(PB said) The founder effect and the population bottleneck, a special case of the founder effect, are the loss of genetic variation, but some genetic variablility will remain.How can he think I thought HE "said bottleneck and founder effects are special cases of a TREND?" Obviously he didn't say that, I did. That's MY argument, with which I am answering his.(Faith said) You really don't read well at all. I've over and over affirmed that SOME genetic variability ALWAYS remains, but that the overall TREND is to decrease and ultimate depletion. And bottleneck and founder effect are merely extremes of the trend, not special cases.Faith, the problem here is your reading skills.
If I state something that you have said, even over and over again, it is because I need to remind you of it to continue further. There is no need to get excited like you do. You misread again if you think I said bottleneck and founder effects are special cases of a TREND. What I said, read it again, is that bottleneck is a special case of founder effect.
I've also not been "excited" at any point in the discussion; I can't imagine what he thinks amounts to that. When communication gets this difficult it becomes an exercise in futility to continue.
The point I've been trying to make is that there is a trend toward genetic depletion which accompanies ALL the processes that are considered to contribute to evolution. This is fact, not speculation, and it is recognized particularly by conservationists because it causes problems for particular species, or for human interest in particular species -- as food perhaps.
These processes I sometimes sum up as "selection" processes although Natural Selection is the only one officially named as a selection process. This term is used to emphasize the adaptedness of the new "species" as something positively selected by the environment for that effect, while I use the term to describe them all because they all lead to the same end, although Natural Selection is survival-determined and the others are random. I haven't yet been able to find a term for the whole package that says the same thing. "Isolating" perhaps comes closest, as it refers to a fact that describes all these scenarios -- that a part of a population becomes cut off from another part so that new genetic potentials become expressed at the expense of old ones.
This isolating effect or selection, whether random or focused on a particular trait as in Natural Selection, occurs in many forms. In Natural Selection something in the environment, perhaps a predator, perhaps a dietary restriction, kills off some number of the population, leaving others to continue to proliferate. Sometimes these others have a feature that adapts them to the diet or other formerly hostile element in the environment so they thrive, sometimes they don't appeal to the predator or are poisonous to it, so they thrive for that reason. Evolutionists call this "speciation" or the formation of a new species. The term is acceptable to a creationist up to a point, because we know that such changes occur frequently in all living things.
But most events that bring about such changes are less severe. Simple migration of a part of a population to another geographic area can bring about changes or "speciation." A new diet in the new area may discourage the settling in of a bird with a certain kind of beak but a kind that is adapted to it will thrive. The change in the bird beak could have come about simply randomly, simply because the gene for the old type was left behind in the original population so that a new type could emerge in the new population. All population splits bring about new genetic expressions, often simply randomly, that may have some particular use in the new environment or simply be a visible variation unrelated to requirements of the environment. When a small population of chipmunks splits off from a larger one to establish a new territory, it develops new characteristics that visibly set it apart from the old, markings, stripings, size of ears, facial features, tails, colorings etc. may all express differences between the populations brought about by the "speciation" which was brought about by the simple fact of a small number of chipmunks from a large population moving to a new location. The same thing happens with human beings. If a small group moves to an isolated place and inbreeds for generations they will come to have an appearance peculiar to themselves. This is how "races" are formed.
"Bottleneck" is the situation where an extremely small number of individuals splits off from the mother population; "founder effect" I always thought referred to a single individual who "founds" a new population, so that it is a special case of the bottleneck and not the other way around as my debate opponent has it. But such distinctions are trivial. The point is that the smaller the new population the more drastic will be the differences that come to characterize it in relation to the mother population. If a large population were to divide almost equally into new isolated areas, both new populations would develop new characteristics in relation to each other.
This is just the way genetics works. A population carries many alternative genetic possibilities within it, alleles for different characteristics of particular genes. There can be a variety of characteristics potential in a large population, for body type, size, shape, markings, colorings, eye colorings, facial features and much much more. As long as they stay together in a large population freely interbreeding, a certain collection of traits will generally characterize the whole population, but when part of it goes somewhere else they will carry with them a mix of alleles in a different proportion from those of the mother population, and these will eventually develop new characteristics in the new population as it interbreeds.
Although the founder effect can affect the population far into the future, itds effect may be overtcome in deep time, the possibiliy of which you reject on biblical grounds.How strange, and clearly he's misreading me here, not the other way around. I was clearly saying that I reject deep time, but not on biblical grounds, on scientific grounds, because deep time would lead to extinction given the facts I am describing -- and they ARE facts, they are not speculations.No I reject it on scientific grounds. Deep time would only lead to extinction, as already said, and this is because the trend is inexorably to genetic depletion. And by the way, the only way deep time COULD overcome the problem is if you put mutation into the mix, which is what my usual opponents argue, but you've already quite rightly shown that mutation couldn't do that anyway[s].[How interesting: I wrote "anyway" not "anyways" but in his quote he has me using the illiterate "anyways."]You are misreading, again. What I said you reject on biblical grounds is not the overcoming of the effect, but the possibility of deep time.
Populations can't go on indefinitely splitting and changing or speciating, because these processes all involve a corresponding loss of genetic variability with each such event. That's what I mean by "evolution defeats evolution." There is a natural limit to the changes that are possible. Each new population that develops from a small number has fewer genetic possibilities than the population it split from. As new groups continue to be formed new changes emerge along with fewer genetic possibilities for further change. This is because for new traits to emerge, competing traits must be suppressed or eliminated altogether. This is the way you get speciation. This is the famous "change in gene frequencies" that is sometimes used as the definition of evolution. Speciation IS change in gene frequencies. These DO bring about changes, but you don't get change unless competing traits are suppressed or eliminated. (This really only describes the more drastic population reductions. It is possible for change to be more gradual even within a population without the absolute loss of genetic potentials from the population as a whole (this would be one form of genetic drift), but Natural Selection and migration of small populations and certainly founder effect and bottleneck DO eliminate genetic potentials in bringing about the new characteristics of the new population).
It is quite possible for a population with very little genetic variability to go on surviving indefinitely, but it will have less ability to form new different types or "species." The hypothetical end point of this trend is complete homozygosity or only ONE allele for a particular trait, for many different traits. This is in fact reached in nature sometimes, as with the cheetah. Total homozygosity for ALL traits probably never occurs, although PB wants to insist this is a necessary condition of my argument. It's not, it's merely the hypothetical end point, while the trend toward it is my argument).
Deep time would only lead to extinction, I said, if your theory were true. But it doesn’t, so it ain’t. Everyone sensible, and beamish, too, accept that the earth is billions of years old. Hence your theory does not hold up. Flood geology does not hold water.Yup, I'm totally not sensible. But my theory isn't a theory. I've been describing what actually happens in reality as populations split in reality, and conservationists KNOW this happens. They deal with it every day.
Mutation does have a non-negligible effect in deep time, not in biblical time. Most mutations are selected out, but in the long run some are bound to be beneficial. Mutation is another random source of variation that does not come to an end when genetic variability decreases.The problem is that the selection processes, the isolating processes, the population-splitting processes, beat mutation to it by a long shot. These are wrongly considered to be the motor that drives evolution, whereas in simple actual reality-based fact they bring about new "species" (varieties of a species or Kind to a creationist) at the expense of genetic variability, which gradually over many such events reaches a dead end beyond which further speciation is simply impossible. And this occurs in what PB calls "biblical" time. All species would be extinct long before we get anywhere near "deep time" or millions of years. The extremely rare beneficial mutation could hardly save the day.
I don't know what he has in mind but it isn't my "theory." This really is the first time I've seen him acknowledge it.you get strikingly more or less common variants, psi bond, and my overall point is that you get REDUCED GENETIC DIVERSITY IN ALL CASES. YOU DO NOT GET PHENOTYPIC CHANGE WITHOUT CONCOMITANT REDUCED GENETIC POTENTIAL."I don’t believe that point has been proven. Repetition is not proof. Nor does uppercasing augment the case for its validity."Do you realize that this is the VERY FIRST time you've even acknowledged my argument? That is the reason for the uppercase and the repetition, to bring it to your attention. Now, please try to keep it in mind.Well, I’m sorry you feel I have slighted your theory. However, the way you fiercely preach it, I could not help but have it in mind.
And I go on to spell it out AGAIN. Yes I know it gets repetitive but it's not easy to grasp and I'm probably neglecting to include some necessary information to make it more accessible, simply because I'm so IN the argument I forget what someone who isn't may need to know to get oriented to it.
I have NO idea where this put down came from. I'm aware that I'm talking in generalities. Everybody talks in generalities about these things; there's really no other way to talk unless you get into such complicated technical territory the forest gets lost for the trees. There's no denial of the complexities of nature involved in generalities; if the generality is correct it remains correct no matter what the details.The proof is a simple matter of THINKING IT THROUGH, another thing I haven't been able to get you to do. You cannot get the expression of a particular allele in a population UNLESS ALL THE OTHER ALLELES for that trait are somehow suppressed. Natural Selection sometimes completely eliminates them from the population -- the snake eats the newts that aren't expressing the poison factor. Bottleneck and founder effect "select" randomly rather than for survival benefit but WHAT they "select" is what remains AFTER ALL THE OTHER ALLELES for a given trait are ELIMINATED. Remember this is a kind of genetic drift. Genetic drift of a quieter sort also eventually drives out some alleles as a random allele comes to expression. Sometimes it merely becomes latent. THIS IS WHAT I AM REFERRING TO AS LOSS OF GENETIC VARIABILITY. If the variability remained you would not have the new trait, you would not have speciation. Speciation REQUIRES the elimination of genetic competition, speciation REQUIRES genetic depletion.I’m afraid, Faith, that you have fallen into the error of thinking the patterns of nature are necessarily as simple as armchair speculating prefers to make them.
And here he goes off on another round of mischaracterizations:
Speciation does not require the elimination of each alternate of every allele that is selected.I never said it did. I've been talking about a TREND -- the reduction of genetic diversity with each speciation, not total elimination. I've said alternatives must be SUPPRESSED OR eliminated and I've tried to be very clear which processes actually eliminate, such as founder effect, bottleneck and some Natural Selection. Clearly he is simply not in a mood to understand what I'm saying and this makes continuing the conversation useless.
Speciation does not require homozygosity.I certainly never said that it did. Again, he just doesn't want to think it through, doesn't care what I'm saying, is quite content to sloppily misstate it.
Loss of genetic variability due to a decrease in genetic diversity is not loss of the capability of genetic variation.I thought I had made it clear that you can have MANY events of speciation still retaining enough genetic variability for the capability of further speciation -- such processes can repeat many many times before total loss becomes a real threat. The only times it happens rapidly are with the more drastic processes like founder effect and bottleneck where the reduction in population is so acute the genetic variability is drastically reduced in one fell swoop. It STILL may not be reduced to total loss, however. Again, I'm talking about a TREND in the DIRECTION of genetic decrease, an inexorable trend in that direction.
You ALWAYS get decreased genetic variability, however slight, however localized or limited, you NEVER get an increase.