Evolution Requires Reduction in Genetic Diversity

I don't get why you want me to "rate genetic diversity"

Yes as far as the event goes, no to the ToE interpretation of it:
Speciation is a term given to an event that does in fact occur and is in fact characterized by inability to interbreed. My argument is that the new species thus formed can't be the basis for further evolution because it lacks sufficient genetic diversity. Spreading through the population is the same thing as forming a new subspecies by a population split: spreading requires the loss of competing alleles or loss of genetic diversity just as I keep saying all the "subtractive" or "selection" processes do.I doubt that mutations contribute much in the way of functioning alleles, but IF THEY DO, which is the concession I always try to make here, then they are NOT "any less able to cause significant phenotypic change than new allele combinations of existing alleles" -- the effect should be the same. Edited by Faith, : No reason given.

Yes, which is what I've said in earlier posts. Interesting thought to ponder. Well, I'd go with genetic drift except I keep finding out there seems to be some way I'm not getting genetic drift. I can't make sense out of the definition "random sampling." The best I can do with it is random selection which implies a random change in the look of a population over time in the direction of a homogeneous subpopulation within the population. Best I can do with the concept. But if it's anywhere in the ballpark then it's one of those "subtractive" processes like a population split that I keep saying can eventually form new races or subspecies and does so by losing alleles for traits other than those that are coming to characterize the new subpopulation.So I'd agree that the changes aren't due to any selection pressure on the traits themselves, but due to a random favoring of some traits. But I think you are overlooking the fact that the initial dividing into small bands as they spread out in itself will bring about new allele frequencies that would already affect the look of the band over time with or without additional genetic drift. How is that selective pressure "demonstrated" as you claim it is though? I don't see any need for selective pressure at all. Why wouldn't the new allele frequencies created by the initial formation of the band of migrants be enough to explain it? Yes, like the finches' beaks are adapted to the foods they eat, like that large-headed lizard has adapted to a particular food its stronger jaws can handle, and so on. But the question I keep raising is how you know the creature genetically changed to adapt to the environment when striking changes can occur simply from the new allele frequencies caused by an isolated small population? In that case the creature would simply find the appropriate food or other accommodation in the environment and adapt simply by using the characteristic it already has for the task it's best suited for. One thing that makes me think this is that even on different islands the environments aren't different enough to force a genetic change. Some change over generations probably as the subspecies continues to prefer its food or other qualities of its niche, but all toward elaborating the main characteristic that was already brought out by the new alleles frequencies due only to the population split. In most cases there would already be enough variability for a great range of changes and adaptations in any of the small populations we've been talking about. Mutation is hardly ever needed for adaptations. And again I go back to the situations where a handy mutation or set of mutations would save a genetically endangered species like the cheetah and it simply doesn't happen, and yet this idea that mutation is the source of new genetic material to widen a creature's range of possibilities is always included in these scenarios, clung to as if it were reality.

This thread is already about to drown me and here I just get started trying to catch up and already have more posts to answer.Have mercy!I'm going to try to resist answering the new ones until I get through the old ones but my eyes are already hurting from what I've done this morning so I'm going to have to come back later.

I'm not comparing breeding and microevolution in the wild on the basis of selection, but rather on the basis of the effect of a population split. There may or may not be selection involved.

I'm answering a recent post even though I said I intended to resist it, and apparently this comment from you should have been answered before this one.I've never said there could be no further events for the original species. The only reason variation or microevolution stops for a smaller population is running out of genetic diversity/variability but that wouldn't be the case in a very large population. I haven't discussed it at any length as I recall but I know I've mentioned it in passing and always have it in mind that if the original population is large enough there could be many lines of microevolution of daughter populations from it. The only reason the evolution stops for a smaller population is running out of genetic diversity/variability but that wouldn't be the case in a very large population.In fact I suppose most of the domesticated animals started from a large wild pool from which smaller populations were taken and domesticated. Herd animals for instance. There are over 800 breeds of cattle from the original cattle herd, which all represent the daughter populations I'm talking about, that would have changed over time in domestication in reproductive insolation to varying degrees due to their new allele frequencies. Some would change randomly but others would have been bred or selected: The process is the same: isolation of a small gene pool. Population splits come in many sizes. If they start from a very large population many splits are possible, and any of the splits could form a population as large as half the size of the original, so you'd have two populations of the same size and both populations would then change due to new allele frequencies. The allele frequencies won't change much if at all in very large populations when a small number splits off, but will change even in two equal populations since there's no reason to think the alleles would have been evenly distributed in the original larger population. But the effect shows up clearest, or at least fastest, in a small daughter population.

The problem I'm responding to is the often-stated idea that mutations are the cause of adaptations. In the case of the large-headed lizard of the Croatian island it had had only thirty years to evolve that large head, having been planted on that island by human beings that many years earlier. Another example was given on that same thread I believe of the rapid evolution of four different populations of Jutland sheep from one original population in a very short period of time. Millions of years are not needed and there is every reason to believe the whole scenario is a delusion, including the reason that I'm giving: that the processes of evolution do eventually lead to genetic depletion. In a lot less than millions of years, though we can perhaps hope yet for a few more thousand. If such mutations ever do exist. Not at all. The cheetah is merely an extreme example of my entire argument, which is that microevolution, the formation of new phenotypes, starts from a new set of allele frequencies that, in a relatively small daughter population, is a reduction in genetic diversity or variability from the previous populations. In fact you are likely to get the most dramatic new phenotypes from the smallest subpopulations and a bottleneck is one of the smallest. You all underestimate how radically a change in allele frequencies affects the character of a breeding population, although if you took the example of domestic breeding more seriously you might get a clue. There's no reason such a drastic bottleneck shouldn't have created the cheetah from the subset of alleles that remained to it from the previous population. I don't find them confounding at all. The ToE fails to address any of it adequately. One can't speak of a given outcome's "needing" a particular precondition? Funny, I would have thought there was plenty of room in the English language for such statements.Wasn't I talking about a particular situation in which RAZD had just said he didn't see selection pressure operating in that case? I think it was about the racial characteristics of northern Europeans? I agreed with him and then gave my scenario to explain it.In general, although I believe selection does operate in some cases, showing how it isn't needed to form new phenotypes or bring about adaptations is a major point of my argument. They get eaten in my scenario too, but that doesn't make their getting eaten the cause of the herd's adaptation to its niche. Uh huh, so I've heard for the last sixty or so years. And surely there is SOME effect I suppose, but I'm sticking to my argument that the MAIN cause of microevolution is usually-random population splits.

Repeating it a few dozen times doesn't do it, eh, just rolls off your hard head? It has nothing to do with quantity, it has nothing to do with "how much" diversity. It's all in the fact that when a smallish daughter population is actively evolving, that is, acquiring new phenotypes due to the new allele frequencies brought about by a population split, it loses genetic diversity in the split. And it MUST lose genetic diversity to bring out a new subspecies from the new phenotypes. That's what I'm saying microevolution IS, It REQUIRES loss of genetic diversity to produce the new subspecies or species.SO, if you get an increase in genetic diversity at any point by any means, whether the reintegration of formerly isolated populations, resumed gene flow, or mutation, the evolutionary processes, meaning the "subtractive" or "selective" processes I'm talking about, are slowed down or stop altogether. You may get a whole new collection of interesting phenotypes but scattered in the population, not forming a collective look toward a new subspecies. That takes removing alleles so the new traits can emerge as a coherent set of group characteristics.Increase in diversity of any amount impedes (micro)evolution; (micro) evolution REQUIRES the culling of genetic diversity,like pruning a hedge to give it a shape. The mutations themselves may be part of the new shape, they don't necessarily get lost; what gets lost is whatever genetic stuff isn't part of the new shape. Sorry to tell you this, NN, but the problem with just about all your posts is that you don't get my argument at all, keep answering bizarre straw man arguments of your own invention, and yet have enormous confidence in your own errors. Without Getting It as usua. Sigh.

Ah well, you can't get blood out of a turnip or sense out of a diehard evolutionist.But I'll make the usual futile attempt again probably tomorrow.

That really is off topic and it's been discussed on many threads here already, but I'll give a brief answer: That's very true, thank you. It's frustrating and disappointing to find so many Christians, if they really are Christians, denying parts of the Bible that don't square with their opinions. If it's God's word you'd think it's, well, God's word, but only part of it according to some,. No, probably not all living things, though mammals, reptiles and birds would have been on the ark. Many others no doubt survived in other ways, as, for instance, what was left of sea life had to survive in the oceans. Otherwise,all the subspecies of the various Kinds or Species that exist today descended from those two or seven on the ark, a fact that underlies the argument I'm pursuing on this thread. There had to have been great genetic diversity in those few representatives of each Kind for so much variation to have come from their genomes, which I've suggested involved much greater heterozygosity than we have today. That genetic diversity has been seriously decreased since then and yet some creatures still have a lot of variability left. There are various theories, I'm not up on them, but one, I think, is that the oceans weren't anywhere near as salty as they are today. Certainly. See above. There were no doubt plenty of plants on the ark, at least seeds, but yes, the survival of that olive tree suggests other trees also survived through the Flood. What I'm saying is that evolution is only microevolution, variation built into the genetic stuff of each Kind, which was enough to evolve all the different races of each Species we have today. My argument here is that the processes that bring about this microevolution necessarily also reduce genetic diversity, (including diversity that is added at any stage in the evolving process by mutation or resumed gene flow etc.) so that after many population splits there wouldn't be enough variability left for further evolution, thus bringing evolutionary processes to an end before "macroevolution" could even get started.ABE: These are all separate lines of microevolution, keep in mind. Even if one should exhaust its genetic variability after many series of subpopulation, there are many other subpopulations of all Species left.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : No reason given.

nobody said the strata exist on every square inch of the planet. Clearly they don't.Not that it matters to a "Christian" like you that what God said should be taken to counter your ridiculous remark.

What?It's just one of those ToE just-sos that are pronounced from time to time but aren't really demonstrated, except for truly lethal conditions. The ToE seems to be full of such articles of faith that may or may not hold up.However, it wouldn't contradict anything I've said about genetic diversity if it were true and I don't know why you think it would.

SOMETIMES selection is the reason for an adaptation. Where have I denied that? I only say that I think MOST such adaptations are not brought about by selection pressures.

You have long since left your position as Moderator and are deep in the debate whether you want to admit it or not. I've never said I expect different alleles from one population to another, so your carrying on about that is just a straw man. Good grief. I've thought that at a certain point of reduced genetic diversity the alleles underlying new traits might not fit with the same alleles in different combinations for the traits of earlier populations. I really haven't yet seen anything that shows that to be such an unlikely idea and I believe I quoted someone who sees it the same way. I don't believe it can be and never said I did, and you obviously have NO idea what I'm trying to say, you ask the weirdest questions. Genetically different species? Can't happen. All I've tried to explain is how two populations of the SAME species might fail to interbreed. I do not think speciation as conventionally understood exists at all. There is an event that is called speciation that does occur that is characterized by loss of interbreeding with what I've always assumed to be other members of the SAME species. So I've been thinking perhaps reduced genetic diversity might bring about a genetic condition that interferes with interbreeding between populations of the SAME species. I still haven't seen anything to show this couldn't be the case. You don't have a clue what I've been saying about these things so anybody waiting for me to see things your way has a long wait. Well, since you are ridiculously wrong that I've ever made any claim that mixing old alleles could create a genetically new species, ---HOW UTTERLY RIDICULOUS -- you've also said nothing relevant to my argument that microevolution always has to lead to reduced genetic diversity. Where do you get your nonsense about reduced genetic diversity creating a genetically new species? Obviously you are imposing some half-baked version of ToE on what I've said though I've never said any such thing or even come close.If you want to suspend me go ahead. You are not behaving like a moderator and you are not contributing anything helpful to this conversation.
Edited by Faith, : No reason given.

dupEdited by Faith, : No reason given.