the phylogeographic challenge to creationism

No, it's not. I mean, you're making this up. How can a variation represent a loss of diversity?If you meant that selection results in a loss of diversity, well, yes, we've all already agreed with that. But either you have no idea what you're talking about, or you're getting really sloppy with the terms. Possibly, you never understood the terms in the first place.Loss of diversity does not accompany phenotypic variation. Phenotypic variation, by definition, is a result of increasing genetic diversity, as well as a result of regular sexual reproduction (which is not the norm among organisms.) Well, you've just done that for me - you've asserted that the mechanisms you refer to can't result in increasing genetic variation. Mutations do, by definition. Thus, the effects of mutation can't be explained by the mechanisms you've just outlined.Like I said, you just proved it for me. I just did. If you don't understand that then you're not familiar enough with molecular biology to intelligently critique evolutionary theory. If you found my information obfuscatory, that's simply because you lack the familiarity with molecular biology required to intelligently assess arguments and evidence from it.

If a kind is everything that is decended from an original ancestor, then there's only one kind in that picture.

But that isn't what evolution says. Unless your talking about "evolutionism", wich could be just about anything you want it to be as there is no such thing.Those two species do have a common ancestor. Otherwise it just ain't evolution. What predictable reduction in genetic diversity? Are you talking about creation? That sure isn't what evolution says is happenning. We do understand about mutations and natural selection? Phenotype or genotype? Perhaps you forgot my explanation for this Faith? In that case here it is: From: Natural Limitation to Evolutionary Processes threadNatural selection does NOT ALWAYS cause a reduction in variation because hidden variation is ALWAYS present in continuously varrying traits. Natural selection can INCREASE variation. How about an example of how this can come about, eh?Suppose you have an environment that favors larger beaks in birds. We'll let + equal the gene for large beaks and - as the gene for small beaks. Because deeper beaks is determined by genes at many loci, a population of even large beaked birds + have some small beak genes -. Now when the birds with the smallest beaks die, alleles for the small beaks are removed from the breeding popuation. This may increase the frequency of the + gene at every loci, but because even the larger beaked birds have some - alleles, variation still remains. Reproduction shuffles these genes within the population and because + genes are more common, individuals in future generations will have more + alleles. Because the more + genes you have the deeper your beak, the population will show a shift to larger beaks, and the new generations biggest beaks will be bigger than the previous generation. If this continues the same thing happens again. The individuals with the biggest beaks will have beaks even larger than the previous generation. As you can see you have MORE variation. This process can even be reversed.An example I have seen used is an experiment on oil content within seeds. The experiment conducted on corn showed that oil content could be increased, after 80 generations, beyond the initial oil content of 4-6%. The researchers were also able to reverse the process and select for low oil content instead. This showed that selection could INCREASE the initial range of variation.
(From Boyd and Silk, ibid, p. 74 with the citing found in the url below) Evolution: Online courseAnd finally, where do you think our domestic dogs have come from? If they come from wolves and we SELECTED traits then of course you should be able to see that we do have MORE dog breeds and MORE variation in this species.It is hidden variation that is selected FOR in many situations of natural selection...It is EXPRESSED variation that is selected for. Hidden variation is later expressed through reproduction/recombination.and:I apologize if I misunderstood what you were saying. It seemed to me that you were talking about variation. Specifically a reduction in variation due to genetic drift/ NS.
I do think I percieve what you are saying and perhaps a misunderstanding about alleles that you might have. In your first post you talked about a reduction in alleles: This is infact not the case. There is no genetic reduction, or reduced allotment of alleles, as if they are somehow reduced. Instead there is a shift in the frequency of alleles by selection working on the expressed alleles. This may or may not cause a reduction in the "FREQUENCY" of an allele, but that is because the frequency of a selected allele is increased. So if we see in our finches with small beaks that they are selected against, we still have a population of larger beaked birds that may have the small beak alleles. In the case of a drastic reduction, such as a bottleneck the allele frequency may shift so much that the allele for small beaks doesn't exist in the population, but the number of alleles for that trait are still there, they may all be large beak alleles.To express this visually, suppose you have a population of birds that vary in beak size according to expressed alleles, as shown below (with - allele for small beaks and + allel for larger beaks). Now remember we are talking about continuouly varrying traits or multiple alleles affect a trait (such as height in humans.)(numbers in parenthesis show hypothetical population)(5) (11) (20) (30) (21) (10) (3)
-- -- -- -+ -+ -+ ++
-- -- -+ -+ -+ ++ ++
-- -+ -+ -+ ++ ++ ++Now if some selection pressure caused the smallest beaked birds to die off you still have - genes in all but the largest beaked birds. There was no "reduction" in the alleles that affect beak size but a reduction in the FREQUENCY of the - allele.This I think is the misperception you have about some reduction.As far as there being a reduction in variability. Variability is the "ability" to vary. What is stopping a mutation to act on or change one of the alleles, even if they were all + alleles? If a mutation acts or changes one of these alleles it will remain hidden and reshuffled among the population if it isn't detrimental to the reproduction of the species UNTIL selective forces act in such a way that this NOVEL ALLELE becomes expressed. This novel allele may or may not help the species to survive.(edited to clarify beak chart a bit)This message has been edited by DBlevins, 11-27-2005 09:55 PM

False. Aside from your very poor use of the term, "species" (if you're going to use a definition that's entirely different from any common biological definition, you might as well just use "kinds"), canines and felines do share common ancestry according to evolutionary biology. This assumes that genetic diversity can only be lost, not gained. Thanks to mechanisms like recombination and mutation, diversity within a founder population tends to increase in the absence of new bottlenecks. If this species proves successful and thrives long enough, it will reach a point where it develops enough genetic diversity within the population so that another divergence is possible under the right circumstances, within the genetic potential of that second species, which is now the ancestor. Repeat this process ad nauseum, and the result of the thousandth iteration may be very different from the 1st species.Again, I think your improper usage of "species" is really confusing things here. It may seem that way to you, but it doesn't seem that way to biologists, and you haven't provided any compelling support for your gut feeling.

Mick understood and agreed. I think I'll stick to discussing it with him.

No, he agreed that selection represents a loss of diversity. You just said that variation represents a loss of diversity, and that's incoherent - diversity is the number of variants in a group, so more variations means more diversity.You're contradicting yourself, and it's probably because you're playing fast and loose with terms.

I haven't assumed it, I have discussed it and made the case for it, and have not ignored that there are a few ways it can be regained -- two to be exact, and it's "regained" not gained in the case of recombination. Those are the only two. There are no others. Mutation as I said hasn't been shown to be able to counteract this effect. Recombination adds nothing new, it merely reverses the bottlenecking/isolating/natural-selecting/genepool-reducing trend and reunites a previously split off part of the population with another part or with the ancestral population. Diversity is recovered this way but it is only one of the many "evolutionary processes" and the others do as I said they do, reduce genetic diversity, and you can't count on "the absence of new bottlenecks" either. The point is that the TENDENCY, the TREND, the OVERALL DIRECTION of all the "evolutionary processes" over time, is toward reduced genetic diversity. I simply refuse to use species in this way as it obscures the point I am trying to make. This is why I said I want to use the terms variation or breed instead. The great differences in phenotype that occur under the majority of the Evolutionary Processes do indeed correspond with a reduction in genetic diversity and I've made this case quite well in earlier posts.

But that's not the trend. The trend is that mutation overcomes the elimination of diversity over time. This is borne out by observation, and in the fossil record.Diversity increases over time, due to mutation. Even though selection reduces diversity, it doesn't reduce as much diversity as mutation puts in. The faucet is bigger than the drain, so the tub fills.To say anything else, to say that the opposite occurs, is make-believe. It's fiction. It's you just making things up. What you say happens, doesn't.

I do not wish to discuss this with you. Mick gets it, you don't.

Mick gets exactly what I get. If you think he's agreed with your entirely counterfactual statements about genetic diversity, then you've completely misunderstood his post.To say that variation means less diversity is to say that up is down, or black is white. It's nonsense. Why can't you see that?

The word is Variation as an alternative term for Species, OK? The establishment of a new Variation or new phenotypic expression involves the reduction of genetic diversity. This is merely a semantic problem that you could easily have resolved with a little thought as Mick did in dealing with my first post.This message has been edited by Faith, 11-27-2005 10:51 PM

That doesn't make any sense. Species are populations. A variation is an individual. Like I said, you're playing fast and loose with terms that aren't synonymous. No, it doesn't. If you have a population with three races, let's say; and later that population has four identifiable races, then diversity has increased. You can't have greater variation from less genetic diversity; it doesn't make any sense.What Mick is telling you is that the reproductive separation of a migrant group from a ancestor group connotes a loss of genetic diversity for the ancestor group. But that has nothing to do with phenotype or variation. It's about interrupting gene flow.You're conflating two entirely different concepts: phenotypic variation of individuals and reproductive separation of populations. They're not the same, and it's your sloppy thinking here that prevents you from understanding Mick's point and seeing the flaws in your own. It's not a sematic problem but a meaning problem - you're using terms without understanding what they mean.

Faith has sealed her mind against anything that contradicts her beliefs.To maintain that seal, she rejects the very notion of evidence and rewrites history.

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Real science did not really get going until Christians began applying the inference of a lawful universe made by a rational God to the study of the physical creation. --Faith

Well, in this thread, I think she's arguing from the evolutionary premise. Seems to be, anyway.

You are generous, crash. I see no evidence in this thread that Faith understands--or wishes to understand--any evolutionary premise.Perhaps I'm too cynical. Please pardon the interruption.

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Real science did not really get going until Christians began applying the inference of a lawful universe made by a rational God to the study of the physical creation. --Faith