which is a reduction in genetic diversity. WHEREVER there is selection of a phenotype there will ALWAYS be a corresponding reduction in genetic diversity as the alleles for other phenotypes get eliminated from the pool.The decrease in genetic diversity is an INEVITABLE concomitant of the development of new phenotypes, the more dramatic where the selection pressure is heaviest but always present in any situation where a new phenotype gets developed. And this inevitable reduction in genetic diversity can only move in the same direction toward complete genetic depletion, beyond which no evolution at all is possible. This extreme is no doubt rarely reached in nature although I think it sometimes is, but it is easy to reach it in domestic breeding programs if they too aggressively eliminate the competing alleles by reducing the population too severely.Edited by Faith, : No reason given.

I'm SO grateful. Truly, NOBODY ever acknowledged that simple fact here before. They might insist they get what I'm saying but spelling it out and agreeing with it, no. So thanks again. And now I'm sure you'll have plenty of objections anyway. Yes and no. In a way it IS the whole story which is what my argument is all about, but I'm certainly aware that there are many other situations that have to be considered on the way there.It is good to get the extreme case of the bottleneck acknowledged because it is an example of the same process of creating a new phenotype by eliminating competing alleles, and in those cases, such as the cheetah which is the classic example, you don't get mutations rushing in to increase the diversity as is claimed happens in all populations. The relevance of the cheetah example is disputed here all the time though, but I like to keep it on the table. Yes, of course I do, and it's been discussed many times before, here and on my blog as well. I went through a phase of trying to figure out what the original genome would have to be like for this scenario to be true, considering such possibilities as polyploidy, and some here ridiculed the idea of the "supergenome" of course. Eventually I came to a different answer, but I'm not sure this is the time to get into discussing it. Well, you'll see what I have in mind as I answer your next points: Actually it isn't as dire as all that. The initial diversity before the Flood was so great that enormous diversity remained in the creatures on the ark. This is all speculative of course but I think you need to think of every gene of every individual as being heterozygous, the maximum genetic diversity you could have, two alleles per gene, and different in each individual as well so that you do have four alleles for each pair of animals, and for the human beings you have twelve different alleles for a single gene (the six reproducing human beings, Noah's three sons and their wives). Then if there are many genes for one characteristic and they are all equally heterozygous you obviously have a LOT of genetic diversity that can continue through quite a few generations before being played out.The clean animals would have even more diversity, EXCEPT that they were used for sacrifice which would have reduced it too.Of course the population has lost an enormous lot of genetic material, and that's going to show up down the generations, and I haven't completely worked out how that happens but I'm convinced that the huge amount of junk DNA in our genome as well as that of most animals, is THE sign of the eliminated genetic material brought about by the Flood. THAT much death would have to be reflected in the genome and that's how I think it is reflected, but it's going to take thinking through how this plays out down the generations from the ark and I've barely begun to think that through. But it can if we're talking all that junk DNA having been alive before the Flood and functioning in the genome, and such a great percentage of heterozygosity in the genome as well. I keep forgetting this statistic and will no doubt have to look it up again, but I believe our genome now has about 7% heterozygosity, and it's heterozygosity that makes for genetic diversity. I figure that before the Flood the percentage was much bigger, who knows how much, maybe not 100% but even 50% heterozygosity would be enormous.The idea here is that when you get far out on a breeding line, or you get the situation of the cheetah what you see is a great deal of homozygosity at many different gene loci in the genome. That is the genetic situation that prevents further evolution. A bottleneck now will certainly have such drastic consequences, but back when the genome was so much richer you could have a bottleneck and still maintain enough genetic diversity for many subvarieties to develop down the generations. Nevertheless the TREND is always in the same direction, toward reduced genetic divdersity as new phenotypes or varieties are developed. See above. But again I would point out that even if it were true that new alleles are added by mutation, consider this: a mutation CHANGES an existing allele, it doesn't add something newer than a different expression of that particular gene. If the mutation occurs in a fur color gene it will only affect fur color. You are not going to get anything really new, a new function for instance, through mutation. You are only going to get variations on whatever that gene does. I personally don't think mutations do anything but destroy and deform of course, but even if I'm wrong and they do create useful new alleles what I've said here has to apply.And then, IF that mutation is SELECTED and proliferates in the population, getting passed on and displacing other alleles for that same gene, then what you have is the reduction of genetic diversity I'm talking about, that is the inevitable concomitant of any -- ANY -- selection process. The selection can be brought about by geographical isolation or mating preference isolation or the actions of a predator on the population or all kinds of things. The point is that getting a phenotype established in a population means that it has to be selected, it has to be reproductively isolated, it has to proliferate, it has to dominate over other allelic competitors, etc etc, and that has to mean that the other alleles are suppressed and ultimately even disappear altogether from the population. There is ALWAYS a loss of genetic diversity wherever you have "evolution."Edited by Faith, : No reason given.

This is PaulK's last post (message 384) on the other thread which I didn't answer there: My point was that it just doesn’t happen as much as you apparently think it should, as breeders aren’t always having to fight new traits, at least after the breed is well established. Even in nature we see pretty homogeneous groups maintaining their character don’t we? Populations of identical individuals keeping to their own kind, birds of a feather flocking together as the saying goes. Darwin’s Galapagos turtles were of an identifiable kind, differing in identifiable ways from those on the mainland. His finches had something like four different styles of beaks that specialized in four different ways of getting food, and these types hung out with others of their same beak. There does seem to be a strong family inclination in nature.But that’s not a particularly important point. the main point about mutations of course is the claim that evolution depends on increasing diversity which mutations supposedly supply. I’ve already argued that as soon as a trait is selected, whether it originated by mutation or by simple sexual recombination of existing alleles for that characteristic, whether by chance or conscious intent, that very selection reduces the genetic diversity of the breed or wild population. My claim is that this IS the definition of evolutionary change, there is no other, it can only proceed by reducing genetic diversity. Wherever there is any kind of selecting or culling process whatever, reduced genetic diversity is the result.Taq said the same thing: Again, the point was it doesn’t happen at such a rate as to interfere with breeding programs. But the second point I’d make here is that there seems to be this odd idea that it will always be the MUTATION that is selected for. I’ve noticed this before. I think it’s probably just a case of imprecise thinking but thought I’d mention it. Why should a mutation be any more likely to be selected than other alleles already in the population?I think I’ve already made the most relevant comments about mutations though.1) First that even if they do create new alleles, once they are selected the population loses genetic diversity by eliminating the competing alleles as it develops whatever new phenotype is favored by the allelic mix. Doesn't matter if it's a mutation that is selected or not.2) And second even if they do create new alleles, they ARE just alleles, variations in the sequence along the gene locus, and whatever changes occur can only occur with respect to whatever that gene does. If it governs fur color then the allele may produce a new fur color. But you aren’t going to get any changes beyond these limited changes within the purview of the gene itself and it really doesn’t do more than a pre-existing allele would do anyway.So in fact mutations don't increase diversity at all.

Not really, as I've argued above. First they don't add anything really new to the gene pool, as they merely change the sequence of an allele for a given gene and can only be a variation on whatever that gene does, which the existent alleles already do quite well anyway, and second, selection eliminates the alleles that don't contribute to the phenotype anyway. In nature this most likely happens through mere geographic isolation. Anything that reproductively isolates a small portion of a population will act as a selection, bringing out new phenotypes based on the new gene frequencies, while the other alleles are not expressed and if the population is small enough eliminated altogether.There is no way to get around the effect of selection or reproductive isolation, it always leads to reduced genetic diversity for a particular lilne of variation or breeding.Edited by Faith, : No reason given.

In the balance the selective processes always win so that mutation actually as a matter of fact does not increase diversity in any way that facilitates evolution, and in a certain sense doesn't increase diversity at all. This is because the selection processes, and I'm including anything that creates a smaller population and isolates it, which can be geographic isiolation, will act on mutations just as on any allele, whichever happen to be in greater numbers dominating the new phenotype, the competitors being eliminated over time. Theoretically you could have many new alleles through mutation but they are still going to be selected and some eliminated and the overall genetic diversity reduced for any new subpopulation that is created from the larger population. You don't get evolution from an expanding population though. Where you get evolution is in the development of new phenotypes and that only comes about through some form of selection, a smaller population portion that gets reproductively isolated etc. All you have in the larger population is a nice healthy population. Also the increasing diversity is assumed, not witnessed. You may get variations of course, in fact you always will, but if it only when a smaller portion of the population gets isolated that the variations could actually develop into a new variety or breed. This could happen within the larger population by genetic drift or reproductive isolation of a particular variation through some sort of mating preferences too. But in any case you will have selection and selection is what reduces genetic diversity. Doesnt' matter how much diversity you start out with, doesn't matter how much might accumulated in a large population (which again I doubt. I don't think new genetic material occurs at all, although new traits certainly would). My point was that the environment may hnot have any effect whatever. You will get new phenotypes, new varieties, new breeds, simply by the isolation of a smallish number of individuals from a larger population. The new gene frequencies all by themselves will bring about the phenotypic change, and this can occur in the same kind of environment as the parent population. Adaptation is not always at work in these selection processes, many new phenotypes are simply what happens when genes are shuffled. That is correct. I've been accepting this for the sake of the argument, and will go on accepting it although I don't think new alleles are ever formed. I think variation or the development of new breeds or phenotypes comes about simply by the changing of frequencies of the occurrences of the alleles in the population. Yeah, OK. As I said I'm accepting mutation although I don't think it actually creates viable alleles. Again, doesn't matter how many new alleles did get created, selection will still have the effect I'm talking about of reducing genetic diversity as new phenotypes are formed. If it occurs at all, which I doubt, then you will get a temporary increase in diversity. If there is no selection the mutations will simply occur here and there in the overall population, and new traits may certainly develop from them, but the only way you'll get a new breed or variety is if there is selection, reproductive isolation, etc etc etc and that can't happen without reducing the genetic diversity. OK And as I have explained above in the end the diversity will be reduced as new phenotypes are created. Any increase in diversity will be temporary at best. It really doesn't play that major a role but I don't care, have that part of it your way for now. But WHENEVER you get selection you are ALWAYS going to get reduced genetic diversity. That's the only way you get new phenotypes. It can never outrun the selection process if you understand what I'm getting at. First of course I don't believe any of those mutations are of any value to us, I believe they are all either "neutral" meaning all they do is damage an existing allele to no particular purpose, or they're deleterious. But again, going along with this belief that they are useful, they are still only going to provide a variation on an existing allele, within the purview of the gene locus, and there isn't all that much variety you could possibly get that isn't already expressed in alleles in the population anyway. But again, even if there is some increase in diversity, that diversity is going to get reduced with any selection/reproductive isolating event. This formula is NEVER going to bring about evolution as you envisage it. You get some variation on existing traits, nothing more than that, and whammo it all gets cut down to size by selection. Yes there is adaptation to the environment but all you need for change to occur, for new phenotypes to develop, is the new gene frequencies created by a population split. Adaptation happens but the environment isn't the driving force in most cases. That would be severe natural selection and while it must happen to some extent, not nearly to the extent evolution supposes. Mere gene shuffling will give you new varieties in nature just as it does in domestic breeding.

Could I please request that posters not pile on here yet. I'm not feeling well and it's hard to get the little done I've already done. I really want to get to all of it and hope to eventually, but it gets harder when there are too many posting at once.Thanks.

Not "collectively." I'm not even sure what that means. * The idea is that any ONE line of development of a new species will have reduced genetic diversity from its parent population. The smaller the new population the greater the phenotypic change and the greater the loss of genetic diversity.It's possible of course that both parent and daughter population will be about the same size, in which case both populations would undergo both phenotypic change and reduced genetic diversity to about the same degree. In fact unless the parent population is a great deal larger in numbers than the daughter population both populations will alter in this same way to some extent so that I would think it could be hard in some cases to know which population was which unless you knew the actual history of the divergences.That's a nice chart.I've proposed a test for my view of this but I gather it wouldn't be easy, and in the wild the results might not be very reliable because of the factors I describe above. The test would be sampling the DNA of many individuals in both parent and daughter populations to see if I'm right that the genetic diversity is reduced in the daughter.It would work better if it could be set up in a laboratory, but you should start with a population that has a lot of genetic diversity to begin with. Which you could only know by examining its DNA, and I don't know if that would require complete sequencing or if you could select particular genes to sample etc. On the Intro to Genetics thread I got the impression it might be a lot harder than I imagine.Anyway the idea is that you start with a cage full of whatever this creature is, mice maybe, test the DNA and then separate out a small portion of individuals to separate cages, let them interbreed for enough generations so that each new population is characterized by its own phenotype and then check the DNA of each.The numbers involved could of course rapidly become too much for a laboratory to keep.You could also separate out a new portion from each of the new populations and do the same thing. You should have new phenotypes after some generations of mixing of each new population AND measurably less genetic diversity from their parent population which you had previously checked. I figure genetic diversity can often be recognized by how much hetero versus homozygosity is present. * ABE: Collectively all the finch varieties together could have all the alleles of the original population, that is, all its genetic diversity. It's as separated varieties that their genetic diversity is reduced.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

I'm not ignoring it, DWise, I'm answering it. It doesn't matter how much genetic diversity you create or think you create, or how much was already present (which is my point of view since I don't think mutations create anything beneficial), you are still only creating the genetic material that will be affected by selection just as I've been describing.It doesn't matter what diversity you begin with, what created it, how much there is, when a smaller population gets isolated it's going to undergo exactly what I'm describing here: that is, to get new phenotypes, such as all those finch varieties in Coyote's chart, the new population will naturally also have reduced genetic diversity from the original.Sure you may have mutation-created alleles in the new mix (if anything other than damage actually occurs by mutation, which again of course I don't believe), but even if you do they are still going to have to either become part of the new phenotype while the gene pool as a whole loses genetic diversity, or they will themselves have been eliminated in the population split.The increase in diversity ends up amounting to very little if anything at all.

No, RAZD, you have misunderstood my point. I'm not talking about VARIATIONS being reduced, variations or phenotypes or new traits actually increase due to population splits and reproductive isolation, it's GENETIC DIVERSITY that gets reduced as new phenotypes or varieties are developed.Also I try to keep it clear but it's not easy, that by "selection" I don't necessarily mean "Natural Selection." That is one form of what I'm talking about. I keep trying to use a collection of phrases such as Reproductive Isolation, Population Reduction, Population Split, Geographic Isolation, to make clear that I'm talking about the effect of reducing the numbers of a population and keeping the new population isolated as the way new phenotypes or varieties get formed, which is ALWAYS accompanied by a reduction in genetic diversity. This process can go as far as what is known as Speciation and sometimes does.Otherwise you are making the same claim about mutations that I've already answered here. This is not like money in, money out as DWise put it, selection in its many forms actually changes gene frequencies so that you have more of some alleles, fewer of others and if the population is small enough (or if natural selection IS involved so that the unadapted ones die off or are eaten or whatever) none at all of some alleles. The overall effect is a reduction in genetic possibilities which is what gives you a new variety or phenotype.Also I'm quite aware of the Greenish Warbler ring species, as I am of other ring species which I use as examples for my own purposes. There is a ring species of chipmunks around the Sierra Nevada, a ring species of salamanders around the Central Valley of California, and a ring species of seagulls around the Northern Atlantic.The thing about ring species is that they demonstrate the effect of geographic isolation from one "species" to another. Each new population split off from an earlier population and because of its new mix of alleles which always involves reduced genetic diversity produced a new phenotype. This continued all around the ring.According to my argument there should be much less genetic diversity in the last of the populations than the first. But I'm also aware that the first will have undergone reduced numbers and hence phenotypic and genotypic change as well so pinning this down isn't always easy.Sometimes there is gene flow that continues between populations so that you get a gradation of phenotypes or you get hybrid zones, sometimes there is a complete isolation and the separate phenotype will be more strikingly defined.In any case it takes the elimination of alleles that underlie the other phenotypes in order to form any given phenotype and that's what I mean by reduced genetic diversity.Mutations are absolutely unnecessary to this as simple sexual recombination of existing alleles in the original population is all that is needed to form all the new varieties or phenotypes. But again I'd make the point that even if mutations are involved all they do is form the collection of alleles from which the new phenotypes are created, and in order for that to occur they have to undergo the same processes of selection, isolation, and concomitant reduced genetic diversity I'm talking about.I think there is a common problem with evoljutionist thinking that often the great variety of phenotypes that can occur both in nature and in domestic breeding gets confused in your minds with the genetic substrate or genotype. You really do not need mutations at all to producde all the variety we see. All you need is a good mix of alleles for many genes that govern many traits, the reduction of numbers of individuals that interbreed, and normal sexual recombination will produce all the wonderful variety we see in nature.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

Hallelujah, another one to hang on my wall!I have to thank the Lord for this because I prayed that SOMEONE would appreciate the content of this argument and at least to this point and this degree HBD has done so. So thank You Lord and thank you HBD.If I were more faithful at praying for God's guidance I'd probably do a better job with the argument, so I'll try to take my advice here more often.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.